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1998 Part 1     Front Cover (1998 - Part 1)    No author information available Summary: Not available         Table of Contents (1998 - Part 1)    No author information available Summary: Not available         Conference Information (1998)    No author information available Summary: Not available         Superconductivity and accelerators: the good companions    M.N. Wilson Summary: This year marks the 30/sup th/ anniversary of the Brookhaven Summer Study on Superconducting Accelerators and Devices, at which many of the basic ideas for exploiting superconducting magnets in high energy particle accelerators were given their first widespread hearing. During the intervening 30 years, superconductivity has made possible the construction of the world's largest accelerators. The authors trace the evolution of superconducting accelerator magnet technology, with particular emphasis on conductor development. Several existing accelerators, both large and small, are described, together with immediate plans and longer term prospects for the future.         Critical current of superconducting Rutherford cable in high magnetic fields with transverse pressure    D.R. Dietderich, R.M. Scanlan, R.P. Walsh and J.R. Miller Summary: For high energy physics applications, superconducting cables are subjected to large stresses and high magnetic fields during service. It is essential to know how these cables perform under these operating conditions. A loading fixture capable of applying loads of up to 700 kN has been developed by NHMFL for LBNL. This fixture permits uniform loading of straight cables over a 122 mm length in a split-pair solenoid in fields up to 12 T at 4.2 K. The first results from this system for Rutherford cables of internal-tin and modified jelly roll strand of Nb/sub 3/Sn produced by IGC and TWC showed that little permanent degradation occurs up to 210 MPa. However, the cable made from internal-tin strand showed a 40% reduction in I/sub c/ at 11 T and 210 MPa while a cable made from modified jelly roll material showed only a 15 % reduction in I/sub c/ at 11 T and 185 MPa.         Testing of the dependence of the number of layers on the performance of a one-meter HTS transmission cable section    J.A. Demko, J.W. Lue, U. Sinha, R.L. Hughey, L. Dresner and S.K. Olsen Summary: A one-meter long prototype transmission cable was constructed by Southwire Company consisting of four layers of helically wound Bi-2223/Ag HTS tapes. Measurements were made at Oak Ridge National Laboratory of the DC V-I characteristics and AC loss of the as received cable and after sequentially stripping the outermost layer so that a series of measurements for four-, three-, two- and one-layer cables were completed. The differences in the cable performance could then be compared with existing theories. In its initial four-layer configuration the measured critical current was over 1500 A. After the removal of the outermost layer to form a three-layer cable, the critical current dropped to 881 A. The performance degradation that was measured is not in direct proportion to the number of tapes in the cable. The DC V-I characteristic curve, critical current and AC losses are reported for each configuration.         Fabrication and test results for Rutherford-type cables made from BSCCO strands    R.M. Scanlan, D.R. Dietderich, H.C. Higley, K.R. Marken Jr., L.R. Motowidlo, R. Sokolowski and T. Hasegawa Summary: Wires based on the Bi-2212 HTS superconductor are becoming available commercially, with current densities that are attractive for some applications. The authors report here on their success in using these Bi-2212 wires to fabricate multistrand, kiloamp conductors that can be used to construct dipole and quadrupole magnets for particle accelerator applications. Multistrand cables have been made from several types of Bi-2212 wire supplied by two manufacturers. These cables were made with cores of various compositions and dimensions in order to optimize the fabrication process. In addition, cables have been made from aspected strands as well as round strands. Cable critical currents are reported and compared for the various cable parameters investigated in this study.         HTS cable test facility: design and initial results    M.J. Gouge, J.A. Demko, J.W. Lue, J.P. Stovall, R.L. Hughey, R. Martin and U. Sinha Summary: A versatile, high-temperature superconducting (HTS) cable test facility has been designed and assembled at Oak Ridge National Laboratory (ORNL) in a joint program between ORNL and Southwire Company. The facility mission is to evaluate the performance of prototype HTS power transmission cables at lengths in the range of 1 to 5+ m. Power supplies are available for steady-state currents of 3000 A (DC) and 2000 A (AC) as well as up to 25000 A (DC) for pulsed loading. Cryogenic cooling is provided by an Air Products liquid nitrogen supply system with the capability of providing about a kilowatt of cooling at pressures up to 10 bar over a temperature range of about 67 to 77 K. Electrical and cryogenic data are taken by dedicated sensors scanned by ten-channel multimeters connected via cable and fiber optic to a personal-computer-based, data acquisition system using the LabVIEW program. These diagnostics allow measurement of the DC V-I characteristics and AC loss of the cable, dielectric integrity via a partial discharge measurement, and cryogenic performance at rated voltage (7.2-kV AC) and current (1250 A). Initial results from facility commissioning and early HTS cable testing are reported,.         Critical current degradation caused by winding process of Bi-2223/Ag HTS wire in the form of a coil    J.X. Jin, S.X. Dou, H.K. Liu, T. Hardono, C. Cook and C. Grantham Summary: High T/sub c/ superconducting (HTS) (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/ Cu/sub 3/O/sub 10+x/ Ag-clad wire has potential for practical applications in the form of a coil or a winding. This HTS wire has strong magnetic field-dependent and mechanical strain-dependent critical currents, consequently it has a severe problem of critical current degradation when it is used in the form of a coil. To design a winding with this conductor, the critical current degradation has to be identified with relation to the magnetic fields and the winding process. This is important to optimize an appropriate coil winding procedure using this HTS wire. A specially designed noninductive sample has been made with a (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/ Cu/sub 3/O/sub 10+x/ Ag-clad 27-filament wire, and the critical current degradation, which is caused by the magnetic field generated and the mechanical winding procedure used to form a coil, has been separated into two factors accordingly, and discussed in this paper.         Stress management of HTS conductor    S.M.O.H. Conductor, N. Diaczenko, T. Elliott, D.A. Gross, P. McIntyre, D. Sattarov, R. Soika and Gan Liang Summary: A Bi-2212 cable-in-conduit featuring incorporated stress management is being developed. By using a compliant thin wall tube made of Inconel X 750 in the center of the CIC the strands of the cable are protected from the accumulated Lorentz stress. This significantly reduces the mechanical loading on the superconductor while it is still being held rigidly in place. A finite element analysis of a cable matrix is presented, and mechanical tests of the Inconel X 750 tubes are shown.         Critical current measurements on large conductors of niobium-titanium/copper cable embedded in an aluminum stabilizer    R.P. Walsh, J.R. Miller and T.G. O'Connor Summary: Insertion of a flat, Rutherford type cable of NbTi/Cu composite strands into a rectangular profile of high purity aluminum is an established method of superconductor fabrication for certain applications. Although this processing scheme has numerous advantages it produces a composite material whose properties are difficult to predict with precision. The BABAR detector magnet being tested at the Stanford Linear Accelerator Center, uses high-purity aluminum stabilized superconducting cable. The performance of the superconductor is dependent on the quality of the fabrication of the composite conductor. Here we present measurements of the critical transport current of BABAR production grade conductors up to 10 kA, and at fields up to 10 T. Data are related to production variables, compared to estimates from simple models, and evaluated with respect to design specifications.         Development of testing apparatus for 10 kA class AC superconductors    K. Takeda, M. Chiba, K. Fukuda, Y. Sakagami, M. Shibuya, N. Higuchi, K. Miyashita and H. Moriai Summary: R&D on NbTi and Nb/sub 3/Sn superconductors has been carried out for application to AC power apparatus in the Super-GM project. 5 kA class NbTi stranded cables have already been tested and then the R&D aiming at the final target of 10 kA class conductors is in progress. However there is no testing apparatus which makes it possible to measure over 5 kArms AC quench current (Iq) and AC loss in AC magnetic field (50-60 Hz). The testing apparatus was developed under the specifications required for evaluating the AC characteristics of 10 kA class conductors. The AC magnet generating the maximum magnetic field of 1 Tpeak in the bore of 150 mm was manufactured. For the Iq measurement, the AC current is directly applied to the specimen in the field of 0.5 Tpeak (50-60 Hz), 10 kArms AC quench current was obtained for the developed large NbTi conductors. As regards the AC loss measurement, the magnetization method using pick-up coils was adopted and its sensitivity has been improved by reducing unnecessary output signal.         1.9 K test facility for the reception of the superconducting cables for the LHC    A.P. Verweij, J. Genest, A. Knezovic, D.F. Leroy, J.-P. Marzolf and L.R. Oberli Summary: A new test facility (FRESCA-Facility, reception of superconducting cables) is under construction at CERN to measure the electrical properties of the LHC superconducting cables. Its main features are: independently cooled background magnet, test currents up to 32 kA, temperature between 1.8 and 4.5 K, long measurement length of 60 cm, field perpendicular or parallel to the cable face, measurement of the current distribution between the strands. The facility consists of an outer cryostat containing a superconducting NbTi dipole magnet with a bore of 56 mm and a maximum operating field of 9.5 T. The magnet current is supplied by an external 16 kA power supply and fed into the cryostat using self-cooled leads. The lower bath of the cryostat, separated by means of a so called lambda-plate from the upper bath, can be cooled down to 1.9 K using a subcooled superfluid refrigeration system. Within the outer cryostat, an inner cryostat is installed containing the sample insert. This approach makes it possible to change samples while keeping the background magnet cold, and thus decreasing the helium consumption and cool-down time of the samples. The lower bath of the inner cryostat, containing the sample holder with two superconducting cable samples, can as well be cooled down to 1.9 K. The samples can be rotated while remaining at liquid helium temperature, enabling measurements with the background field perpendicular or parallel to the broad face of the cable. Several arrays of Hall probes are installed next to the samples in order to estimate possible current imbalances between the strands of the cables.         Application of superfluid helium cooling techniques to the toroidal field systems of tokamaks    J.L. Duchateau and B. Turck Summary: The operational performance, during the last 10 years, of the toroidal field (TF) system of the Tokamak TORE SUPRA based at CEA Cadarache, has demonstrated that superconductivity associated to superfluid helium is a reliable and realistic option for fusion by magnetic confinement. This solution is now widely used in cryoelectricity. With superfluid helium associated to cable in conduit superconductor (CICS), new paths can also be opened for cryoelectricity and especially for fusion. The operation at FZK of the EURATOM LCT coil at 1.8 K and 11 T has also demonstrated, that the use of niobium-titanium can be extended up to very high fields. In the frame of the Large Hadron Collider program (LHC) at CERN, relevant commercial NbTi composites from different companies have been extensively characterized at 1.8 K between 9 and 11 teslas. Based on this characterization, practical considerations on conductor design criteria in superfluid helium are presented, discussed and compared to design criteria in supercritical helium. The operating temperature has an important impact on the cost of the system and can be determinant in the choice of the superconducting material. Some economical evaluations are given on the basis of a reference TF magnet concept.         Scaling of the critical current in ITER type niobium-tin superconductors in relation to the applied field, temperature and uni-axial applied strain    A. Godeke, B. ten Haken and H.H.J. Ten Kate Summary: The three dimensional surface of the critical current density versus field and temperature J/sub c/(B,T) of niobium-tin is a function of the strain state of the superconductor. A brief review of literature on this subject is presented. The J/sub c/(B) function is described by the relations for flux pinning. The temperature and strain dependencies are added to this relation, This results in a unifying scaling law for A15 materials, which is verified for different niobium-tin conductors with respect to all the relevant variables, i.e. field, temperature and uni-axial strain. Nb/sub 3/Sn conductors from 9 manufacturers are measured in the frame work of the third ITER benchmark tests on critical current. The investigated ranges are: applied field from 7 to 13 T, temperature from 4.2 to 8 K and applied strain from -0.4 to +0.8%. Special attention is paid to the region of compressive axial strain, which is the most relevant state of strain for superconductors under thermal compression in practical applications.         Electromagnetic and mechanical characterisation of ITER CS-MC conductors affected by transverse cyclic loading. III. Mechanical properties    A. Nijhuis, N.H.W. Noordman, O.A. Shevchenko, H.H.J. Ten Kate and N. Mitchell Summary: The magnetic field and current of a coil wound with a cable-in-conduit conductor causes a transverse force pushing the cable to one side of the conduit. This load causes elastic and plastic deformation with friction as well as heating due to friction. A special cryogenic press has been built to study the mechanical and electrical properties of full-size ITER conductors under transverse mechanical loading. The cryogenic press can transmit at 4.2 K cyclic forces of 650 kN/m to conductor sections of 400 mm length representative of the peak load on a 50 kA conductor at 13 T. In order to transmit the force directly onto the cable, the conduit is opened partly to allow the cable deformation. The force acting on the cable as well as the displacement are monitored simultaneously in order to determine the mechanical heat generation due to friction. The mechanical loss under load is investigated for the Nb/sub 3/Sn, 45 kA, 10 and 13 T, central solenoid model cell conductors (CSMC). The mechanical heat generation is determined from the hysteresis in the measured curves of displacement versus applied force. The first results of the effect of some 40 loading cycles are presented and the two conductors are compared. A significant decrease of the cable mechanical heat generation after loading cycles is observed.         Shape memory effect of cable-in-conduit conductors    W. Specking and A. Nyilas Summary: In fusion magnets, cable-in-conduit conductors (CICCs) are foreseen, consisting of an outer conduit and an inner niobium-tin cable produced by a simultaneous heat treatment. The heat treatment and the different thermal contractions of the various conductor materials lead to prestress onto the niobium-tin filaments during cool down, degrading the superconducting parameters considerably. These parameters show, during external mechanical loading, a maximum dependence on strain (E). For example, the critical current (I/sub c/) of steel jacketed CICCs increases by about a factor of 2 at /spl epsi//spl ap/0.7% and decreases again at further straining (B=13 T, T=4 K). This characteristic is reversible up to /spl epsi//spl ap/1.2% in stressed and unstressed condition of the conductor. If the conductor is plastically deformed at 4 K up to a remaining strain (/spl epsi//sub r/) and then warmed up to 295 K, /spl epsi//sub r/, decreases by about a factor of 5, which is coupled to a phase transition resulting in a change of volume in the microstructure of the steel conduit. This reduced /spl epsi//sub r/ remains constant after cooling to 4 K again (shape memory) and the critical current corresponds to this decreased /spl epsi//sub r/. In case of an accidental over-straining of a CICC, a further temperature cycle of 4 K/spl rarr/295 K/spl rarr/4 K would recover I/sub c/. Recovery strain results with different jacket materials (aged) of Type 316L, 316LN, Incoloy 908, and titanium are investigated.         Development of a 1 kA, 25-ohm magnetically controlled persistent current switch for SMES    K. Goto, N. Sadakata, T. Saitoh, O. Kohno, H. Honma, Y. Nagai and K. Note Summary: A 1-kA, 25-/spl Omega/ magnetically controlled persistent current switch (PCS) was developed and tested. In a single test of the PCS, it was found that the primary consideration to realize switching from normal state to superconducting state, PCS recovery, for large current should be a control of PCS current. In a connecting test of the PCS and 1-MJ SMES, the PCS showed rapid switching characteristics of less than 0.4 s. In the persistent current mode operation, PCS operation at 1 kA for a six-hour period was demonstrated. By the various tests, primary factors affecting design of magnetically controlled PCS are analyzed.         A fast persistent switch for microSMES    S.D. Peck and J.C. Zeigler Summary: The economics of microSMES for a potential customer are adversely affected by the costs associated with cooling both the magnet cryostat and the power electronics in the system. One way to reduce these loads, and hence the cost, is to operate the magnet in persistent mode while waiting for a power interruption to occur. The reason this has not been implemented to date is because conventional persistent switches cannot be opened fast enough to respond to transients on an incoming power line. The Technology Development Laboratory of the Houston Advanced Research Center has successfully developed a persistent switch with opening times from fifty microseconds to two milliseconds, depending on the triggering mechanism. This switch provides enough resistance to be appropriate for microSMES applications. The paper describes a design and test results for a persistent switch appropriate for a one megawatt, fifteen ampere microSMES application. With this switch, a microSMES cryostat can be equipped with power leads rated for transient operation, with a greatly reduced heat leak. Cooling requirements for the power electronics are similarly reduced.         Niobium-tin persistent-current switch for the superconducting magnet of Maglev    K. Nemoto, S. Saito, Y. Sanada, K. Sasaki, S. Miyake and H. Hashiguchi Summary: We designed and manufactured a persistent-current switch consisting of Nb/sub 3/Sn superconductive wire with an on-state current capacity of 600 A and an off-state resistance of 52 /spl Omega/ for the superconducting magnet of Maglev. To design a persistent current switch, it is important to suppress the instability such as degradation and training. Nb/sub 3/Sn has a higher critical temperature than that of NbTi which is commonly used for conventional persistent-current switches. Nb/sub 3/Sn wire is considered, therefore, to have higher stability to disturbance than NbTi wire. We reduced the volume and weight of the Nb/sub 3/Sn persistent-current switch to around 0.6 times and 0.7 times, respectively, that of the conventional NbTi persistent-current switch. Current-carrying capacity was tested both under the static and vibrating states. Test results of switching performance were compared with a computer simulation of temperature distribution in heating and cooling.         Persistent joint development for high field NMR    C.A. Swenson and W.D. Markiewicz Summary: A large NMR magnet links several Nb/sub 3/Sn and NbTi coils in series. The circuit can contain as many as fifty superconducting joints. The persistence requirements of NMR impose limits on the total circuit resistance. Ideally the magnets total resistance is determined by the field integrated n-value loss in the coils and the resistive sum from the joints. Designing sufficient margin into each coil's conductor can mitigate the decay resulting from n-value loss. Joint losses are the remaining aspect of the design that must be controlled for NMR, joint losses can be conservatively estimated from the upper limit in the resistance measurement sensitivity used during process development. An NMR magnet requires several joint configurations to allow fabrication and assembly of the circuit. There are joints between Nb/sub 3/Sn conductors inside coils, joints between NbTi conductors, and persistent joints between NbTi and Nb/sub 3/Sn conductors. A range of processing methods is required given the complexity of the assembly. This paper presents a review of this subject concerning the available methods for joint fabrication, a measurement method for process development, and supporting measurement results.         Methods for the analysis of the joints between superconducting cables    F. Bellina and M. Ghin Summary: The paper presents two procedures developed to analyse the electromagnetic behaviour of the joints between superconducting cables. These procedures have been applied to the US preprototype joint between the ITER central solenoid conductors. In these analyses the joint is represented by equivalent electrical networks which are studied in an analytical or a numerical way. By means of these models it is possible to have an idea of the current distribution in the joint and to calculate the magnetic field in the surrounding space. The computed and the measured fields have been compared, showing a good accuracy of the model reconstruction.         Thermal and electrical behavior of a resistive joint in the ATLAS toroids    G. Volpini, E. Acerbi, G. Ambrosio and M. Sorbi Summary: ATLAS air core toroids exploit aluminum-clad NbTi/Cu superconducting cables. Several joints along the conductor are presently foreseen, e.g. between pancakes and between coils. The operating current (20.5 kA) is about 4 times larger than in the previous comparable magnets, and so the power dissipated in a similar joint is substantially higher, making the resistance value critical. In this work, the authors have developed some analytical models describing the temperature profile along the conductor given a localized or distributed heat source. By means of these models, they found the highest resistance permissible in order not to exceed a given local temperature rise. Later, they calculated, through a 2-D finite elements program, the specific resistance that can be expected when the joint is performed by TIG-welding the aluminum matrices. Such a value depends strongly on the aluminum-copper interface resistance and on the aluminum RRR in the welding region. They have shown that, with reasonable assumptions, specific resistances lower than 10/sup -9/ /spl Omega/m should be achieved. The results from the first measurements, confirming such a value, are reported and discussed.         Developments of electrical joints for aluminum-stabilized superconducting cables    B. Cure and I. Horvath Summary: Electrical joints for the aluminum-stabilized conductors of the LHC experiment magnets have been studied. Two techniques have been tested: electron beam welding and MIG welding. The joint resistance was measured as a function of the magnetic field on ring shaped samples using the MA.RI.S.A. test facility, wherein current is induced in the test conductor by a varying magnetic field. The resistance is obtained by measuring either the voltage drop or the decay time. Calculation and finite-element simulation have been performed in order to separate the effect of both the copper-aluminum contact resistivity and the aluminum resistivity from the effect due to the joint technique (joint configuration, resistivity of the filler material, increasing of aluminum resistivity in the welding zone). The copper-aluminum contact resistivity and the current transfer length were obtained by measurements of the joint resistance of butt welded samples.         Qualification of joints for the inner module of the ITER CS model coil    P.C. Michael, Chen-Yu Gung, R. Jayakumar, J.V. Minervini and N.N. Marzovetsky Summary: The US-ITER home team has constructed a prototype, low-loss, low-resistance lap joint sample using materials, fabrication techniques, machine tooling and quality assurance procedures identical to those for the layer-to-layer joints in the inner module of the ITER Central Solenoid Model Coil. The joint sample was tested at the MIT Pulse Test Facility to 50 kA current, in both parallel and transverse time-varying fields at ramp rates from 0.05 to and background induction to 4T, to qualify performance to ITER-relevant operating conditions. The joint shows DC below 2.5 nOhm and pulsed, transverse field losses for a 1.5 ramp at 0.4 T/s below 90 J; both values are well within target limits for the ITER-CS joints.         Winding of the Navy SMES background coil    T.D. Hordubay, O.R. Christianson, D.T. Hackworth and D.W. Scherbarth Summary: The Navy SMES background coil was made by stacking 18 double pancakes and connecting them in series to form a superconducting magnet capable of storing 48 MJ of energy. Each double pancake was wound starting in the middle of the conductor and winding outward for each layer. Insulators were placed between each pancake layer which were also used for lifting support. Instruments for the coil protection system control and magnetic field monitoring were attached after final assembly.         Production and qualification of the 60-kA, aluminum-stabilized conductor for the ATLAS B0 coil    L. Rossi, M. Sorbi, D. Pedrini, C. Berriaud and I.L. Horvath Summary: For the toroidal ATLAS magnet system, some 90 km of aluminum stabilized conductor are required. The conductor is a Rutherford cable, coextruded with very pure aluminum. The main characteristics of the conductor are: (1) a very large critical current, 60 kA at 5 T and 4.2 K; (2) RRR of the stabilizing aluminum of at least 1000 on the finished conductor; (3) a good bonding between the Rutherford cable and the stabilizer: a shear stress of 20 MPa is required; and (4) 1750 m of unit length. To assure a good quality of the conductor all along the production and to minimize the risk of rejection of such expensive units, a strict quality assurance was established. The paper describes the results of the R&D phase to set all parameters to produce the first two unit lengths necessary for the winding of the B0 coil (a 9 m long model coil of the ATLAS Barrel Toroid). It also describes the control system based on continuous ultrasonic inspection, able to provide images of the cable inside the aluminum that is used to evaluate on line the quality of aluminum to cable bonding.         Measurements of modulus of elasticity and thermal contraction of epoxy impregnated niobium-tin and niobium-titanium composites    K.P. Chow and G.A. Millos Summary: In the high field magnet program at Lawrence Berkeley National Laboratory, accelerator magnet prototypes are designed with epoxy impregnated niobium-tin and niobium-titanium superconductor. Accurate mechanical property values are essential for magnet mechanical design and prediction of conductor performance. Two key mean property values are measured on coil samples: modulus of elasticity (Young's modulus) and mean thermal contraction. Measurements are made in compression and are conducted in three orthogonal directions. Modulus of elasticity measurements are conducted at room temperature and the mean thermal contraction is measured from room temperature to liquid nitrogen temperature. Room temperature values are compared with values estimated using the individual coil component.         Tailoring of insulation and adhesives for superconducting magnets and devices    M.L. Tupper and N.A. Munshi Summary: Polymer-based insulation and adhesives are integral components of superconducting devices. These materials primarily provide mechanical strength and electrical insulation. Specialized formulations and evaluation techniques have been employed to make these materials suitable for the harsh cryogenic environment. Many devices require specialized or unique properties or processing. Composite Technology Development, Inc, (CTD) has developed substantial capability to tailor these products for use at cryogenic temperatures. Tailoring can provide enhanced mechanical and electrical properties. In addition, products can be tailored to provide more cost effective processing. Furthermore, thermal expansion, thermal conductivity, adhesion, and several other properties can also be tailored. Product tailoring techniques, test methods, product performance characteristics and processing parameters are discussed in the context of several case studies.         Mechanical and electrical properties of wrappable ceramic insulation    J.A. Rice, P.E. Fabian and C.S. Hazelton Summary: High field accelerator and fusion magnets demand superior electrical insulation for top performance. To achieve maximum field strength and system lifetime, high strength and high modulus insulation must be employed. A new wrappable inorganic insulation system has been developed that combines the high strength and modulus of a ceramic composite with the ease of processing of an organic insulation. This new ceramic insulation is applied prior to the superconductor heat treatment and can be processed from 600/spl deg/ to 900/spl deg/C. These properties make it ideal for wind and react manufacturing methods, thus allowing more complex coil designs and reduced processing costs. Development work on the ceramic insulation described here has achieved double the compression modulus of current high strength organic insulation. This paper describes the thermal, mechanical and electrical performance of this wrappable inorganic insulation system. Shear, compression, and dielectric breakdown strength tests results are presented.         Insulation system test for the KSTAR central solenoid (CS) model coil    Han-Sung Kim, Sang-Ho Kim, Young-Hwan Kim, Yong-Hwan Kim, Kie-Hyung Chung, R.P. Reed and D. Evans Summary: The insulation system for a tokamak superconducting magnet should ensure the mechanical and electrical reliability and must have resistance to the radiation environment during operation. The winding scheme of the whole KSTAR (Korea Superconducting Tokamak Advanced Research) CS (central solenoid) coil using Nb/sub 3/Sn CICC (cable in conduit conductor), it is found that there is considerable shear due to tensile force. To obtain a proper resin system two candidates were tested and compared with the ITER (International Thermonuclear Experimental Reactor) standard resin system as a benchmark. This work includes viscosity measurement, flexural strength, shear strength and thermal contraction at room temperature and 77 K. Test procedures and the results of each measurement are presented.         Mechanical analysis of the KSTAR CS model coil    Yong-Hwan Kim, Sang-He Kim, Young-Hwan Kim, Han-Sung Kim and Kie-Hyung Chung Summary: KSTAR (Korea Superconducting Tokamak Advanced Research) CS (central solenoid) model coil made with CIC (cable in conduit) superconductor had been developed in the Department of Nuclear Engineering, Seoul National University. In superconducting magnets, there are mechanical stresses by Lorentz force and thermal stresses by the difference of thermal contraction between conduit and insulator. In this study, the computational analysis with ANSYS, a common FEA (finite element analysis) code, and experimental measurements of KSTAR CS model coil with resistance foil type strain gages have been performed. According to the results of computational analysis, KSTAR CS model coil satisfies safety design limitations. Experimental results obtained from the test of KSTAR CS model coil were compared with those of computational analysis.         Fabrication of the KSTAR central solenoid model coil (II)    Sang-He Kim, Young-Hwan Kim, Yong-Hwan Kim, Han-Sung Kim and Kie-Hyung Chung Summary: The Korea Superconducting Tokamak Advanced Research (KSTAR) Central Solenoid (CS) model coil has been developed. The conductor type is Nb/sub 3/Sn CICC (cable-in-conduit conductor). The entire manufacturing equipment and tooling have been established along with an online manufacturing system. The major role of the KSTAR CS model coil is to demonstrate the manufacturing feasibility of the KSTAR superconducting coils. The winding type is continuous pancake winding without joints in one coil. This paper gives a full account of the detailed manufacturing processes such as winding, jacket removing, welding, termination, heat treatment, insulation and resin impregnation, etc.         Measurement of thermo-mechanical properties of NbTi windings for accelerator magnets    P. Vedrine, B. Gallet and C. Nouvel Summary: In the framework of the development of superconducting accelerator magnets, one has to determine the apparent elastic modulus and thermal contraction of NbTi windings. This knowledge is required to calculate the prestress needed to compensate thermal shrinkage differentials during cool-down and stress redistribution due to Lorentz forces during excitation. A compression mold was developed to measure the apparent elastic modulus of ten alternately stacked insulated superconducting cables, both at room temperature and in a cryostat at liquid helium temperature. The thermal contraction is measured in another stainless steel mold, designed to simulate the prestress application. A force sensor based on a strain gage measurement technique is inserted between the conductor stack and the cover of the mold to monitor the applied prestress during cool-down. The force sensor is calibrated at room and liquid helium temperature. Reference samples made with known materials such as stainless steel, copper, aluminum and titanium have been also measured to calibrate the test apparatus.         Three dimensional stability analysis of high-temperature superconductors using the finite element method    E. Burkhardt and J. Schwartz Summary: As the properties of high-temperature superconducting tapes improve, practical design considerations require more detailed analysis to prevent quenching. An important issue for high-temperature superconductors is stability; i.e. the ability to maintain or recover superconductivity in the event of a thermal disturbance or flux jump. As a result of the broad range of temperature during a transition and the strong temperature dependence and anisotropy of the material properties, the finite element method (FEM) is used to solve the three-dimensional heat conduction equation. The minimum quench energy for several sources is determined. The different cases considered include: convective boundary condition, source in BSCCO or Ag, increased anisotropy of thermal conductivity of BSCCO, increased critical current density and a constant source in Ag Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O-Ag.         Designing stable and high-current density rotor windings of superconducting generator    O. Tsukamoto, M. Furuse, T. Takao, M. Morita, S. Maeda and T. Hirao Summary: A method to statistically predict quench training characteristics of a rotor windings of a superconducting generator is presented. In the method, energy of a disturbance due to a conductor motion and a quench current is statistically estimated. The authors apply this method to a rotor of the 70 MW class superconducting generator being developed in the Super-GM project and study the dependence of the stability on parameters of the rotor conductors, such as amount of copper stabilizer, accuracy of conductor dimensions and operating current density. To predict the stability, compliance of the rotor winding pack is a key parameter and estimated by a finite clement method. In the study, it is shown that there is an optimum value of ratio of copper to superconductor to maximize the current density of the winding pack keeping necessary stability. Based on the study, a designing method for stable and high current density rotor winding is discussed.         Quench detection of superconducting bus-line of LHD by fuzzy theorem    Y. Uriu, A. Ninomiya, Y. Kanda, T. Tanabe, T. Ishigohka, T. Mito and S. Yamada Summary: In the LHD (Large-scale Helical Device) system, superconducting coils are fed by superconducting bus-lines. For sound operation of the LHD, a reliable quench detection system of the superconducting bus-lines is essential. The first difficulty for the quench detection is the lack of the voltage monitoring leads closely running along the conductors. The conductors of the bus-lines are covered by thick thermal insulation pipe. Taking care for the electrical insulation, no voltage lead is inserted inside the pipe. Therefore, one has to locate the voltage leads outside the pipe. This situation will bring heavy voltage noise induced by the stray magnetic field. So, the authors have proposed a voltage detection system which utilizes a noise cancellation technique. In this system, the difference of the voltage of the plus polarity lead and that of the minus one is monitored. The magnetically induced noises of both leads almost cancel each other in the monitoring voltage. All the voltage signals are converted to digital ones using 16-bit A/D converters, and processed digitally. These digitized voltage signals and other signals, like the current and liquid He, levels are input to PCs. The PCs carry out the fuzzy computation and calculate the "dangerous rate" which stands for the state of the superconducting bus-lines. To obtain further fine adjustment to minimize the noise voltage, a digital differentiation technique is also introduced. Experiments of the proposed fuzzy SC-bus monitoring system were carried out in May 1998, with the LHD system of NIFS, Told, Gifu, Japan. These experimental results are shown in this paper.         Minimum quench energy measurements on single strands for LHC main magnets    A.K. Ghosh, W.B. Sampson, P. Bauer and L. Oberli Summary: The stability of magnet conductors can be characterized by their minimum quench energies (MQE), i.e. the minimum energy pulse of small extent and short duration needed to initiate a quench. The MQE of a considerable number of prototype strands for the superconducting LHC magnets have been measured at BNL within the framework of the US-CERN accelerator collaboration. The main interest of this work was to study the effect of different strand designs, copper to superconductor ratios (Cu/Se) and the source of the niobium-titanium alloy on MQE. Although MQE varied significantly between the strands, the measurements revealed that except for Cu/Se ratio, these above stated parameters do not affect MQE in a consistent way. Numerical simulations indicate that these tests made with a restricted helium volume and heat exchange surface were quasi-adiabatic in nature, and hence the influence of the cooling even in superfluid helium was minimal.         Minimum quench energy measurements on prototype LHC inner cables in normal helium at 4.4 K and in superfluid He at 1.9 K    A.K. Ghosh, A. Prodell, W.B. Sampson, R.M. Scanlan, D. Leroy and L.R. Oberli Summary: The minimum energy of short duration (MQE) required to quench superconducting cables at fixed field for currents close to the critical current has been measured for several prototype LHC inner type cables. Measurements done both in normal helium at 4.4 K and also in superfluid helium at 1.9 K show that the level of cable compaction has a substantial effect on the conductor stability. It also appears that another parameter that significantly influences the ability of the conductor to absorb transient energy pulses is the inter-strand resistance, which can vary greatly depending on the cable design and the nature of the strand surface. This parameter seems to make a bigger difference to MQE at 1.9 K than at 4.4 K. Details of these measurements are presented.         Quench energies and stagnant normal zones in cryostable magnets    Y. Lvovsky Summary: In a cryostable magnet cooled by pool boiling helium, an area with deteriorated heat transfer, such as a vapor lock, can locally destroy stability in the winding. When a thermal disturbance occurs in this area, depending on its energy and the size of the area, it can: (a) lead to recovery of the superconducting state; (b) develop into a local steady normal zone; or (c) create an ever-growing stagnant zone. The stagnant zone is characterized by an uncontrollable temperature growth in the center, reaching hundreds of K in several minutes, while its fronts slowly advance into cryostable regions. It represents the most probable quench scenario in a cryostable magnet and should be considered as a main target for a quench protection system. Classification of different normal zones in a cryostable winding with a vapor lock is presented. Criteria are derived which determine regions of existence of steady and stagnant zones in conductors with nonlinear properties and heat transfer. Critical sizes of the uncooled area are defined, and quench energies are calculated for copper and aluminum stabilized conductors.         Influence of interstrand current redistribution on acceleration of quench propagation in eight-strand Rutherford cables    K. Sasali, T. Ogitsu, T. Nakamoto, K. Tsuchiya, T. Shintomi, H. Yonekawa and N. Amemiya Summary: In order to study the relationship between quench propagation velocity and current redistribution during a quench, heater quench tests were performed. The cable used was eight-strand Rutherford cable coated with Sn-5Ag, which was subjected to a uniform magnetic field of 4 T. The quench process was measured by using voltage taps and sets of pickup coils. The authors found that, over a certain transport current, the quench propagation velocity accelerated as the normal zone propagated. The relationship between the quench propagation velocity and the current redistribution is discussed.         The LEP2 superconducting RF system    J. Tuckmantel Summary: The LEP2 superconducting RF system supplies at present about 2600 MV per turn to the electrons and positrons of the LEP beams, giving a beam energy largely above 90 GeV to create the desired massive W/sup /spl plusmn//-pairs for physics. It is by far the largest such system worldwide and a further upgrade is still under way to increase the W/sup /spl plusmn// production rate and cover new physics grounds. More than 10 MW RF power were routinely transmitted to the beam during last year's smooth operation. The authors present the technical parts of this system: the cavities, couplers, tuners, cryostats, the cryogenics and the RF generation and distribution. They also report on operational experience and future plans.         Developments and achievements at the TESLA test facility (TTF)    C. Pagani Summary: The TESLA Test Facility (TTF), under construction and commissioning at DESY International Collaboration, is an R&D test bench for the superconducting option for future linear electron-position colliders. TTF consists of an infrastructure to process and test the SC cavities and of a 400 MeV linac (Phase I), to be upgraded up to 1.2 GeV (Phase II). The infrastructure is fully operational and the first cryomodule of the three planned for Phase I has been successfully in operation since June 1997. Each cryomodule contains eighty nine cell. Cavities at 1.3 GHz. The planned performances (15 MV/m with a Q of 3 10/sup 9/) have been outreached. The achievements on cavity development and cryomodule design allow expected cavity operation at 20 MV/m (at least) in the second cryomodule, that is planned to be in operation by November 1998. The TESLA goal of 25 MV/m is expected for the last six modules. An overview of the facility and of the results obtained so far in the critical technologies are presented in this paper, with a particular focus on the superconducting cavities.         Application of RF superconductivity to a high-current linac    K.C.D. Chan Summary: In 1997, Los Alamos National Laboratory (LANL) initiated a development program for high-current, superconducting, proton-linac technology to build prototype components of this linac and demonstrate the feasibility. Seven hundred-MHz niobium cavities with elliptical shapes are being built, as well as power couplers to transfer high RF power to these cavities. The cavities and power couplers will be integrated in cryostats as linac cryomodules. This paper describes the linac design and the status of the development program.         Review of low beta structures [superconducting linear accelerators]    G. Bisoffi Summary: A number of superconducting linear accelerators for heavy ions are operational in the world, and their resonators are characterized by an optimum velocity in the range v/c=0.008-0.2. The design issues for these kinds of cavities are discussed. The choice of the superconductor, the various construction techniques, the most proper surface treatments and the conditioning procedures are reviewed, and updated performances reported. Advantages and drawbacks of the three major construction techniques are discussed. The most recent kinds of low beta superconducting cavities, such as modified quarter wave resonators and radiofrequency quadrupoles, are presented.         The performance of BSCCO racetrack coils at 4.2 K    W.B. Sampson and A.K. Ghosh Summary: Small racetrack shaped coils have been fabricated from commercial 2223 and 2212 BSCCO tape conductors and tested in liquid helium at 4.2 K. These coils are insulated with Kapton film and provided with an array of voltage taps so that the characteristics of both straight and curved elements can be examined at various positions in the windings. The performance of the coils is compared to short sample measurements of the conductor. These small coils are prototypes of longer units which will be used in a test magnet designed to explore the potential of high temperature materials for the construction of dipoles and quadrupoles for future high energy accelerators and colliders.         The performance of Bi-Sr-Ca-Cu-O superconducting quadrupole coils    M.D. Manlief, H. Picard, G. Snitchler, A.K. Ghosh, M. Harrison, W.B. Sampson, P. Wanderer, G. Dugan, J. Rogers, A. Temnykh, J.S. Brandt, P.J. Limon and R.C. Sood Summary: A small saddle coil for quadrupole magnets was made in industry from BSCCO-2223 high temperature superconducting tape. The coil was made to help develop methods for winding the ends of small-aperture magnets. This coil has a radius of 35 mm. It was tested in liquid helium, and liquid nitrogen. Voltage taps have been installed so that V-I characteristics of both straight and curved elements can be examined. The performance of the coil is compared to short sample measurements of pieces of conductor taken from the start and finish of the windings.         Flywheel energy storage advances using HTS bearings    T.M. Mulcahy, J.R. Hull, K.L. Uherka, R.C. Niemann, R.G. Abboud, J.P. Juna and J.A. Lockwood Summary: High-temperature-superconducting (HTS) bearings have the potential to reduce rotor idling losses and make flywheel energy storage economical. Demonstration of large, high-speed flywheels is key to market penetration, Toward this goal, we have developed and tested a flywheel system with 5- to 15-kg disk-shaped rotors. Rim speeds exceeded 400 m/s, and stored energies were >80 Wh. Test implementation required technological advances in nearly all aspects of the flywheel system, Features and limitations of the design and tests are discussed, especially those related to achieving greater energy storage levels.         Preliminary study of a superconducting bulk magnet for the Maglev train    H. Fujimoto, H. Kamijo, T. Higuchi, Y. Nakamura, K. Nagashima, M. Murakami and Sang-Im Yoo Summary: One of the prospective applications of high critical temperature superconductors is a superconducting magnet for the magnetically levitated (Maglev) train. Development shows that RE (rare earth) BaCuO and LRE (light rare-earth) BaCuO superconductors prepared by melt processes have a high critical current density at 77 K and high magnetic fields. LRE-Ba-Cu-O bulk superconductors melt-processed in a reduced oxygen atmosphere, named oxygen-controlled-melt-growth (OCMG) process, are very promising for high field application as a superconducting permanent magnet with liquid nitrogen refrigeration. Compared to good quality melt-grown REBaCuO bulks, LREBaCuO bulks exhibit larger critical current densities in high magnetic fields and much improved irreversibility field at 77 K, implying that more effective flux pinning can be realized in a commercially feasible way. In this study, we discuss the possibility of a superconducting bulk magnet for a Maglev train. A preliminary design of the bulk magnet and also melt processing for REBaCuO and LREBaCuO bulk superconductors and their characteristic superconducting properties are presented.         Analytical models for a mechanical strain of a modified D-shaped toroidal coil for 1 kWh experimental SMES    T. Ezaki, Y. Horiuchi, T. Fujii, F. Irie, K. Tsutsumi and H. Hayashi Summary: Several interesting characteristics in the strain force measurement of the supporting structure of the modified D-shaped toroidal coil for 1 kWh experimental SMES (ESK) have been observed. A simple analytical model is developed to simulate the measured characteristics. With this model, the mechanical behavior of the superconductor in the coil is studied. Calculated results based on this model show good agreement with the observed characteristics. Mechanical losses of the superconducting coil are also discussed using this model.         Opportunities for "dual use" of special superconducting magnetic systems in TRINITI    E.P. Polulyakh, A.V. Spiridonov, L.A. Plotnikova, V.A. Afanas'ev and M.I. Kharinov Summary: A brief description of the superconducting MHD-magnets and magnetic energy storage (SMES) constructions, their performances and experimental results are presented. Optimization of their weight-dimension characteristic are shown. Opportunities for "dual use" of such superconducting magnetic systems are considered.         Results of tests on components and the system of 1 kWh/1 MW module-type SMES    H. Hayashi, K. Honda, H. Kanetaka, T. Sannomiya, T. Imayoshi, K. Tsutsumi, F. Irie, M. Takeo, K. Funaki, T. Ezaki, H. Okada, R. Ito, F. Sumiyoshi, S. Ioka, K. Atano, S. Nose and H. Yamamura Summary: A full system of 1 kWh/1 MW superconducting magnetic energy storage (SMES) has been completed early this year. This SMES is the first step to the realization of practical SMES system for power line stabilization. Main points in its design are two module type arrangement of six coils having three coils and one converter as one unit of module, modified-D-shaped coils with mechanical supports, liquid helium vessel type cooling of coils, and high-temperature superconducting current leads. The first test experiment was carried out on the site recently. The above design points were examined. A preliminary test for power line control was also made in the distribution line at the site. Satisfactory results were obtained.         Active damping for electromagnetic transients in superconducting systems    B.K. Johnson and H.L. Hess Summary: The use of superconductors for power transmission has been studied for decades. The lossless nature of superconducting cables makes the system less stable operationally because damping normally provided by resistive losses is eliminated. Breaker actions during routine system operations or in response to faults can trigger high frequency oscillations between the inductances and capacitances from either power factor correction capacitors or parasitic phase-to-phase or phase-to-ground capacitances in the lines or cables. Transient overvoltages may exceed double the nominal operating voltage. In a power system using conventional conductors, series resistance damps these oscillations within a number of 60 Hz cycles. In a superconducting system, these oscillations persist, with only the light damping from the frequency-dependent resistance of the superconductors, creating a long-lasting distortion on voltage and current. Traditional methods to damp transient oscillations may not be effective for every situation. Power electronic converters may damp these oscillations. Either a shunt- or a series-connected power converter is an option. However, a series connected converter must carry the full line current at all times, but a shunt-connected converter damps oscillations only when they occur. Key issues are rating the power converter and reducing energy losses.         Application of SMES coordinated with solid-state phase shifter to load frequency control    I. Ngamroo, Y. Mitani and K. Tsuji Summary: This paper proposes a sophisticated application of SMES to load frequency control (LFC) in an interconnected power system. The SMES is coordinated with a solid-state phase shifter to enhance the LFC. The frequency control concept and control design of a SMES coordinated with a phase shifter are presented. Numerical results demonstrate the significant effects of LFC by the proposed control and the economical advantage of MJ capacity of SMES.         Experimental study on power system stabilizing control scheme for the SMES with solid-state phase shifter (SuperSMES)    D. Kamolyabutra, Y. Mitani, T. Ise and K. Tsuji Summary: The combination of superconducting magnetic energy storage (SMES) and a high speed phase shifter is considered to be a unified power system controller. The combined system has been named as SuperSMES from the viewpoint of its capability. A new control scheme of the SuperSMES for power system stabilization with a simple control sequence composed of local signals has been proposed. This paper shows the results of a new stabilizing control scheme of the SuperSMES for power system stabilization based on experimental results with a 10 kJ superconducting magnet and a 10 kVA model power transmission system.         Line-current control with a series thyristor-controlled reactance based on a superconducting coil for electric-energy systems    A. Garcia-Cerrada, P. Mingorance, C. Fernandez, A. Robertson, L. Garcia-Tabares, A. Gran, V. Gonzalez, J.M. Rodriguez and J.F. Alonso Summary: This paper describes the experiments carried out with a series controlled reactance to be used for line-current control in an electric power transmission line. The controlled reactance has been built with a superconducting coil which can be short-circuited by two inverse parallel thyristors. It is shown that, if the thyristors are fired at a variable angle every cycle, the effective series impedance of the device can be varied continuously as a function of the firing angle. A single-phase prototype has been built for closed-loop current control in an AC circuit. Conventional thyristors and firing circuits have been used for the prototype and no switching-off control is necessary. The same technology is frequently used in electric energy systems. The controller has been fully implemented using a digital signal processor (DSP) and a commercial real-time interface. This gives good flexibility to the controller design and test. The paper investigates experimental results for the steady state and the transient performance of the prototype.         Compensation of harmonics and negative sequence components in line current and voltage by a SuperSMES    T. Ise, J. Ishii and S. Kumagai Summary: A SuperSMES is composed of inverters connected in series to a power system and another inverter in parallel, and a superconducting magnet for energy storage. It is a universal power quality controller because of its multi-purpose ability. The application presented here aims at a general filtering system in large industrial power consumers. The SuperSMES can provide sinusoidal and balanced voltage to loads which are sensitive for voltage distortion and unbalancing. It also eliminates current harmonics and unbalance in three phase lines of the distribution system, which flow upstream of the connecting point. The ability was demonstrated by simulation results.         Linearization of generator power swing property by controlling power output of SMES for enhancement of power system stability    M. Hojo, Y. Mitani and K. Tsuji Summary: This paper proposes a control scheme to achieve a robust power system stabilization by superconducting magnetic energy storage (SMES). The control applied in this study is to linearise the power swing property by the active power control of SMES. The control is robust in the sense that the effect is not affected by the changes of the power system configuration, the operating condition, etc. As a result, the power system stability in the transient state as well as in the steady state is significantly improved. Some numerical studies demonstrate the distinguished effect of the SMES using the proposed control scheme on power system stabilization in comparison with SMES using the conventional feedback control of generator speed deviation.         Experimental study on energy transfer between two superconducting magnets with voltage ripple reduction control    Y. Shirai, D. Matsubara and T. Nitta Summary: A power supply for superconducting pulse magnets which consists of a small power converter, a superconducting magnet for energy storage and an inverter converter bridge (ICE) energy transfer circuit have been proposed and studied. In this paper, a new control method of ICB energy transfer circuit to reduce voltage ripples across a load superconducting magnet is proposed and discussed. A test power supply of the proposed type which was designed and made is shown. Results of fundamental tests on the energy transfer between two superconducting magnets are shown and discussed. It is confirmed that the voltage ripples across the magnets can be reduced with the proposed ripple reduction control.         SMES coil configurations with reduced stray field    T. Hamajima, M. Shimada, S. Hanai, Y. Wachi, M. Tezuka and H. Takano Summary: The stray field of SMES restricts its site location, although SMES has an attractive potential for power management and quality control. The stray field outside a solenoid is analyzed by a series of Legendre polynomials and the result is applied to the stray fields of various SMES coil configurations. As long as the summation of magnetic moments from all coils is zero, the term of a stray field decreasing as r/sub p//sup -3/ can be cancelled out. The higher order of the stray field can vanish if the coil arrangement is optimized. In this paper, the authors consider a single solenoid as a reference, active shield coils, axially displaced coils and multipole coils to reduce the stray field. The multipole coil configuration has high potential to drop the stray field, since the stray field behaves like r/sub p//sup (3+n/2)/, where n is the coil number.         Optimum design of superconducting magnet coil for a micro SMES unit    K. Venkataratnam, V.V. Rao, K.N.V. Subba Rao and A. Arun Kumar Summary: The paper outlines a systematic procedure for the design of a solenoidal coil to obtain maximum stored energy for a given length of normal conductor and superconductor. In case of normal conductor, it would suffice if we design the coil to obtain maximum inductance. For superconducting coil, it is essential to maximize (1/2Li/sup 2/) as a whole since the value of allowable current depends on flux density which in turn is linked with L. This results in the design of a coil, whose inductance is much lower than the maximum possible value and has relatively large diameter as compared to its length and radial thickness. Since such a coil requires a cryostat of unusually large neck, one may choose a sub-optimal design based on commercially available drum type cryostat for transportable micro SMES units. The paper concludes with the dimensions of a solenoidal coil for optimum and sub-optimum designs using superconducting (Nb-Ti) wire of 8 km length and 1 mm diameter.         Force-balanced coil for large scale SMES    S. Nomura, T. Osaki, J. Kondoh, H. Tsutsui, S. Tsuji-Iio, Y. Sato and R. Shimada Summary: In large scale SMES, huge electromagnetic force caused by high magnetic fields and coil currents is a serious problem. In order to solve this problem, we propose a concept of force-balanced coil (FBC) applied to the SMES. The FBC balances the centering force with the hoop force, both of which are exerted in the major radius direction. Moreover, for the optimization of large aspect ratio superconducting coils, we propose a stress-balanced coil (SEC) concept, improving the concept of FBC, which balances magnetic pressures at the coil nose part where the produced magnetic field reaches its maximum value. Comparing the toroidal magnetic field coil (TFC) and FBC with SEC, the last can reduce coil stresses and obtain large stored energy with shorter length conductors and/or lower magnetic fields.         Determination of the magnet assembly tolerances required to satisfy the optical resolution of the G/sup 0/ superconducting toroidal spectrometer    T.A. Antaya, E.S. Bobrov and R.M. Laszewski Summary: We discuss in this paper the procedures and the results of Monte Carlo simulations used to determine the room-temperature magnet assembly tolerances providing for the required optical resolution of the G/sup 0/ superconducting toroidal spectrometer.         Superconducting magnets for generating uniform magnetic force field    T. Kiyoshi, O. Ozaki, H. Morita, H. Nakayama, Hong-Beom Jin, H. Wada, N.I. Wakayama and M. Ataka Summary: We report a new application of high magnetic fields to structural biology. We usually design and fabricate a magnet to achieve uniform magnetic field as well as uniform magnetic field gradient. In this new application we adopt a uniform magnetic force field. It has been found that the growth of protein crystals is affected by the presence of magnetic force. Development of uniform magnetic force field magnets is now in progress at the Tsukuba Magnet Laboratory of the National Research Institute for Metals. These magnets are superconducting magnets because they must be continuously run for several days to grow protein crystals. The first magnet wound with NbTi is now under installation. This magnet is designed to generate a uniform force field of 240 T/sup 2//m in a cylindrical space of 10 mm in diameter and 10 mm in height, and the magnetic force field fluctuation along z-direction is better than 0.4%. In liquid helium, it could achieve the design current.         A study on optimal coil configurations in a split-type superconducting MRI magnet    S. Kakugawa, N. Hino, A. Komura, M. Kitamura, H. Takeshima and T. Honmei Summary: Optimal coil configurations in a split-type superconducting MRI magnet have been investigated, and the feasibility of the compact and high performance magnet is presented. A highly homogeneous magnetic field of about 10 ppm/50 cm diameter spherical volume (DSV) is attainable by eliminating error fields of higher orders and, moreover, the radius of the outermost coil can be reduced to about 70 percent of that of the magnet with positive current simply by alternately arranging coils with positive and negative currents.         Three dimensional field calculations for a short superconducting dipole for the UCLA Ultra Compact Synchrotron    M.A. Green and C.E. Taylor Summary: The Ultra Compact Synchrotron (UCS), proposed for UCLA, is a compact 1.5 GeV electron light source with superconducting magnets to produce X-rays with a critical energy of about 10 keV. The design physical length (cold length) for the dipole is 418 mm. The synchrotron requires that a uniform field be produced in a region that is 180 mm wide by 40 mm high by about 380 mm long. The end regions of the dipole should be short compared to the overall length of the dipole field region. A Vobly H type of dipole was selected for the synchrotron bending magnets. In order for each dipole to bend a 1.5 GeV electron beam 30 degrees, the central induction must be in the range of 6.4 to 6.9 T (depending on the dipole magnetic length). The pole width for the dipole was set so that over 90 percent of the X-rays generated by the magnet can be extracted. The three dimensional field calculations were done using TOSCA. This report shows that Vobly type of dipole will behave magnetically as a conventional water cooled iron dominated dipole. The uniformity of the integrated magnetic field can be controlled by varying the current in the shield coil with respect to gap and cross-over coils. The two dimensional in center of the magnet can be tuned to be very uniform over a width of 110 to 120 mm. The three dimensional calculations show that the magnetic length along a particle track in the dipole is about 29 mm longer than the length of the iron pole pieces. This report presents the three dimensional design of the UCS Vobly dipole and the results of the field calculations for that magnet.         Magnetic measurements of the Fermilab high gradient quadrupoles for the LHC interaction regions    R. Bossert, J. Brandt, J. DiMarco, M.J. Lamm, F. Nobrega, G. Sabbi, P. Schlabach, C. Sylvester, M.A. Tartaglia, J.C. Tompkins, A.V. Zlobin and S. Caspi Summary: Three short models of the MQXB quadrupole magnet for the LHC interaction regions have been built and tested at Fermilab. In this paper we present the magnetic field measurement results and compare them with expectations based on as-built dimensional parameters and with a preliminary table of field quality requirements.         The Levitated Dipole Experiment (LDX) magnet system    J.H. Schultz, J. Kesner, J.V. Minervini, A. Radovinsky, S. Pourrahimi, B. Smith, P. Thomas, P.W. Wang, A. Zhukovsky, R.L. Myatt, S. Kochan, M. Mauel and D. Garnier Summary: In the Levitated Dipole Experiment (LDX), a hot plasma is formed about a levitating superconducting dipole magnet in the center of a 5 m diameter vacuum vessel. The levitated magnet is suspended magnetically during an eight hour experimental run, then lowered and recooled overnight. The floating F-coil magnet consists of a layer-wound magnet with 4 sections, designed to wrap flux lines closely about the outside of the levitated cryostat. The conductor is a niobium-tin Rutherford cable, with enough stabilizer to permit passive quench protection. Lead strips are used as thermal capacitors to slow coil heating. An optimized system of bumpers and cold-mass supports reduces heat leak into the helium vessel. Airbags catch the floating coil on quenches and faults, preventing collision with the vacuum vessel.         Superconducting open-gradient magnetic separator utilizing the braking effect of an axial component of magnetic force    J. Pitel and F. Chovanec Summary: The computer simulation of particles' trajectories in a simple cylindrical coil shows that the magnetic force acting on paramagnetic particles at the bottom part of the coil bore has a predominantly axial component which aims upwards and opposite to the force of gravity. In case of a superconducting coil and depending on the value of the particle mass susceptibility, the axial force component can exceed several times the force of gravity. As a result, an expressive braking of the motion of particles in the vertical downwards direction appears. This effect was utilized in an unconventional design of magnetic separator, the main advantage of which is the high selectivity of separation process. The separator operates either in a deflecting or attracting mode. The cylindrical orifice feeder and the splitter are located in the warm bore of a liquid helium cryostat with the inner diameter of 140 mm. A Magnetic force field with a magnetic flux density up to 7 T is generated by the NbTi superconducting coil. The experiments with the siderite and quartz classified particles have been performed and compared with the theory.         A conduction-cooled, 680-mm-long warm bore, 3-T Nb/sub 3/Sn solenoid for a Cerenkov free electron laser    W.A.J. Wessel, A. den Ouden, H.J.G. Krooshoop, H.H.J. Ten Kate, T. Wieland and P.J.M. van der Slot Summary: A compact, cryocooler cooled Nb/sub 3/Sn superconducting magnet system for a Cerenkov free electron laser has been designed, fabricated and tested. The magnet is positioned directly behind the electron gun of the laser system. The solenoidal field compresses and guides a tube-shaped 100 A, 500 kV electron beam. A two-stage GM cryocooler, equipped with a first generation ErNi/sub 5/ regenerator, cools the epoxy impregnated solenoid down to the operating temperature of about 7.5 K. This leaves a conservative operational margin for the MJR type of Nb/sub 3/Sn conductor of about 350% (I/sub c/) at 3T. Current leads with HTS sections between the first and second stage of the cryocooler effectively reduce the conductive heat leak. In the warm bore, 60 mm in diameter and 680 mm long, an operational magnetic field of 2 T has been achieved during laser operation without any quench. The field homogeneity is better than 99.5% over 450 mm axial length. Design details and test results of this magnet system are presented.         Gravimeter using high-temperature superconducting bearing    J.R. Hull and T.M. Mulcahy Summary: We have developed a sensitive gravimeter concept that uses an extremely low-friction bearing based on a permanent magnet (PM) levitated over a high-temperature superconductor (HTS). A mass is attached to the PM by a cantilevered beam, and the combination of PM and HTS forms a bearing platform that has low resistance to rotational motion but high resistance to horizontal, vertical, or tilting motion. The combination acts as a low-loss torsional pendulum that can be operated in any orientation. Gravity acts on the cantilevered beam and attached mass, accelerating them. Variations in gravity can be detected by time-of flight accelerator, or by a control coil or electrode that would keep the mass stationary. Calculations suggest that the HTS gravimeter would be as sensitive as present-day superconducting gravimeters that must be cooled to liquid helium temperatures, but the HTS gravimeter needs cooling only to liquid nitrogen temperatures.         A high gradient magnetic separator fabricated using Bi-2223/Ag HTS tapes    J.X. Jin, S.X. Dou, H.K. Liu, R. Neale, N. Attwood, G. Grigg, T. Reading and T. Beales Summary: Bi-2223/Ag HTS wire provides a new opportunity to build an HTS magnet for use in a high separation efficiency, low operational cost, high gradient magnetic separator. A magnet has been designed using HTS wires and the results analyzed for use in this application. The magnet configuration consisted of 12 units and generated 3 T magnetic field. The capability of the Bi-2223/Ag HTS wire for this application was analyzed with consideration of its critical transport current density, conductor filling factor, and magnet field distribution.         Continuous superconducting-magnet filtration system    N. Saho, H. Isogami, T. Takagi and M. Morita Summary: We developed a new water purification system using a continuous superconducting-magnet filtration system that removes phytoplankton. The system consists of twin-type magnets with a helium refrigerator: a reciprocating magnetic main filter, and a rotating magnetic sub-filter. This system removes phytoplankton from lake water by separating coagulated magnetic flocks with the magnetic filters. The filters can be continuously cleaned and regenerated under low magnetic fields while flocks are being separated under high magnetic fields. This system removed more than 93% of the phytoplankton from lake water at flow rates of 400 m/sup 3//day.         Cryogen free operation of a niobium-tin magnet using a two-stage pulse tube cooler    C. Wang, G. Thummes, C. Heiden, K.-J. Best and B. Oswald Summary: A conductively cooled superconducting Nb/sub 3/Sn magnet system has been designed and tested that employs a two-stage 4 K pulse tube cooler. The Nb/sub 3/Sn coil has a clear bore of 11 mm and a mass of 2.6 kg. High-T/sub c/ current leads are used to reduce the heat leak to the 4 K stage. After a cooling time of about six hours the 2nd stage and the magnet surface attained stationary temperatures of 3.4 K, and 4.1 K, respectively. The 1st stage cold head was then at 54 K. The magnet coil was repeatedly charged with a current of 120 A corresponding to a central field of 2.8 T. Stable operation of the energized system has been demonstrated for 25 hours.         Development of HTS power transmission cables    M. Leghissa, J. Rieger, H.-W. Neumuller, J. Wiezoreck, F. Schmidt, W. Nick, P. van Hasselt and R. Schroth Summary: The Siemens company is developing a high-temperature superconducting (HTS) 110 kV/400 MVA cable for future power transmission systems in densely populated areas. The cable consists of coaxial conductors made of 2223 BPSCCO multifilament tapes, a LN2-high-voltage insulation, a flexible cryostat, terminations and a LN2 cooling system. This paper gives an overview on the project status.         HTS current leads for the LHC    T.M. Taylor Summary: Leads for transferring heavy current from power converters, working at room temperature, into the liquid helium environment required to operate superconducting magnets, have been long recognized as being an immediate application of the emerging technology of high temperature superconductivity. By correct dimensioning of such leads it should be possible to reduce significantly the cryogenic load which these leads represent. The Large Hadron Collider (LHC) under construction at CERN is by far the largest user of superconducting magnets requiring the transfer of over 3 million amperes of current, and therefore has much to gain from the use of this technology. After a brief reminder of the motives and the outline of the project, a review is given of the program to provide helium gas cooled current leads incorporating HTS sections.         AC losses of prototype HTS transmission cables    J.W. Lue, J.A. Demko, L. Dresner, R.L. Hughey, U. Sinha, J.C. Tolbert and S.K. Olsen Summary: Since 1995 Southwire Company and Oak Ridge National Laboratory (ORNL) have jointly designed, built, and tested nine, 1 m long, high temperature superconducting (HTS) transmission cable prototypes. This paper summarizes the AC loss measurements of five of the cables not reported elsewhere, and compares the losses with each other and with theory developed by Dresner. Losses were measured with both a calorimetric and an electrical technique. Because of the broad resistive transition of the HTS tapes, the cables can be operated stably beyond their critical currents. The AC losses were measured in this region as well as below critical currents. Dresner's theory takes into account the broad resistive transition of the HTS tapes and calculates the AC losses both below and above the critical current. The two sets of AC loss data agree with each other and with the theory quite well. In particular, at low currents of incomplete penetration, the loss data agree with the theoretical prediction of hysteresis loss based on only the outer two layers carrying the total current.         Multilayered Bi-2223 conductors for current-lead applications    L. Martini, F. Barberis, R. Berti, L. Bigoni, F. Curcio and G. Volpini Summary: The "accordion-folding method" enables us to fabricate large current carrying capacity multilayered Bi-2223 conductors suitable for applications as current lead (CL). At present, silver-gold alloys, with Au 3% and 11% wt, sheathed Bi-2223 conductors up to 500 mm long, having an overall critical current density J/sub c, eng/ exceeding 3000 A/cm/sup 2/ at 77 K are reproducibly obtained. The high J/sub c, eng/ values are a direct consequence of the high fill factor of these conductors. In this work, we first compare the low-temperature heat load for multilayered Bi-2223/Ag-Au conductors and for an optimised vapour-cooled CL and then show the results of simulations of the temperature evolution after a quench event. Self-field I/sub c/, I/sub c/(Be/sub ext/) and R/sub cont/(I) results on individual, as well as stacked multilayered, Bi-2223/Ag-Au conductors are presented and discussed in perspective of their possible use as CL.         Characterizing thermal runaway in HTS current leads    J.M. Pfotenhauer and J.W. Lawrence Summary: Following a brief review of the many issues pertinent to HTS current lead design, we describe the performance of a pair of 1500 A HTS current leads during the transient warm-up following a loss of intercept cooling. Results describing the subsequent temperature evolution are provided both from experimental measurements and from an associated ANSYS model. The study confirms that HTS current leads must be analyzed on a system basis-incorporating the thermal and electrical characteristics of all components-to provide useful information for the end user. A performance contrast is provided between conduction-cooled and convection-cooled modes. It is found that when heat generation in the HTS conductor exceeds convective cooling by a factor of 10 or more, that part of the current lead is thermally decoupled from the rest of the lead.         Influence of mechanical properties of HTS cable to its critical current    K. Miyoshi, S. Mukoyama, H. Tsubouchi, T. Yoshida, M. Mimura, N. Uno, M. Ikeda, H. Ishii, S. Honjo and Y. Iwata Summary: Mechanical properties of HTS cable cores have been experimentally investigated. As is well known, HTS tapes with Ag-sheathed Bi-2223 have weak mechanical properties. Most attention to the weakness have been concentrated on the tape itself. However for realizing HTS cables, it is necessary to examine mechanical properties of the cable, because the performances of HTS cables are affected by stresses during cable production and their final uses. Three mechanical tests were performed; (1) a thermal cycle test, (2) a bending test and (3) a tensile test. In the thermal cycle test, Ic was not influenced. In the bending test, Ic depended on a bending radius, and a bending radius of less than 500 mm caused a significant problem to the conducting and shielding layers of the cable. It was also found that a flexible former was more suitable for the HTS cable than a copper pipe former, although its pressure drop was higher for liquid nitrogen. The tensile test indicated that tensile strains of up to 0.3% did not decrease Ic, and at 0.5% tensile strain Ic decreased to 10% of the initial Ic. These results are useful for HTS cable design.         R&D studies on mechanical stress of 1 GHz NMR magnet    O. Ozaki, M. Kosuge, T. Kiyoshi, M. Yuyama, H. Wada, T. Kamikado, Y. Murakami, T. Miyazaki, S. Hayashi and Y. Kawate Summary: In order to make a 1 GHz NMR magnet compact, it is operated under high hoop-stress conditions. In our design the hoop-stress of a 1 GHz NMR magnet exceeds 180 MPa. We prepared two types of sample coils. One of them was constructed with niobium-tin superconducting wire, which has a tantalum core. The other one was wound with niobium-titanium superconducting wire. These wires are rectangular in cross-section. The niobium-tin sample coil was energized in a backup magnetic field of 13.5 T and 14 T. It was possible to operate it up to a hoop-stress of 272 MPa. The niobium-titanium sample coil was tested up to 99% of its critical current where the hoop-stress was 226 MPa. These results confirm that our design of the 1 GHz NMR magnet is appropriate.         A cryocooler cooled 10 T split pair superconducting magnet for neutron scattering experiment    K. Jikihara, H. Mitsuboti, H. Ookubo, J. Sakuraba, S. Katano, N. Minakawa, N. Metoki and T. Osakabe Summary: The authors have designed and constructed a cryocooler cooled 10 T split-pair superconducting magnet for a neutron scattering experiment with a vertical room temperature bore of 51 mm. The magnet, which is directly cooled by two 4 K Gifford-McMahon cryocoolers, consists of (Nb,Ti)/sub 3/Sn coils, NbTi coils, Bi(2223) superconducting bulk current leads and a cryostat. The inner coil with an inner diameter of 78 mm, an outer diameter of 191 mm, a height of 106 mm and a gap of 45 mm is made using (Nb,Ti)/sub 3/Sn conductor and a stainless steel bobbin. The outer coil with an inner diameter of 201 mm, an outer diameter of 300 mm, a height of 104 mm and a gap of 50 mm is made using NbTi conductor and a stainless steel bobbin. The Bi(2223) superconducting bulk current leads are thin walled sintered cylindrical tubes. The outer diameter, height and weight of the system are 600 mm, 760 mm and 280 kg, respectively. The magnet can be cooled down in approximately 52 hours. A continuous operation at 10 T, which is generated by an operating current of 151 A, has been performed. It takes about 15 minutes to excite the magnet up to 10 T.         Cryocooled large bore superconducting magnet for a hybrid magnet system employing highly strengthened (Nb,Ti)/sub 3/Sn wires with CuNb stabilizer    K. Watanabe, S. Awaji, M. Motokawa, S. Iwasaki, K. Goto, N. Sadakata, T. Saito, K. Watazawa, K. Jikihara and J. Sakuraba Summary: Employing newly developed high strength and good conductive (Nb,Ti)/sub 3/Sn wires with CuNb composite stabilizer, it is possible to reduce a coil weight of a large bore superconducting magnet by 50-70%. A cryocooled large bore (Nb,Ti)/sub 3/Sn superconducting magnet for a hybrid magnet is made compactly by a react and wind and tension-winding method. This (Nb,Ti)/sub 3/Sn coil formation technique results in no need of a large heat-treatment furnace and a vacuum epoxy-impregnation equipment for a large-scale superconducting magnet. A 10 T-360 mm room temperature bore cryocooled superconducting magnet is being developed for a hybrid magnet system.         Development of a high homogeneity 14 T magnet    G. Masullo, M. Ariante, V. Cavaliere, M. Mariani, A. Matrone, E. Petrillo and R. Quarantiello Summary: A high homogeneity magnet, up to 14 Tesla at 4.2 K with magnet bore of 74 mm was developed. This magnet is the starting point in order to develop a 600 MHz/52 mm magnet system for NMR spectroscopy. The field homogeneity is better than 5 ppm over 1 cm diameter sphere volume without any shim-coils. The magnet can be operated in persistent mode and driven mode. The required magnetic field decay rate is 0.1 ppm/hour. A quench analysis has been studied. Magnetic and structural analysis has been performed. Main data of the magnet system, phases of technological development and test results are reported in this paper.         Design of structure and quench-stability of sector magnets for RIKEN superconducting ring cyclotron    T. Kawaguchi, H. Okuno, A. Goto, T. Mitsumoto, T. Tominaka and Y. Yano Summary: Design, especially about the structure and quench stability, of the superconducting sector magnets for the RIKEN superconducting ring cyclotron is described. Special features of the sector magnets are the triangular shape superconducting coil, cold pole arrangement for supporting of the huge magnetic forces and the cryogenic stable coils. A full-scale superconducting model is now under construction as a prototype sector magnet.         Magnetic field measurements of a 1-m long model quadrupole magnet for the LHC interaction region    N. Ohuchi, K. Tsuchiya, T. Ogitsu, Y. Ajima, M. Qiu, A. Yamamoto and T. Shintomi Summary: The magnetic field measurements of the first l-m long model magnet for the LHC interaction region were performed at 1.9 K. The measured field gradient of the magnet was 227.7 T/m at 7200 A. The multipole fields as a function of axial position and magnet current were measured. The major higher multipole at the magnet center was the sextupole and the ratio to the quadrupole field was 1.4/spl times/10/sup -4/ at 7200 A and at a reference radius of 17 mm.         Tests of a 70 mm aperture quadrupole for the LHC low-beta insertions    M. Lamm, G. Kirby, R. Ostojic, F. Rival, F. Rodriguez-Mateos, A. Siemko, T.M. Taylor, L. Walckier, S.R. Milward and J.R. Treadgold Summary: Three 70 mm aperture 1-meter superconducting quadrupole magnets for the LHC low-/spl beta/ insertions have been designed and built in collaboration between CERN and Oxford Instruments. These magnets feature a four layer coil wound from two 8.2 mm wide graded NbTi cables. In this paper, the authors present the results from the tests at 4.4 K and 1.9 K of the third quadrupole (Q3), with an emphasis on studies concerning quench protection. After a summary of Q3 training in three thermal cycles, quench velocities, peak temperatures in the two superconducting cables and the performance of the layer strip heaters are reported.         Mechanical design and performance of the Fermilab high gradient quadrupole model magnets for the LHC interaction regions    R. Bossert, D. Chichili, S. Feher, T. Heger, J. Kerby, A. Nobrega, I. Novitski, J.P. Ozelis and A.V. Zlobin Summary: The mechanical design of the Fermilab high gradient quadrupole (HGQ) magnet cold mass is presented, along with its expected behavior and performance under fabrication and operational conditions. Coil stresses, end forces and collared coil diameter measurements obtained during fabrication and cryogenic testing are also presented, and are discussed in the context of expected behavior and feedback into the design.         A superconducting quadrupole magnet array for a heavy ion fusion driver    S. Caspi, R. Bangerter, K. Chow, A. Faltens, S. Gourlay, R. Hinkins, R. Gupta, E. Lee, A. McInturff, R. Scanlan, C. Taylor and D. Wolgast Summary: A multi-channel quadrupole array has been proposed to increase beam intensity and reduce space charge effects in a heavy ion fusion driver. A single array unit composed of several quadrupole magnets, each with its own beam line, will be placed within a ferromagnetic accelerating core whose cost is directly affected by the array size. A large number of focusing arrays will be needed along the accelerating path. The use of a superconducting quadrupole magnet array will increase the field and reduce overall cost. The authors report here on the design of a compact 3/spl times/3 superconducting quadrupole magnet array. The overall array diameter and length including the cryostat is 900/spl times/700 mm. Each of the 9 quadrupole magnets has a 79 mm warm bore and an operating gradient of 50 T/m over an effective magnetic length of 320 mm.         Test results of a single aperture dipole model magnet for LHC    T. Shintomi, T. Nakamoto, N. Higashi, N. Kimura, T. Ogitsu, K. Tanaka, A. Terashima, K. Tsuchiya, A. Yamamoto, A. Orikasa, K. Makishima, N. Siegel, D. Leroy and R. Perin Summary: The 56 mm single aperture superconducting dipole model with a 5-block coil configuration was reassembled and tested to investigate the full support of electromagnetic forces using a high-manganese steel collar structure without mechanical contribution from an iron yoke. The reassembled model, which has a gap between the high manganese steel collar and the horizontally split iron yoke, reached a central field of 9 tesla (93% of short sample) at the first quench and attained the short sample limit with a few following quenches. The test results of the training quenches and the mechanical behavior after the modification are described.         Design study of a large-gap superconducting spectrometer dipole    D.C. George, V. Vrankovic, J.A. Zichy and R.K. Maix Summary: The conceptual design of the large gap spectrometer dipole for the LHC-b experiment is presented here. The required acceptance implies a gap height of 3.6 m and a width of 4.3 m. Although the magnetic induction of the 1.92 m long magnet is only 1.1 T, it turns out that a superconducting (SC) coil is the most economic solution. The design considerations for the yoke and the SC-coil are explained, the parameters of the conductor, coil, cooling system are presented and the quench behavior is estimated.         Performance of a superconducting solenoid magnet for BELLE detector in KEKB B-factory    Y. Makida, K. Aoki, Y. Doi, J. Haba, M. Kawai, Y. Kondo, A. Yamamoto and H. Yamaoka Summary: A large superconducting solenoid magnet with an inner warm bore of 3.4 m in diameter and 4.1 m in length has been developed for the BELLE particle detector, which is installed in the KEKB colliding beam ring. The solenoid was installed into the BELLE iron structure. The solenoid was cooled down by using a computer-controlled cooling system and was successfully energized up to a design field of 1.5 T with no training quenches.         Test of a high-field bend magnet for the ALS    C.E. Taylor, S. Caspi, K. Chow, A. Lietzke, A. Jackson, S.T. Wang and J.Y. Chen Summary: It is possible to replace several of the existing 36 conventional 1.5 T, 1 m long bend magnets in the ALS (Advanced Light Source) at LBNL with short, higher field superconducting magnets to produce synchrotron radiation with higher energy. The authors have built and tested four prototype magnets using different conductors, coil shapes, structural support and fabrication methods. All reached the required field for bending 1.9 GeV electrons 10 degrees; however, the first three had excessive training. The final design, Superbend 4, reached short-sample current with no training. Construction details, stress analysis and test results are presented for Superbend 4.         Development of a 7 tesla superconducting wiggler    Y. Mikami, S. Yamada, Y. Matsubara, K. Watazawa and S. Ogawa Summary: A 7 T three poles superconducting wiggler has been constructed to be used as a light source in AURORA-2D, a 700 MeV compact SR ring. The wiggler is cooled by compact Gifford-McMahon cryocoolers without liquid helium. The main components of the wiggler are three pairs of racetrack superconducting coils in an iron yoke, bismuth based oxide superconducting current lead unit and Gifford-McMahon cryocoolers. The coils generate a magnetic field of 7 T in a 40 mm coil gap within 360 seconds. The magnetic field period along the electron beam of the SR ring is 342 mm. The magnetic field integral is less than 4/spl times/10/sup -4/ Tm. The coils and the yoke are cooled by a Gifford-McMahon cryocooler with Joule-Thomson valve. The current lead unit and the thermal shield plate are cooled by separate Gifford-McMahon cryocoolers without Joule-Thomson valves. The current lead unit is designed to be easily removed for maintenance. The performance test in AURORA-2D was successfully completed. The maximum beam current was 19 mA at 700 MeV.         13 kA current lead with textured YBCO plates    J.G. Larsen, B. Kristensen, J.G. Sommerschield and E. Frost Summary: At Haldor Topsoe A/S, the authors have developed a texturing process by which they produce YBCO high temperature superconductor plates with high current densities and low thermal conductivity suitable for current leads between 77 K and 4 K. In their design of such a lead, the superconductor is quench protected by a shunt with low heat leak and the brittleness of the YBCO material has been overcome by reinforcement. The lead has been tested by CERN and has fulfilled CERN's specifications concerning current capacity, total heat leak, contact resistances and quench protection of the superconductor.         Development of kA-class gas-cooled HTS current lead for superconducting fault current limiter    S. Odaka, S.B. Kim, A. Ishiyama, Y. Sato, S. Honjo, Y. Iwata and S. Shingo Summary: A current lead with kA capacity and small AC loss is being developed for use in superconducting current limiting devices cooled with liquid helium. A gas-cooled type current lead using Bi-based oxide superconducting bulk materials was examined to clarify the effects of the current lead geometry and the use of multiple current leads. This paper presents the results of experiments and numerical simulations based on the finite element method taking consideration of nonuniform transport current distribution among multiple current leads connected in parallel. The simulations are performed to investigate the relationship between the geometry of current leads and the amount of heat flow into a cryostat. In the simulations, the AC loss caused by both mutual and self-induced magnetic fields of multiple current leads is taken into account. The influence of AC loss, the joule heat generated by the contact resistance at joints of NbTi/CuNi multi-strand cables and the HTS bars, and the return passage for gas on the operating characteristics of the HTS current leads are evaluated.         HTc current leads in commercial magnet systems applying Bi 2212 MCP BSCCO material    A. Hobl, D. Krischei, M. Schillo, P. Schafer, J. Bock and S. Gauss Summary: The authors have designed, fabricated and integrated HTSC current leads in the range from a few ten to several hundred amperes in advanced magnets being in operation for many years now without failure of the leads. Their design experience is transferred into the prototype work for 13 kA leads for the main magnets of the LHC accelerator at CERN.         Design of Bi-based superconducting current lead for SMES    Q.-L. Wang, D.Y. Jeong, S.S. Oh, H.J. Kim, J.W. Cho and K.C. Seong Summary: 2.1 kA-class hybrid-type current leads for superconducting magnetic energy storage (SMES) magnets, consisting of conventional gas-cooled copper leads and high-T/sub c/ superconducting (HTSC) current leads, were designed. The HTSC parts of the leads are made of Bi-2223/99.8%Ag0.2%Au tape. For the design, numerical analysis was performed to find an optimum shape factor and an optimum varying rate of the cross-sectional area of HTSC lead which result in minimum refrigeration power consumption, and then the minimum evaporation rate of LHe. In the present study, the main results of the design are presented.         Development of current leads using electrolytically deposited BSCCO 2212 tapes    J. Le Bars, T. Dechambre, P. Regnier and K. Gagnant Summary: Prototype current leads of BSCCO 2212 are being developed using the sequential electrolytic deposition of precursors on a silver or a silver alloy tape and heat treatments. The tapes are made using a continuous industrial process. This method of deposition, gives great flexibility in minimizing the mechanical stresses, the thermal conductivity and in ensuring the quench protection. Functional models were tested at 4.2 K in magnetic fields up to 7 T and in self-field at 77 K. The maximum currents reached were 1000 A at 4.2 K and 100 A at 77 K.         Status of the development program of a 60 kA HTSC current lead for the ITER toroidal field coils    R. Heller, G. Friesinger, W. Goldacker, M. Quilitz, M. Tasca, A.M. Fuchs, W. Pfister and M. Vogel Summary: In the frame of the European Fusion Technology Programme, FZK Karlsruhe and CRPP Villigen have started a development program for the design and construction of a 60 kA current lead for the ITER toroidal field coils using high temperature superconductors. The task is composed of four parts: material selection based on test results of 1 kA current leads; construction and test of a 10 kA and a 20 kA lead using the selected HTSC material; giving proof of the modularity and scaleability of the design; and finally construction and test of a 60 kA current lead which will replace an existing conventional lead in the TOSKA facility at FZK. As result of part one, Bi-2223 tapes electrically stabilized by AgAu material were selected for the further development program. Two 10 kA HTSC modules using different conductor designs have been manufactured in industry and are being fabricated in the institute. The paper describes the status of the development program. Experimental results of the first step and first results of the 10 kA HTSC lead are given.         Optimization of the niobium-tin inserts for the 80 kA current lead to be used in the TOSKA facility for the ITER toroidal field model coil test    R. Heller and Th. Schneider Summary: One essential tool in the construction of the forced-flow cooled 80 kA current lead to be used in the TOSKA facility at FZK for the ITER TFMC tests is the use of niobium-tin inserts in the lower temperature region of the heat exchanger allowing the operation of the lead with minimum He mass flow rate in a wide current range. Due to the fact that there is only limited space for the superconductor inserts in the 80 kA current lead, it was necessary to look for niobium-tin strands having a very high critical current at low magnetic fields and high temperatures. It was decided to use internally stabilized bronze routed strands because of the absence of an outer barrier which may hinder the current transfer from the copper of the current lead to the superconductor filaments. During the test measurements, it was found that the current transfer from the external copper to the superconductor was a second important criterion for the strand choice. A series of measurements were done using superconductor strands embedded in profiles made of different copper materials. The result of the test measurements are presented which were the base for the decision which strand material is appropriate for the inserts.         Steady state and transient current lead analysis [superconducting cables]    G. Citver, E. Barzi, A. Burov, S. Feher, P.J. Limon and T. Peterson Summary: A mathematical model of the gas-cooled, resistive portion of a binary current lead has been developed. An analytical solution of the time-dependent differential equations for the resistive portion of the forced flow cooled current lead is presented which allows one to calculate the evolution of the temperature profile and voltage drop. A comparison of analytical with numerical calculations and a comparison of the calculations with experimental data are given.         Test results of high temperature superconductor current lead at 14.5 kA operation    T. Isono, K. Hamada, T. Ando, H. Tsuji, Y. Yasukawa, A. Tomioka, M. Nozawa, M. Konno and K. Sakaki Summary: High temperature superconductor (HTS) current leads have been developed for the International Thermonuclear Experimental Reactor (ITER) magnet system, which are required not only to reduce the lead heat leak but also to maintain safety in a fault condition. A pair of 10-kA class HTS current leads was fabricated and tested. The lead consists of a copper part and an HTS part. The HTS part is composed of 192 Bi-2223 silver-alloy sheathed tapes in a cylindrical array on a stainless steel tube. Thermal performance and stability were tested. The current leads could carry up to 14.5 kA by placing magnetic materials between the HTS elements, which were installed to reduce the perpendicular magnetic field in the HTS elements.         High temperature superconducting current leads for the large hadron collider    A. Ballarino Summary: The large hadron collider (LHC) will be equipped with about 8000 superconducting magnets. Some 3380 leads will feed the currents ranging from 60 to 13000 A. To reduce the heat inleak into the liquid helium, CERN aims to use high temperature superconducting material for leads having current ratings between 600 and 13000 A. Specifications have been written for 13000 A current leads, incorporating a high temperature superconducting section, for the main magnets of the LHC, and contracts have been placed with several firms for the supply of prototypes for comparative testing. The leads used for feeding locally the 60 and 120 A dipole orbit correctors will be conventional conduction cooled resistive leads. An optimized lead of variable cross section has been tested, and an integral design has been initiated. This report describes the design status of the current leads for the LHC, emphasizing, for the different solutions, the principle of optimization and the choice of cooling methods.         High temperature superconducting current lead test facility with heat pipe intercepts    P.E. Blumenfeld, C. Prenger, E.W. Roth and J.A. Stewart Summary: A high temperature superconducting (HTS) current lead test facility using heat pipe thermal intercepts is under development at the Superconductivity Technology Center at Los Alamos National Laboratory. The facility can be configured for tests at currents up to 1000 A. Mechanical cryocoolers provide refrigeration to the leads. Electrical isolation is maintained by intercepting thermal energy from the leads through cryogenic heat pipes. HTS lead warm end temperature is variable from 65 K to over 90 K by controlling heat pipe evaporator temperature. Cold end temperature is variable up to 30 K. Performance predictions in terms of heat pipe evaporator temperature as a function of lead current are presented for the initial facility configuration, which supports testing up to 200 A. Measurements are to include temperature and voltage gradient in the conventional and HTS lead sections, temperature distribution and heat transfer rate in the heat pipes, as well as optimum and off-optimum performance of the conventional lead sections.         Optimized HTS current leads    A.V. Gavrilin, V.E. Keilin, I.A. Kovalev, S.L. Kruglov, V.I. Shcherbakov, I.I. Akimov, D.K. Rakov and A.K. Shikov Summary: The problem of optimizing HTS current leads by varying their cross-section along the length is investigated both experimentally and numerically at 500 A current level. Bi-2223-based HTS multi-filament composite tapes were used with two types of matrices: pure Ag and (Ag+1 at.% Au) alloy. The warm ends of the HTS parts of the current leads were cooled with liquid nitrogen. Very low evaporation rates in the case of Au-doped matrix and rather long time constants to reach thermal equilibrium were observed.         Technologies for high field HTS magnets    J.F. Picard, M. Zouiti, C. Levillain, M. Wilson, D. Ryan, K. Marken, P.F. Hermann, E. Beghin, T. Verhaege, Y. Parasie, J. Bock, M. Baecker, J.A.A.J. Perenboom and J. Paasi Summary: Six partners from five European countries are cooperating within a R&D BRITE EURAM project named SHIFT (superconducting high-T/sub c/ coils for high field technologies). The objective of this 3-year project is to develop basic technologies for manufacturing magnets producing high fields operating in the temperature range 20-30 K: HTS wires, coils based on bulk parts, coil structures and cooling system. The potential applications are pulsed magnets for power quality SMES and DC magnets for MRI, instrumentation and laboratory use. Specifications and designs of SMES for the voltage sags smoothing application have been performed and will be presented together with SMES designs for flicker mitigation. Main deliverables are the realization of a 6 Tesla demonstration coil cooled by closed cycle refrigeration and the design of a SMES coil for power quality applications. Target performances, conductors, test coil developments and designs are discussed in this paper.         SMES for power utility applications: a review of technical and cost considerations    V. Karasik, K. Dixon, C. Weber, B. Batchelder, G. Campbell and P. Ribeiro Summary: Advances in both superconducting technologies and the necessary power electronics interface have made SMES a viable technology for high power utility and defense applications. The power industry's demands for more flexible, reliable and fast active power compensation devices make the ideal opportunity for SMES applications. However, in order to make this technology attractive to the deregulated utility market, it is necessary for industry to provide cost-effective systems. The information presented herein is taken from results to date of a DARPA technology Reinvestment Program SMES Commercialization Demonstration. This program is currently in the design and risk reduction phase. Completion is expected in 2001. This system will provide +/- 100 MW peak and +/- 50 MW oscillatory power with 100 MJ of stored energy. The base line for the coil design assumes a cable-in-conduit conductor (CICC), with rated voltage of 24 kV, and operating at nominal temperature of 4.5 K. This paper reviews the possible utility industry applications and discusses a number of technical issues and trade-offs resulting from the design optimization process for SMES utility applications. The conductor design options, system configuration, current/voltage levels and insulation issues for a low temperature superconducting coil are discussed. The power electronics interfaces (system configuration, circuit topology and devices and switching technologies) are also discussed. Finally, consideration is given to the impact of the new business environment, potential markets and overall cost.         Recent technical trends of superconducting magnets in Japan, Part I: Magnet data base and recent progress in magnet winding current density    O. Tsukamoto, S. Torii, T. Takao, N. Amemiya, S. Fukui, T. Hoshino, A. Ishiyama, A. Ninomiya, H. Yamaghuchi and T. Satow Summary: The Committee on Applied Superconducting Apparatuses and Characteristics of Superconductors, the Institute of Electrical Engineers of Japan (IEEJ) has made a database on low temperature superconducting magnets which have been built over the last ten years in Japan. Based on the data, trends of magnet technology are investigated. In this paper, an outline of the database is explained and, based on it, recent trends of magnet technology are investigated, focusing on sizes and configurations of magnets, current density of magnet windings and conductor configurations.         High-field warm-bore HTS conduction cooled magnet    G. Snitchler, S.S. Kalsi, M. Manlief, R.E. Schwall, A. Sidi-Yekhief, S. Ige, R. Medeiros, T.L. Francavilla and D.U. Gubser Summary: A 7.25 T laboratory magnet utilizing Bi 2223 conductor has been designed, built, and installed at the Naval Research Laboratory. Operating at 21 K at full field, the coil provides field homogeneity of /spl plusmn/1% in a 2-inch warm-bore. The system is conduction cooled with a pair of Leybold single stage cryocoolers that allow cooldown in less than 36 hours and allow extended fast ramp operation. Operation at a total refrigerator input power of 6 kW is facilitated by the use of ASC Cryosaver/sup TM/ HTS current leads. The fully integrated system consists of the magnet, cryogenic system, control and protection system and power supply. This paper presents information on the magnet design, construction and subsequent testing.         Development of 1 GHz superconducting NMR magnet at TML/NRIM    T. Kiyoshi, A. Sato, H. Wada, S. Hayashi, M. Shimada and Y. Kawate Summary: Development of a 1 GHz superconducting NMR magnet is in progress at the Tsukuba Magnet Laboratory of the National Research Institute for Metals. The magnet will consist of two parts. The outer magnet of LTS coils is designed to generate a field of 21.1 T (900 MHz) in persistent current mode. The inner coil is designed to generate an additional 2.4 T, resulting in a central field of 23.5 T (1 GHz) in a 54 mm diameter bore at room temperature. As a high-resolution NMR magnet, field stability as well as field homogeneity is very important, which is especially difficult to achieve in the inner coil when exposed to extremely high magnetic fields that superconducting magnets have not yet encountered. The engineering design is complete and fabrication of the superconductors has begun. This report presents the results of the engineering design and R&D studies on the candidate superconductors for the inner coil, such as BSCCO, and improved Nb/sub 3/Al and Nb/sub 3/Sn.         Development of 3 T class Bi-2212 insert coils for high field NMR    H.W. Weijers, Q.Y. Hu, Y.S. Hascicek, A. Godeke, Y. Vouchkov, E. Celik, J. Schwartz, K. Marken, W. Dai and J. Parrell Summary: Based on a successful 1 T Class PIT insert coil, the authors are now pursuing a 3 T Class insert coil. This paper describes the design and the latest conductor and coil test results, as well as supporting experiments. The final product is envisioned to contain 3 concentric sections, requiring over one kilometer of conductor. This will be tested in a 20 T large bore resistive magnet at the NHMFL. Experimental work focuses on the use of conductor with a silver-alloy matrix in the outer sections, that are subject to the largest stresses when operated in a background field. Results from heat treatment optimization for wound coils, mechanical test of conductors and coil design studies are reported.         Void fraction effect on AC loss in saturation regime for NbTi CIC conductor    B. Baudouy, C. Berenguer, M. Takeda, J. Miller and S.W. Van Sciver Summary: A superfluid helium calorimetric technique (the underlying principle of the NHMFL TACL Facility) was used to perform AC loss measurements on NbTi cable-in-conduit conductor samples. AC loss tests have been performed over a range of field variation rates, high enough that the saturation regime is obtained and low enough that hysteresis losses are significant. From these measurements, the effective coupling current time constant of the CICC is determined, and the losses in the saturation regime are used to determine the effective radius of the saturated cable stage. The comparison of time constants and saturation radius as a function of the void fraction of the CICC yield to a better understanding of saturation regime in multi-stages conductors.         Mechanical behavior of strands in CIC conductor analyzed by Monte Carlo method    T. Sasaki and S. Nishijima Summary: The computer simulation of mechanical behavior of strands in a cable-in-conduit (CIC) conductor analyzed by Monte Carlo method has been carried out for analyzing the stability of the CIC conductor. In the CIC conductor, the mechanical behavior of strands during energizing has not been evaluated sufficiently and hence the quantitative evaluation of the frictional heating, the contact stress between strands and the coupling losses that determine the stability of a CIC conductor hare not been clarified. A CIC conductor with 38% of void fraction were constructed in a computer by compressing the cable. In the Monte Carlo method, the position of strands which mere divided into mesh were changed to minimize the potential energy. It could simulate the strand motion induced by the Lorentz force and the change of the contact stress distribution between strands. The method developed in this work is also used to calculate the load-displacement curve of the cables and the position of strands. By using the method, it would be possible to estimate the stability of a CIC conductor.         Current measurements of the individual strands in CICC magnet    Seohko Kim, Kwanwoo Nam and Sangkwon Jeong Summary: Non-uniform current distribution in CICC (cable-in-conduit conductor) is one of the major concerns for developing a successful magnet system. The three-strand CICC magnet has been constructed in KAIST (Korea Advanced Institute of Science and Technology) for the study of current nonuniformity. The magnet is equipped with a forced flow supercritical helium system at variable temperature to simulate the various thermohydraulic conditions of superconducting Tokamak. Each strand of the magnet has its own shunt resistor to measure the current it carries during the DC and AC operations. This paper describes an experimental apparatus and some current measurement results of the individual CICC strands. The unbalanced current distribution has been obtained directly from the shunt resistor voltage data. The surface contact resistance of the superconducting strands was small enough to allow current redistribution inside the conduit rather than at the terminal joints of the magnet.         Non-uniform current distribution in superconducting cables exposed to external magnetic field and its influence on stability    H. Yonekawa, N. Amemiya, T. Ogitsu, T. Shintomi, K. Tsuchiya and K.-I. Sasaki Summary: Current distribution in a Rutherford cable made with noninsulated strands was measured with small Hall sensors in an external magnetic field. Eight pairs of Hall sensors were placed around the eight-strand cable. One sensor of each pair was used to cancel the external magnetic field. Nonuniform current distributions induced by the external magnetic field ramp and transporting current were observed with this technique. The current distribution was artificially controlled using heater switches installed at the end of strands to study the influence of a nonuniform current distribution on stability. A local heat pulse was applied to a strand in the cable to determine the minimum quench energy against local disturbance. The initial current distribution varied was varied by the heater switches, and the current redistribution during quench or recovery process and the MQE was studied.         Experimental investigation on current imbalance of stranded conductors    A. Ninomiya, S. Sekine, T. Ishigohka and S. Yamaguchi Summary: Multiple-stranded superconducting cable conductors have an essential problem-the so called current imbalance phenomenon. Generally, it is said that the current imbalance problem is caused by the inductance imbalance among strands. However, it does not explain why the inductance imbalance is generated in a symmetrically assembled strand and what is the main factor of current imbalance. In such a situation, the authors have experimentally investigated about the current imbalance problem using several experimental coils. Experimental results show that the current imbalance is strongly dependent on the magnetic coupling coefficient among the strands. In addition, it is also shown that the inductance distribution between the strands strongly depends on the cabling formation.         Current distributions at steady-state of superconducting cable conductors for AC use    S. Kawabata, D. Terashi and M. Tsuji Summary: In order to obtain information towards achieving uniformity of current distribution in superconducting cable conductors for AC use, the authors have developed a compact measuring system that enables them to quantitatively evaluate the current distribution. In this system, current distribution is found from the observed results of the self-field measured by a group of coils, each of which is composed of six small pick-up coils, located around the sample conductor. It is confirmed that the accuracy and the sensitivity of this system are good enough to measure the current distributions for the superconducting cable conductors for AC use by adopting it to a dummy conductor composed of insulated copper wires. Using this system, they experimentally investigated how the localized transport current, in the steady-not quenched state, is made uniform in the superconducting cable conductor composed of strands without insulation for AC use. By this experiment, they observed how the localized current transfers among the noninsulated strands. At the same time, the frequency dependence of the change of the current distribution can also be observed as well. These measured results are discussed using approximate analysis relating to the inter-strand coupling effect.         Numerical analyses for ramp rate limitation from the standpoint of heat generation during current redistribution [in superconducting cables]    K. Seo, M. Morita, K. Shimohata and H. Yoshimura Summary: The ramp rate limitation (RRL) must be improved for large applications, for instance fusion machines. In superconducting multi-strand cables, adding to the coupling loss, the heat generation during current redistribution (moderation of a nonuniform current) causes temperature rises. Especially for cables in conduit-type conductors (CICC), the relation between the heat capacity of the coolant and the total heat dissipation determines the temperature rise. When this rises above the current sharing temperature, the conductor must quench. To establish stability against nonuniform current distribution, a small contact resistance between strands is preferable. However a smaller contact resistance results in a larger inter-strand coupling loss. Therefore, the contact resistance must be optimally designed to prevent the cable from RRL. In this study, the authors analyzed the current redistribution in a three-strand cable with electrical contact between strands. The heat generation due to: (1) normal resistance; (2) contact resistance between strands; and (3) terminal joint resistance were evaluated in the cases of a variety of contact resistances and cooling conditions. Finally, some of the particular phenomena reported as being found in experiments with multi-strand cables were simulated by analyses and then discussed.         Philosophy of a quench; two case studies-LTS wiggler magnet and HTS /spl mu/-SMES    R. Mikkonen, J. Lehtonen and J. Paasi Summary: The utilisation of HTS composites raises the obvious question of how the stability of these materials differs from that of classical ones. The improved stability of HTS is due to the increased specific heat and a wider temperature margin between the operating and critical temperature. The quench analysis of HTS magnet system is however quite different from their LTS counterparts because of the slanted E(J) characteristic due to the thermally activated flux creep and macroscopic material inhomogeneities. The comparison of different quench parameters of a 6 T LTS wiggler and a 5 kJ HTS SMES have been evaluated. The former system is installed in a 1.5 GeV electron storage ring in the University of Lund, Sweden, and the latter has been demonstrated to compensate a short term loss of power. The stability considerations are projected to the essential quenching factors, for example normal zone propagation (NZP), hot spot temperature, current decay and internal voltage.         Recent technical trends of superconducting magnets in Japan. Part II: Stability and quench characteristics    T. Takao, S. Torii, N. Amemiya, S. Fukui, T. Hoshino, A. Ishiyama, A. Ninomiya, H. Yamaguchi, T. Satow and O. Tsukamoto Summary: The committee on applied superconducting apparatuses and characteristics of superconductors, the Institute of Electrical Engineers of Japan (IEEJ) has made a database on superconducting magnets which were built over last ten years in Japan. The outline of the database is explained part I. In part II, stability and hot-spot temperature of a magnet are investigated. Minimum quench energies, minimum propagating zones, and Stekly's stability factors are calculated using the database. Dependence of those stability parameters on the magnet scale is studied and the design trends of the stability are discussed. Hot-spot temperatures of the pool-cooled magnets at quench and energy dump process are also calculated based on the database, and the trends of design rules for the quench protection are studied.         Computer simulation for stability analysis using a one-dimensional model    M. Emoto and S. Yamaguchi Summary: A simulation program of normal-state propagation was built using a one-dimensional model. The results of the simulations were compared with those of the short-sample tests of the helical coil conductor for the LHD at the National Institute for Fusion Science. This paper deals with the magnetic field profile effect of the recovery currents and the initial temperature profiles of the minimum propagation current. The first purpose of the study is to determine the appropriate length of the short-sample experiment when estimating the properties of conductors in a uniform magnetic field. The second purpose is to examine the behavior of a superconductor when it is heated at several points at the same time instead of at only one point. The results of the simulation shows: (1) when the length of the typical short-sample experiment, which has a helical coil conductor 0.25 m long, is increased by at least four times, the same recovery currents are obtained in a uniform field; and (2) when the total input energy is less than 0.1 J, the minimum propagation current increases as the number of peaks in the initial temperature profile increases. The minimum propagation currents does not depend on the number of peaks when the total input energy is greater than 0.1 J.         Effects of bundle/hole coupling parameters in the two-fluid thermal-hydraulic analysis of quench propagation in two-channel cable-in-conduit conductors    R. Zanino, L. Savoidi, F. Tessarin and L. Bottura Summary: Thermal-hydraulic modeling of cable-in conduit conductors (CICC) with a two-channel bundle/hole (B/H) topology contains several uncertainties in the BM coupling model. Here we study numerically with the 2-fluid MITHRANDIR code some effects of the major coupling parameters, i.e., degree of perforation of the B/H interface and heat transfer coefficient through it, on quench propagation in a two-channel CICC. A semi-quantitative discussion of the results is presented.         Stability analysis of the ITER TF and CS conductors using the code Gandalf    C. Marinucci, L. Savoldi and R. Zannino Summary: The stability of the toroidal field and central coil cable-in-conduit conductors for the International Thermonuclear Experimental Reactor (ITER) has been analyzed with the code Gandalf. The energy margins, computed for a number of disturbance scenarios, are in the order of some 100 mJ/ccst, well above the expected disturbances. A detailed convergence study is shown to be essential not only in principle but also in practice, e.g. dual stability was found in some cases, but disappeared when the integration time step was refined.         The hydraulic solver Flower and its validation against the QUELL experiment in SULTAN    C. Marinucci and L. Botturak Summary: Knowledge of the hydraulic boundary conditions is a prerequisite for accurate estimates of the quench characteristics of superconducting magnets. A set of routines (Flower) has been designed and interfaced to the code Gandalf to provide a simplified model of the hydraulic connections to a cryogenic plant of a coil using cable-in-conduit conductors with central cooling channel. The validation against experimental data provided by the Quench Experiment on Long Length (QUELL) in the CRPP facility SULTAN have shown that Flower is able to simulate the hydraulic boundary conditions within engineering limits of accuracy.         Numerical analysis of stability margin and quench behavior of cable-in-conduit NbTi conductors for KSTAR    Q.L. Wang, S.S. Oh, K.S. Ryu, C.S. Yoon and K.M. Kim Summary: A numerical model has been proposed to analyze the stability margin and quench characteristics of the cable-in-conduit NbTi conductors for the KSTAR-PF (Korea Superconducting Tokamak Advanced Research) magnets. The dependence of the thermal, hydraulic and electrical properties on the external thermal disturbance was investigated. The algorithm of the program is based on the finite volume method which adopts space discretization and time integration by multi-step Runge-Kutta method to obtain stable numerical solutions. It was confirmed that the disturbance duration can influence the conductor stability and limiting current.         Transient stability of large aluminum stabilized superconductors    S. Noguchi, A. Ishiyama, T. Satow and N. Yanagi Summary: Very large current composite superconductors have been considered and adopted to use in SMES coils and fusion applications, such as the Large Helical Device (LHD). These superconductors have large cross-sectional area of high purity aluminum stabilizer to improve their stability and to enhance the overall current density. Once a normal-zone is initiated in such a composite superconductor, the current transfers to the aluminum stabilizer according to the temperature distribution. The time constant of current diffusion in the stabilizes however is very long due to the low electrical resistivity of aluminum and the large conductor size. Therefore, an excess Joule heat is generated in a small area near superconducting filaments and the temperature increases locally. In this paper, to evaluate this peculiar property, we carry out some simulations with regard to quench process in the superconductor applied to the helical coil of LHD in the National Institute for Fusion Science. The simulations, by using a newly developed computer code, are compared with the experimental results of the stability tests on the short samples of LHD conductor. Furthermore, we focus on the influence of the CuNi alloy clad adopted to the LHD conductor on the normal transition and normal-zone propagation properties.         Fabrication of ITER central solenoid model coil-outer module    T. Ando, T. Hiyama, Y. Takahashi, H. Nakajima, T. Kato, M. Sugimoto, T. Isono, K. Kawano, N. Koizumi, K. Hamada, Y. Nunoya, K. Matsui, K. Ishio, K. Sawada, K. Azuma, K. Yamaoto, H. Kubo, T. Shiuba, G. Nishijima, Y. Tsuchiya, T. Terakado, Y. Miura, H. Tsuji, H. Takano, O. Osaki, T. Fujioka, S. Ikeda, J. Inagaki, Y. Mizumaki, H. Ogata, T. Hirumachi and T. Sasaki Summary: The central solenoid (CS) model coil-outer module being fabricated to demonstrate the justification of the CS design for the ITER, was almost completed except for epoxy impregnation to concrete whole layers. All the wound and heat treated layers have been assembled symmetrically with the insulation on the same axis, and for layer-to-layer joints the newly developed butt joint, has been installed.         Electrical insulation systems for the ITER Central Solenoid Model Coil    P.E. Fabian and N.A. Munshi Summary: Insulation systems developed by Composite Technology Development, Inc., have been fabricated specifically for use in the US section of the International Thermonuclear Experimental Reactor (ITER) Central Solenoid (CS) Model Coil. The insulation system used in these fusion devices must be capable of withstanding significant mechanical loads at cryogenic temperatures and enduring high doses of radiation, all without compromising their electrical insulation properties. Two materials that have seen extensive use in the CS Model Coil are the CTD-112P tetrafunctional epoxy pre-preg system and the CTD-618 epoxy system. Fabrication methods for these materials were developed and implemented specifically for use on the model cell. The CTD-112P system has been successfully used as the primary turn insulation, and as such, has been tested extensively for its mechanical and electrical properties, before and after irradiation. The CTD-618, a room-temperature cure system, has been specified as the insulation system for repair of damaged turn insulation and also as the insulation for the noncritical areas of the tension links and terminations. The development of these materials and the method of application for each of these materials as they apply to the model coil are examined. Pertinent mechanical and electrical properties are also analyzed.         R&D activity of SAGBO avoidance for the CS insert fabrication    M. Sugimoto, T. Isono, N. Koizuumi, H. Nakajima, T. Kato, K. Hamada, Y. Nunoya, K. Matsui, K. Sawada, Y. Takahashi, T. Audo, H. Tsuji, T. Ichthara, T. Minato, B. Ikeda, T. Murai and H. Yoshimura Summary: The fabrication of the center solenoid (CS) insert is under way in the engineering design activity (EDA) of International Thermonuclear Experimental Reactor (ITER), the purpose of the CS insert is to measure the performance of Nb/sub 3/Sn conductor for ITER, the R&D activities of the strain accelerated grain boundary oxidation (SAGBO) avoidance was carried out for the CS insert fabrication. The shot peening and the flow control were established for the heat treatment of Nb/sub 3/Sn processing. The effect of the chromium plating on the Nb/sub 3/Sn strands was clarified by the several specimens.         First cool-down performance of the LHD    T. Mito, R. Maekawa, S. Yamada, A. Nishimura, K. Takahata, A. Iwamoto, S. Imagawa, K. Watanabe, N. Yanagi, H. Tamura, T. Baba, S. Moriuchi, K. Ohu, H. Sekiguchi, I. Ohtake, T. Satow, S. Satoh and O. Motojima Summary: The first cool-down test of the Large Helical Device (LHD) and the performance of the LHD cryogenic system during the first cycle operation are described. The first cool-down started on Feb. 23, 1998 and finished on Mar. 22. After the cool-down, the excitation tests of the SC coils up to 1.5 T and the first cycle operations for plasma physics experiments were conducted until May 18. The first cycle operation was successfully completed after the warm-up process to room temperature from May 19 to Jun. 15. The cooling characteristics of the LHD, such as temperature distribution during cool-down, heat loads under steady state condition, reliability during long-term operation, are reported.         ITER niobium-tin strands reacted under model coil heat-treatment conditions    M. Takayasu, R.A. Childs, R.N. Randall, R.J. Jayakumar and J.V. Minervini Summary: Heat-treatment conditions were studied for ITER Central Solenoid model coils wound with Nb/sub 3/Sn cables jacketed in Incoloy-908 conduits. The heat treatments recommended by the strand manufacturers had to be modified to meet various requirements for the large coils and to prevent Stress Accelerated Grain Boundary Oxidation (SAGBO) of Incoloy 908. Single-strand tests of ITER wires produced by Vacuumschmelze, IGC, Furukawa and Mitsubishi were carried out prior to the model coil heat treatments to verify the heat-treatment conditions. The modified heat treatments improved the performance of all four wires. Especially, critical currents of Furukawa wire were improved significantly. Test results of the witness samples co-reacted with ITER CS coils indicate that the heat treatments of all 10 layers of the inner module were successfully completed.         Fabrication of the first European full-size joint sample for ITER    D. Ciazynski, P. Decool, M. Rubino, J.M. Verger, N. Valle and R. Maix Summary: The European Home Team is responsible for the design, the fabrication and the test of the Toroidal Field Model Coil (TFMC) of the ITER project. Within this task, three full-size samples have to be fabricated in industry and tested. Each sample is made of two parallel straight bars of full-size conductor, connected at the bottom through a joint designed according to the EU proposal for the ITER coils, and having at the top, two connections for the test facility. The first sample uses an ITER type Nb/sub 3/Sn cable-in-conduit embedded in a thick steel square jacket, the lower joint being similar to the inner joints of the TFMC. The second sample uses the TFMC conductor which is an ITER type Nb/sub 3/Sn cable-in-conduit embedded in a thin steel circular jacket, the lower joint being similar to the outer joints of the TFMC. Last, the third sample will use the same cable embedded in a thin incoloy jacket, fully relevant to the ITER TF coils. This paper reports on the fabrication by Ansaldo of the first sample, emphasizing the differences between the original design and the final design produced after preliminary trials, as well as pointing out the main technical issues.         Performance test of the KSTAR Central Solenoid (CS) model coil    Sang-Ho Kim, Yong-Hwan Kim, Young-Hwan Kim, Han-Sung Kim and Kie-hyang Chung Summary: The KSTAR (Korea Superconducting Tokamak Advanced Research) CS (Central Solenoid) model coil has been developed and the performance test for the selection of materials and demonstration of manufacturing procedures at each steps have been carried out. Before the stability performance test in the vacuum cryostat, the preliminary cryogenic test, with full data acquisition, quenching detection and power supply system in the pool-type cryostat, have been done. In this cryogenic preliminary test, the major parameters related to structural integrity, quenching properties, cool-down and warm-up condition, and loss problems, etc. were measured under the various operational scenarios, and compared with the analysis. The main results of the test during the manufacturing and the preliminary cryogenic test are described in this paper.         Resistive fault current limiters with YBCO films 100 kVA functional model    B. Gromoll, G. Ries, W. Schmidt, H.-P. Kraemer, B. Seebacher, B. Utz, R. Nies, H.-W. Neumueller, E. Baltzer, S. Fischer and B. Heismann Summary: Within the Siemens current limiter program a 100 kVA functional model has been realized and tested successfully. According to the modular concept of the limiter the functional model is assembled of ten switching elements. YBCO-films with a thickness of 250 nm and a critical current density above 2/spl times/10/sup 6/ A/cm/sup 2/ are deposited by thermal coevaporation (TU Munich) on 4" sapphire wafers. To support homogeneous switching the superconducting film is covered with a 100 nm Au-shunt layer. Good current limiting performance is achieved: the steady limiting current is below the nominal current, the peak fault current increases up to 3 times the nominal current within an action time of one millisecond. The operational recovery time of the limiter, within which the switching elements return to the superconductive state again is about 2 s. Following our limiter program the next step will be a model device with a nominal switching power of 1 MVA.         Fault current limiting properties of YBCO-films on sapphire substrates    A. Heinrich, R. Semerad, H. Kinder, H. Mosebach and M. Lindmayer Summary: We have studied the switching of YBCO thin film resistive fault current limiting devices. Films of 300 nm thickness were deposited on 2 inch and 4 inch sapphire substrates by thermal co-evaporation. Bridges 10 mm wide and 22 mm long (2 inch) or 42 mm long (4 inch) were structured by standard photolithography. Contacts were made by in-situ gold overlayers and soft solder. The gold film was removed from the switching area so that the YBCO film was not shunted. The films were tested by 30 /spl mu/s DC pulses and 50 Hz AC pulses for 50 ms. We find evidence that at the AC tests heat propagates over several cm under these conditions in sapphire so that hot spots can be avoided even without shunt layer with the prospect of higher switching power. The highest destruction free switching power-the RMS critical current times RMS voltage after switching-was 57 kVA. The highest switching power density achieved was 2.5 kVA/cm/sup 2/. To our knowledge, these are the highest switching power densities observed so far.         Current limitation at 1080 A under 1100 V with bulk Bi-2223    J. Noudem, J.M. Barbut, O. Belmont, J. Sanchez, P. Tixador and R. Tournier Summary: The superconducting current limiter could bring a solution to a problem not satisfactory solved: the limitation of fault currents under high voltages. We carry out a research and development program based on bulk bismuth materials. They are attractive due to their homogeneous quench into the resistive state and after the normal state even if their critical current densities are not very high (several MAm/sup -2/ at 77 K, self field). They limit efficiently currents without any risk of burning (no hot spots) even under high electrical fields. These materials are elaborated in the form of Bi-2223 bars formed by an isostatic pressure and classical sintering. Sixty bars (/spl phi/=4 mm, /spl Lscr/=120 mm, I/sub c/=35 A) were assembled. This assembling was tested up to 1100 V at 1080 A instead of a theoretical value of 5000 A. The superconductor was exposed to a maximum power density of 12 GW/m/sup 3/ without damage. We present the measurements obtained on the bars and their assembly.         A fault current limiter in toroidal form to maximise effective Jc    T. Okazaki and P.D. Evans Summary: The performance and characteristics of a new form of inductively coupled fault current limiter (FCL) are described. It has a toroidal geometry and the prototype windings comprise 20 series connected primary coils interleaved with 20 independent superconducting secondary coils. By reducing leakage fields around the windings, the interleaving reduces the leakage impedance of the unit by an order of magnitude and significantly increases the effective critical current density of the superconductor. These effects are examined theoretically and experimentally and the benefits of reduced leakage fields on the performance of the FCL are assessed. It is shown that the benefits of symmetrically positioned superconducting coils which ensure that current is shared equally enable thick film materials to be used effectively for high currents, and that switching from superconducting to nonsuperconducting conditions is not a slow thermal effect, but the result of increasing magnetic field on the critical current density. To investigate the effect of current distribution across the width of the superconducting coils, the single turn versions were replaced by 3-turn, double-sided, interconnected spirals of equivalent conductor dimensions, which demonstrate superior performance, in terms of higher resistivity under nonsuperconducting conditions. The toroidal FCL is shown to be a useful vehicle with which to demonstrate the effect of magnitude and direction of the magnetic field on FCL performance. It has benefits in terms of leakage impedance and effective use of superconductor material and resistivity.         Development of a 7.5 MVA superconducting fault current limiter    K. Tekletsadik, M.P. Saravolac and A. Rowley Summary: Using a new design concept, a 7.5 MVA superconducting fault current limiter (SCFCL) is being developed. The basic principles of operation and its practical application has been successfully demonstrated using a 12 kVA experimental SCFCL. The current limiting effect has been achieved by the almost instantaneous increase in the device impedance due to the superconducting to resistive state transition of the HTSC material, triggered by combined effect of magnetic field and fault current in excess of the critical levels. The design concept is hybrid (inductive/resistive) with the SC elements placed inside a low inductance winding, which is used to generate an external magnetic field for uniform quenching and first response. A composite reaction textured Bi-2212 has been modified to optimise its electrical, mechanical and thermal properties, specifically for use in a SCFCL. Experience gained during manufacturing and testing of the SCFCL and its technical and economical implications of a typical SCFCL at a distribution system level are summarized in this paper. The way forward, future considerations and applicability of the results for the development of future superconducting power systems components are summarized in the concluding part of the paper.         HTS thick film components for fault current limiter applications    C. Meggs, G. Dolman, T.C. Shields, J.S. Abell, T.W. Button and F.J. Mumford Summary: Fault current limiters are potentially one of the first applications of HTS materials in the power engineering field, and both inductive and resistive devices are being actively developed by many groups world-wide. A wide range of HTS materials is being considered for these devices including biaxially textured planar YBCO films, BSCCO silver clad wires, and textured bulk BSCCO and YBCO. Each type of device has its own particular requirements and restrictions with respect to acceptable component geometries, but the important physical property requirements of the materials appear to be similar in both cases. ALSTOM Research and Technology Centre is building a model current limiter based on an inductive design requiring superconducting components in the form of thick film materials on ceramic substrates. In this paper the design requirements for the current limiter are considered and the development and characterisation of the YBCO thick film materials for the device are reported. In particular, the property and performance issues concerning the scale-up of component sizes required for the demonstrator device are discussed. Preliminary results of the behaviour of the thick film components in an inductive FCL environment are also reported.         Performance of a 1-MVA HTS demonstration transformer    S.W. Schwenerly, B.W. McConnell, J.A. Demko, A. Fadnek, J. Hsu, F.A. List, M.S. Walker, D.W. Hazelton, F.S. Murray, J.A. Rice, C.M. Trautwein, X. Shi, R.A. Farrell, J. Bascuhan, R.E. Hintz, S.P. Mehta, N. Aversa, J.A. Ebert, B.A. Bednar, D.J. Neder, A.A. McIlheran, P.C. Michel, J.J. Nemce, E.F. Pleva, A.C. Swenton, W. Swets, R.C. Longsworth, R.C. Johsnon, R.H. Jones, J.K. Nelson, R.C. Degeneff and S.J. Salon Summary: We report on test results for a single phase, 60-Hz, 13.8 kV/6.9 kV, 1-MVA high temperature superconducting (HTS) transformer which was completed in February, 1998. This transformer models in many ways a full scale section of a 30-MVA HTS commercial transformer design. The transformer windings are cryocooled in the range of 25 K and are made with a low-cost, surface-coated BSCCO-2212 conductor. Heat leaks are reduced using a liquid nitrogen thermal ballast and reservoir. The use of high temperature superconductors can substantially reduce transformer losses, weight, size, noise and potential fire and environmental hazards. Designs promise stable operation through faults without thermal degradation, and at temperatures that allow efficient and reliable refrigeration.         Superconducting AC/DC power coversion using high-temperature superconducting components    D.A. Barton and G.O. Zimmerman Summary: The trend towards DC transmission of power, especially when using superconductors, has made the conversion of power from AC to DC and DC to AC a critical element of many electrical systems. We designed and tested an AC to DC and DC to AC converter which used HTS cryotron switches. The superconducting elements were made from yttrium barium copper oxide, and the converter was operated at 77 Kelvin. Both AC to DC and DC to AC conversion has been demonstrated, and the conversion has been shown to be relatively independent of frequency over a wide range. The converter was tested with a current of a few amperes, but is upwardly scalable to thousands of amperes, At larger currents the converter is more efficient as much of the power loss occurs in a separate control circuit which carries a current that does not scale with the amount of current controlled. Significant sources of inefficiencies remain which make the initial device impractical for actual use; however, the proposed improvements in material and design should allow the converter to be used in practical applications and outperform conventional methods of conversion such as thyristors.         Design, development and test of 2 m quadrupole model magnets for the LHC inner triplet    J. Kerby, A.V. Zlobin, R. Bossert, J. Brandt, J. Carson, D. Chichili, J. DiMarco, S. Feher, M.J. Lamm, P.J. Limon, A. Makarov, F. Nobrega, I. Novitski, D. Orris, J.P. Ozelis, B. Robotham, G. Sabbi, P. Schlabach, J.B. Strait, M. Tartaglia, J.C. Tompkins, S. Caspi, A.D. McInturff and R. Scanlan Summary: Fermilab and LBNL are in the midst of a model magnet program to develop and prove the design of quadrupoles for use in the LHC Interaction Region inner triplets. These magnets have a nominal gradient of 205 T/m in a 70 mm bore, and operate in superfluid helium at 1.9 K. The R&D program addresses magnetic, mechanical, thermal design and quench protection issues. This paper describes design, fabrication experience and test results from the first 2 m models.         Testing of large aperture superferric quadrupoles    A.F. Zeller, R. Zink, J. Wagner, S. Hitchcock, J.C. DeKamp and A. Balint Summary: Five different types of superferric quadrupoles are being built for the A1900 Fragment Separator at the NSCL. At least one of each type has been built and tested in an open helium vessel. Quench behavior was recorded and analyzed. Results were compared to calculated quantities such as internal voltages. The measured internal voltages were always less than those calculated with any set of reasonable parameters. All magnets exhibited some training, but every one met or exceeded the required maximum gradients.         Quench and mechanical behavior of an LHC low-/spl beta/ quadrupole model    T. Nakamoto, K. Tanaka, A. Yamamoto, K. Tsuchiya, E. Barkhardt, N. Higashi, N. Kimura, T. Ogitsu, N. Ohuchi, K. Sasaki, T. Shintomi, A. Terashima, G.A. Kirby, R. Ostojic and T.M. Taylor Summary: A one meter model of the high gradient 70 mm aperture superconducting low-/spl beta/ quadrupole has been developed at KEK. The design field gradient is 240 T/m at a current 7677 A with a superconducting load line ratio of 92% and peak field of 9.64 T in the coil. A first series of training tests of the magnet was carried out at 1.9 K including a full thermal cycle to room temperature. The highest quench current was 8007 A corresponding to a field gradient of 250 T/m. The magnet was subsequently reassembled to improve its longitudinal mechanical structure. In this paper, quench characteristics and mechanical behavior of the first model magnet are presented.         A high field magnet design for a future Hadron collider    R. Gupta, K. Chow, D. Dietderich, S. Gourlay, G. Millos, A. McInturff, R. Scanlan, S. Ramberger and S. Russenschuck Summary: US high energy physics community is exploring the possibilities of building a Very Large Hadron Collider (VLHC) after the completion of LHC. This paper presents a high field magnet design option based on Nb/sub 3/Sn technology. A preliminary magnetic and mechanical design of a 14-16 T, 2-in-1 dipole based on the "common coil design" approach is presented. The computer code ROXIE has been upgraded to perform the field quality optimization of magnets based on the racetrack coil geometry. A magnet R&D program to investigate the issues related to high field magnet designs is also outlined.         Block-coil dipole for future hadron colliders    A. Abreu, C. Battle, G. Cryer, N. Diaczenko, T. Elliott, H. Eucker, D. Gross, E. Hill, B. Henchel, A. Jaisle, D. Latypov, P. McIntyre, P. McJunkins, S. Munson, D. Sattarov, Weijun Shea, R. Soika, M. Spears and R. Gaedke Summary: A first model dipole is being built for a block-coil dipole for future hadron colliders. The design incorporates stress management, in which Lorentz stress is intercepted between successive sections of the coil and bypassed through a support matrix. By controlling stress, the dipole should make it possible to utilize Nb/sub 3/Sn and BSCCO superconductors without strain degradation at high field. The first model dipole is being built using NbTi cable in order to evaluate fabrication techniques and stress management performance.         Electromagnetic properties of bronze processed Nb/sub 3/Sn superconducting wires and multi-strand cables for AC use with a Cu-Sn-X(X; Ge,Ni,Mn,Si) matrix and a Nb-Ta core    K. Miyashita, K. Sugiyama, H. Moriai, K. Kamata, K. Tachikawa and K. Fukuda Summary: A bronze processed 0.275 mm-dia. Nb/sub 3/Sn strand composed of Nb-0.5at%Ta cores and a Cu-2.7at%Sn-1.0at%Ge matrix was fabricated into cables of 6 and 36 strands. Each strand contained 75990 filaments 0.28 /spl mu/m in diameter. The AC quench current for the 36-strand cable reached 2500 A/sub peak/ at 50 Hz and 0.5 T DC field. The 6-strand cable showed a significantly improved irreversible bending strain limit of over 10% due to the fine filament size. This result enabled building of a magnet through the react and wind method. A 50 mm-bore 2T-class magnet wound by the 6 strand cable was successfully operated at 52.7 Hz and 4.2 K. In order to reduce AC losses another bronze processed 0.218 mm-dia. Nb/sub 3/Sn strand with 147510 0.15 /spl mu/m-dia. filaments was fabricated from Nb05%Ta/Cu-4.9%Sn-2.0%Ge/Cu-2.7%Sn-2%Ni-1%Mn double matrix composite. The strand showed a hysteresis loss of 447J/m/sup 3/ at /spl plusmn/0.5 T/cycle and /spl lambda/J/sub c/ of 857A/mm/sup 2/ at 0.5 T after the heat treatment at 500/spl deg/C for 100 h.         Influence of field orientation on proximity effect induced filament coupling in NbTi wires    K. Yasohama and Y. Kubota Summary: Filament coupling induced by the proximity effect was studied through ac susceptibility measurements on Cu-matrix NbTi multifilamentary wires in fields oriented with various directions to the wire axis. The sample wires with a different twist pitches (1.7, 3.3 and 6.1 mm) are made from VAMAS reference sample H-1. The wires have a diameter of 0.20 mm and a filament number of 931. The orientations of AC and DC fields are varied in the range from 0/spl deg/ to 90/spl deg/. The susceptibilities are measured while increasing the sample temperature after zero field cool down to 4.2 K. From the results of the field orientation and temperature dependencies of peaks in the imaginary part of AC susceptibility, we discuss the magnetic behavior of the superconductivity of the matrix induced by the proximity effect and estimate the critical current density of the matrix at low field.         3D FEM analysis of inter-strand coupling losses in Rutherford cables with composite core    T. Kawashima, F. Sumiyoshi, S. Kawabata and T. Shintomi Summary: Improved Rutherford cables have been proposed for magnets for experiments of high energy physics. They have either a sheet of stainless-steel or a composite metal sheet as a core put in the usual Rutherford cable. The cable with this composite core sheet in it is a candidate for a new cable with both low losses and high stability. In order to estimate the interstrand coupling losses produced in this cable, three dimensional finite element method (3D FEM) analysis is carried out. The results obtained show that the existence of 3D shielding current in it determines the profile of loss properties under changing magnetic fields of face-on orientation. The effect of spatial period of the core structure along the cable axis on the loss is also elucidated. This will be a useful aid for the design of the cable.         Interstrand resistance measurements on Nb/sub 3/Sn Rutherford-type cables    A. Devred, L. Bacquart, P. Bredy, C.E. Bruzek, Y. Laumond, R. Otmani and T. Schild Summary: We review a series of interstrand resistance measurements performed on two Rutherford-type cables made from unplated niobium-tin strands produced by Alstom: a regular cable and a cable with a stainless steel core inserted between the two strand layers. The interstrand resistance measurements are interpreted in terms of crossover and adjacent resistances and are compared to published data on similar cables.         Increase of inter-strand coupling losses in superconducting cable-in-conduit conductor under actual condition of sweep rate    A. Kawagoe, F. Sumiyoshi, T. Mito, A. Iwamoto, S. Satoh and N. Hirano Summary: Basic studies are carried out on causes of the increase of inter-strand coupling losses in cable-in-conduit conductors used for windings of large scale magnets, such as a single inner vertical (IV) coil in the Large Helical Device. In this paper, the effect of AC transverse magnetic fields periodic changing along a two-strand cable axis on loss properties of the cable is considered as a candidate of the cause. The evidence that the periodic changes produce additional inter-strand coupling losses characterized by another long coupling time constant in addition to the intrinsic one is theoretically shown. We confirmed properties by measurements on two kinds of sample wires, using inter-filament coupling in a strand instead of inter-strand coupling in cable.         AC losses in Nb/sub 3/Sn Rutherford cables with a stainless steel core    F. Sumiyoshi, S. Kawabata, T. Gohda, A. Kawagoe, T. Shintomi, E.W. Colings, M.D. Sumption and R.M. Scanlan Summary: Electric measurements of coupling losses in five-layer stacks of Nb/sub 3/Sn Rutherford cables with a stainless steel (SS) core are made with the applied transverse magnetic-field both normal and parallel to the plane of the cable. For the former (face-on, FO) field case, a one-order reduction of the FO inter-strand coupling loss due to the existence of the resistive core is clearly observed. The measured loss for the latter (edge on, EO) field case is very small, that is, about 1/5000 times as large as the reduced loss. In order to explain these loss properties, two dimensional FEM analysis is carried out taking into account the details of the cable cross-section. The theoretical results show that the FO inter-strand coupling loss in the SS-cored cable is determined mainly by the thickness and conductivity of not only the SS core but also of the outermost bronze region, and that the negligible EO loss corresponds to the intra-strand coupling loss produced in isolated strands due to high surface-resistance of the side-by-side contact.         Strand coating for the superconducting cables of the LHC main magnets    D. Richter, J.D. Adam, D. Leroy and L.R. Oberh Summary: The electrical resistance of contacts between strands in the Rutherford type superconducting cables has a major effect on the eddy current loss in cables, and on the dynamic magnetic field error in the LHC main magnets. In order to guarantee the value and constancy of the contact resistance, various metallic coatings were studied from the electrical and mechanical points of view in the past. We report on the molten bath Sn/sub 95wt/Ag/sub 5wt/ coating, oxidized thermally in air after the cabling is completed, that we adopted for the cables of the LHC main magnets. The value of the contact resistance is determined by the strand coating and cabling procedures, oxidation heat treatment, and the magnet coil curing and handling. Chemical analysis helps to understand the evolution of the contacts. We also mention results on two electrolytic coatings resulting in higher contact resistance.         Measurement of AC loss and magnetic field during ramps in the LHC model dipoles    Z. Ang, I. Bejar, L. Bottura, D. Richter, M. Sheahan, L. Walckiers and R. Wolf Summary: We describe the systems for AC loss and magnetic field measurements developed for the LHC superconducting magnets. AC loss measurements are performed using an electric method, while field measurements are performed using either fixed pick-ups or rotating coils. We present results obtained on 1-m long model dipoles, and compare the results of the different methods in terms of average interstrand resistance.         Influences of geometrical configuration on AC loss measurement with pickup-coil method    K. Kajikawa, M. Iwakuma, K. Funaki, M. Wada and A. Takenaka Summary: We usually measure AC losses of superconducting wires and cables exposed to a transverse AC magnetic field by a pickup-coil method. In this case, a main pickup coil is coaxially located around the sample wire wound as a solenoidal coil. An additional pickup coil (a cancelling coil) is also placed inside or out side the sample coil. This method is advantageous to obtain detailed electromagnetic properties of the sample. In the present study, we discussed the effect of the geometrical configurations of the sample and pickup coils on AC losses measured by the pickup coil method for three types of arrangements of the cancelling coils. We analytically calculated interlinkage magnetic flux into the pickup coils due to magnetic moments induced in the sample wire, and formulated the geometrical errors in the pickup-coil method. We also prepared some sets of sample and pickup coils, and compared observed AC losses with the theoretical predictions.         Calculation of self-field losses in a superconducting cable considering the twist of strands    Ji-Kwang Lee, Gueesoo Cha and Song-Yop Hahn Summary: AC superconducting cables are usually to be bundled by many strands to make large current capacity for AC power applications. Superconducting strands composing multistage cables have twisted structure in each stage for lower AC loss and higher stability. So, when transport currents flow in a cable, each strand is exposed to longitudinal and azimuthal magnetic fields produced by transport current flowing in the strand itself and longitudinal and transverse magnetic fields by transport current flowing in the twisted cable. In this paper, we calculate the self field loss generated in a second stage superconducting cable considering twist of strands in cables and filaments in strands. Also, we describe the influence on self field loss by twist direction of filaments and strands.         Electromagnetic and mechanical characterisation of ITER CS-MC conductors affected by transverse cyclic loading. II. Interstrand contact resistances    A. Nijhuis, N.H.W. Noordman, H.J. ten Kate, N. Mitchell and P. Bruzzone Summary: A special cryogenic press has been built to study the mechanical and electrical properties of full-size ITER multistrand Nb/sub 3/Sn cable-in-conduit conductor samples under transverse, mechanical loading. This simulates the transverse magnetic force that occurs when the conductors are used in a coil. The cryogenic press can transmit a variable (cyclic) force up to 650 kN/m to a cable section of 400 mm length at 4.2 K. The jacket is opened partly in order to transmit the force directly onto the table. The various interstrand contact resistances (R/sub c/s) between strands selected from sub-cables at different positions inside the cable are measured. A summary of the results obtained with up to several tens of full loading cycles is presented. The cables consist of six last stage sub-cables (petals) which are wrapped with an Inconel 600 ribbon. A significant increase of the intra-petal R/sub c/ after several cycles is observed. An opposite effect is noticed for the inter-petal R/sub c/. Upon applying a load of 650 kN/m, the R/sub c/ drops for the intra-petal as well as for the inter-petal resistance with respect to zero load.         Low coupling loss core-strengthened Bi:2212/Ag Rutherford cables    E.W. Collings, M.D. Sumption, R.M. Scanlan, D.R. Dietderich and L.R. Motowidlo Summary: In a comprehensive "vertically integrated" program multifilamentary (MF) high temperature superconducting (HTSC) Bi:2212/Ag strand was fabricated using the powder-in-tube process and heat treated in oxygen by a modified standard procedure. The reaction-heat-treatment (HT) was adjusted to maximize critical current (density), I/sub c/ (J/sub c/), as measured in various magnetic fields, B. A series of Rutherford cables was designed, each of which included a metallic (Nichrome-80) core for strengthening and reduction of coupling loss. Prior to cable winding a series of tests examined the possibility of strand "poisoning" by the core during HT. Small model Rutherford cables were wound, and after HT were prepared for I/sub c/(B) measurement and calorimetric measurement of AC loss and hence interstrand contact resistance I/sub c/(B). It was deduced that, if in direct contact with the strand during HT, the core material can degrade the I/sub c/ of the cable; but steps can be taken to eliminate this problem. Otherwise the core is unequivocally beneficial: the cored Bi:2212/Ag cable is mechanically strong and easy to handle and, from AC-loss results, yields an ICR that when extrapolated to Large Hadron Collider (LHC) inner-winding specifications predicts a cable with a fairly satisfactory combination of low coupling loss and stability.         AC losses in multifilamentary low AC loss Bi(2223) tapes with novel interfilamentary resistive carbonate barriers    H. Eckelmann, M. Quilitz, C. Schmidt, W. Goldacker, M. Oomen and M. Leghissa Summary: For the AC application of multifilamentary BSCCO-tapes at 50-60 Hz in power cables and transformers, the main components of the AC losses are hysteresis losses in the filaments and coupling current losses in the normal conducting matrix. Coupling losses can be reduced by enhancing the matrix resistivity and by applying a twist to the filaments. The authors developed a novel multifilamentary BSCCO tape in an Ag matrix with resistive SrCO/sub 3/ barriers between the filaments to enhance the transverse resistivity. AC loss measurements on two different types of conductor designs are shown in this paper. In the first series of conductors the barrier forms something like a honeycomb structure in the cross-section between the filaments (DCB tapes). From this conductor type, a series with Ag and AgAu(8 wt.%) matrix was prepared. The AgAu was chosen to increase the matrix resistivity compared to Ag. In the second series of tapes the conductor structure is similar to a Rutherford cable (RBB tapes). Six bundles of 7 filaments are stacked round a central SrCO/sub 3/ core and deformed to a tape. All types of tapes have been twisted with a twist length down to 7.5 mm. In the AC transport current loss measurements, they find a loss reduction in the RBB tapes due to the fact that the filaments in these tapes are nearly fully transposed. In external AC fields, loss reductions in parallel as well as in perpendicular fields are found in both conductor series due to the decoupling of filaments.         The electrical aspects of the choice of former in a high T/sub c/ superconducting power cable    C. Traeholt, A. Kuhle, S.K. Olsen and O. Tonnesen Summary: Centrally located in a superconducting power cable the former supplies a rigid means onto which to wind the superconducting tapes and enables a continuous supply of cooling power via a flow of liquid cryogen through it. Therefore, the choice of former has a broad impact on the construction and design of a cable. The diameter of the former determines the overall diameter of the total cable, influences the heat loss to the ambient and enters into the total AC-losses. Depending on whether the former is made of a good or poor electrical conductor, eddy currents in the former itself may also contribute significantly to the AC-loss of the cable; the choice between an open and a closed former determines how and where the pressure load (pressurized coolant) has to be accommodated. In this work the electrical impact of the choice of material and diameter of the former on the AC-loss of a cable conductor is addressed.         Measurement and FEM analysis of magnetization loss in HTS tapes    K. Miyamoto, N. Amemiya, N. Banno, M. Torii, E. Hatasa, E. Mizushima, T. Nakagawa, H. Mukai and K. Ohmatsu Summary: Magnetization loss of Bi-2223/Ag tapes was measured with several types of pick-up coils to study the influence of pick-up coil configuration and sample length on the measured losses. Magnetic flux distributions in tapes were calculated numerically by the finite element method to obtain their AC losses. The numerical and experimental losses were compared with each other to clarify the nature of the measured AC losses. In the parallel magnetic field, the height of the pick up coil must equal or be larger than the tape height for the accurate loss measurement. In the perpendicular magnetic field, the size pick up must be much larger than the width for accurate loss measurement. If the length of the sample tape is short, the measured loss contains coupling loss component at commercial frequencies, while the filaments are almost decoupled in DC measurement by a SQUID magnetometer.         Self-field AC losses of assemblies of Ag sheathed PbBi2223 tapes    T.J. Hughes, Y. Yang, C. Beduz and A. Power Summary: Magnetic interaction between two neighbouring superconducting tapes carrying a transport current can cause them to become coupled so that they react as one tape. One of the consequences of such coupling is the increase in the self-field loss per tape. The critical distance at which the tapes begin to couple is important in the assessment of the interactions among tapes in systems such as a power cable or coil. Experimental measurements of the self-field losses in two neighbouring Ag sheathed PbBi2223 tapes carrying the same transport current were carried out with the two tapes separated by various distances, while placed one on top of the other (stack-configuration). This configuration is similar to that found in adjacent layers in a coil. The results indicate that the critical coupling distance for the top-configuration is about 5 mm, where the increase in loss per tape is about 10%. Measurements are also undertaken for the more realistic situation where each of the tapes has a different critical current.         Single and multi-phase AC losses in HTS prototype power transmission conductors    J.O. Willis, D.E. Daney, M.P. Maley, J.Y. Coulter and S. Fleshler Summary: AC losses in several 1 m long high temperature superconductor (HTS) prototype multi-strand conductors (PMCs) have been measured with a temperature-difference calorimeter. Both single-phase and three-phase losses were examined with AC currents up to 1000 A rms in the PMC. In addition, "two-phase" losses, with current flowing in the two normal conductor phases but not in the PMC, were also investigated. The calorimeter, designed specifically for these measurements in the liquid nitrogen temperature range, has a precision of 1 mW. The PMCs consist of two layers of helically-wound Bi-2223/Ag sheathed HTS tape, each layer wrapped with opposite pitch. Losses were found to depend on about the third power of the current-a result in agreement with the Bean-Norris model adapted to the double-helix configuration. Increasing either the critical current I/sub c/ of the tapes or decreasing the temperature of a PMC at fixed current resulted in decreased single-phase losses, in accord with the model. The three-phase losses indicate a significant interaction between phases and a smaller dependence on tape I/sub c/ than expected.         Effects of filament arrangement and wire geometry on the AC losses in Bi(2223) tapes    M. Dhalle, A. Polcari, F. Marti, Y.B. Huang, G. Witz and R. Flukiger Summary: AC losses in multi-filamentary tapes depend on various parameters. Among them, geometrical factors such as overall tape width and thickness as well as the precise arrangement of the filaments are expected to have an important influence. Several theoretical models describe this dependency. In order to study these geometrical effects experimentally, we prepared a series of Bi(2223)/Ag tapes with gradually changing filament arrangements and tape aspect ratio, and characterized them by AC transport and magnetic measurements. The results are compared to model predictions.         Losses in HTS carrying AC transport currents in AC external magnetic fields    N. Magnusson and S. Hornfeldt Summary: Any high-temperature superconductor (HTS) that is developed for power applications will have an optimal working point in temperature (T), magnetic field (B), and transport current (I), when the cost of both the conductor and the AC losses are considered. To optimise the use of an HTS in a specific application, there is a need for design tools based on models of the AC losses. The models can be of the form Pac=Pac(T, B, I, f), where f is the frequency. In this paper we present a semi-empirical model and apply it to experimental results of AC losses measured on a multifilamentary Bi-2223 tape produced for DC applications. The model is based on the Bean critical state model and it accounts for the combined action of a DC transport current and an AC magnetic field applied parallel to the face of the tape. To measure the losses we used a calorimetric apparatus in which T, B, I, and f can be varied independently of each other.         AC losses of filamentary HTS twisted filament round wires and flat tapes    F. Darmann, R. Zhao, G. McCaughey, M. Apperley, T.P. Beales and C. Friend Summary: Samples of multifilamentary Bi-2223/Ag/alloy twisted filament tapes and Z stack round wires, consisting of untwisted and twisted stacks (or z-arrays) of flat filaments have been prepared. It was found that twist pitches of less than 10 mm may be incorporated into multifilament tapes while maintaining the Jc at 20 kA/cm/sup 2/. The self-field AC loss has been investigated at low frequencies up to 100 Hz. The round wire was found to exhibit isotropic electromagnetic properties.         AC losses of HTS tapes and bundles with de-coupling barriers    J.W. Lue, M.S. Lubell and M.J. Tomsic Summary: Plastronic Inc. is working on a project for the Ballistic Missile Defence Organization to improve the strength and AC loss characteristics of Bi-based high temperature superconductors (HTS) for AC applications like motors, generators, and transmission cables. High strength, high amperage conductor is made by encapsulating bundles of HTS tapes with a nonsilver sheath. With this technique, Cu-alloy spacers can be placed between Bi-2223/Ag HTS tapes to de-couple the tapes under AC currents. AC losses were measured on conductor bundles with and without Cu-alloy spacers at AC currents up to 70 A and frequencies from 50 to 400 Hz. At frequencies up to about 100 Hz, it was found that the bundle with resistive barriers had AC loss equal to the sum of individual tapes as expected from the Norris ellipse model. At higher frequencies, the Cu-alloy barrier was not as effective in reducing the AC loss. For single tapes, Zr-oxide was used to coat the HTS filaments before stacking to form a multifilament tape. AC loss measurements of 6-filament tapes with and without the oxide coating showed little effect of the coating when the loss was normalized to the square of the critical current as the theory suggests.         Modeling the current distribution in HTS tapes with transport current and applied magnetic field    T. Yazawa, J. Rabbers, O.A. Shevchenko, B. ten Haken, H.H.J. Ten Kate and H. Maeda Summary: A numerical model is developed for the current distribution in a high temperature superconducting (HTS) tape, (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/-Ag, subjected to a combination of a transport current and an applied magnetic field. This analysis is based on a two-dimensional formulation of Maxwell's equations in terms of an integral equation for the current density J. The finite thickness of the conductor and an arbitrary voltage-current relation (e.g. n-power relation, magnetic field dependency) for the conductor are included in the model. Another important feature is that the model also covers an applied magnetic field in arbitrary directions and a rotating field perpendicular to the conductor, which is of great interest for analyzing the AC loss of HTS (transformer) coils or three-phase electric power cables. A comparison is made with transport current loss measurements on an HTS tape with an AC applied field.         Transport current loss of BSCCO/Ag tape in different orientations of the external alternating magnetic field    J.J. Rabbers, B. ten Haken and H.H. ten Kate Summary: BSCCO/Ag tapes are being developed for electrical power applications at liquid nitrogen temperatures. In these applications, conductors are exposed to an alternating magnetic field and fed simultaneously with an alternating transport current. In this contribution the influence of an external alternating magnetic field on the transport current loss of a single tape is studied experimentally. Special attention is paid to the loss as a function of the orientation of the external magnetic field. The transport current loss in a DC external magnetic field can be described well by the decrease of the critical current due to the magnetic field. In the case of an AC external magnetic field this is only a minor effect. Effects responsible for the increase of the transport current loss in external AC magnetic field are investigated with respect to their angle dependency. A model based on a 1 dimensional modelling of the conductor and an average critical current density during the magnetic field cycle is presented. This model describes the measured results reasonably well below the critical current.         Measurement of AC losses in textured polycrystalline Bi-2212 thin rods    E. Martinez, T.J. Hughes, Y. Yang, C. Beduz and L.A. Angurel Summary: AC losses of textured polycrystalline Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+x/ thin rods carrying AC transport currents have been measured in self-field and in DC magnetic fields at 77 K. Measurements of the first and third harmonic of the voltage are presented. The current amplitude and frequency dependence of losses as well as the ratio between the different harmonics of the voltage is analysed. The results are compared with the losses calculated numerically for a superconductor characterised by power-law current-voltage dependence.         Bi(2223) Ag sheathed tape Ic and exponent n characterization and modelling under DC applied magnetic field    B. Dutoit, M. Sjostrom and S. Stavrev Summary: We use a dual channel digital lock-in to perform electrical measurement of AC losses at power frequencies. A DC magnetic field between 2 and 400 mT is applied with a varying angle from parallel to perpendicular to the tape surface, thus having a complete view of the loss behavior under DC applied field. Furthermore, the same experimental layout is used to acquire time series of current and voltage across the sample. Using a triangular input current, we measure and average the voltage, which then is fitted to a power law (I/I/sub c/)/sup 11/. The measurements are repeated for the mentioned magnetic field and angle domain to give the dependencies of I/sub c/ and n with magnetic field and angle. For device modeling purposes, we can then express a phenomenological law giving I/sub c/ and n as a function of the applied magnetic field's intensity and direction.         Measurements of AC losses in HTSC wires exposed to an alternating field using calorimetric methods    T. Hardono, C.D. Cook and Jian-Xun Jin Summary: Calorimetric methods for AC loss measurement for short superconducting wires have been investigated. The design, operation and results obtained from an experimental calorimeter are described. With these methods the total loss of a short superconducting sample exposed to a 50 Hz alternating field, both perpendicular and axial, have been measured with an accuracy of microwatts per centimeter. The sample is a 6 centimeter long (Bi,Pb)SrCaCuO-2223 silver-sheathed multifilamentary wire prepared by powder-in-tube techniques. The hysteresis part of the loss may be obtained by taking the eddy current component of the silver sheath from the total loss and by neglecting the coupling loss in the silver matrices. It is shown that the hysteresis losses are dominant in this frequency and its values correspond to the theoretical approximation.         Angular dependence of AC transport losses in multifilamentary Bi-2223/Ag tape on external DC magnetic fields    M. Ciszek, O. Tsukamoto, N. Amemiya, M. Ueyama and K. Hayashi Summary: AC transport losses, in multifilamentary BSCCO-2223 silver sheathed tapes, as a function of the applied external magnetic field and its direction with respect to the plane of the samples, are reported. The measurements were carried out at 77 K and at frequency of 80 Hz. The AC transport current values through the tapes, in the range of 10 to 70 percent of their DC critical current values, were kept constant, while rotating the external magnetic field. Also, in a similar way, DC critical current angular characteristics were measured. The transport losses, as a function of the angle and the magnetic field, scale when using the analogous DC critical current relations. Obtained results are compared with theoretical models for the self-field losses.         Magnetic AC loss in twisted-filament Bi-2223 tapes    M.P. Oomen, J. Rieger, M. Leghissa, B. Fischer, B. ten Haken and T. Arndt Summary: In AC power-engineering applications, the energy dissipation in the superconductor is dominated by the magnetization due to alternating fields. To reduce this type of loss, conductors are being developed with twisted filaments and an increased matrix resistivity. The magnetic AC loss has been well described for low-T/sub c/ (wire) conductors. In Bi-2223 tapes the picture is different due to strong anisotropy, granularity, flux creep and large aspect ratio of the tape. The magnetic AC loss is investigated at power frequencies in various Bi-2223 tapes (twisted and nontwisted) and with different materials for the matrix (Ag, Ag alloys and ceramic barriers). When the field is parallel to the tape plane, the filaments in twisted tapes can be decoupled and the AC loss is decreased even when the matrix is silver. In tapes with ceramic barriers between the filaments, first indications of filament decoupling are observed also in perpendicular field. Compared to a round wire, there are essential differences between the AC loss mechanisms occurring in a long twisted tape and those in a short piece of nontwisted tape.         AC loss of multifilamentary superconducting AC wire caused by longitudinal and azimuthal AC magnetic field components    S. Fukui, K. Negishi, O. Tsukamoto, K. Miyashita and K. Fukuda Summary: AC loss characteristics of multifilamentary NbTi AC wires under AC external magnetic field were experimentally and theoretically investigated. The authors measured AC transport current losses of AC wires with various twist pitches under the AC external magnetic field which included longitudinal and transverse components. It was shown by the measurement that the AC transport current losses decreased with decreasing the twist pitches when the external and self longitudinal fields were in the same direction. The measured dependence of the AC losses on the twist pitches and the applied longitudinal field component were well explained by their previously derived model. They also theoretically estimated the AC losses caused by the longitudinal and azimuthal field components. It was found that the AC losses can be substantially reduced by properly selecting the twist pitch and the external longitudinal field component.         AC losses of HTS coils carrying transport current    T. Honjo, T. Hasegawa, K. Kaiho, H. Yamaguchi, K. Arai, M. Yamaguchi, S. Fukui, K. Kato and K. Itagaki Summary: In the paper, the authors report the experimental results for AC losses in an HTS coil carrying AC transport current. The tests of AC losses were performed by the electrical method at 77 K and 4.2 K. The HTS tape consists of 55 multifilamentary silver-sheathed BSCCO 2223 tape without twisting. The sample coil was made by the react-and-wind method using insulated tape conductor. The coil has an inner diameter of 46 mm, outer diameter of 87 mm, height of 14.5 mm, and the number of turns is 300. The measured AC losses were compared with the conventional theory based on the critical state model. In the region of low transport current, the theoretical results agreed well the experimental results. The authors also investigated the distribution of the AC losses in the coil to study the effects of magnetic field distribution on AC losses.         Loss and inductance investigations in a 4-layer superconducting prototype cable conductor    S.K. Olsen, C. Traeholt, A. Kuhle, O. Tonnesen, M. Daumling and J. Ostergaard Summary: One important issue in the design and optimization of a superconducting cable conductor is the control of the current distribution between single tapes and layers. This presentation is based on a number of experiments performed on a 4-layer three meter long prototype superconducting cable conductor. The self and mutual inductances of the layers are studied theoretically. The current distribution between the superconducting layers is monitored as a function of transport current. The results are compared with the expected current distribution given by the authors' equivalent electrical circuit model. The AC losses are measured as a function of transport current and a given current distribution and compared with the monoblock model. Recommendations for design of future cable conductor prototypes are given.         Status report on the CMS superconducting solenoid for LHC    F. Kircher, B. Levesy, Y. Pabot, D. Campi, B. Cure, A. Herve, I.L. Horvath, P. Fabbricatore and R. Musenich Summary: The CMS (Compact Muon Solenoid) experiment is one of the two large experiments approved to be installed on the Large Hadron Collider (LHC) at CERN, and is now at an early stage of construction. For good momentum resolution, a superconducting solenoid is needed, the main characteristic of which is a nominal magnetic field of 4 T in a 5.9 m diameter and 12.5 m long warm bore, leading to a stored energy of 2.7 GJ. These characteristics make this superconducting solenoid the largest and most powerful one ever designed. The main technical choices are: the use of a mechanically reinforced Al-stabilized conductor, the subdivision of the coil in five modules, each internally wound and vacuum impregnated before final assembly, the use of indirect cooling with circulation of liquid helium in a thermosyphon mode and quench back protection process to enhance the energy dump. All these choices need developments which will be reported together with the detailed description and the status of each main component of the cold mass of the solenoid.         Superconducting magnet system for the ATLAS detector at CERN    H.H. ten Kate Summary: The ATLAS Collaboration has started the construction of the superconducting magnet system of the ATLAS Experiment which will be installed in the ring of the new Large Hadron Collider at CERN, operational in year 2005. The ATLAS detectors require, for the particle separation, a specific distribution of magnetic field that will be generated by a system of superconducting coils. The system with overall dimensions of 20 meter diameter and 26 meter length consists of three toroidal magnets and a 2.5 m diameter central solenoid. The system is unique in size and complexity. In this paper, the various magnets are introduced as well as the common infrastructure and services required. The status of the project is also reviewed.         Design and testing of the 1.5 T superconducting solenoid for the BaBar detector at PEP-II in SLAC    T.G. O'Connor, S. Shen, P. Fabbricatore, S. Farinon, R. Musenich, C. Priano, R.A. Bell, M. Berndt, W. Burgess, W. Craddock, L. Keller, O. Dormicchi, P. Moreschi, R. Penco, P. Valente and N. Valle Summary: The 1.5 T superconducting solenoid is part of the BaBar detector located in the PEP-II B-Factory machine at the Stanford Linear Accelerator Center. The solenoid has a 2.8 m bore and is 3.7 m long. The two layer solenoid is wound with an aluminum stabilized conductor which is graded axially to produce a +/3% field uniformity in the tracking region. The 24 month fabrication, 3 month installation and 1 month commissioning of the solenoid were completed on time and budget. This paper summarizes the culmination of a 3 year design, fabrication and testing program of the BaBar superconducting solenoid. Critical current measurements of the superconducting strand, cable and conductor, cool-down, operation with the thermosyphon cooling, fast and slow discharges, and magnetic forces are discussed in detail.         Design and development of the ATLAS central solenoid magnet    A. Yamamoto, T. Kondo, Y. Doi, Y. Makida, K. Tanaka, T. Haruyama, H. Yamaoka, H. ten Kate, L. Bjorset, K. Wada, S. Meguro, J.S.H. Ross and K.D. Smith Summary: The ATLAS central solenoid magnet is being constructed to provide a magnetic field of 2 T in the central tracking part of the ATLAS detector. As a key technology for a solenoid coil as thin as possible, a high-strength aluminum stabilized superconductor has been developed, achieving a yield strength of >100 MPa at 4.2 K. This paper describes the status of the design and development of the solenoid magnet.         Engineering design optimisation of the superconducting end cap toroid magnets for the ATLAS experiment at LHC    D.E. Baynham, J. Butterworth, F.S. Carr, M.J.D. Courthold, D.A. Cragg, C.J. Densham, D. Evans, E. Holtom, S. Robertson, D. Sole and E.F. Towndrow Summary: Precision muon momentum measurements at the highest LHC luminosity is a prime objective for the ATLAS experiment. To realise this objective the muon detector is based on a large, superconducting, air-cored toroid magnet system consisting of a long barrel and two end cap toroids. The end-cap toroids are required to produce strong bending powers, 4-8 Tm, over a radial span from 1.5-5 m. This paper presents the final engineering design which includes a number of design optimisation features. The optimisation of the cold mass structure to reduce internal stresses, the developments in resin technology to give greater safety margins in operation and novel techniques for cold mass support systems are described. Final design proposals for quench protection and control are presented with manufacture, assembly and installation plans.         The HADES detector magnet-a large superconducting torus    S.M. Harrison, J.S.H. Ross and R.J. Riggs Summary: HADES, the High Acceptance Di-Electron Spectrometer, is an experiment at the Gesellschaft fur Schwerionenforschung mbB (GSI) at Darmstadt in Germany. Its purpose is to investigate hot and dense nuclear matter formed in heavy ion collisions at incident beam energies of a few GeV per nucleon. At the heart of the system is a large, six-coil detector magnet producing a toroidal field of up to 3.8 T over a total volume of approximately 8 m/sup 3/. The contract to design, manufacture, install and commission the magnet system was awarded to Oxford Instruments in November 1995, and the system was delivered to GSI-three months ahead of schedule-in April 1998. This paper describes the design, manufacture and commissioning of the magnet.         Superconducting linacs as free electron laser drivers    H.A. Schwettman Summary: The superconducting RF linac played a central role in the early development of free electron lasers. Now as FEL facilities are being constructed in the far-infrared and the vacuum ultraviolet in order to pursue frontier optical science, and as the feasibility of near-ultraviolet FEL facilities for commercial surface processing of materials is being evaluated, there is renewed interest in the special characteristics that superconducting RF linacs offer. These special characteristics include long pulse or CW operation, feedback regulation of accelerating fields, high efficiency, and availability of high gradient, low impedance structures. There are exciting new opportunities on the horizon for FEL facilities and it is clear that superconducting linacs will play an important role in their development.         Superconducting accelerators for nuclear waste transmutation    C. Pagani, D. Barni, G. Bellomo, R. Parodi and P. Pierini Summary: High intensity proton accelerators, with energies in excess of 1 GeV, have been proposed for nuclear waste transmutation applications. The large neutron flux, obtained by the spallation target, further multiplied in a subcritical reactor, could open the possibility of closing the fuel cycle in nuclear energy production. This new accelerator application asks for high overall plug efficiency and reliability, together with low particle losses for hands-on maintenance. Superconducting RF technology seems to be the best solution above an energy of 100-200 MeV, for the design of a cost effective machine in terms of both capital and operational costs. In this paper we review the design of the INFN/ENEA TRASCO high-energy accelerator.         Temperature optimization for superconducting cavities    C.H. Rode Summary: Since our previous analysis of optimized operating temperature of superconducting cavities in an accelerator a decade ago, significant additional information has been discovered about SRF cavities. The most significant is the Q/sub 0/ (quality factor) shift across the Lambda line at higher gradients as a result of a slope in Q/sub 0/ vs. E/sub acc/ above Lambda. This is a result of the changing heat conduction conditions. We discuss temperature optimizations as a function of gradient and frequency. The refrigeration hardware impacts and changes in cycle efficiency are presented.         Feasibility study of Nb/Cu clad superconducting RF cavities    K. Saito, T. Fujino, H. Inoue, N. Hitomi, E. Kako, T. Shishido, S. Noguchi, M. Ono, Y. Yamazaki and V. Palmieri Summary: For the future large scale application of superconducting (SC) RF cavities like TESLA, one has to fabricate the cavities cheaply to achieve high gradients and high Q values (E/sub acc/>25 MV/m, Q>1/spl times/10/sup 10/). The amount of niobium material has to be decreased and the complex welding structure should be eliminated to reduce the fabrication cost. Here, the authors propose to fabricate seamless clad cavities of niobium and copper material and report the results of a feasibility study.         Thermal analysis of the APT power coupler and similarities to superconducting magnet current leads    J.A. Waynert, D.E. Daney and F.C. Prenger Summary: A detailed thermal analysis has been performed on the 210 kW, 700 MHz RF power coupler (PC) which transfers microwave energy from high power klystrons to the superconducting (SC) resonant cavities for the acceleration of protons. The work is part of the design for Accelerator Production of Tritium funded by the US Department of Energy. The PC is a co-axial design with the RF power transmitted in the annular region between two concentric cylinders. The PC provides a thermal connection from room temperature to superconducting niobium operating at 2.15 K. Heat transfer mechanisms considered are conduction, infra-red radiation, RF joule heating in normal and superconducting materials, and, forced and natural convection cooling. The objective of the thermal analysis is to minimize the required refrigeration power subject to manufacturability and reliability concerns. The problem is reminiscent of the optimization of superconducting magnet leads. The similarities and differences in the results between SC leads and PCs are discussed as well as the critical parameters in the PC optimization.         Performance of the FEL cryomodules    M. Drury, J. Fischer, J. Preble and Q.-S. Shu Summary: The Thomas Jefferson National Accelerator Facility (Jefferson Lab, formerly known as CEBAF) is building a highly efficient, kilowatt-level infrared free-electron laser, the IR Demo FEL. The IR FEL uses superconducting radiofrequency (SRF) cavities to accelerate the electron beam that provides energy for the laser. These cavities provide the high-gradient acceleration for the high average currents necessary for a compact FEL design. Currently, a quarter cryomodule injector and a full eight-cavity cryomodule have been installed in the FEL linac. These units were tested as part of the IR FEL commissioning process. The main focus of these tests was to determine the maximum stable operating gradient. The average maximum gradient reached by these ten cavities was 11 MV/m. Other tests included measurement of cavity parameters such as the unloaded Q (Qo) vs. gradient, the input coupling, calibration of field probes and behavior of the tuner mechanisms. This paper presents the results of those tests.         Statistical analysis of cavity RF faults    J.F. Benesch Summary: During commissioning of the CEBAF accelerator, it was found that cavities could not be operated reliably at the gradients achieved for short periods during individual cavity commissioning. The principal hypothesis for the cause of about two thirds the faults seen is charging of the cold ceramic RF window, which is 7.6 cm off the beam axis. Beginning in February 1995, most RF systems faults were automatically logged. Simple statistical analysis of the accumulated fault data was first applied in July 1995, with a substantial drop in fault rate recorded. The intent of the analysis was to predict the gradient for each cavity at which it would fault once every ten days, leading to a fault rate for the machine of about 33/day (330 cavities). This analysis method was pursued through July 1996 with substantial benefit. Cavity gradients were increased thereafter to obtain information for an upgrade to 6 GeV, with concomitant fault rate increases. In late 1996 and early 1997, in situ helium discharge processing was employed in 88 cavities to reduce field emission. The methods used for the analysis of 30000+ faults recorded between February 1995 and December 1997 are presented. Comparisons of performance before and after helium processing are presented.         Effect of oxygen on RF properties in a single domain YBCO cavity resonator for microwave applications    Dehui Qu, B.A. Tent, Donglu Shi, Shih-Lin Lu, A.M. Ferendeci and D. Mast Summary: A cylindrical single domain superconducting cavity resonator for microwave applications has been made by a net-shape melt processing using YBCO. The quality factor (unloaded Q) has been measured on the cavity sample, below the transition temperature, T/sub o/ in microwave frequencies. Experiments have been carried out to study the dependence of Q on the annealing temperature, as well as the influence of oxygen annealing history on Q value. Other factors, which influence the Q value, are also discussed.         Preparation and RF tests of L-band superconducting niobium-coated copper cavities    P. Bosland, A. Aspart, E. Jacques and M. Ribeaudeau Summary: The development of niobium sputter coated copper cavities is in progress for high gradient applications. Single cell 1.5 GHz cavities have been prepared and tested at CEA Saclay. Performances better than the CEBAF and TTF specifications have been reached: Q/sub 0/=1.7 10/sup 10/ at low field, and E/sub acc/=25 MV/m with Q/sub 0/=1.5 10/sup 9/ limited by the power supply. The high pressure rinsing performed at 30 and 85 bars suppressed field emission without stripping off the coating from the copper surface.         Study of the surface resistance of niobium sputter-coated copper cavities    C. Benvenuti, S. Calatroni, I.E. Campisi, P. Darriulat, M.A. Peck, R. Russo and A.-M. Valente Summary: A systematic study of the superconducting properties of niobium films deposited on the inner wall of copper radiofrequency cavities is presented. Films are grown by sputtering with different discharge gases (Xe, Kr, Ar and Ar/Ne mixtures) on substrates prepared under different conditions. The measured quantities include the surface resistance at 1.5 GHz, the critical temperature and the penetration depth. The surface resistance is analyzed in terms of its dependence on temperature, RF field and the density of trapped fluxons. Once allowance for electron scattering is made by means of a single mean free path parameter, good agreement with BCS theory is observed. The residual resistance is observed to be essentially noncorrelated with the superconducting properties, although influenced by specific coating conditions. On occasions, very low residual resistances, in the nano-ohm range, have been maintained over a broad range of RF field, indicating the absence of fundamental limitations specific to the film technology in practical applications.         A scheme of Maglev vehicle using high T/sub c/ bulk superconducters    Wang Jiasu, Wang Suyu, Ren Zhongyou, Dong Xiaogang, Lin Guobin, Lian Jisan, Zhang Cuifang, Huang Haiyu, Deng Changyan and Zhu Dequi Summary: High T/sub c/ superconductors are highly attractive because they can operate at liquid nitrogen temperature. The high performance of high T/sub c/ bulk superconductors is exciting to people in the application research work on superconducting magnetic levitation (Maglev) vehicle. The Maglev concept using high T/sub c/ bulk superconductors has been demonstrated by the Beijing Small Model. In this paper, schemes relating to the use of high T/sub c/ YBaCuO superconducting bulk materials for Maglev vehicle are discussed. First, the YBaCuO bulk superconductors are arranged above the rail using NdFeB permanent magnets. The second scheme is the electromagnetic suspension (EMS) Maglev vehicle using high T/sub c/ superconducting permanent magnets (SCPM) or high T/sub c/ superconducting wire. The third is the EMS Maglev using high T/sub c/ SCPM. The third scheme is chosen after making a comparison. The key problems of the EMS Maglev vehicle using high T/sub c/ SCPM are discussed.         Vibration isolation for space structures using HTS-magnet interaction    Jang-Horng Yu, E. Postrekhin, Ki Bui Ma, Wei-Kan Chu and T. Wilson Summary: We employ the HTS-magnet interaction in the mechanical design of a vibration isolator. One common element of space structures is the coupling between multiple substructures or mechanical parts. Often, such coupling needs to provide a transmission of force between the two systems while blocking out the propagation of the vibration energy from one system to the other. A solution to this is to establish a soft link between the two systems. In this paper, we design a passive vibration isolation device employing the characteristics of the HTS-magnet interaction. The configuration of the vibration isolator consists of a ring magnet and a thin disk HTS where the HTS is located in the middle of the magnet and is levitated. Experiments show that the natural frequency of the system is 4 Hz and the frequencies above 10 Hz are successfully isolated. Such a passive device in space applications is superior to similar active devices that often require bulky control circuit boxes and consume considerable energy that is not readily available in the space environment. The concept can also be used as an isolation platform and can combine with the active vibration isolation technology so as to attenuate the vibration of all frequencies.         Characterization of superconducting bearings for lunar telescopes    Eunjeong Lee, Ki Bui Ma, T.L. Wilson and Wei-Kan Chu Summary: The hybrid superconductor magnet bearing system for a lunar telescope has been developed based on passive magnetic levitation and the flux pinning effect of high-temperature superconductivity. The rationale lies in the unique capability of high-temperature superconductors (HTS) to adapt to the low temperature and vacuum environments in space or on the Moon, and to enhance system stability passively without power consumption. Characterization experiments have been conducted to understand its dynamic behavior and to estimate the required motor torque for its driving system design. Characterization experiments show that the hybrid HTS-magnet bearing system has periodical oscillation of drag torque. The bearing also suffers from small periodic oscillation on top of it due to discontinuous distribution of HTS. However, the magnitude of drag torque is velocity independent and very small. It makes the bearing attractive for high speed application. Finally, design guidelines for superconducting bearing systems are suggested based on experimental results.         Beam confinement magnets based on single-grain Y-Ba-Cu-O    A.C. Day, M. Strasik, D. Garrigus, K.E. McCrary, T.S. Luhman and W.P. Geren Summary: Flux-trap magnets based on high-temperature superconductors were studied for their potential as electron-beam control elements. Applications could include accelerators, klystrons, and MM-wave amplifiers. The authors have constructed compact magnets using bulk YBCO crystals that exhibit axial fields of 1.0-1.2 T at operating temperatures from 65 K to 77 K. Transverse fields and field stability have also been measured. Finally, methods and mechanisms involved in pulse-charging the superconducting rings are discussed.         Fabrication of Bi-2212/Ag magnets for high magnetic field applications    M. Okada, K. Tanaka, T. Wakuda, K. Ohata, J. Sato, H. Kumakura, T. Kiyoshi, H. Kitaguchi, K. Togano and H. Wada Summary: Bi-2212/Ag multifilamentary tapes show practical transport properties in high magnetic field regions above 20 T and 4.2 K, where it is considered difficult to use metallic superconductors. In this paper, the recent progress of the authors' development for the Bi-2212/Ag insert magnets is presented. The Bi-2212/Ag stacked double pancake coils with a 45-150 mm outer diameter, 15-55 mm inner diameter and 50-220 mm in height have been fabricated and tested in various backup magnetic fields up to 20 T at the Tsukuba Magnet Laboratory of NRIM. A high resolution X-ray CT apparatus was used to observe a cross section of the magnet nondestructively. The transport properties of the magnets are discussed in relation to the defects of the coil identified by this X-ray CT observation.         Recent progress of HTS magnet using Bi-2223 Ag-sheathed wire    K. Ohmatsu, S. Hahakura, T. Kato, K. Fujino, K. Ohkura and K. Sato Summary: The authors have succeeded in developing two types of refrigerator cooled high-Tc superconducting magnets-a high magnetic field type and a large bore type. The high magnetic field type has a room temperature bore of 50 mm, an inner diameter of 80 mm and an outer diameter of 300 mm. The coil height is 200 mm, using 24 double pancakes. The magnet generated 7.1 T over 24 hours and was excited at a rate of 7 T/minute. This high ramp rate was ten times faster than that of a refrigerator cooled magnet using metallic superconducting wires. The large bore type magnet has a room temperature bore of 280 mm, an inner diameter of 400 mm and an outer diameter of 520 mm. The coil height is 18 mm using 2 double pancakes. The magnet generated 0.17 T and was excited at a rate of 0.034 T/s. These two types of HTS magnets, produced by using only Bi-2223 Ag-sheathed tapes, have been continuously operated at 20 K for practical applications.         Development of a 1 T cryocooler-cooled pulse coil with a Bi2223 superconducting parallel conductor for SMES    M. Iwakuma, K. Funaki, K. Kajikawa, H. Kanetaka, H. Hayashi, K. Tsutsumi, A. Tomioka, M. Konno and S. Nose Summary: The authors designed and fabricated a 1 T cryocooler-cooled pulse coil operating at 40 K. A 4-strand interlayer-transposed parallel conductor composed of Bi-2223 rectangular cross-sectional multifilamentary wires was adopted to realize a uniform current distribution and to reduce the AC loss density down to the level of that of a single strand. The pulse coil is a 16-layer solenoidal one with an inner diameter of 52 mm, an outer diameter of 111 mm and a height of 120 mm. The heat drains of AlN plates, which are insulators, are arranged between layers for the cooling of the heat due to the AC loss by heat conduction. They could continuously operate the coil in a triangular waveform mode with an amplitude of 1 T and a frequency of 1 Hz. The AC loss was 10.6 W and the other thermal load was 13 W.         Experimental results of the model coil for cooling design of a 1 T cryocooler-cooled pulse coil for SMES    A. Tomioka, T. Bohno, S. Nose, M. Konno, M. Iwakuma, K. Funaki, K. Kajikawa, H. Kanetaka, H. Hayashi and K. Tsutsumi Summary: The authors have been developing high-Tc superconducting coils for SMES applications. Their primary goal is to make a HTS coil which is cooled to 40 K by a single-stage cryocooler and continuously operated at 1 Hz with a field amplitude of 1 T. The coil has heat drains of AlN plates to remove heat because of AC losses. They made a cooling model coil system to study the effective arrangement of the heat drains. The system consisted of a model coil using Cu conductors, current leads and a cryocooled system. The test coil was divided into three sections in different arrangement of heat drains. The model coil was daubed with a high thermal conductivity epoxy resin to improve thermal contact resistance between the conductors and AlN plates. They tested the coil by Joule heating which was equal to AC losses. They measured the temperature distribution in the coil and the temperature difference between Cu conductors and AlN plates. The temperature difference was measured between 0.2 K and 0.7 K. The results will be applied to the 1 T HTS coil design.         Development of high temperature superconducting coils using Bi-2223/Ag tapes    A.B. Sneary, C.M. Friend, P. Richens, H. Jones and D.P. Hampshire Summary: Four double wound pancakes with inner diameters of 98 mm have been successfully fabricated with multifilamentary Bi-2223/Ag tape using the react and wind technique. Two pancakes were impregnated with wax and the other two with resin. The pancakes have been tested at 77 K producing critical current (I/sub c/) values up to 14.5 A and index of transition values (n) of up to 11.4. The field profiles produced by the pancakes have been modelled. The I/sub c/ field dependence of short samples of the component Bi-2223/Ag tape has been studied. I/sub c/ is most sensitive to field when the field is parallel to the c-axis of the tape, reducing I/sub c/ from 28 A to 13.2 A between 0 T and 30 mT. Although the bending strain of the tape in the coil is /spl sim/0.3%, the fabrication procedure for the pancakes has produced very little handling damage to the tapes. It is demonstrated that the I/sub c/ of the coils is almost entirely self field limited.         Performance of DC reactor type fault current limiter using high temperature superconducting coil    M. Yamaguchi, S. Fukui, T. Satoh, Y. Kaburaki, T. Horikawa and T. Honjo Summary: The purpose of this work is to study a DC reactor type fault current limiter (FCL) using high temperature superconducting (HTS) coil which is connected with the secondary winding of a transformer through a diode bridge. The high temperature superconductors provide the advantages of a higher temperature operation and they are preferably applied to the DC reactor type fault current limiters, where a superconducting coil can be operated at both low voltage and DC current. The authors propose a DC reactor type three-phase FCL incorporating only one HTS coil and present its test result. A three-phase FCL for 6.6 kV-2000 A requires one HTS coil of 2.9 MJ.         Transport current properties of double-pancake coils wound by Ag-sheathed Bi-2223 tapes    S. Torii, S. Akita, K. Ueda, H. Okamoto, K. Honda, K. Tsutsumi and F. Irie Summary: In order to apply high T/sub c/ superconducting (HTS) tape to the power apparatus, it is necessary to evaluate the property of the coil shape. In particular, the stability of the coil is important, because it is expected to influence both the machine design and the operating conditions. In order to study the feasibility of HTS power application, they used double-pancake coils wound by Ag-sheathed Bi-2223 multi-filament tapes, and measured the transport current properties. From the experimental and analytical results, it was noted that the HTS double-pancake coils exhibited very stable properties, even beyond the critical current of coils. They believe that they can show the possibility of application of the HTS tape to the winding of power apparatus, although further improvements in superconducting properties of the tapes are needed. The stabilities of HTS and LTS (low T/sub c/ superconductor) are quite different, so it is also necessary to establish an analytical method for determining the stability of HTS winding.         Performance test of a refrigerator cooled magnet fabricated using Bi-2212 multilayer superconducting tapes    T. Hasegawa, Y. Hikichi, T. Koizumi, N. Ohtani, H. Kurnakura, H. Kitaguchi and K. Togano Summary: A stacked pancake coil was fabricated by Ag-alloy sheathed Bi-2212 multilayer tapes and tested using a refrigerator. The magnet consisted of ten double pancakes wound with 100 m class tapes. The I/sub c/ values of the tapes varied from 80 A to 150 A at 4.2 K and 10 T because of the scattering of the thickness in the superconducting layers. The magnet carried a critical current of 57 A at 12 K and generated B/sub max/ of 1.4 T in a 60 mm bore. At 12 K, the magnet could operate with an operating current of 45 A which corresponded to about 80% of I/sub c/. Thermal runaway was not observed even with a ramp rate of 10 T/min.         Transport properties of Bi-2212/Ag multifilamentary tape under a large electromagnetic stress state    T. Wakuda, M. Okada, S. Awaji and K. Watanabe Summary: Transport and mechanical properties of two Bi-2212 superconducting coils under a large hoop stress were measured. The coils were 11-turn R&W type double pancake coils with an outer diameter of 280 mm reinforced against electromagnetic stress by co-winding with an Ag-50%Cu or a Hastelloy X tape. They were measured in an external magnetic flux density of 10 T and liquid helium (4.2 K). Critical current of the coil with the Ag-50%Cu reinforcement tape was 240 A and its transport property was severely degraded by more than 0.4% deformation at I=388 A. The coil with the Hastelloy X tape with a critical current of 350 A, showed good performance against an electromagnetic stress of 262 MPa at I=500 A and could repress deformation of the coil to within 0.22%.         HTS insert coils for high field NMR spectroscopy    D.W. Hazelton, Xing Yuan, H.W. Weijers and S.W. Van Sciver Summary: The availability of high field insert coils will extend the operating point of future NMR systems above the 1 GHz level. We report here on the continuing development of HTS insert coils fabricated with BSCCO-2212 surface coated (SC) superconductor in a tape form. In addition, we review a number of issues associated with the application of HTS superconductors to high resolution NMR. The latest conductor and coil test results to date are presented for a prototype layer wound magnet with a 52 mm bore. In order to accommodate the high stresses associated with high field operation, a nested set of coils is utilized. This coil set provided up to an additional 1.9 Tesla central field while operating at 4.2 K in a 19 Tesla background field.         Optimum reduction of self field effects in a Bi-2223 stacked superconducting bus bar    Wansoo Nah, Hyoungku Kang, Il-Han Park, Jinho Joo, Sang-Soo Oh, Kang-Sik Ryu and Jaimoo Yoo Summary: High T/sub c/ superconductors, such as Bi-2223, have been promising candidates for an electrical busbar because the busbar has a relatively low self magnetic field. It has been found that the critical current of Bi-2223 stacked tapes is much less than the total summation of critical currents of each tape, which is mainly attributed to the self magnetic fields. Furthermore, since the critical current degradation of Bi-2223 tape is greater in the normal magnetic field (to the tape surface) than in the parallel one, detailed magnetic field configurations are required to reduce the self-field effects. Conceptually, by rearranging each stacked tape properly, the self field effects could be minimized. In this paper, we calculate the self field effects of a stacked conductor, defining self field factors of normal and parallel magnetic fields to the tape surface. We propose an optimum shape of octagonal structured busbar which has minimum self field effects.         Superconducting axial bearing for induction machines with active radial magnetic bearings    R. Nicolsky, Y. Gorelov, A.S. Pereira, D.F.B. David, A. Santisteban, R.M. Stephan, A. Ripper, R.D. Andrade Jr., W. Gawalek, T. Habisreuther and T. Strasser Summary: A superconducting passive axial bearing has been developed for an induction machine with vertical rotor and two active radial magnetic bearings, resulting in a fully levitating system. This prototype has been designed on the basis of a previous one reported by Salazar-Stephan as a 4-pole 2-phase induction machine using windings of a standard motor. Each active radial bearing measures four shaft-positions using eddy-current sensors, each displaced by 90 degrees. The levitation has been performed using two NdFeB permanent magnets and bulk pieces of seeded-melt-textured YBCO. The YBCO pieces have been characterized by measuring the levitation forces and mapping the remanent magnetic field with Hall probes. The radial stability of the system is modeled and discussed.         Superconducting magnetic bearings for energy storage flywheels    T. Coombs, A.M. Campbell, R. Storey and R. Weller Summary: We are investigating the use of flywheels for energy storage. Flywheel devices need to be of high efficiency and an important source of losses is the bearings. In addition, the requirement is for the devices to have long lifetimes with minimal or no maintenance. Conventional rolling element bearings can and have been used, but a noncontact bearing, such as a superconducting magnetic bearing, is expected to have a longer lifetime and lower losses. We have constructed a flywheel system. Designed to run in vacuum this incorporates a 40 kg flywheel supported on superconducting magnetic bearings. The production device will be a 5 kW device storing 5 kWh of retrievable energy at 50000 rpm. The Cambridge University system is being developed in parallel with a similar device supported on a conventional bearing. This will allow direct performance comparisons. Although superconducting bearings are increasingly well understood, of major importance are the cryogenics and special attention is being paid to methods of packaging and insulating the superconductors to cut down radiation losses. The work reported here is part of a three-year program of work supported by the EPSRC.         A measurement of rotation loss characteristics of high-Tc superconducting magnetic bearings and active magnetic bearings    H. Kameno, Y. Miyagawa, R. Takahata and H. Ueyama Summary: As the demand for electric power has been increasing steadily, the introduction of a flywheel energy storage system (FESS) using a superconducting magnetic bearing (SMB) is needed to level daily load as much as possible (daily load-leveling). We have studied rotation loss characteristics of SMBs with high Tc superconductors (YBCO) and permanent magnets (PM) for supporting a flywheel in FESS. We have designed and manufactured a testing machine for measuring rotation loss characteristics of SMBs. The rotor is suspended by two sets of radial active magnetic bearings (RaAMBs), a set of axial active magnetic bearings (AxAMB) and a set of SMB. Then, we obtained rotation loss characteristics of the rotor levitated by RaAMBs, AxAMB and SMB on this testing machine.         Flux-trapping characteristics of oxide superconducting bulks in array    H. Kamijo, T. Higuchi, H. Fujimoto, H. Ichikawa and T. Ishigohka Summary: The authors are investigating the possibility of using bulk magnets in the Maglev system. It is considered that bulk magnets for the Maglev system must be composed of numerous superconducting bulks arranged in rows and columns for each magnet pole because a bulk superconductor with a high critical current density doesn't have a sufficiently large size for Maglev magnet. Therefore, it is necessary to examine the flux-trapping characteristic of superconducting bulks arranged in array. Flux-trapping experiments are performed using the melt-processed YBaCuO superconducting bulks arranged in rows and columns, in which each bulk individually has a magnetizing coil, and the bulks are magnetized by field cooling. It is found that, when the superconducting bulks are arranged in rows and columns, the trapped flux density and the generated magnetic field are smaller than those when a superconducting bulk is used alone. The rate of decreases in the trapped flux density and the generated magnetic field becomes larger with increases in the number of superconducting bulks arranged in array. The trapped flux decreases conspicuously in particular at a superconducting bulk surrounded by other superconducting bulks.         Three-dimensional structure of magnetic field in the mixed-/spl mu/ levitation system using bulk superconductors    Y. Fukasawa and H. Ohsaki Summary: A permanent-magnet type mixed-/spl mu/ levitation system, which only needs an iron, permanent magnets and bulk superconductors, can realize an advantageous levitation system-for example, for transportation over a relatively long distance because of its simple structure and stable levitation without active control. A three-dimensional numerical analysis of electromagnetic force characteristics in the mixed-/spl mu/ levitation system is carried out and the results of the analysis are compared with experiments. From these results, the authors have confirmed that the three-dimensional structure of the magnetic field and the electromagnetic performance of superconductors strongly influence the characteristics of the electromagnetic force acting on the iron, which become unstable in some cases.         Electromaglev-levitation data for single and multiple bulk YBCO disks    Y. Iwasa, H. Lee, M. Tsuda, M. Murakami, T. Miyamoto, K. Sawa, K. Nishi, H. Fujimoto and K. Nagashima Summary: This paper presents recent results of a small-scale electromaglev experiment, focusing on lift data for YBCO samples of a 30-mm/spl phi/ single disk and multiple disks comprised of seven, six, and three 10 mm/spl phi/ disks. The data are interpreted with the zero-order theory developed earlier. A phenomenological scaling law that correlates lift forces among samples has been developed.         Levitation characteristics of the HTSC-permanent magnet hybrid flywheel system    S. Ohashi, S. Tamura and K. Hirane Summary: A basic experimental device for a flywheel system using high temperature superconducting material (HTSC) is introduced. In this system, a circular shaped permanent magnet is installed on the rotor, and a YBaCuO plate is used for the stator. To increase the levitation force of the flywheel, an additional circular permanent magnet is installed under the YBaCuO plate in the stator. The maximum levitation force and rotational loss were examined. From the experimental results, this hybrid system shows better levitation characteristics than that without an additional permanent magnet.         Fabrication of HTS monoliths for a bearing system in a cryogenic vessel    A. Leenders, M. Ullrich, H.C. Freyhardt, M. Kesten, H. Fieseler, W.R. Canders, H. May, H. Weh, S. Gauss and J. Beck Summary: Melt-textured YBCO monoliths were prepared by the top-seeded-melt-growth (TSMG) method with quadratic shape and dimensions of 38 mm/spl times/38 mm/spl times/12 mm. Generally, 16 samples of that size are prepared in one batch by carefully adjusting the processing parameters. Typical values of the maximum frozen-in field vary from 600-700 mT. A remarkably high value of 865 mT was recorded for a sample with dimensions of 17 mm/spl times/17 mm/spl times/12 mm. The levitation forces of these samples typically amount to 60-70 N. A demonstration model of a cryogenic vessel using arrangements of TSMG-YBCO monoliths and permanent magnets showed an improved performance compared to that of a conventional vessel.         A 0.5 kWh flywheel energy storage system using a high-T/sub c/ superconducting magnetic bearing    Y. Miyagawa, H. Kameno, R. Takahata and H. Ueyama Summary: A flywheel rotor having a main shaft, two flywheel disks and one permanent magnet for a SMB (superconducting magnetic bearing) was designed and manufactured. The flywheel was made of CFRP material which is light weight and has high tensile strength. The permanent magnet was hooped by CPRP in order to prevent centrifugal bursting. The rotor was levitated by a SMB in the axial direction. The radial vibration of the rotor was damped by active magnetic bearings. The superconducting magnetic bearing was made of YBa/sub 2/Cu/sub 3/O/sub 7-X/ which had a strong pinning force. The whole rotor system was stably accelerated up to 30000 rpm by an induction motor in a vacuum chamber, and then its energy storage value reached 479 Wh. In this paper, the rotor design, bearing and rotational properties of the rotor are discussed.         Development of a modified superconducting magnet for Maglev vehicles    H. Nakao, T. Yamashita, Y. Sanada, M. Yamaji, S. Nakagaki, T. Shudo, M. Takahashi, A. Miura, M. Terai, M. Igarashi, T. Kurihara, K. Tomioka and M. Yamaguchi Summary: In superconducting magnets for magnetically levitated transport system's (Maglev) vehicles, mechanical loss occurs due to the vibration caused by electromagnetic forces during the train's operation. The heat load including the mechanical loss needs to be reduced within the capability of the onboard refrigerator. It is necessary that the vibration phenomena of the superconducting magnet during the train operation are made clear for the reduction of the mechanical loss. As an important part of the development, it was confirmed that the vibration analysis is accurate enough in comparison with the measured results in running tests on the Yamanashi Maglev Test Line. Moreover, for commercial use, superconducting magnets should be operated with no supply of either liquid helium or liquid nitrogen. To meet the requirement, we have been developing a new type on-board Gifford-McMahon refrigeration (GM refrigerator application) system.         Cryotank with superconducting, magnetic suspension of the interior tank    S. Gauss, J.H. Albering, J. Bock, M. Kesten, H. Fieseler, W.R. Canders, H. May, H.C. Freyhardt and M. Ullrich Summary: A cryotank for liquefied hydrogen for automotive application was developed with considerably improved heat insulation and thus prolonged holding time. This goal was achieved by the contact free suspension of the interior tank with the help of high-temperature superconductors and strong permanent magnets. Here, the large bulk parts made of both melt processed YBCO and melt cast process BSCCO 2212 are placed on the interior container. Comparative measurements with a similar conventional hydrogen tank showed that the new storage improves the insulation quality of the container by 50 percent. Thus time almost doubles during which hydrogen can be stored without any losses.         Completion and trial operation of the superconducting magnets for the Large Helical Device    T. Satow, N. Yanagi, S. Imagawa, H. Tamura, K. Takahata, T. Mito, H. Chikaraishi, S. Yamada, A. Nishimura, R. Maekawa, A. Iwamoto, N. Inoue, Y. Nakamura, K. Watanabe, H. Yamada, A. Komori, I. Ohtake, M. Iima, S. Satoh and O. Motojima Summary: The Large Helical Device (LHD) is a plasma physics experimental device having two superconducting helical coils and three pairs of poloidal coils. All assembly and attachment works of LHD were completed in January 1998. The trial operation and the first plasma ignition of the eight-year Phase I project for LHD were finished in March just as planned. After that time the first cycle plasma experiment was carried on at a plasma central field of 1.5 T. The second cycle experiment is now conducted. The LHD magnets will be excited to a central field of 3.0 T in December 1998.         Strand resistance distribution in an improved full size joint for the ITER conductors    P. Bruzzone Summary: An improved joint layout is proposed for the electrical connections of the large Nb/sub 3/Sn cable-in-conduit conductors for the central solenoid and toroidal field coils of ITER, International Thermonuclear Experimental Reactor. The driving design criteria are a reliable electrical performance and an easy manufacturing procedure, limiting the risk of failure and allowing generous assembly tolerances. The development results are reported, as well as the manufacture of a hairpin joint using sections of the ITER CS conductor. The joint sample has been used to investigate the resistance between strand pairs belonging to the two conductor sections. From the distribution of the strand-to-strand resistance, it is possible to infer the current distribution in the conductor under DC conditions, which is a crucial issue for the stability analyses.         Field emission and thermal breakdown in superconducting niobium cavities for accelerators    J. Knoblock Summary: Field emission and thermal breakdown are the main mechanisms limiting the accelerating gradient of niobium radiofrequency cavities. Diagnostic tools to study these mechanisms include quality measurements, thermometry and microscopy. Results presented here demonstrate that micron-size, conducting particles are the source of field emission. Thermal breakdown is caused by a variety of defects such as inclusions, pits and submillimeter-size particles. Techniques developed to minimize field emission and thermal breakdown include clean-room assembly, high-power processing (to avoid field emission) and the use of high-purity niobium (to avoid thermal breakdown). With these techniques, accelerating gradients of 20-30 MV/m can be achieved in niobium cavities.         High gradient superconducting niobium cavities. A review of the present status    P. Kneisel Summary: Superconducting niobium cavities used in particle accelerators are limited in their RF performance by two phenomena: quench field levels below the theoretical limit of the material caused by defects; and field emission loading resulting from artificial contamination of the superconducting surfaces during surface treatment and assembly procedures. In recent years, the community involved in SRF technology developments has successfully improved cavity performances by applying advanced surface treatment methods such as chemical polishing, electropolishing, tumbling, high temperature heat treatment, high pressure rinsing, "in situ" high peak power processing and clean room assembly procedures. In addition, improvements in the material properties such as thermal conductivity by "solid state gettering" and very strict QA methods, both in material inspection and during cavity fabrication, have resulted in cavity performance levels of E/sub acc/ up to 40 MV/m in monocells and gradients in the vicinity of 30 MV/m in multicell structures at Q-values of /spl ap/10/sup 10/ at a temperature of 2 K. More recently, the fabrication of "seamless" cavities by spinning is being pursued with encouraging results. This process eliminates electron beam welds, which sometimes are the cause of performance degradations.         Development of superconducting cavities for high intensity proton accelerator at JAERI    N. Ouchi, J. Kusano, N. Akaoka, S. Takeuchi, K. Hasegawa, M. Mizumoto, H. Inoue, E. Kako, S. Noguchi, M. Ono, K. Saito, T. Shishido, K. Mukugi and Y. Honda Summary: The Japan Atomic Energy Research Institute (JAERI) is proposing a high intensity proton accelerator for the Neutron Science Project. A superconducting (SC) RF structure is the main option for the high energy part of the linac. Design and development work of the SC proton linac is in progress in JAERI. Three single-cell SC prototype cavities were fabricated and their performances were tested. The test results were good enough to apply to the SC linac. This paper describes the present status of the design and development work for the SC proton linac.         New technologies in superconducting cavity fabrication    V. Palmieri Summary: Besides the progressive achievement of higher and higher accelerating fields, the drastic reduction in resonator production costs is compulsorily for the feasibility of building more and more powerful particle accelerators. If costly and time-consuming electron beam welds can be avoided, a significant saving in manufacturing costs can be achieved by seamless cavities produced by means of simple and cheap fabrication techniques. The paper reviews the status of those new forming techniques, such as hydroforming or spinning, under development in several laboratories and suitable for prototype fabrication and, at least in principle, applicable to mass scale production.         Test results on the long models and full scale prototypes of the second generation LHC arc dipoles    J. Billan, M. Bona, L. Bottura, D. Leroy, O. Pagano, R. Perin, D. Perini, F. Savary, A. Siemko, P. Sievers, G. Spigo, J. Vlogaert, L. Walckiers, C. Wyss and L. Rossi Summary: With the test of the first full scale prototype in June-July 1998, the R&D on the long superconducting dipoles based on the LHC design of 1993-95 has come to an end. This second generation of long magnets has a 56 mm coil aperture, is wound with 15 mm wide cable arranged in a 5 coil block layout. The series includes four 10 m long model dipoles, whose coils have been wound and collared in industry and the cold mass assembled and cryostated at CERN, as well as one 15 m long dipole prototype, manufactured totally in industry in the framework of a CERN-INFN collaboration for the LHC. After a brief description of particular features of the design and of the manufacturing, test results are reported and compared with the expectations. One magnet reached the record field for long model dipoles of 9.8 T but results have not been well reproducible from magnet to magnet. Guidelines for modifications that will appear in the next generation of long magnets, based on a six block coil design, are indicated in the conclusions.         Superconducting magnets for the interaction region of KEKB    K. Tsuchiya, T. Ogitsu, N. Ohuchi, T. Ozaki, N. Toge and H. Sakurabata Summary: A superconducting final focus magnet system for the interaction region of KEKB was constructed. It consists of two solenoid field compensation magnets and two superconducting quadrupoles with three kinds of correction coils. The system test has been successfully completed. This paper describes the design, construction and the test results of these magnets.         The use of superconducting solenoids in a muon collider    M.A. Green, Y.M. Eyssa, J.R. Miller, R.B. Palmer and R.J. Weggel Summary: Superconducting solenoids are integral part of the proposed muon collider and Higgs factory. Superconducting solenoids that produce inductions up to 15 T will be used to capture pions that are produced by a proton beam impinging on a target contained within the solenoid. After the pions are captured they are phase rotated and allowed to decay to muons. The phase rotation and pion decay channel keeps the pions and muons captured in a 1.25 T rotation system. Superconducting solenoids will also be integral part of the muon cooling system. Within the muon cooling channel, which is projected to be up to 300 meters long, solenoidal fields up to 30 T are needed. This report presents the latest thoughts on how superconducting solenoids will be used as part of the muon collider.         Application of electrical and calorimetric methods to the AC loss characterization of cable conductors    G. Coletta, L. Gherardi, F. Gomory, E. Cereda, V. Ottoboni, D. Daney, M. Maley and S. Zannella Summary: Due to higher currents (and therefore higher losses) compared to individual wires and tapes, the AC loss characterization of HTS cable conductors carrying transport current can be performed using calorimetric as well as electrical methods. We discuss the main features of two calorimetric methods, one based on temperature profile determination, and one based on nitrogen boil-off rate, and of the electrical method, substantially derived from that already established for tapes, based on voltage measurement by a lock-in amplifier. Advantages and limits of each approach are analysed and compared. Tests have been carried out with the three methods on samples 1 to 1.5 m long cut from a Bi-2223 cable conductor prototype fabricated by Pirelli in a longer length. Results obtained from measurements covering a wide range of currents are compared and thoroughly discussed.         Current distributions and AC losses in self-fields for superconductor tapes and cables    T. Fukunaga, R. Inada and A. Oota Summary: The alternating current losses in self-fields for superconductor tapes are investigated using numerical calculations. In the calculation, the current distributions and self-field losses for straight superconductors with the arbitrary sectional geometry are calculated as a parameter of current amplitude. For the 7-filamentary tapes, the losses depend on the filament configurations, which is also observed experimentally in the 7-filaments samples. In the case of cables, the values of the losses are strongly influenced by the tape arrangements. The losses for altered cables, which are composed of a number of similar tapes, are different from each other. These results suggest that the optimization of tape and cable structure, i.e. the arrangement of the superconductor cores in the cables, is useful to reduce the loss generation in the cables.         AC losses due to magnetic fields and transport currents    S.P. Ashworth and M. Suenaga Summary: The AC losses in a superconductor subjected both to an applied field and transport current may be considered as the losses of two power supplies, one providing the field the other driving the transport current, to the HTS sample. We present a brief justification of our method to measure these losses and then give the results of simultaneous measurements of the losses of both these power supplies to an HTS tape in an AC applied field and carrying an AC or DC transport current. The magnetic losses for the case of field applied perpendicular to the tape face are shown to be very much larger than for the field parallel case, but both are small compared to the transport losses in the regions of field and currents of practical interest (i.e. when the superconductor is carrying currents comparable to the critical current).         Effect of combining a DC bias current with an AC transport current on AC losses in a high temperature superconductor    P. Dolez, B. Des Ligneris, M. Aubin, Wen Zhu and J. Cave Summary: Creating complex flux configurations by superposing a DC current or magnetic field onto the AC current in a type II superconducting tape should lead to a variety of peculiar behaviors. An example is the appearance of the Clem valley, a minimum in the AC losses as a function of the DC bias amplitude, which has been theoretically studied by LeBlanc et al., in the continuation of Clem's calculations. These situations have been investigated by applying a DC current to a silver-gold sheathed Bi-2223 tape at 77 K (critical current 29 A), in addition to the usual AC transport current. The AC losses were measured by the null calorimetric method to ensure that the total losses were being accounted for. These were recorded for different values of the AC and DC currents, leading to the observation of two different behaviors depending on the AC current. Our revelation of the Clem valley is, to our knowledge, the first experimental validation of this phenomenon in high temperature superconductors, and may provide a simple way of reducing the AC loss in industrial applications of these materials.         Electromagnetic and mechanical characterisation of ITER CS-MC conductors affected by transverse cyclic loading. I. Coupling current loss    A. Nijhuis, N.H.W. Noordman, H.H.J. Ten Kate, N. Mitchell and P. Bruzzone Summary: The magnetic field generated by a coil acts on the cable which results in a transverse force on the strands. This affects the interstrand contact resistances (R/sub c/), the coupling current loss and current redistribution during field changes. A special cryogenic press has been built to study the mechanical and electrical properties of full-size ITER conductor samples under transverse, mechanical loading. The cryogenic press can transmit a variable (cyclic) force up to 650 kN/m to a conductor section of 400 mm length at 4.2 K. The jacket is partly opened in order to transmit the force directly onto the cable. In addition a superconducting dipole coil provides the magnetic field required to perform magnetisation measurements using pick-up coils. The various R/sub c/'s between strands selected from different positions inside the cable have been studied. The coupling loss time constants (n/spl tau/) during and after loading are verified for the Nb/sub 3/Sn, 45 kA, 10 and 13 T, ITER Model Coil conductors. A summary of the results obtained with up to several tens of full loading cycles is presented. A significant decrease of the cable n/spl tau/ after several cycles is observed. The values of the n/spl tau/'s are discussed with respect to the R/sub c/ measurements and a multiple time constant model (MTC).         Quench characteristics in HTSC devices    T. Kiss, M. Inoue, K. Hasegawa, K. Ogata, V.S. Vysotsky, Yu. Ilyin, M. Takeo, H. Okamoto and E. Irie Summary: Quench dynamics in a YBCO HTSC film and a Bi-based small HTSC coil have been studied. While the stability margin of HTSC against a local disturbance was very large, quench current was limited by a catastrophic temperature rise originated from the nonlinear characteristic of Joule heating in HTSC. The crucial parameter for the quench becomes the nonlinear resistance in HTSC as a function of temperature and transport current. It has been shown that the dynamic characteristics of the quench in both the film and the coil can be described quantitatively by the simplified one-dimensional heat balance equation even though the time scales are different by more than six orders, i.e., several hundreds micro seconds for the film and several hundreds seconds for the tape coil.         Quench propagation properties in HTS pancake coil    S. Shimizu, A. Ishiyama and S.B. Kim Summary: In this paper, the authors present the results of experiments and computer simulations to make clear the quench propagation properties in Bi-2223/Ag superconducting multifilament tape. They developed a computer code based on the two dimensional finite element method (2-D FEM). Computed voltage and temperature traces during a quench agree well with the experimentally recorded voltage and temperature traces. Good agreement validates the computer code, making a useful tool in developing protection strategies for high-temperature superconducting (HTS) coils. Therefore, they simulate the quench process in a single pancake coil wound with Bi-2223/Ag superconducting multifilament tape with background magnetic field up to 10 T at 20 K using the developed computer code. The quench propagation properties and stability in HTS coils are discussed and compared with those in low-temperature superconducting (LTS) coils.         Quench characteristics of Bi-2223 coil at liquid helium temperature    S.S. Oh, Q.L. Wang, H.S. Ha, H.M. Jang, D.W. Ha, K.S. Ryu and W. Nah Summary: The quench characteristics of Bi-2223 single and four double pancake coils operating at liquid helium temperature were investigated based on experiments and numerical simulations. Broad resistive transition was observed in the double pancake coils. The Bi-2223 double pancake coil operating at liquid helium showed a slow normal zone propagation velocity. The stability margin of the coil was confirmed to be high because of the low operating temperature and a good cooling condition. The quench characteristics of a four double pancake coil system was simulated by a numerical method. It is clear that the protection resistance has a great influence on the current decay, transient voltage and hot-spot temperature.         Quench characteristics of parallel circuit of two mechanical PCSs    S. Ohtsuka, T. Nakamura, D. Tsuji, J. Suehiro and M. Hara Summary: In order to increase current capacity of a mechanical persistent current switch (PCS) which realizes zero contact resistance, parallel connection is suitable for no reduction in the total OFF resistance due to infinite OFF resistance of each PCS. In this study, a mechanism of the sequential quench in the parallel circuit of two mechanical PCSs was clarified by numerical analysis of changes in the currents before and after the quench as well as by considering the quench time lag property investigated with the pulsed current. Additionally, it was discussed whether a quenched PCS in the parallel circuit could recover its superconducting state by making it open and then close again.         Quench propagation in large area YBCO films    V.S. Vysotsky, Yu.A. Ilyin, T. Kiss, M. Takeo, M. Lorenz, H. Hochmuth, J. Schneider and R. Woerdenweber Summary: We studied quench propagation in double-sided samples of YBCO thin films covered by a gold top layer and deposited on sapphire wafers. The length of the YBCO structures was up to 0.5 m. A critical current density /spl sim/2-3 MA per centimeter square at 77.8 K was found over the entire YBCO film. Quench development in large-area YBCO thin film appears to be a complicated process. Depending on test conditions and external circuit parameters, normal spots may appear and disappear during the quench process. In double-sided samples quench development is strongly affected by thermal interaction between the two films through the substrate's heat conductivity. This thermal conduction should be considered during the design of fault current limiters made from such films. Mutual thermal interaction of a film through a substrate may also be used for acceleration of normal zone propagation using active or passive heaters on opposite sides of the substrate.         Current transfer lengths in multifilamentary superconductors with composite sheath materials    M. Dhalle, L. Porcar, M. Ivancevic, A. Polcari, Y.B. Huang, G. Witz and R. Flukiger Summary: We describe current transfer processes between a metallic matrix and superconducting filaments through high-resistance layers, using a simple model to analyze current-voltage data of composite superconductors in terms of basic material parameters. Multifilamentary high Tc conductors nearly always consisted of ceramic filaments embedded in a uniform metallic matrix. This has changed with the introduction of highly resistive barrier layers, aimed at reducing filament coupling under alternating-field conditions. While such layers indeed have significant effects on the AC loss properties of the conductor, they also tend to complicate issues such as current injection at terminals and current 'healing' around local filament defects. In order to gain a better understanding of these processes, we use a simple and quantitative model which relates the barrier and matrix resistivity directly to a characteristic current transfer length. This relation can be used to gain direct experimental access to the electrical barrier properties. We illustrate its usefulness with typical data obtained on composite-sheathed Bi(2223) tapes.         Heat transfer characteristics of Rutherford-type superconducting cables in pressurized He II    N. Kimura, A. Yamamoto, T. Shintomi, A. Terashima, V. Kovachev and M. Murakami Summary: The heating induced by beam-loss in superconducting cables must be absorbed by pressurized He II through the cable insulation in operation of the LHC accelerator superconducting magnets. As a fundamental study, the heat transfer characteristics through the insulated cable to pressurized He II were measured in case of "Rutherford" type compacted strand cables. This report describes the experimental results and discusses possible heat transfer models.         The protection system of the superconducting coils in the Barrel Toroid of ATLAS    E. Acerbi, M. Sorbi, G. Volpini, A. Dael and C. Lesmond Summary: An analysis of the discharge of the Barrel Toroid under several operating conditions has been carried out. The main critical parameters of the discharge (i.e. the maximum temperature inside the coils, the maximum temperature gradient, the maximum voltage at the coil ends and the maximum decentering forces acting on the BT and ECT magnets) have been calculated for several operating conditions (heaters on, heaters off, short circuit with heaters on or off). The aim of this analysis is to provide a cross check of the protection design of the Barrel Toroid coils with an independent study. The results validate the choice to use a low value of dump resistance, and give some important warning in the case of heater failure or presence of a short circuit.         Quench protection studies of short model high gradient quadrupoles    R. Bossert, J. DiMarco, S. Feher, J. Kerby, M.J. Lamm, P.J. Limon, A. Nobrega, D. Orris, J.P. Ozelis, J. Strait, M.A. Tartaglia, J.C. Tompkins, A.V. Zlobin and A.D. McInturff Summary: High gradient quadrupoles (HGQ) being developed for the CERN Large Hadron Collider (LHC) interaction regions will rely on strip heaters for quench protection. Tests were performed on strip heaters in two locations on 1.9 meter model quadrupoles to study heater response times from strip heater induced quenches and quench velocities and peak temperatures from spot heater induced quenches. The results for the two heater locations are presented and compared to prediction.         Transient stability of LHC strands    D.E. Baynham, D.A. Cragg, R.C. Coombs, P. Bauer and R. Wolf Summary: The Large Hadron Collider (LHC) machine will operate at 1.9 K in order to achieve the high bending fields required in the dipole magnets. The cable and coil matrix is designed to be 'porous' in order to allow the He II coolant to penetrate within the cable for stability enhancement. This paper describes transient stability measurements and theoretical modelling carried out on single strands from the LHC cable. The experimental work has been carried out at the Rutherford Appleton Laboratory under an agreement with CERN. The aim of the experimental work has been to measure the influence of the strand surface treatment on the quench energy. The surface treatment, oxidized copper, tin-silver, nickel etc., determines the transient heat transfer coefficients to the He II under high heat flux, short timescale (approximately 20 microseconds) conditions. The test equipment, based on an inductive heating technique, is described and quench energy measurements presented. The experimental results are compared with theoretical models developed at CERN and RAL in order to derive the heat transfer coefficients.         Stability test results on the aluminum stabilized superconductor for the helical coils of LHD    N. Yanagi, T. Satow, T. Mito, S. Imagawa, K. Takahata, A. Iwamoto, H. Chikaraishi, S. Yamaguchi, S. Satoh, O. Motojima, S. Noguchi and A. Ishiyama Summary: Stability tests have been carried out on short samples of the aluminum/copper stabilized composite-type superconductors developed and used for the pool-cooled helical coils of the Large Helical Device. The waveform of the longitudinal voltage initiated by resistive heaters shows a short-time rise before reaching a final value, which seems to correspond to the diffusion process of transport current into the pure aluminum stabilizer. The propagation velocity has a finite value even for the transport current being lower than the recovery current, and it differs depending on the direction with respect to the transport current.         Quench heater simulation for protection of superconducting coils    Y.M. Eyssa, W.D. Markiewicz and C.A. Swenson Summary: Protection of large energy stored epoxy impregnated magnets requires careful design and analysis of protection heaters which are attached to the winding of a solenoid at a specified radial position (usually the winding outer surface) and at periodic circumferential locations. The heaters can be activated passively or actively depending on the desired protection scheme. The heaters are insulated from the winding by glass cloth and in some cases are sandwiched between the winding and a steel overband for structure support. An update report on the National High Magnetic Field Laboratory (NHMFL) efforts on quench heaters design, simulation and analysis is presented. All protection analysis discussed is based on internal dump.         Possible solution of the "single strand stability" problem-special cable design    V.S. Vysotsky, Yu.A. Ilyin, K. Kajikawa, K. Funaki, M. Iwakuma, M. Takeo and T. Kumano Summary: The widely used multistrand superconducting cables demonstrate quench current degradation in AC mode. Often it happens due to premature quench of one strand. It was suggested that changing of the cable's design may improve the "single strand stability", or stability of a cable in relation to the quench of a single strand. We are checking this idea by testing several AC multistrand superconducting cables made from insulated superconducting strands with different cabling technique. We determined their quench current at different frequencies and current redistribution process in case of the quench of one single strand. The experimental results are presented and influence of the cable design on the "single strand stability" is discussed.         Quench time lag and its statistical characteristics of NbTi mechanical PCS measured with pulsed current    J. Suehiro, D. Tsuji, K. Tsutsumi, S. Ohtsuka and M. Hara Summary: This paper describes quench time lag characteristics of NbTi mechanical PCS through which pulsed current flows. The quench of the mechanical PCS takes place when the switch current is slowly increased and exceeds a critical value I/sub T0/. On the other hand, quench of the PCS through which pulsed current flows does not occur at the moment of the instantaneous current exceeding I/sub T0/, but takes place after a time delay T/sub D/. The quench time lag T/sub D/ depends on rise time and peak value of the pulsed current I/sub p/. A theoretical model is proposed to show that T/sub D/ corresponds to time in which a superconducting connection bridge is heated up to a critical temperature mainly by flux flow loss. T/sub D/ sharply fluctuates when I/sub p/ is just over the static critical current I/sub T0/, but remarkably decreases when I/sub p/ is further increased. It is found that statistical characteristics of T/sub D/ are well fitted to the Weibull distribution function.         Dependence of quench current level of superconducting wire and cable on the winding tension    H. Shimizu, T. Shiroki, Y. Yokomizu and T. Matsumura Summary: Mechanical instabilities in an AC Nb-Ti superconducting wire and cable are experimentally investigated. The quench current levels of the sample conductors were measured for different winding tensions and current increase rates. We have developed a new type of experimental bobbin to apply the tension uniformly and to adjust it to the specified value from the outside of the cryostat. It is found that the influence of the mechanical instabilities on the quench current level decreases with an increase in the winding tension and/or the current increase rate.         Influence of thermal expansion of coil bobbins made of DFRP and GFRP on quench characteristics of superconducting coils    T. Takao, K. Watanabe, T. Kubosaka, T. Suzuki, T. Kashima, A. Yamanaka and S. Fukui Summary: We have excited two types of superconducting coils having same specifications. One is made of DFRP (Dyneema(R) fiber reinforced plastic) bobbins which expands during cooling process from room temperature to liquid helium temperature. The other is made of GFRP (glass fiber reinforced plastic) bobbins which contract during the cooling process. Firstly, we have numerically estimated changes of winding tensions of the two types of the coils by the cooling down. And then, training behaviors of the DFRP and GFRP coils wound with the same winding tension at room temperature were measured. Influence of quench currents in the training quenches and the number of quenches to reach to the maximum currents on the winding tensions at liquid helium temperature is systematically discussed.         Minimum quench energies of LHC strands    P. Bauer, R. Wolf, L. Oberli and M.N. Wilson Summary: Within the framework of the LHC project a program has been initiated at CERN to establish the influence of various strand parameters (coating, Cu/Sc ratio, RRR, billet design, cooling) on the minimum quench energy (MQE) of LHC prototype strands operating in superfluid helium at 1.9 K in peak-fields of 9 T. The experimental technique is based on a graphite-paste tip heater. The analysis of the measurements was facilitated by a theoretical model based on the numerical solution of the one-dimensional heat balance equation.         Tip heater for minimum quench energy measurements on superconducting strands    P. Bauer, J. Donnier and L. Oberli Summary: Superconducting strands can be characterized by their minimum quench energy (MQE), i.e. the minimum heat pulse needed to trigger a quench in operation conditions (field, temperature, current), in the limit of a (temporally and spatially) /spl delta/-shaped disturbance. The sub-mm//spl mu/s range of perturbation space has only been achieved using the electrical graphite-paste heater technique. The present work has put this technique into practice for the strands of the LHC main magnets, which are designed to operate at 1.9 K in peak fields of up to 9 T. No way has been found yet to calibrate MQE measurements. To make relative statements on the MQE of different samples possible, the reproducibility of the measurements was emphasized. First heater prototypes did not come up to this stipulation. Finally the tip-heater configuration was found to meet the requirements. It generates a heat pulse in a thin resistive graphite paste deposit on top of a small tip that is pressed against the sample with a clamp. The clamp guarantees a maximum of exposure of the sample to the surrounding cryogen. The most striking aspect of repeated measurements on a reference sample is that in open bath conditions the MQE as a function of transport current in subcooled helium can reach hundred times the corresponding value in adiabatic conditions (i.e. with the sample potted in a low conductivity medium). This extraordinary cooling performance of superfluid helium, predicted by many has rarely been shown in superconductor stability experiments.         Stability measurements of Rutherford cables with various treatments    S.W. Kim, D. Leroy, M.N. Wilson, A.K. Ghosh and W.B. Sampson Summary: To improve the stability of Rutherford type superconducting cables, various methods of treating cables were considered and tested. These treatments include strand coating, partial soldering, "barber-pole" insulation and "porous metal" solder filling. To study the effect of these treatments, several cables were prepared and MQE (minimum quench energy) values were measured. Coating, partial soldering or "barber-pole insulation" improved the relative stability for some cables. The "porous metal" filled cables showed higher MQE. However the results suggest that the porous metal process needs to be improved. The measured data for cables with various treatments are presented.         Behaviour of copper matrix in quench process calculated by 2-strand 4-wire model    S.W. Kim and D. Leroy Summary: In a simulation of a superconducting strand, it is usual to treat the strand as superconducting wire and copper wire in a parallel connection. When simulating a multi-stranded cable, strands are treated as a mixture of superconductor and copper, usually. All parameters are calculated from a combination of those for superconductor and copper. This means the role of copper was just changing properties of the strand. However in real current transition process, the copper matrix may play a role of a path of current and heat. In this paper, one strand is considered as two wires; superconductor and copper, and calculations were done for a cable with two strands. The simulation model and some results which show behavior of the copper matrix in quench process are presented in this paper. The difference between 'matrix heating' and 'filament heating' is also discussed.         A method to evaluate the temperature profile in a superconducting magnet during a quench    V. Maroussov and A. Siemko Summary: A simple method to derive the temperature profile in a superconducting magnet during a quench from measured voltage signals is described. The method was applied to several Large Hadron Collider single aperture dipole models. These measurements show the strong correlation between parameters of the magnet protection system and powering on the one hand and the resulting temperature gradient in the magnet coil on the other. The method allows the localisation of critical points in the magnet design, in particular, the efficiency of the magnet protection system can be evaluated.         The response characteristics of cowound voltage sensors in cable-in-conduit conductor    Yong Chu, Ho Min Kim, Tae Kuk Ko and Kee Man Kim Summary: When a superconducting magnet is exposed to time-varying, nonsymmetrical transverse and parallel fields, the balanced bridge for quench detection is ineffective. To make quench detection possible, the inductive voltage must be reduced, or canceled, to a level less than the resistive voltage due to quench. The internal cowound voltage sensors in the cable cross-section as the primary mechanism to cancel the inductive noise are analyzed and tested in this research. The signal to noise ratio under a variety of conditions with different sensor locations, field sweeping rates and quenched lengths are improved to a factor of 1000 or more by using cowound voltage sensors.         Time-frequency distribution of acoustic emission signals induced from a rotating NbTi superconducting winding    K. Arai, H. Nomura, N. Higuchi, I. Ishii, H. Tateishi, S. Sekine, N. Natori, S. Fuchino, H. Yamaguchi, K. Kaiho, K. Tsugawa and K. Fujima Summary: Experimental analyses using the time-frequency distribution of acoustic emission (AE) signals were studied in terms of quench propagation along a NbTi superconducting winding in a rotor cooled by liquid helium. Data acquisition of the AE signals was carried out with a sampling frequency of 2 MHz to cover almost the full frequency range of the signals. Short-time spectrum analyses were performed for the AE signals when the voltage between taps at the superconducting winding rose after applying heat energy to the winding. A similar test with a heat pulse of lower energy, which did not cause quench propagation, were also carried out. The spectra in this case are equivalent to the background noise of the AE signals in the quench case, and so the AE components resulting from the quench propagation can be estimated.         A European project on the AC losses of Bi-2223 tapes for power applications    C.M. Friend, C. Beduz, B. Dutoit, R. Navarro, E. Cereda and J. Alonso-Llorente Summary: The progress of a European-funded project on the ac losses of Bi-2223 tapes for power applications, co-ordinated by BICC Superconductors, is partially reviewed. Results of loss measurements by four of the partners are presented including: a round-robin of electrical measurements; a consideration of the influence of the E-J characteristic; measurements at frequencies up to 2.5 kHz and a measurement of the losses in a twisted tape due to an applied AC field.         Measuring AC-loss in high temperature superconducting cable-conductors using four probe methods    A. Kuhle, C. Traeholt, S. Kruger Olsen, C. Rasmussen, O. Tonnesen and M. Daumling Summary: Measuring the AC-loss of superconducting cable conductors have many aspects in common with measuring the AC-loss of single superconducting tapes. In a cable conductor all tapes are connected to each other and to the test circuit through normal metal joints at each end. This makes such measurements considerably more complex, especially for samples of laboratory scale (1-5 meters). Here we discuss different measurement configurations using four probe methods and lock-in detection. We conclude that the voltage should be picked up at end of the connecting joints, and we show how the resistive contribution from these joints can be identified and subtracted from the measured data. We also show measurements which indicate that the size of the loop constituted by the voltage leads has no influence on the measurements.         Oxide barriers and their effect on AC losses of Bi,Pb(2223) multifilamentary tapes    Y.B. Huang, M. Dhalle, F. Marti, G. Witz, R. Flukiger, St. Clerc and K. Kwasnitza Summary: The transverse electrical resistivity in multifilamentary Ag/Bi, Pb(2223) tapes is considerably enhanced after introducing inert oxide barriers, a new concept in which each single filament is surrounded by a highly resistive BaZrO/sub 3/ layer of <2 /spl mu/m thickness. With these oxide barriers, we have so far obtained a shift of the AC loss maximum from 5 Hz to >100 Hz. This corresponds to a marked lowering of AC coupling losses. The highest critical current density of these tapes is actually 15000 A/cm/sup 2/ at 77 K, 0 T, i.e. still below that of our tapes without barriers (35000 A/cm/sup 2/). The fabrication processes leading to Bi,Pb(2223) tapes with oxide barriers is described, with an emphasis on new deformation processes developed in our laboratory for the fabrication of long multifilamentary Bi,Pb(2223) tapes, comprising four roll (or two-axes) rolling and periodic pressing. The developed tapes with oxide barriers are promising in view of their use in transformers and cables.         Reduction of AC loss in Ag sheathed PbBi2223 tapes with twisted filaments in external and self-fields    Yifeng Yang, T.J. Hughes, E. Martinez, C. Beduz and F. Darmann Summary: The hysteretic AC losses in multifilament tapes can be reduced by filament twisting with a pitch shorter than a critical pitch which is dependent upon the material parameters of the tape and dB/dt. To determine the effectiveness of twisting, measurements of AC losses have been carried out on Ag sheathed multifilamentary PbBi2223 tapes with different twist pitches (minimum 10 mm). Self-field loss measurements showed clear uncoupling of filaments for current up to 50% of Ic for a twist pitch shorter than 15 mm. In parallel external fields, the effect of filaments uncoupling by twisting was identified with 10 mm pitch showing a reduction in the hysteretic loss of the superconducting core, at power frequency, between 10 mT and 35 mT. This corresponds well with the theoretical predictions for a tape with a twist pitch of 10 mm and Ic=40 A (/spl sim/20 kAcm/sup -2/) operating at 43 Hz. We also observed that the losses in the normal matrix are dominant for fields above 30 mT although losses in the superconductor are reduced by twisting.         Dependence of AC transport current losses of HTS wires on their structures and synthesizing processes    O. Tsukamoto, D. Miyagi, S. Ishii, N. Amemiya, S. Fukui, O. Kasuu, H. Li, K. Takeda, M. Shibuya, M. Mimura, K. Hayashi and H. Yoshino Summary: HTS wires of various structures and synthesizing processes are being developed for power apparatus applications in the Super-GM project. AC transport current losses of four of those wires were measured by an electric method using a lock-in amplifier. Measured wires are a Bi2212 rod fabricated by the laser pedestal growth method, a Y123 tape fabricated by the pulsed laser deposition and multilayered Bi2223/Ag sheathed wires of square and tape shapes. In this paper, based on measured data, dependence of AC transport current losses of HTS wires on their structures and synthesizing processes is discussed.         Magnetisation and transport current loss of a BSCCO/Ag tape in an external AC magnetic field carrying an AC transport current    J.J. Rabbers, D.C. van der Laan, B. ten Haken and H.H.J. Ten Kate Summary: In practical applications, BSCCO/Ag tapes are exposed to external AC magnetic field and fed with an AC transport current. The total AC loss can be separated in two contributions: first, the transport current loss influenced by an external AC magnetic field, and second, the magnetisation loss that depends on the transport current running through the conductor. In this paper the total AC loss is considered and the role of the electric and magnetic components is compared. This comparison is made with an available analytical model for the AC loss in an infinite slab and verified experimentally for a BSCCO/Ag tape conductor. For small transport currents the magnetisation loss dominates the total loss. When the current increases, a field dependent crossover occurs, after which the transport current loss also plays a role. Qualitatively the measurements can be described well in terms of the critical state model. For magnetic field parallel to the wide side of the conductor the CSM for an infinite slab describes the measurements also quantitatively.         Recent progress on 70 MW class superconducting generators    T. Shimada, M. Shibuya, R. Takahashi, Y. Imai, H. Kusafuka, R. Shiobara, K. Yamaguchi, M. Takahashi, K. Suzuki and K. Miyaike Summary: Super-GM has been continuously developing 70 MW class superconducting model generators to verify the basic technologies required for the design and manufacture of a 200 MW class superconducting pilot generator. Three types of 70 MW class superconducting model generators, two slow response excitation type and a quick response excitation type, have been developed on the project. A test run for one of the slow response excitation type generators was completed successfully in December 1997. The other slow response excitation type generator is undergoing a verification test at the Super-GM Testing Center. On the other hand, factory test of the quick response excitation type rotor is finished. This paper describes the progress of the Super-GM activities together with the latest test results.         Measurement and analysis of 70 MW superconducting generator constants    K. Ueda, R. Shiobara, M. Takahashi and T. Ageta Summary: The constants of a superconducting synchronous generator (SC-generator) were measured to prove its design method and electromagnetic analysis. This paper describes the test results related to the measurements of synchronous machine constants, and the comparison between the test results and the values which are calculated by a 3 dimensional finite element method (3D-FEM) for the electromagnetic analysis of SC-generator. The test items compared with the analysis are no load saturation curve of armature voltage at rated speed, armature current of steady state short circuit, air gap magnetic flux to add the armature current and synchronous reactance (Xd). The constants for the transient state of SC-generator were measured by three-phase sudden short circuit current. The effect to improve the electric power system stability is analyzed by decreasing Xd of SC-generator and by comparing the stability of a conventional generator for the same power system disturbances.         Status of the 1000 HP HTS motor development    D. Aized, B.B. Gamble, A. Sidi-Yekhlef, J.P. Voccio, D.I. Driscoll, B.A. Shoykhet and B.X. Zhang Summary: Progress has been made in the development of high efficiency HTS motors with the aid of Department of Energy funding under the Superconductivity Partnership Initiative. This effort includes the fabrication and testing of synchronous motors with HTS field windings. The objectives of this development effort include saving half the losses of conventional motors in a package with half the volume. In Phase I of the present program, a 125 HP synchronous motor with an HTS field winding was designed and tested to levels in excess of 200 HP. This paper summarizes the status of a 1000 HP motor development which is part of a Phase II effort. The program elements to be reviewed include the overall design characteristics of the motor, the status of the field coils and refrigeration system, and a description of other components of the 1000 HP motor system. The 1000 HP motor fully represents the design issues to be addressed in the 5000 HP motor also to be developed in Phase II.         Superconducting reluctance motors with YBCO bulk material    B. Oswald, M. Krone, M. Soll, T. Strasser, J. Oswald, K.-J. Best, W. Gawalek and L. Kovalev Summary: Superconducting reluctance motors with YBCO bulk material have been built and tested up to more than 10 kW. They have been operated in liquid nitrogen at 77 K, at different frequencies (speeds) and loads. The specific power achieved is significantly higher than that in conventional motors. The small size and low weight of such motors can be considered as important advantages for special applications. The test results and the theory applied are in good accordance.         150-kW experimental superconducting permanent-magnet motor    P. Tixador, F. Simon, H. Daffix and M. Deleglise Summary: A permanent-magnet motor with a superconducting armature associates the high current densities in superconductors and the simplicity of a rotating permanent-magnet inductor. Those characteristics make them very attractive drives for moving systems with low weight requirements. We carry out a research and development program on this structure. After a first 15-kW, 750-rpm successfully tested model, a demonstrator of 150-kW and 400-rpm has been built. The layout of this eight-pole, 150-kW machine is conventional with a horizontal axis and a rotating neodymium-iron-boron inductor cooled at 150 K. The three phase winding is made with a (6+1) superconducting ultra fine niobium-titanium cable. The 24 saddle-shape coils are distributed among four concentric tubes. Their holding has been well studied. The liquid-helium cryostat (1000 mm long and 630 mm in diameter) was built using essentially composites. It has successfully suffered first cryogenic and some electrical tests which are reported.         70 MW class superconducting generator test    K. Yamaguchi, M. Takahashi, R. Shiobara, T. Taniguchi, H. Tomeoku, M. Sato, H. Sato, Y. Chida, M. Ogihara, R. Takahashi and H. Kusafuka Summary: Since 1989 development of a practical superconducting generator has been carried out in Japan. The authors have developed a rotor having a superconducting field winding and a stator having an air gap winding composed of a double transposed copper coil. A series of tests were completed at the end of 1997. The output of 78.7 MW was recorded which is the highest value yet obtained world wide. Test results of the shop test in 1996 and the site test in 1997 and analysis are described.         Cryogenic and electrical performance at a factory test of a rotor for 70 MW class slow-response excitation type superconducting generator    K. Shimohata, I. Kodera, M. Morita, T. Inaguchi, H. Yoshimura, S. Nakamura, S. Maeda, K. Suzuki, A. Ueda and T. Hirao Summary: 70 MW class superconducting generators are under development as a national project in Japan. This is an eleven-year program which commenced in 1988. The manufacturing of the slow response excitation type rotor was completed at the beginning of 1996, and performance test of the rotor was carried out in the factory at the beginning of 1997. The factory test has been completed successfully. This paper describes the factory test results of the cryogenic performance and the electrical performance.         Design and construction of a superconducting cylindrical linear induction motor with AC superconducting primary windings    A. Ishiyama and K. Hayashi Summary: Levitated metal casting and superconducting elevators are but two of the potential applications of superconducting cylindrical linear induction motors (SCLIMs). We are constructing a model device to clarify the behavior of AC superconducting windings in a realistic operational environment of electrical rotating machines. This paper presents design, construction, and experimental results of the model SCLIM.         Turn off trigger energy characteristics of the superconducting power electronics device (S-PED)-in case of type d    T. Hoshino, M. Eguchi, T. Konishi, I. Muta, T. Nakamura, H. Tsukiji, Y. Noguchi and M. Suzuki Summary: S-PED means a superconducting power electronics device. We made some thermally controlled S-PED which is a normally-on device. They work up to 100 Hz as a full wave rectifier. For the power supply of superconducting magnets, the flux pump can be used as SPEED (superconducting power electronics excitation device). In this paper, we describe the turn off characteristics of one of the S-PED (type d). The relations between generated resistance, gate-trigger energy and channel current were obtained.         Requirements for the industrial application of superconducting rotating electrical machines    I. Vajda, A. Szalay, N. Gobl, V. Meerovich and V. Sokolovsky Summary: The objective of the project reported in the paper is the design and construction of an experimental high Tc (HTS) synchronous machine. The machine is excited with rare-earth permanent magnets on the rotor and rod-shaped armature conductors on the stator. The machine incorporates Bi-based HTS conductors supplied with electrical contacts. In the design procedure special attention has been paid to the considerations regarding industrial applications of HTS rotating electrical machines both in motor and generator modes of operation. Possible applications have been analyzed to formulate the requirements for the machine to be applied and calculations have been performed to check how the above requirements can be met by HTS machines. Comparisons have been made between conventional and HTS machines designed for particular practical cases.         Trapped-flux internal-dipole superconducting motor/generator    J.R. Hull, S. Sengupta and J.R. Gaines Jr. Summary: A new class of motor/generator utilizes the magnetic flux trapping capability of high-temperature superconductors (HTSs). The rotor consists of a cylindrical shell composed of HTS segments that act as trapped-field magnets, magnetized in such a way that a dipole magnetic field is produced in the interior of the shell. A stator coil assembly is placed in the interior of the shell, and current passing through the conductors of the coil produce a rotational torque, either as a hysteresis motor or as a synchronous motor. The coil may be either conventional, with copper wires and an iron core, or composed of superconductors that establish the trapped fields.         Performance of high temperature superconducting coils for implementation into megawatt class generators    A.J. Rodenbush and S.J. Young Summary: The United States Air Force and Ballistic Missile Defense Organization are developing a 1 MW exciter/generator for airborne applications. The exciter is constructed with an eight-pole external field winding and rotating hydrogen cooled armature with integral rectifier. The exciter was originally designed with high purity aluminum field coils cooled with liquid hydrogen. The United States Air Force is presently investigating the potential for replacing the aluminum field coils with high temperature superconductor (HTS) field coils cooled with hydrogen. Eight HTS racetrack-shaped field coils were built with BSCCO-2223 tapes for operation at 20 K. They were constructed to be consistent in geometry with the aluminum coils. The electrical performance of the HTS coils exceeded the required 72000 ampere-turns at the 1-/spl mu/V per cm electric field criteria. This paper reviews the design, construction and testing of the field coils and discusses the potential of this technology for airborne applications.         Conceptual design of a high temperature superconducting generator    S.K. Singh, D.W. Scherbarth, E.S. Ortoli, J.R. Repp, O.R. Christianson, J.H. Parker Jr., J.W. Carr Jr. and B. Gamble Summary: This paper describes the conceptual design of a high temperature superconducting (HTS) generator for mobile radar (MR) applications. The power system for MR consists of a diesel engine, a generator and power conditioning electronics. Significant improvements in power density, performance and system efficiency result if the generator and the power electronics are cryogenically cooled. The generator supplies power to the radar and the auxiliaries of the system. The generator output required is less than 50 volt AC (RMS phase to neutral) to maximize the efficiency of the cryogenically cooled power electronics. The auxiliaries of the system consume power at 120 V AC, 3-phase, at 60 Hz. The generator is designed to meet both requirements. The diesel engine provides the prime power to the generator at 1800 RPM. The generator is a four-pole two stator winding machine supplying power at 50 V AC, 60 Hz, 12-phase to the power electronics, and 120 V AC, 60 Hz, 3-phase to the auxiliaries of the system. The field winding of the generator consists of HTS coils; the stator has two ambient temperature air gap windings. The cooling of the field winding is provided by heat exchange with helium gas cooled by a Gifford McMahon cryocooler.         The design, manufacture and characteristic experiment of a small-scaled high-Tc superconducting synchronous motor    Myungkon Song, YongSoo Yoon, WonKap Jang, Taekuk Ko, GyeWon Hong and InBae Jang Summary: This paper describes a series of experiments investigating the operational characteristics of a high-Tc superconducting synchronous motor of five to six hundred watts capacity. In this experiment, AC 220 V stator phase voltage and DC 4 A excitation current are used, and the synchronous speed runs at 1800 rpm. Hall sensors are installed on the pole face and at the side of the Ag/Bi-2223 high-Tc superconducting tape in order to analyze the effect of the time-varying magnetic field on the motor performance when the load changes its value. The experimental observations are compared with the theoretical predictions.         Dynamic performance and design of a high-Tc superconducting synchronous motor    Minseok Joo and Tae Kuk Ko Summary: The electrical and electromechanical behavior of the high-Tc superconducting synchronous motor has been investigated. The rotor of a high-Tc superconducting synchronous motor is equipped with the high-Tc superconducting field winding and one or more flux dampers. Due to magnetic asymmetries in the case of the salient-pole machine, reference frame theory has been used to establish the machine equations which explain the flux damper placed on the rotor of the motor. After a description of a motor design concerning the density of the high-Tc superconducting wire, computer traces are given to illustrate the complete dynamic responses in various modes of operation, which are calculated by using a detailed set of nonlinear differential equations.         Radial and axial flux superconducting motors in a levitating rotor configuration    I. Marquez, X. Granados, X. Obradors, J. Pallares and R. Bosch Summary: The capability of superconducting blocks to be partially magnetized allows both bearing and powering functions in a conventional stator and superconducting rotor configuration. This levitating rotor concept is investigated by means of the basic parameters: torque, levitation and centering forces in two motors with radial and axial excitation respectively. We report on the design and behavior of a high speed motor with a cylindrical HTSC rotor excited by a conventional four poles four phases armature generating a radial field. We also report on a second motor with a disk shaped HTSC rotor excited by a conventional, four poles three phases, double armature which generates an axial field in the gap. Torque, power and centering and levitating forces measurements are also provided.         Development of superconducting DC machines using bulk YBCO    R.J. Storey, T.A. Coombs, A.M. Campbell, R.A. Weller and D.A. Cardwell Summary: An investigation is being made into building superconducting machines using YBCO bulks as quasi-permanent magnets. To investigate the performance of the superconductors in motor applications a test rig has been built in which a moving or vibrating magnetic field can be applied to the superconductor. The test rig allows two-dimensional motion of a magnet relative to a superconductor, in order that two-dimensional vibration modes can be investigated. This allows more accurate simulation of the conditions in a motor, and allows values of the absolute forces between magnet and superconductor during the motion to be inferred. The vibration methods used in the paper are suitable for measuring long-term behaviour of the superconductor-magnet interaction, including long-term decay of the trapped field when exposed to oscillations. The shorter tests reported here measure force/torque characteristics, and the stable limits of operation. Beyond these limits, a superconductor will be de-magnetised, resulting in a sudden loss of torque and machine damage.         Comparison of characteristics of large-scale high-Tc superconducting synchronous motor and conventional iron-core motor    Minseok Joo and Tae Kuk Ko Summary: The large high-Tc superconducting synchronous motors are expected to become cost-competitive with the conventional iron-core motors owing to the energy consumption and its small size and lightness compared to the copper field winding motors. The geometric and electromagnetic factors affect the performance of the high-Tc superconducting motors. The machine equations can be used directly to predict the performance of the motors by transforming the variables to a rotor reference frame. Computed results of the characteristics of the high-Tc superconducting synchronous motor and conventional motor are compared.         Hysteresis and reluctance electric machines with bulk HTS rotor elements    L.K. Kovalev, K.V. Ilushin, S.M.-A. Koneev, K.L. Kovalev, V.T. Penkin, V.N. Poltavets, W. Gawalek, T. Habisreuther, B. Oswald and K.-J. Best Summary: Two new types of HTS electric machines are considered. The first type is hysteresis motors and generators with cylindrical and disk rotors containing bulk HTS elements. The second type is reluctance motors with compound HTS-ferromagnetic rotors. The compound HTS-ferromagnetic rotors, consisting of joined alternating bulk HTS (YBCO) and ferromagnetic (iron) plates, provide a new active material for electromechanical purposes. Such rotors have anisotropic properties (ferromagnetic in one direction and diamagnetic in perpendicular one). Theoretical and experimental results for HTS hysteresis and reluctance motors are presented. A series of hysteresis HTS motors with output power rating from 1 kW (50 Hz) up 4 kW (400 Hz) and a series of reluctance HTS motors with output power 2-9 kW (50 Hz) was constructed and successfully tested by the cooperation of MAI (Moscow, Russia) and IPHT (Jena, Germany). It was shown that HTS reluctance motors could reach 2-5 times higher specific output than conventional asynchronous motors of the same size and will have higher values of power factor (cos/spl phi//spl ges/0.7-0.8).         AC losses in Bi-2223 tapes and in the 1-kA transmission line model    L.M. Fisher, A.V. Kalinov, S.E. Savel'ev, I.F. Voloshin, P. Haldar, H.W. Myron and U. Balachandran Summary: The authors present here results of their study of the 5 m long AC transmission line model with 1 kA current capability at 77 K. Primary attention was paid to the current characteristics and AC losses in individual tapes and in the core of the cable. The losses were measured as a function of AC magnetic field amplitude in various orientations of magnetic field with respect to the plane of the tape and filaments. Hysteresis losses were close to the losses in the AC regime, meaning that eddy current losses in tapes may be neglected when compared with hysteresis losses. They designed and constructed a 5 m long model of the AC transmission line using multifilamentary Bi-2223 tapes. The current core of the model contains 120 tapes for the forward line and 120 tapes for the backward line. AC losses in the current core were substantially greater than those seen in the individual tapes. The reason for this is related to a complex magnetic field distribution inside the current core.         Uniform current distribution conductor of HTS power cable with variable tape-winding pitches    S. Mukoyama, K. Miyoshi, H. Tsubouti, T. Yoshida, M. Mimura, N. Uno, M. Ikeda, H. Ishii, S. Honjo and Y. Iwata Summary: In the multilayer conductor, the inner layers have higher impedance than the outer layers. As a result, the current concentrates in the outer layers. Our early study showed that its AC losses were reduced to one-tenth by making the current of each layer uniform. From such a point of view, a trial to realize the uniform current distribution was made by adjusting the winding pitches of high-temperature superconducting (HTS) tapes layer by layer. A 1 m long conductor was fabricated, where the inner layer had longer winding pitch than the outer layer. Experimental results showed that the currents flowing in individual layers were almost the same and that this conductor had lower AC losses than the nonuniform current distribution conductor.         Design of a termination for a high temperature superconducting power cable    C. Rasmussen, A. Kuhle, O. Tonnesen and C.N. Rasmussen Summary: A cable conductor consisting of superconducting tapes wound onto a tight flexible tube (former) is placed inside a thermally insulating jacket (cryostat). This assembly is electrically insulated with an extruded polymer dielectric kept at room temperature. Cooling is provided by a flow of liquid nitrogen inside the former. The purpose of an end termination is to connect the superconducting cable conductor at cryogenic temperature to an electrical wire at room temperature and an external cooling machine at ground potential. Here we describe the design and construction of such an end termination. Aspects considered in the design include the thermal insulation of the termination, the transition from superconducting tapes to a normal conductor, the current lead carrying current between high and low temperatures, the transfer of liquid nitrogen over a high voltage drop and that of providing a well defined atmosphere inside the termination and around the cable conductor.         Conductor pitch effect on an eddy current loss of the superconducting power cable using the disassembled cable "N" data    T. Hoshino, M. Shibayama, S. Itoh, I. Muta, N. Higuchi, N. Natori, S. Fuchino and K. Arai Summary: The origin of the difference between measured AC loss and that of the short sample test has been studied. The axial field due to disordered pitch of conductor and shield tapes has a trivial effect on the eddy current loss in the stabilizer. The displacement of the current direction on the conductor from its lay angle makes comparable eddy current loss.         High current transport test of a YBCO bulk conductor up to 25 kA    K. Maehata, T. Taino, M. Mizokami, K. Ishibashi, M. Takeo, T. Mito, A. Iwamoto, S. Yamada, S. Sato, O. Motojima, T. Shintomi, M. Morita and T. Tokunaga Summary: A melt-textured YBCO bulk material was employed to obtain high current transport characteristics of a bulk high temperature superconductor. A disk-shaped YBCO bulk material 65 mm in diameter and 15 mm thick was fabricated by a modified quench and melt growth (QMG) process. An "H" shaped bulk conductor was cut from the YBCO disk. The cross sectional area and length of the conductor were 7 mm/spl times/7 mm and 20 mm, respectively. The bulk conductor was mounted in a high current bus line with a conductor-holder which allows high current feed and mechanical support against the thermal stress and electromagnetic force. Both ends of the conductor were soldered to electrodes of the conductor-holder. At 4.2 K, high current transport experiments were carried out up to 25 kA.         Power applications for superconducting cables in Denmark    S.K. Olsen, O. Tonnesen and J. Ostergaard Summary: In Denmark a growing concern for environmental protection has lead to wishes that the number of overhead lines is reduced as much as possible and that the energy supply should be shifted to renewable energy sources, e.g. windmills. Superconducting cables represent an interesting alternative to conventional cables, as they have other characteristics than conventional cables and will be able to transmit two or more times the current. Superconducting cables are especially interesting as a target for replacing overhead lines. Superconducting cables in the overall network are of interest in cases such as transmission of energy into cities and through areas of special beauty. The planned large groups of off-shore windmills in Denmark generating up to 400 MVA or more will be an obvious case for the application of superconducting AC or DC cables. These opportunities can be combined with other new technologies such as high voltage DC (HVDC) based on isolated gate bipolar transistors (IGBTs). The network needed in a system with a substantial wind power generation has to be quite stiff in order to handle energy fluctuations. Such a network may be possible, e.g., using superconducting cables.         Modelization and test of a 500 J superconducting pulsed power transformer    E. Floch, P. Hiebel, Y. Laumond and A. Lacaze Summary: The aim of this work is to prove the feasibility of pulses through the use of a power transformer. This article presents the design and tests of a 500 J pulsed power transformer. This paper also describes the computer code created to simulate the primary quench development. During the tests, the primary winding was charged to its rated current (500 A). The secondary being connected to a 0.7 m/spl Omega/ and 0.2 /spl mu/H load, we obtained through this load a pulsed discharge of 7.2 ms duration. The current rose to 12.3 kA in 0.5 ms and 38% of the energy stored in the primary winding was transferred to the load. This current and energy transfer between primary and secondary is the best one ever recorded for such a device.         Development of a three phase 100 kVA superconducting power transformer with amorphous cores    Ji-Kwang Lee, Woo-Seok kim, Song-Yop Hahn, Kyeong-Dal Choi, Gueesoo Cha and Seung-Chan Chang Summary: The advent of AC superconducting wires with ultra-fine filaments promoted the development of superconducting transformers, but most superconducting transformers with large capacity had been single phase ones. This paper describes the development of a 100 kVA three phase superconducting transformer (440/220 V). Fundamental characteristics of the transformer are obtained through no-load tests, short circuit tests and load tests under various conditions. The transformer cores are made of amorphous films and immersed in liquid helium with transformer windings for simplifying the structure of it. The losses and efficiency are analyzed.         Design method of volt/turn for minimizing life cost of a superconducting transformer    T. Ise and Y. Murakami Summary: Many transformers using low Tc or high Tc superconductors have been built and tested, but it is still not clear how to design the volt/turn ratio property. This paper shows one design method, which minimizes total cost including initial cost and running cost. According to the results, the optimized volt/turn will be around 1 volt which is considerably lower than the volt/turn ratio of a conventional transformer of 10 to 20 volts.         Analysis of a 3-phase air-core superconducting power transformer    H. Yamaguchi, T. Kataoka and Y. Sato Summary: The air-core superconducting power transformer has been investigated as one type of superconducting transformer. According to previous investigations, the air-core superconducting power transformer has many advantages compared to an iron-core superconducting or conventional power transformers. However, since these investigations about air-core superconducting power transformers have mainly been done for single-phase transformers, investigations of 3-phase transformers are indispensable as the next step. In this paper, results of previous investigations about single-phase air-core superconducting transformers, such as theoretical characteristics, are expanded into 3-phase. Then, the results of load tests obtained by using an experimental 3-phase air-core superconducting transformer are shown to confirm the results of the theoretical investigations.         Development of a 1 T/1 kA-class AC superconducting coil    H. Yamaguchi, K. Kaiho, K. Arai, H. Fuji, N. Sadakata, T. Saito, M. Yamaguchi and M. Yamamoto Summary: In order to develop AC superconducting apparatus for power use, 10 kA/sub r.m.s./-class AC superconducting coils should be developed. From such a viewpoint, the authors have been investigating AC superconducting coils having a large AC transport current capacity. In this paper, the specification and experimental results of an 1 T/sub r.m.s.//1 kA/sub r.m.s./-class AC superconducting coil are shown. Two experimental AC coils using the sub-cable and single strand of this AC superconducting coil are also fabricated and tested to investigate the stability of AC coils. The quench current of each AC coil is measured and is compared to the DC critical current characteristics of the strand. From the result of the comparison, it is confirmed that the AC quench current of each superconducting coil is close to the DC quench current, and is close to the current which is determined by the critical current characteristics defined by 0.1 /spl mu/V/cm criterion. It is also confirmed that the quench point of the developed AC coil reaches to 1.396 T/sub peak//1288 A/sub peak/.         Hybrid superconducting fault current limiter based on bulk melt textured YBa/sub 2/Cu/sub 3/O/sub 7/ ceramic composites    X. Granados, X. Obradors, T. Puig, E. Mendoza, V. Gomis, S. Pinol, L. Garcia-Tabares and J. Calero Summary: A hybrid fault current limiter (FCL) based on single domain bars of Y123/211 melt textured composites has been designed to operate at a 1 kV/400 A line. This consists of a conventional Cu primary coil inductively coupled to a secondary coil formed by the paralleling of single Cu turns each one shorted by a superconducting bar. The superconducting material has been prepared by the solidification techniques of Bridgman and top seeding in air which has allowed us to obtain bars with transport critical current densities of 20000 A/cm/sup 2/ at 77 K. Preliminary tests on the quench current, recovery time and AC-losses in normal operation have been performed. The differences and advantages of a hybrid FCL in comparison with a resistive and an inductive FCL is discussed.         kA class resistive fault current limiting device development using QMG HTC bulk superconductor    D. Ito, C. Yang, O. Miura, M. Morita and T. Tokunaga Summary: kA class HTC bulk superconducting elements of devices for a resistive type fault current limiter for 6 kV distribution networks have been developed and tested. The YBCO devices made with the quench melt growth (QMG) method has 20000 30000 A/cm/sup 2/ critical current densities at 77 K and 1 T determined by the 1 /spl mu/V/cm criterion for the current flow parallel to the a-b plane. The QMG device has 5 /spl mu//spl Omega/-m normal state resistivity and an n-value of approximately 6 for the same direction of current flow. An element of the device with a 1.5/spl times/1.5 mm/sup 2/ cross-section with silver electrodes formed by sputtering could successfully carry exceeding 2200 A/sub peak/ AC transport current in self field at 77 K.         S-N transitions of QMG current limiting elements with metal coat    M. Morita, T. Tokunaga, C. Yang, O. Miura and D. Ito Summary: To estimate the feasibility of resistive type FCL (fault current limiter) consisting of QMG (melt processed YBa/sub 2/Cu/sub 3/O/sub 7-x//Y/sub 2/BaCuO/sub 5/ composite bulk superconductor), S-N transitions of various metal-coated samples made from large bulk QMG were studied at 77.3 K and 87.3 K (boiling point of argon) using single rectangular pulse current. It was found that the metal coating dramatically improves the endurance of element against the current flow after S-N transition and that optimization of the endurance and resistance should be required to realize QMG-FCL.         Measurement of critical current and transient characteristics of a high-temperature superconductor tube with a pulsed current supply    Y.S. Cha, D.J. Evans and J.R. Hull Summary: The transient response of a melt-cast-processed BSCCO-2212 superconductor tube was investigated by using a pulsed current supply, it was found that (a) the maximum induced current and the excitation current at field penetration increase with the maximum excitation current, and (b) there is a time delay between peak excitation current and peak magnetic field inside the superconductor. These observations can be explained by magnetic diffusion. The AC steady-state critical current of the superconductor was found to compare favorably with that of the pulsed current test when the excitation current is relatively low, but it falls below that of the pulsed current test when the excitation current is relatively high.         Over critical-current behaviour of Bi-2223 tapes [for fault current limiters]    L. Le Lay, D.M. Spiller and O. Belmont Summary: The authors have tested the response of Bi-2223 tapes in over-critical current conditions with a view to exploring this material's prospects for fault current limiter applications. Silver and silver-alloy clad multifilamentary tapes have been put in series with a transformer and a resistor. Currents exceeding I/sub c/ were allowed to flow through the samples when the resistor was short-circuited. AC peak currents up to 100 I/sub c/ (about 2000 A) have thus been applied to the samples for up to 50 ms. The authors measured the samples' resistivity and electric field as a function of the applied current. Samples had a resistivity of 0.6 /spl mu/ohmcm for peak currents up to several tens I/sub c/ and no sample degradation was observed. However, a resistivity of nearly 10 /spl mu/ohmcm was measured for peak currents over 2000 A and samples were damaged by heating effects. The electric field was 2.2 V/m for a current of 400 A. Therefore, controlling a 400 A fault current (about 20 I/sub c/) would require 0.45 km of tape for a 1 kV fault current limiter.         Enhancement of power system transient stability using superconducting fault current limiters    M. Sjostrom, R. Cherkaoui and B. Dutoit Summary: Transient stability investigations consist of studying the rotor oscillations of generators (electro-mechanic oscillations, 0.1-2 Hz) after the occurrence of a fault of large amplitude, e.g. a short circuit. The goal is to indicate if the generators are capable to stay synchronous after a fault has occurred. The fault duration is one of the most important factors to be determined. In fact, the shorter the fault, the more the maintaining of synchronisation can be guaranteed. Now in case of a fault, a fault current limiter has an extremely fast current transition in comparison to electromechanical time constants. This implies a quasi-instantaneous elimination of the fault through a limitation of the current and consequently a better ability to maintain the synchronisation of the system. The authors recall that in a classic system, the elimination of a fault, by opening a circuit breaker, is carried out in two or three cycles in the best case. They have studied a simple, radial electric network configuration with a machine and an infinite network. The study covers simulations of a fault that can occur in a network and the consequences of the recovery time of the fault current limiter.         Characterisation of a high-T/sub c/ coil using short sample data    O.A. Shevchenko, J.J. Rabbers, H.J.G. Krooshoop, B. ten Haken and H.H. ten Kate Summary: Characteristics of a circular superconducting coil made with BSCCO-2223/Ag tape depend on the amplitude and direction of the magnetic field in the windings. The effect can be estimated by studying a short sample of the same tape. However, the loss voltage-current and the frequency characteristics of a coil deviate considerably from those that are measured on a short sample. In order to estimate the deviation, the authors compared measured characteristics of a few small coils employing up to /spl sim/10 m of tape with those calculated from the short samples data. The comparison includes several arrangements of coils and field shaping elements around the coil edges and is performed in the frequency and temperature range typical for power applications (1-100 Hz and 64-78 K respectively). The results are applied to the design of a 100 kVA-50 Hz resonator coil with a high quality factor.         Development of inductive fault current limiters up to 100 kVA class using bulk HTS materials    J. Cave, D. Willen, R. Nadi and Y. Brissette Summary: Since 1992, Hydro-Quebec has been developing prototypes of screened iron core fault current limiters for medium voltage distribution networks. Fault current limiters (FCLs) are amongst the most promising applications of high temperature superconductors. The unique properties of HTS such as high T/sub c/ and high resistivity in the flux flow state make them suitable for a design based on bulk materials. A 100 kVA class inductive study prototype of SFCL built around five commercial Bi-2212 hollow tubes (Hoechst) has been repeatedly tested at /spl sim/600 V RMS in nominal and fault conditions. In particular, the thermal stability has been investigated as a function of the temperature of the nitrogen bath (67-77 K). Simulation of the behaviour of the inductive limiter using differential equations are presented where both electromagnetic and thermal behaviour are considered. Part of this work is done within the joint collaboration between Hydro-Quebec and Siemens.         AC transport characteristics of QMG elements for fault current limiting devices    C. Yang, O. Miura, D. Ito, M. Morita and T. Tokunaga Summary: To study the quenching behavior of a HTSC YBa/sub 2/Cu/sub 3/O/sub 7-/spl sigma// pseudo single crystal bulk superconductor (QMG) as a resistive type fault current limiting device, the E-J characteristics, n-value and propagation velocity of the flux flow state and the resistive state of the QMG elements at 87 K were measured. The n-values, which varied from 5.4 to 7.3 at 87 K, were obtained for the QMG which has 1.6/spl times/10/sup 3/ A/cm/sup 2/ critical current densities at 87 K in 250 G. Based on the heat transfer characteristics between the QMG elements and coolant, the quench propagating velocity of the element in liquid argon is discussed.         DC-transport properties of QMG current limiting elements    T. Tokunaga, M. Morita, O. Miura and D. Ito Summary: V-I properties of YBCO bulk superconductor (QMG: YBa/sub 2/Cu/sub 3/O/sub x/ bulk single crystal containing Y/sub 2/BaCuO/sub x/ particles) were measured using pulse current at 77 K and 87 K to obtain basic data for super-normal transition. Because of its high Jc property QMG is a promising bulk material for HTC-FCL application. I-shaped QMG rods having cross section of 0.5 mm/spl times/1.0 mm were prepared to measure voltage due to pulse current. The plots of InV vs. InI yielded a straight line with a slope ranging from 5.8 to 7.9 at 77 K. By changing the amplitude and duration of pulses the time from the start of feeding current till the occurrence of quench were obtained for various amplitudes of pulse current. In this experiment, it is considered that the quench did not occur in the whole rod but only in a small part.         Technical and economical benefits of superconducting fault current limiters in power systems    M. Noe and B.R. Oswald Summary: There is no doubt that superconducting fault current limiters (SFCL) will be used if their technical and economical benefits are high enough. Up to now a number of studies have been carried out to show suitable applications of SFCL but very few reports have been published on their technical and economical benefits in existing networks. This paper shows favourable places of SFCL in an urban network up to a voltage of 110 kV, lists technical benefits and calculates the economical savings. In the investigated network it was found that feeder locations of power stations and wind generators are the most economical places for SFCL.         Experimental study on adjustability of superconducting fault current limiter with adjustable trigger current level    K. Fujikawa, Y. Shirai, T. Nitta, K. Hagiwara and T. Shibata Summary: Fault analyses of power systems including superconducting fault current limiters (SCFCLs) point out that accuracy of the trigger current level of an SCFCL should be in a few tens of percents. An SCFCL with an adjustable trigger current level is proposed. A trial SCFCL of this type was designed and made; basic tests on the SCFCL were carried out. Adjustability of the trigger current level of the proposed SCFCL is studied experimentally in this paper.         Setting method of specific parameters of a superconducting fault current limiter considering the operation of power system protection-resistance-type and rectifier-type SFCLs in overhead transmission    H. Kameda and H. Taniguchi Summary: We have developed an EMTP model of a resistance-type and a rectifier-type super-conducting fault current limiter (SFCL) and defined their parameters which a user specifies when he plans to introduce an SFCL into a power system. Using these models, we propose the setting method of these parameters so as not to affect the response of protective relays when SFCLs operate.         AC losses in BSCCO cylinders operating in inductive current limiter    V. Sokolovsky, V. Meerovich, S. Goren, G. Jung, J. Bock and S. Gauss Summary: AC losses in hollow BSCCO cylinders used in an inductive fault current limiter model have been investigated theoretically and experimentally. Discrepancies, becoming more pronounced with increasing current, between the experimental results and predictions of Bean's critical state model were observed. A simple procedure of calculating AC losses by taking into account the real form of the E-J characteristics was proposed. AC loss characteristics were employed to evaluate the nominal and activation currents of the full-scale fault current limiter.         A new model of fault current limiter using YBCO thin film    H. Kubota, Y.K. Arai, M. Yamazaki, H. Yoshino and H. Nagamura Summary: Resistive fault current limiters which consist of a YBCO film and a normal conducting film were constructed. The YBCO film was connected by indium wires to the normal conducting film in parallel at intervals of about 10 mm to increase the allowed voltage across the fault current limiter during the current-limiting operation. Current limiting experiments show that an allowed voltage across the fault current limiter during current-limiting operation of over 13 V/cm was achieved. Moreover, by combining in parallel 2 sets of 3 serially connected fault current limiters fabricated using 100 mm/spl times/10 mm YBCO film, a rated power of over 20 kVA is obtained.         Current limiting properties of YBCO-films on sapphire substrates    M. Lindmayer and H. Mosebach Summary: This work presents results of switching experiments with meander shaped YBCO films on sapphire substrates. For the experiments YBCO-layers with a thickness of 0.3 micrometer deposited on sapphire substrates with 2 inch in diameter were available. The critical current densities of the superconducters were about 10/sup 6/ A/cm/sup 2/. The films were coated with additional gold shunt layers to protect them against thermal destruction during the limiting process. Test results with a 30 cm long and 0.4 cm wide sample up to a nominal power of 3.4 kVA (235 V rms and 14.4 A rms) are reported. During the measurements attention was directed to the expansion of the first quenching zone. To detect the expansion several voltage taps along the entire length of the meander were mounted. It is shown that the thermal conductivity of the substrate exerts a strong influence on the quench expansion over the whole sample and therefore on the switching properties of FCLs.         Magnetic characteristics of a high-T/sub c/ superconducting cylinder for magnetic shielding type superconducting fault current limiter    J. Nakatsugawa, S. Noguchi, A. Ishiyama, H. Kado and M. Ichikawa Summary: The superconducting fault current limiter (SCFCL) is expected to be the first application of high-T/sub C/ superconductors (HTSs) in power systems. To develop a magnetic shielding type superconducting fault current limiter, we have carried out some fundamental experiments concerning the magnetic shielding characteristics of an HTS bulk cylinder. In this paper, the experimental results of magnetic flux penetration into a Bi(2223) cylinder are shown. AC magnetic field is applied to the sample by a primary winding (copper coil) excited by AC triangular- and sinusoidal-waveform currents in the frequency range of 0.1 Hz to 100 Hz. We also developed a finite element method (FEM) computer program for evaluation of the dynamic electromagnetic behavior of the HTS cylinder in a time-varying external magnetic field. The results of computer simulations considering the voltage-current (E-J) characteristic are compared with experiments.         Computer modelling of superconducting film type fault current limiters    R.A. Weller, A.M. Campbell, T.A. Coombs, D.A. Cardwell, R.J. Storey and J. Hancox Summary: Investigations are being carried out into the use of superconductors as fault current limiters. The authors are investigating devices constructed from various high T/sub c/ materials. Of particular interest are limiters constructed from superconducting YBCO thick films on YSZ substrates. In order to predict the limiting characteristics of a fault current limiter and to optimise the design parameters, an accurate numerical simulation has been developed. This model includes measured data in the form of E-J characteristics, thermal properties and R-T data. Data sets for different materials can be selected in order to compare the performance of candidate materials. A major concern during limiting is the way that heat is generated in the superconducting film. The authors' simulation treats the superconductor and substrate as a number of small elements in order to determine the temperature distribution within the film and substrate. Further additions model the heat loss mechanisms to the surrounding environment. This thermal model is included in an overall FCL model, which includes voltage sources and line or load impedances. One can use this model to accurately predict the current-time waveforms achievable with typical limiters, and to easily explore the effect of a change in operating conditions.         Recovery characteristics of fault current limiter with adjustable trigger current level    Y. Shirai, K. Fujikawa, K. Hagiwara, T. Nitta and T. Shibata Summary: A superconducting fault current limiter (SCFCL) of a transformer type with adjustable trigger current level is proposed. A trial SCFCL of this type is designed and made. Basic tests on the SCFCL are carried out. The current limiting impedance of SCFCL of the transformer type is almost determined by an inductance of a primary coil. The trigger current level and recovery characteristics of the SCFCL depends upon the design of a secondary coil. In this paper, recovery characteristics of the proposed SCFCL are studied experimentally. Joule heat in the secondary winding in the current limiting mode is measured. It is pointed out that the resistance of the secondary winding, that is the normal zone length, decreases as the line current decreases. Problems in the design of secondary windings are discussed. It is confirmed that the trial SCFCL recovers successfully from the current limiting mode to the waiting mode in shorter than ten cycles.         Author Index (1998 - Part 1)    No author information available Summary: Not available

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