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1996 Part 2     Front Cover (1996 - Part 2)    No author information available Summary: Not available         Table of Contents (1996 - Part 2)    No author information available Summary: Not available         Proximity effect current strengths in NbTi multifilamentary samples with and without Nb barriers and processed under various conditions    M.D. Sumption and E.W. Collings Summary: Conventional magnetization measurements of proximity effect (PE) coupling in superconducting (S) multifilamentary (MF) strands have been made, and a previously developed technique has been used to quantify the coupling strength in terms of a PE coupling supercurrent, J/sub cn/. This quantity has been determined for a number of MF strand types processed under various conditions. All are NbTi/Cu MF composites in some of which the NbTi filaments were surrounded by Nb "barriers", while in the others they were not. The magnetic field dependence of J/sub cn/ was also explored. The measured differences in J/sub cn/ are attributed to differences in the properties of the filament/matrix (normal metal, N) interface treated as a S1-S2-N trilayer. These results, together with those of an earlier series of experiments confirm that PE coupling between the filament and the matrix, and hence the normal-state coherence length, /spl xi//sub N/, is enhanced by the presence of a Nb (S2) barrier; and furthermore that the field-dependent coupling strength, gauged in terms of J/sub cn/ or /spl xi//sub N/, depends on the thickness of that barrier. It is demonstrated that magnetic PE-coupling studies not only provide a technique for extracting /spl xi//sub N/, a quantity central to artificial pinning center (APC) design, but also may help in the investigation of S-N boundary conditions in the clean limit.         High field flux pinning and the upper critical field of Nb-Ti superconductors    M.T. Naus, R.W. Heussner, A.A. Squitieri and D.C. Larbalestier Summary: Nb-Ti wires of different composition and metallurgical state have been studied near the upper critical field (H/sub c2/) in an attempt to separate H/sub c2/ the irreversibility field (H*) and the resistively measured transition field (H/sub r/). For optimized multifilamentary Nb-47wt.%Ti wire, we find that H*=10.2 T, H/sub c2/=10.8 T and H/sub r/=11.8 T at 4.2 K. The transitions were studied by extended electric field vs. current density curves, magnetization and small current transport measurements. We found a strong correlation between magnetization, bulk flux pinning (F/sub p/) extrapolation and extended E-J curves for the value of H*, all giving H*=10.2 T. We have also shown that the maximum in H/sub r/ occurs for Nb-44wt.% Ti.         Variable composition NbTi superconductors produced by artificial pinning center process    T. Wong, M.K. Rudziak, J.M. Seuntjens and J. Wong Summary: An artificial pinning center (APC) process, that utilizes pure niobium and titanium as the starting material, has been used to manufacture NbTi superconductors. The Ti content has been varied from 45.4wt% to 59.3wt% by adjusting the relative thicknesses of the Nb and Ti sheets in the starting monofilaments. Any composition can be produced in this manner, as compared to the conventional alloy which is commercially available in only one composition. The higher Ti content is designed to improve critical current density (J/sub c/s) in the low field range (<5T) and lower raw material costs, thus reducing the overall cost to the end user. The APC process does not suffer from the poorer ductility of the conventional NbTi approach when utilizing higher Ti content alloys. The new conductors would be suitable for applications such as magnetic resonance imaging (MRI), superconducting magnetic energy storage (SMES) and detector magnets.         Flux pinning in multifilamentary superconducting wires with ferromagnetic artificial pinning centers    J.-Q. Wang, N.D. Rizzo, D.E. Prober, L.R. Motowidlo and B.A. Zeitlin Summary: We demonstrate that ferromagnets are effective artificial pinning centers for the enhancement of critical current (J/sub c/) in multifilamentary superconducting wires. We have analyzed theoretically the proximity effect due to the FM pins near the final size of several nanometers and determined that one should achieve a large pinning force by such centers at these sizes. There is also additional pinning strength resulting from the interaction between ferromagnetic moments of the pins and the magnetic field gradient of the fluxon lattice. The measured results of J/sub c/, T/sub c/ and H/sub c2/ are analyzed, and compared with our model analysis.         Pinning and vortex lattice structure in NbTi alloy multilayers    J.D. McCambridge, N.D. Rizzo, S.T. Hess, J.Q. Wang, X.S. Ling, D.E. Prober, L.R. Motowidlo and B.A. Zeitlin Summary: We made thin film multilayers of Nb/sub 0.37/Ti/sub 0.63//Nb and Nb/sub 0.37/Ti/sub 0.63//Ti (d/sub NiTi/=14-27 nm and d/sub N/=4-11 nm) to examine geometries and materials relevant to flux pinning in commercial NbTi conductors. Samples were characterized by transport measurements between 4.2 K and T/sub c/, in magnetic fields nearly parallel to the layers, up to 6 T. For some multilayers, pinning forces had a large peak at intermediate fields whose onset occurred near /spl sim/0.2 H/sub c2/. We suggest this peak effect is caused by a change in the vortex lattice structure, driven by the strong intrinsic pinning. We have measured the highest pinning force density (113 GN/m/sup 3/ at 4.2K and 5 T) ever achieved in the NbTi system.         Critical current anisotropy in conventional and artificial pinning center round wire Nb-Ti superconductors    C.B. Nunes, R.W. Heussner and D.C. Larbalestier Summary: Critical current density anisotropy was detected in conventional and artificial pinning center (APC) Nb-Ti round wires by means of a relevant increase of the magnetization M as the wire aspect ratio A/sub w/ (length L/filament diameter d/sub f/) was increased. However, contrary to what is observed in APC wires, the critical current density J/sub /spl par// calculated from the SQUID measured saturated-magnetization in conventional wires using an anisotropic Bean model (BM), is significantly different from the transport critical current density J/sub ct/. We suggest that the mismatch between SQUID measured J/sub /spl par// and J/sub ct/ is due to a combination of the discontinuity of the ribbons along the wire length in conventional Nb-Ti wires and also to the low electric fields generated in SQUID measurements. The low electric fields allows the magnetization-induced currents to redistribute inside the wire due to the local inhomogeneities associated with the presence of /spl alpha/-Ti ribbons. In this case anisotropic BM cannot be used to extract J/sub c/ from M because it will be function of the intrinsic lengths of these ribbons.         Artificial pinning center Nb-Ti superconductors with alloyed Nb pins    R.W. Heussner, C.B. Nunes, L.D. Cooley and D.C. Larbalestier Summary: A magnetic interaction has been proposed as the dominant fluxon-defect interaction in conventional and artificial pinning center (APC) Nb-Ti, emphasizing the proximity length (/spl xi//sub N/) of the pinning center as the important parameter for optimizing the high field critical current density. We have characterized APC composites containing 25 vol.% of Nb pins alloyed with 7.5 wt.% Ta and 10 wt.% W to deliberately test the predictions of this model. We found that the bulk flux pinning force of the Nb10W-pin composite (/spl xi//sub N/(Nb10W)/spl sim/32 nm) exhibited a magnetic field (H) and pin size (d/sub p/) dependency that is more consistent with conventionally processed Nb47Ti (/spl xi//sub N/(/spl alpha/-Ti)<32 nn) than with existing pure Nb-pin APC composites (/spl xi//sub N/(Nb)/spl sim/83 nm). The Nb7Ta-pin composite (/spl xi//sub N//spl sim/59 nm) had intermediate F/sub p/(H,d/sub p/) behavior, thus qualitatively supporting the model.         Flux pinning scaling behaviors of ultrafine multifilamentary NbTi superconducting wires with Nb island-type artificial pins    O. Miura, C. Tei, D. Ito and S. Endo Summary: In order to engineer composites for high critical current densities Jc, the establishment of an artificial pinning center (APC) composite technique based on the flux pinning mechanism is desired. For that purpose, we investigated temperature and magnetic field scaling behaviors on the flux pinning properties of several kinds of Nb island-type artificial pin wires. The temperature and magnetic field dependence of bulk pinning force densities Fp was evaluated from magnetization curves at 25-7.5K to exclude influences due to external effects such as filament sausaging. As a result it was found that the scaling law holds true in a wide range of temperatures and magnetic fields for all of the APC specimens, which is in contrast to /spl alpha/-Ti specimens. This result suggests that Nb island-type pinning is much stronger than ribbon-like /spl alpha/-Ti pinning.         Irreversibility lines and pinning force density of aligned (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ single crystals    Shaoyan Chu and M.E. McHenry Summary: DC magnetic properties of aligned (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ single crystals have been measured for the first time using a SQUID magnetometer in field up to 5 T and in the temperature range from 5 K to 150 K. The results confirm the existence of a broad temperature and field regime with completely reversible magnetization for these crystals. The temperature dependence of the irreversibility field H*(T) is determined from both M-H and M-T curves with fields oriented perpendicular to the ab plane of the crystal lattice. A strong field dependence of critical current density has been observed in these pristine single crystals with very weak pinning. These observations emphasize the importance of artificially introducing pinning sites in BSCCO material used for applications. Non-linear scaling models have been used to fit our experimental results to estimate the elemental pinning force density and the effective pinning potential.         Preparation and magnetic properties of Ba/sub 1-x/K/sub x/BiO/sub 3+y/ and YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// single crystal films    S. Barilo, S. Shiryaev, G. Bychkov, V. Gatalskaya, N. Orlova, A. Pushcarev, A. Shestac, D. Zhigunov, A. Kaul, V. Svechnikov and H. Zandbergen Summary: Large area Ba/sub 1-x/K/sub x/BiO/sub 3+y/ and YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films were grown by LPE techniques on (Ba,K)BiO/sub 3/ and NdGaO/sub 3/ substrates, respectively. The good quality of epitaxy and small crystal mosaicity of the films were confirmed by X-ray measurements. Chemical homogeneity and microstructure of the films and interfaces were investigated by SNMS, HREM and SEM, depending on growth parameters. A comparative study of magnetic hysteresis loops in the reversible (irreversible) regions were done for both types of films. The VSM data show that the irreversible line follows the flux creep model.         Hysteretic flux dynamics in a detwinned YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// crystal from SQUID picovoltmeter measurements    S.N. Gordeev, A.V. Volkozub, P.A.J. de Groot, R. Gagnon, L. Taillefer, V.V. Khanin, A.N. Matlashov, Yu.A. Polyakov and V.Yu. Slobodchikov Summary: We report measurements of resistivity hysteresis in both temperature and magnetic field performed on a detwinned YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// single crystal in the region of the vortex lattice melting transition. We have found evidence that the observed hysteresis cannot be explained by current-induced nonequilibrium effects. The measured voltage-current characteristics for the sample in the overheated state also display hysteretic behaviour. This strongly supports the idea that the vortex solid can be melted by transport current.         Transport characteristics and flux dynamics in high T/sub c/ superconductors under the influence of pin fluctuation    T. Kiss, T. Nakamura, M. Takeo, K. Yamafuji and F. Irie Summary: Flux dynamics in a random pin medium have been studied with the Monte-Carlo method. It has been shown that flux depinning occurs percolatively in the disordered system and the scaling of electric field, E, vs. current density, J, curves reflect the stochastic property of the pin fluctuation. The analytical expressions for temperature and magnetic field dependent E-J curves have also been derived. The analytical expressions agreed quantitatively with the simulation and the in a Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin film at various temperature and magnetic field. Moreover, combining the analytical E-J relationship with Maxwell's equations, we estimated the internal current distribution for alternating bias currents.         Hysteretic and ac dynamic losses of high T/sub c/ superconductors by numerical solution of the nonlinear magnetic diffusion equation    D. Di Gioacchino, P. Tripodi, F. Celani, A.M. Testa and S. Pace Summary: The complex ac susceptibility (/spl chi/) of high T/sub c/ superconducting materials has been described in terms of hysteretic and dynamic losses. By including both flux creep and flux flow resistivities in the expression of the flux flow resistivities in the expression of the flux diffusivity, induction profiles have been numerically calculated from the nonlinear flux diffusion equation. The imaginary part of /spl chi/ has been evaluated as function of temperature, frequency and amplitude of the applied magnetic field. The role of pinning and dynamic losses occuring in high T/sub c/ materials is discussed.         Static and dynamic properties of Josephson fluxons and their implications on critical currents, especially in cuprate superconductors    J. Halbritter Summary: Below 1 Tesla pinned JF yield j/sub c//spl ap/j/sub cJ//spl les/5/spl middot/10/sup 7/A/cm/sup 2/ with j/sub cJ/ the critical Josephson current. The pinning is due to irregularities in the Josephson junctions (weak links) consisting of insulating seams of finite length and varying width, e.g., grain or twin boundaries. At higher fields Abrikosov fluxons (AF) in single crystalline parts may dominate j/sub c/, where j/sub c/ still has to be carried by strong and weak links in series, i.e., by Josephson fluxons (JF) strongly pinned. In addition, the insulating regions at strong and weak links amount to the largest concentration of insulating material in cuprate superconductors able to pin fluxons. Dynamic properties, like, the strong field and frequency dependencies of the surface impedance or the fast transition from normal-to-superconducting state are solely explainable by fast JF with their low loss insulating cores. Because j/sub c/ is given by a critical amount of dissipation, the viscous dynamics of JF- or AF-sliding along weak links play a critical role in superconductors containing strong or weak links.         Current dependence of pinning energy and flux dynamics in high temperature superconductors    C. Attanasio, C. Coccorese, L. Maritato, M. Salluzzo, M. Salvato, S.L. Prischepa, V.N. Kushnir and A. Varilci Summary: We show that the usually observed logarithmic U(J) dependence at large magnetic fields is related to the increasing number of free flowing vortices distributed in the weak pinning centers, with respect to the vortices in the strong pinning centers in the flux creep regime. Increasing the flux density (i.e. Increasing the external magnetic field) the flux distribution on the pinning centers has a larger dispersion (/spl sigma//sub u//spl Gt/k/sub B/T) and this leads to a logarithmic U(J) behavior. The comparison with the experimental data seems to prove this idea.         Influence of magnetic field on the flux motion in superconducting YBCO/PYBCO superlattice    H.E. Horng, S.Y. Yang, J.T. Jeng, J.M. Wu and H.C. Yang Summary: Angular dependent critical current densities J/sub c/(H,/spl theta/) for the YBa/sub 2/Cu/sub 3/O/sub 7-y//Pr/sub 0.5/Y/sub 0.5/Ba/sub 2/Cu/sub 3/O/sub 7-y/ (120 /spl Aring//24 /spl Aring/)/spl times/8 superlattice under various magnetic fields were measured to investigate the influence of the applied magnetic fields on the dimensionality of the flux pinning and flux dynamics. J/sub c/(H,/spl theta/) was obtained by applying current through x- or y-direction and analyzed by Kes model. It is found that the dissipation of the flux line system in the mixed state is mainly due to the pancake motion along ab-plane as H<1 T, while the flux lines begin to move along c-axis when the magnetic field reached 1 T. The causes will be discussed.         Continuous YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// film deposition by optically controlled reactive thermal co-evaporation    B. Utz, S. Rieder-Zecha and H. Kinder Summary: We built a thermal co-evaporation system to deposit YBCO films on large areas in a continuous process which requires some basic modifications to the established standard co-evaporation setup. An optical rate control system based on atomic absorption spectroscopy has been developed to measure the individual metal fluxes, in addition the metal sources can be reloaded in-situ for long times. The performance of these new components is discussed and results of first YBCO films grown on small samples are shown.         Superconducting NdBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin films prepared by the laser ablation method    Seung-Hyun Moon and Byungdu Oh Summary: NdBa/sub 2/Cu/sub 3/O/sub 7-/spl delta//(NBCO) thin films were deposited on (100) SrTiO/sub 3/(STO) substrates by the laser ablation method. The transition temperature of thin films was very sensitive to the deposition parameters such as substrate temperature, chamber pressure, and the distance between target and substrate. Thin films of T/sub c//spl sim/93 K were obtained when we deposited at 770/spl deg/C and 800 mTorr of oxygen pressure. The NBCO thin films were grown epitaxially with c-axis preferred orientation. The critical current density of the thin films was /spl sim/1/spl times/10/sup 6/ A/cm/sup 2/ at 77 K. We have also studied the surface morphology with AFM, and the typical smoothness is /spl sim/3 nm.         High-quality YBCO thin films grown by off-axis PLD geometry    V. Boffa, T. Petrisor, U. Gambardella, L. Ciontea, R. Bruzzese, F. Fabbri and S. Barbanera Summary: In order to improve the surface quality of the pulsed laser deposited YBCO thin films an off-axis deposition geometry is proposed. Using this new PLD geometry, YBCO thin films have been grown on SrTi0/sub 3/ substrates. These films were found to have a good surface morphology without droplets or other particulates, and good supelrconducting and structural properties. We have obtained Tc(R=0)=89 K, R(300)/R(100)=2.6, /spl tri/T=1.5 K, Jc=2x10/sup 6/ A/cm/sup 2/ (at 77 K and zero magnetic field), and the FWHM of the rocking curve of (005) YBCO peak is about 0.12°. A study regairding the influence of the deposition parameters on the film quality is also presented.         Fabrication of high quality YBa/sub 2/Cu/sub 3/O/sub y/ thin films using pulsed laser deposition    Eun-Hong Lee, Sang-Jin Park, I-Hun Song, Insang Song, Junho Gohng, Junghyun Sok, Jo-Won Lee, Duk Young Jeon and C.Y. Dosquet Summary: High quality YBa/sub 2/Cu/sub 3/O/sub y/ (YBCO) thin films for directly coupled DC-SQUIDs were fabricated by pulsed laser deposition. Several critical parameters have been optimized through systematic studies. The best quality YBCO thin films on MgO and on LaAlO/sub 3/ substrates were made under the O/sub 2/ pressure of 400/spl sim/500 mTorr at the substrate temperature of 780/spl sim/800/spl deg/C and target to substrate distance of 50/spl sim/60 mm. Films showing a T/sub c/ above 91 K and J/sub c/ above 2/spl times/10/sup 6/ A/cm/sup 2/ at 77 K were routinely obtained. Extensive AFM and x-ray diffraction studies have been conducted for morphological and structural analyses. The directly coupled DC-SQUIDs were fabricated from the YBCO thin films deposited on SrTiO/sup 3/ bicrystals under the optimized conditions. Measurement of 2I/sub c/ and swing voltage gives values of 420 /spl mu/A and 30 /spl mu/V at 77 K, respectively.         Development of APC NbTi superconductors with internal high purity aluminum stabilizer    M.K. Rudziak, T. Wong and J. Wong Summary: It has long been known that high purity aluminum is superior to copper as a stabilizer for NbTi conductors, due primarily to its low density and excellent low temperature thermal and electrical conductivity. Unfortunately, it is difficult to co-process high purity aluminum with conventional NbTi conductors due to mechanical and diffusional problems caused by precipitation heat treatment, Supercon NbTi artificial pinning center (APC) material makes it possible to eliminate these problems. The concept has been demonstrated in APC composites containing /spl sim/15% high purity aluminum by volume. The recent development effort will be described and the results of mechanical and electrical testing will be given.         Nb/sub 3/Sn artificial pinning microstructures    D.R. Dietderich and R.M. Scanlan Summary: Extension of the APC approach to Nb/sub 3/Sn requires that a second phase be incorporated into the Nb/sub 3/Sn layer. The second phase would increase pinning strength by either reducing the grain size or by the second phase pinning the flux itself. The following criteria for elements to be candidates for the APC approach are: (1) they must form intermetallic compounds with Cu or Sn and (2) they must have negligible solubility in Cu and Nb or they must be strong oxide formers. Many of the rare earth elements satisfy these criteria. To circumvent the large strains required to produce wires with a fine distribution of the second phase, film deposition techniques have been used. Critical current densities for Nb films doped with Ti and Y are about 4000 A/mm/sup 2/ at 6T and 4.2K.         Multiple peaks in the angular and field dependence of the critical currents in Nb-47wt%Ti/Cu multilayers    E. Kadyrov, L.D. Cooley, A. Gurevich, P.J. Lee and D.C. Larbalestier Summary: The effect of Nb-Ti layer thickness d/sub s/ on the angular and field dependencies of J/sub c/ in Nb-47wt.% Ti/Cu multilayers was investigated. J/sub c/ exhibits several peaks in the field and angular dependencies for superconductor and pin layer thickness comparable to the coherence and proximity lengths. The shape of the J/sub c/(B) curve strongly depends on the thickness of Nb-Ti layer. A single peak is present for d/sub s/>10 nm and multiple peaks (two and three) are observed in a sample with d/sub s/=10 nm. The low field peak is temperature independent, while the high-field peaks have a pronounced temperature dependence. We suggest that a crossover between dominant pinning mechanisms and orientational transitions in the vortex lattice is responsible for the observed behavior of J/sub c/(B).         Angular dependent flux pinning studies of superconducting layered structures    A.N. Lykov and Yu.V. Vishnyakov Summary: Angular dependences of the critical current density (J/sub c/(/spl theta/)) in superconducting multilayers based on Nb/NbO/sub x/ were investigated in this work. In rotating of the sample at a fixed magnetic field, it,vas found that the direction of the external field at which the maximum of J/sub c/(/spl theta/) was obtained formed an angle with the planar direction. The rotation leads to the existence of the kink structure even in a magnetic field parallel to the layers. This results from the difficulties of the transition of the flux vortex lattice into the ground state with minimum energy. In accordance with the model, bringing of the lattice into the ground state before every measurement at a new angle results in the symmetrical angular dependence of the critical current.         Numerical calculation of magnetic fields in melt processed YBCO magnets    X.H. Jiang and A.M. Campbell Summary: The use of melt processed YBCO in permanent magnet applications requires the calculation of magnetic fields in the interior of superconductors. Although the Bean model can be used, analytic solutions are only available for simple shapes and numerical methods are required for most cases. In this paper, the technique of adjusting the boundary between current carrying and current free regions to ensure zero field within the boundary is used, in combination with the Kim model for Jc. The results are applied to discs being magnetised in a uniform field and trapping fields after saturated magnetisation. It was found that a good approximation can be obtained by using a constant Jc of the value at half the applied field instead of the Kim model. This may be of great importance for the practical applications of melt processed YBCO permanent magnets.         Critical state of superconducting strip array systems in perpendicular magnetic fields    Y. Mawatari Summary: The electromagnetic properties of strip-array systems, which are composed of periodically arranged thin superconducting strip lines in perpendicular magnetic fields, are theoretically analyzed based on the critical state model. It is shown that magnetic field and current density of the strip-array systems in the critical state are obtained using simple transformations of those for an isolated strip line. Theoretical expressions of magnetization and ac susceptibility of the strip-array systems are presented.         The thin-film disk and ring shaped type II superconductors in perpendicular magnetic fields    E.S. Borovitskaya, V.M. Genkin and G.I. Leviev Summary: Properties of small, thin-film, disk-shaped and ring-shaped superconductors in the presence of perpendicular magnetic fields were considered within the framework of a model that takes into account the difference between magnetic induction and vortex density, vortex movement, and generation of vortices if current density exceeded its critical value. The linear complex magnetic susceptibility of a ring was calculated. It was shown that the distribution of the dissipative current differed considerably from the reactive one. The influence of the edge barrier on the form of the hysteresis loop, and current and field patterns for the ring in the critical state were shown.         Magnetic properties of melt processed YBaCuO by micro Hall probe    H. Fujimoto, T. Higuchi, K. Kawano and T. Ban Summary: Magnetic properties of a melt-processed YBaCuO superconductor were studied by using a microsize Hall probe. A bulk of YBaCuO superconductor, 30 mm/spl times/30 mm/spl times/1.9 mm, with a high critical current density at 77 K was prepared by the melt process. Two-dimensional distributions of the local magnetic induction, B/sub t/ over the surface of the YBaCuO superconducting plate, were measured at 77 K, when a magnetic field up to 100 mT was applied perpendicular to the sample surface. The distribution of the local magnetic induction indicates the magnetic shielding effect when the external magnetic field is applied. By using the microsize Hall probe with an active area of 50 /spl mu/m/spl times/50 /spl mu/m, the inhomogeneous distribution of the local magnetic induction due to the existence of a weak link region was observed. External magnetic field dependence of B/sub t/ at several positions was also measured in perpendicular magnetic fields of up to 1.4 T. The magnetization process on these positions of the YBaCuO superconductor clearly indicated the behavior of the critical state and the edge effect.         Shielding current flowing in oxide superconducting plates    H. Kamijo and K. Kawano Summary: The shielding currents flowing inside (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub y/ oxide superconducting plates are estimated by reverse calculation based on the results of magnetic shielding experiments. The relationship of the magnitude of the external field to the distribution and magnitude of the shielding current was derived. The critical current density of the shielding current agrees approximately with the results obtained by the susceptibility method, but is smaller than the results obtained by the four-probe electrical resistance method.         Microwave surface resistance of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films on polycrystalline alumina and Ni-based alloy substrates with ion-beam-assisted-deposited buffer layers    A.T. Findikoglu, P.N. Arendt, J.R. Groves, S.R. Foltyn, E.J. Peterson, D.W. Reagor and Q.X. Jia Summary: We measured the microwave surface resistance R/sub s/ of superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/(YBCO) films on buffered polycrystalline alumina and Ni-based alloy substrates using parallel-plate technique. We observed a strong between the low-power R/sub s/ and the in-plane mosaic spread of the YBCO films. A 0.4-/spl mu/m-thick YBCO film with an in-plane mosaic spread of 6.60 (7/spl deg/) on a buffered polycrystalline alloy (buffered polycrystalline alumina) showed an R/sub s/ of 0.51 m/spl Omega/ (1.89 m/spl Omega/) at 76 K and 0.17 m/spl Omega/ (0.21 m/spl Omega/) at 4 K.         Surface resistance and nonlinear dynamic microwave losses of epitaxial HTS films    W. Diete, M. Getta, M. Hein, T. Kaiser, G. Muller, H. Piel and H. Schlick Summary: Many applications of high-temperature superconductor (HTS) films in microwave devices require high power-handling capabilities. Therefore we have studied the temperature and power dependence of the surface resistance R/sub s/(T,B/sub s/) of unpatterned HTS films with a very sensitive dielectric resonator technique at 19GHz. R/sub s/-values as low as 120/spl plusmn/15 /spl mu//spl Omega/ (100/spl plusmn/15 /spl mu//spl Omega/) and 760/spl plusmn/80 /spl mu//spl Omega/ (610/spl plusmn/30 /spl mu//spl Omega/) at 4.2 and 77K were obtained for YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (Tl/sub 2/Ba/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8/) films. In contrast to the small scattering in R/sub s/ at low fields, the high-field behavior varied strongly. Maximum surface magnetic fields (B/sub s/) between 1 and 15 mT (2-28 mT) were achieved at 77K (4.2K). Different loss mechanisms, like defects, heating, and intrinsic phenomena, could be identified. Besides time-domain measurements in the pulsed mode, the dynamic nature of the nonlinearities was investigated by two-tone intermodulation measurements. The very high sensitivity of this technique was applied to proof the existence of fast nonlinearities (t<100 ps) in high quality films.         Large-area and double-sided pulsed laser deposition of Y-Ba-Cu-O thin films applied to HTSC microwave devices    M. Lorenz, H. Hochmuth, D. Natusch, H. Borner, T. Tharigen, D.G. Patrikarakos, J. Frey, K. Kreher, S. Senz, G. Kastner, D. Hesse, M. Steins and W. Schmitz Summary: Pulsed laser deposition (PLD) of YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) thin films on both sides of 3-inch diameter sapphire wafers and LaAlO/sub 3/ (LAO) cylinder substrates, respectively, is a basic and flexible technique in order to optimize microwave bandpass filters for wireless communication systems. The large-area and double-side PLD technique allows homogeneous and reproducible YBCO deposition on both substrate sides with inductively measured critical current densities j/sub c/ of 3/spl times/10/sup 6/ to 5/spl times/10/sup 6/ A/cm/sup 2/ at 77 K with a YBCO thickness of 350 nm to 600 nm. Selected results of compositional, structural, electrical, and microwave characterization of the PLD-YBCO films are reported.         Fabrication of double sided YBa/sub 2/Cu/sub 3/O/sub 7/ thin films on 2 inch diameter LaAlO/sub 3/ wafers by direct wafer bonding    C.B. Eom, L. Huang, R.A. Rao, Q.Y. Tong and U. Goesele Summary: We have demonstrated a novel fabrication process for double-sided YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) thin films on 2 inch diameter (100) LaAlO/sub 3/ wafers by direct wafer bonding. YBCO thin films were deposited on one side of two LaAlO/sub 3/ wafers by a 90/spl deg/ off-axis sputtering technique. These two LaAlO/sub 3/ wafers were then polished on the opposite side and directly bonded at room temperature. We have also developed and optimized the process of LaAlO/sub 3/ wafer bonding. The effect of annealing on the roughness, twin structure and bonding strength of bonded LaAlO/sub 3/ wafers has been investigated. After annealing at 120/spl deg/C for 100 hours, the bonded LaAlO/sub 3/ pairs remained intact even after immersion in deionized water for 20 hours. This process can be used for fabricating double sided high temperature superconducting thin films on heterostructure substrates, which have important applications in high frequency devices.         Tl-Ba-Ca-Cu-O thin films on buffered substrates for microwave device applications    A.P. Bramley, B.J. Glassey, C.R.M. Grovenor, M.J. Goringe, J.D. O'Connor, A.P. Jenkins, K.S. Kale, K.L. Jim, D. Dew-Hughes and D.J. Edwards Summary: Tl-Ba-Ca-Cu-O thin films have been grown on a variety of substrates, both with and without the use of buffer layers. Differences in processing routes required for the various film-substrate combinations are highlighted and the effect of the buffering layers on the microstructure, transport and microwave properties of the films are discussed.         Residual surface resistance of YBa/sub 2/Cu/sub 3/O/sub x/ thin films-weakly coupled grain model    K. Yoshida, K. Nagasawa, T. Kiss, H. Shimakage and Z. Wang Summary: The residual surface resistance and the magnetic penetration depth of high-T/sub c/ superconducting YBa/sub 2/Cu/sub 3/O/sub x/ thin films have been measured using the coplanar waveguide resonator technique, and are discussed with the weakly coupled grain model, where the superconducting polycrystalline thin film is described as a network of superconducting grains coupled via Josephson junctions. The observed dependence of the residual resistance and the magnetic penetration depth on the critical current density and the grain size is shown to demonstrate the weakly coupled grain model of YBa/sub 2/Cu/sub 3/O/sub x/ thin films.         Microwave surface resistance of cuprate superconductors    B.A. Tonkin and Y.G. Proykova Summary: Microwave surface resistance measurements have recently been playing an important role in assessing the suitability of superconducting materials for applications. The temperature (10-100K) dependence of the surface resistance of bulk polycrystalline ReBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (Re=Y, Gd and Sm) specimens at 27.4GHz has been extracted using a resonant cavity end wall replacement technique. The superconducting transition temperature was found to be increasing for rare earth atoms with larger ionic radius. The results seem to show that the surface resistance in the superconducting state is insensitive to the type of the rare earth ion and is mainly governed by the size of the superconducting grains and their alignment. The normal state surface resistance however is dependent on how well the grains are connected.         Nonlinear response of HTSC thin film microwave resonators in an applied DC magnetic field    D.P. Choudhury, B.A. Willemsen, J.S. Derov and S. Sridhar Summary: The non-linear microwave surface impedance, Z/sub s/=R/sub s/+iX/sub s/, of patterned YBCO thin films, was measured using a suspended line resonator in the presence of a perpendicular DC magnetic field, H/sub DC/, of magnitude comparable to that of the microwave field, H/sub rf/. Signature of the virgin state was found to be absent even for relatively low microwave power levels. The microwave loss was initially found to decrease for small applied H/sub DC/ before increasing again. Also, non-linearities inherent in the sample were found to be substantially suppressed at low powers at these applied fields. These two features together can lead to significant improvement in device performance.         Fundamental limits of the linear microwave power response of epitaxial Y-Ba-Cu-O films    M. Hein, W. Diete, M. Getta, S. Hensen, T. Kaiser, G. Muller, I. Piel and H. Schlick Summary: The microwave field dependent surface resistance R/sub s/(B/sub hf/) of unpatterned epitaxial YBa/sub 2/Cu/sub 3/O/sub 7/ films was measured at 19 GHz between 4.2 and 80 K with a Nb-shielded sapphire resonator. In addition, the dc field dependence R/sub s/(B/sub dc/) was investigated at 87 GHz and 4.2 K with a Cu host cavity. Maximum microwave field amplitudes B/sub cr//sup hf//spl ges/27, 23 and 15 mT were obtained at 4.2, 50 and 77 K with no detectable degradation of R/sub s/ at lower fields. Similarly, R/sub s/ stayed constant at 4.2 K up to maximum dc fields, B/sub cr//sup dc//spl les/40 mT. There is increasing evidence from both data sets that the maximum fields B/sub cr//sup hf/ and B/sub cr//sup dc/ are fundamentally limited by the lower critical field B/sub c1/(/spl lambda//sub L/) at a given, quality-dependent, penetration depth /spl lambda//sub L/. The R/sub s/(B/sub hf/) performance obtained for the best YBa/sub 2/Cu/sub 3/O/sub 7/ films comes already close to this limit. Microwave field limitation in less optimized films is expected to be caused by local heating at non-superconducting defects.         YBCO films deposited on YAlO/sub 3/ substrates: microstructure and transport properties    C. Dubourdieu, J.P. Senateur, O. Thomas, F. Weiss, S. Hensen and G. Muller Summary: Epitaxial YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) thin films have been grown by Metal Organic Chemical Vapor Deposition on YAIO/sub 3/ (001) substrates. The twinning directions [110] and [110] of YBCO are aligned along [110] direction of YAI0/sub 3/. This epitaxial relationship can be explained by lattice strain considerations. The microwave surface impedance has been measured at 87 Ghz between 4.2k and 150k using a resonant copper cavity. The best films exhibits a surface resistance of 43m/spl Omega/ at 77K and 87 GHz an a residual surface resistance of 3 m/spl Omega/ at 4.2K.         Deposition of YBCO and NBCO films on areas of 9 inches in diameter    B. Utz, R. Semerad, M. Bauer, W. Prusseit, P. Berberich and H. Kinder Summary: High quality YBa/sub 2/Cu/sub 3/O/sub 7/ thin films can be grown by reactive thermal co-evaporation. Combined with a rotating disk heater this method allows to fabricate even double sided homogeneous films on substrate areas up to 9" diameter. A scanning inductive j/sub c/ probe is used to monitor the homogeneity of critical current densities of typically >2 MA/cm/sup 2/. Surface resistance values are found to be below 500 /spl mu//spl Omega/ at 10 GHz. On biaxially aligned buffer layers on polycrystalline substrates j/sub c/ values of 1.3 MA/cm/sup 2/ are achieved as well. The properties of Nd/sub 1-x/Ba/sub 2+x/Cu/sub 3/O/sub 7/ films grown with the same system are presented and evaluated.         Deposition of YBCO thin films over large areas by a 90/spl deg/ off-axis sputtering technique    R.A. Rao, C.B. Eom, M. Santer and S.M. Anlage Summary: We report the deposition of YBCO thin films with uniform thickness (87.5 K) and critical current density (J/sub c/ /sub 77/ /sub K/>1/spl times/10/sup 6/ A/cm/sup 2/, J/sub c/ /sub 4.2/ /sub K/>1/spl times/10/sup 7/ A/cm/sup 2/) over an 8" diameter area. Considering only the better optimized samples the films displayed high critical current densities (J/sub c/ /sub 77 K/ >3/spl times/10/sup 6/ A/cm/sup 2/, J/sub c/ /sub 4.2 K/ >3/spl times/10/sup 7/ A/cm/sup 2/). The variations in the film properties have been correlated to the variations in crystalline quality, amount of c-axis grains and substrate temperature during deposition.         Advances in HTS films for high power microwave applications    D.W. Face, C. Wilker, J.J. Kingston, Zhi-Yuan Shen, F.M. Pellicone, R.J. Small, S.P. McKenna, Shiquan Sun and P.J. Martin Summary: This paper describes recent work at DuPont to extend the high power microwave performance of YBa/sub 2/Cu/sub 3/O/sub 7/ and Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ high-T/sub c/ superconducting (HTS) films. The YBa/sub 2/Cu/sub 3/O/sub 7/ films grown by in-situ off-axis magnetron sputtering using are produced by in-situ off-axis sputtering with radiant substrate heating. The Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ films are produced by off-axis sputtering followed by annealing in oxygen and Tl/sub 2/O vapor. The microwave surface resistance and power handling of these films has been measured over a wide range of temperature (20 K to 100 K) using a HTS-sapphire resonator technique. At 70 K, the surface resistance of YBa/sub 2/Cu/sub 3/O/sub 7/ films remains below 65 /spl mu//spl Omega/ (@5.56 GHz) with microwave surface current densities up to 5/spl times/10/sup 6/ A/cm/sup 2/. At 70 K, the surface resistance of Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ films remains below 200 /spl mu//spl Omega/ (@8.1 GHz) with microwave current densities up to 2/spl times/10/sup 6/ A/cm/sup 2/.         Double-sided YBa/sub 2/Cu/sub 3/O/sub 7-/spl part// films for planar high-power filters    G. Muller, B. Aschermann, H. Chaloupka, W. Diete, M. Getta, B. Gurzinski, M. Hein, M. Jeck, T. Kaiser, S. Kolesov, H. Piel, H. Schlick and R. Theisejans Summary: We have extended the planar DC high oxygen-pressure sputtering process for the successive non-scanning deposition of epitaxial YBa/sub 2/Cu/sub 3/O/sub 7-/spl part// (YBCO) films up to 2" in diameter and 600 nm in thickness. Contamination of the heater-facing side of the LaAlO/sub 3/ substrates could be prevented by use of a thin quartz glass plate. For optimized deposition parameters, inductive measurements indicated comparable and homogeneous quality of both film sides, i.e. T/sub c/>88 K and J/sub c/(77 K) >2 MA/cm/sup 2/. Surface resistance measurements at 19 GHz with a Nb-shielded sapphire resonator resulted in R/sub s/<1 (0.2) m/spl Omega/ at 77 (4) K, which, in some cases, did not show any significant increase up to surface field levels B/sub s/=10 (25) mT. In order to obtain planar microwave filters of small size and high power-handling capability, disc resonators for TM/sub 010/-mode operation at 3.5 and 1.8 GHz were patterned from 1" and 2" diameter double-sided YBCO films. Strongly temperature dependent quality factors Q/sub 0/ as high as 7.2/spl middot/10/sup 4/ (6/spl middot/10/sup 5/) have been achieved at 77 K (30 K) and 3.5 GHz, which are limited by losses in both the superconductor and the dielectric. A circulating power of about 1 kW, corresponding to peak B/sub s/-values above 1 mT, could be achieved without significant Q/sub 0/ degradation. Evidences for field limitations by local defects were found.         Variation of microwave losses induced by DC and RF magnetic fields in Gd123 thin films    L.F. Cohen, A. Cowie, J.C. Gallop, I.S. Ghosh, J. Chrosch and I.N. Goncharov Summary: Using a 5 GHz parallel plate resonator, several Gd123 thin films have been studied. The low RF power dependence, the DC field dependence and the power dependence in the presence of DC fields have been measured. Two films were modified by introducing intragranular defects by high energy irradiation of either Kr ions or /spl alpha/ particles. By using a simple model, values for high frequency pinning constant /spl kappa//sub p/ were extracted. The DC screening current density J, was also measured. We examine whether the irradiation has improved the DC and high frequency pinning properties and the impact this has on the power dependence of the surface resistance. Comparison between the DC and the power dependence losses are made.         Nonlinear surface impedance of Y-Ba-Cu-O films in a DC magnetic field    M. Tsindlekht, M. Golosovsky, D. Davidov and A.F. Jacob Summary: We study the microwave power dependence of the surface impedance of YBCO epitaxial films in a DC magnetic field up to 0.7 T. We demonstrate that the surface impedance of our films in the linear regime is dominated by weak links at low DC field and by vortices at high DC field. However, the microwave power dependence of the surface impedance arises mostly from the hysteretic RF vortex penetration.         Identification and modeling of microwave loss mechanisms in YBa/sub 2/Cu/sub 3/O/sub 7-X/    J.S. Herd, D.E. Oates and J. Halbritter Summary: It has been proposed that the nonlinear microwave response of YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin films is due to small- or large-angle grain boundaries which behave as weak links. To identify dominant loss mechanisms in the measured response of stripline resonators, the relative change in surface reactance and resistance, r=/spl Delta/X/sub s///spl Delta/R/sub s/, is used as a characteristic signature for the different mechanisms. We show that Meissner state and flux flow losses can be differentiated from hysteresis loss for a variety of films across a range of microwave powers, frequencies, and temperatures. In addition, a coupled-grain/RSJ model has been augmented to include Josephson currents up to and beyond the critical currents J/sub cj/ of the weak links. The model can account for a distribution of grain and boundary properties including I/sub c/R/sub n/ products, junction capacitances, and grain dimensions. The r-values predicted by the model are discussed and compared to measurements.         Statistical analysis of the degradation of 2223-BSCCO tapes aged under mechanical stress by the Weibull function    G.C. Montanari, I. Ghinello, L. Gherardi and R. Mele Summary: Specimens of 2223-BSCCO tapes were subjected to mechanical aging, with their voltage-current (V-I) characteristic measured at different aging times. Two types of mechanical stresses were applied: cyclic (vibration) and static. Probability distributions were obtained from V-I data by numerical-analytical differentiation, and the Weibull function was used to fit the cumulative and density probability distributions thus obtained. It is shown that the time behavior of the parameters of the Weibull functions thus obtained provides useful information on the level and kind of degradation.         Strength and flexibility of bulk high-T/sub c/ superconductors    K.C. Goretta, Ming Jiang, D.S. Kupperman, M.T. Lanagan, J.P. Singh, N. Vasanthamohan, D.G. Hinks, J.F. Mitchell and J.W. Richardson Jr. Summary: Strength, fracture toughness, and elastic modulus data for bulk high-temperature superconductors, commercial 99.9% Ag, and a 1.2 at.% Mg/Ag alloy have been collected. These data have been used to calculate fracture strains for bulk conductors. The calculations indicate that the superconducting cores of clad tapes should begin to fracture at strains below 0.2%. In addition, residual strains in Ag-clad (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ tapes have been measured by neutron diffraction. An explanation is offered for why many tapes appear to be able to tolerate large strains before exhibiting a reduction in current transport.         Current carrying properties of high-T/sub c/ Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8/ tapes in a large electromagnetic stress state    K. Watanabe, S. Awaji and M. Okada Summary: Transport properties under a large electromagnetic stress state of up to 190 MPa were investigated at 4.2 K for high-T/sub c/ Bi-based superconductors. A double pancake test coil employing Ag-sheathed multifilamentary Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8/ (Bi2212) tapes was fabricated by a react and wind method reinforced with a Cu-50Ag tape. It is shown that the use of a parallel co-wound Cu-50Ag tape leads to improvement of mechanical properties. A quite stable behavior for the Ag-sheathed multifilamentary Bi2212 coil is observed with appearance of large normal zone voltages.         Strain dependence of critical currents in commercial high temperature superconductors    P.E. Richens, H. Jones, M. Van Cleemput and D.P. Hampshire Summary: We describe two versions of a simple device that enable the J/sub c/ (B,T,/spl epsi/) characterisation of a <40 mm diameter single loop of HTS tape. The loop is mounted on a cylinder that is slit longitudinally at regular intervals around its circumference. Strain is applied by forcing a conical plug into the tapered bore of the cylinder which expands evenly as a consequence. The strain is measured by a strain gauge glued to the surface of the tape. The advantage of this configuration is that it enables insertion in the small bores of the highest field superconducting magnets and thus permits access to fields levels not easily available in more traditional linear pulling devices. Also the loop configuration is more representative of the coil geometry encountered in magnet applications. Representative data are presented and discussed critically.         Noncontacting ultrasonic and electromagnetic HTS tape NDE    K.L. Telschow, F.W. Bruneel, J.B. Walter and L.S. Koo Summary: Two noncontacting nondestructive evaluation techniques, one electromagnetic the other ultrasonic, for inspection of high temperature superconducting tapes are described. Results for Ag-clad BSCCO tapes are given.         The effect of bending radius on V-I characteristics of mono- and multicored BiPb-2223 tapes with and without Ag additions    I.I. Akimov, E.V. Antipova, S.N. Barabanov, N.I. Kozlenkova, P.A. Kuznetsov, A.D. Nikulin, D.N. Rakov, A.K. Shikov, N.E. Khlebova and D.A. Filitchev Summary: The effect of bending strain on Voltage-Current Characteristics (VCC) of BiPbSrCaCuO-2223/(Ag and Ag-alloy sheathed) tapes with and without Ag additions into the core have been studied. The testing probe allows us to carry out all set of bending tests up to radius 5 mm on the same specimen. The critical current Ic and shape of high-sensitivity VCC as a function of bending strain are analysed. Degradation of current carrying capacity under bending deformation is caused by the formation of microcracks. The overlapping of microcracks in Bi-2223/Ag sheathed tapes without Ag additions leads to current overflow into the Ag sheath and to appearance of linear resistance segment in the V-I curve at low electric field.         Studies on several factors in the critical current measurement of HTS tapes relating to the VAMAS intercomparison    K. Tachikawa, Y. Yamada, Y. Hishinuma and F. Yamashita Summary: The recent VAMAS intercomparison on critical current, Ic, measurement in Bi-based oxide tapes revealed that Ic of the tapes was quite sensitive to the heat cycle between room temperature and cryogen temperature. Then, the effect of several factors on Ic of high-Tc tapes with respect to the heat cycle has been studied. Ag-sheathed monocore Bi-2212 and Bi-2223 tapes, and 55 multicore Bi-2223 tapes were prepared by PIT method. The Ic measurement was performed at 4.2 K and 77 K following the guide line of VAMAS intercomparison. The degradation in Ic of the tapes seems to be caused by the waving of those fixed between current terminals. Furthermore, the Ic is drastically degraded by the bubbling in tapes, although the frequency of bubbling is small. Smaller Ag ratio of monocore tapes produces more significant drop in Ic by the heat cycle. The 55 multicore Bi-2223 tapes scarcely show the waving, and the Ic of the tapes is much less sensitive to the heat cycle than that of monocore tapes. The dimension of the core seems to be a key parameter against the Ic degradation in the heat cycle.         Origin of J/sub c/ lateral spatial distribution in Ag-sheathed Bi-2212 HTSC tapes    A.V. Pan, M.H. Ionescu and S.X. Dou Summary: Critical current density (J/sub c/) spatial distribution in the superconducting core of the Ag-sheathed Bi-2212 tapes prepared by "powder in tube" technique has been measured by means of tape cutting along the rolling direction to a few narrow strips and separate J/sub c/ measurements each of them. The J/sub c/ value on the edges of tapes has been found to be higher by a factor of about 3 in comparison with the central area. Unexpectedly, the measured oxide core density is shown to be in contrary the lowest in the edge regions. The thin interface layer (about 10 /spl mu/m thick) with no secondary phase has been observed by SEM on the whole circumference of Ag-sheath/core boundary. This interface layer is assumed to be responsible for the dominant contribution to the supercurrent-carrying ability of a tape. However, in fact the J/sub c/-values on the very edge of the core still are twice as high as J/sub c/ in the central region (3.6/spl times/10/sup 4/ against 1.8/spl times/10/sup 4/ A/cm/sup 2/). Thus, an optimal structure formation can be promoted by the core edge geometry.         Spatial distribution of transport current in low and self field in BSCCO tapes    M. Daumling Summary: The spatial current distribution in monofilamentary BSCCO-2223 tapes is evaluated numerically using the critical state model with a field dependent critical current density. The overall transport current density is the sum of the local currents which perceive different magnetic fields depending on their location within the tape. In self field a current peak in the center of the specimen occurs. This is caused by the field dependence of j/sub c/. If a monofilamentary tape is sliced longitudinally the self field effect leads to an enhancement of j/sub c/ in the slices that formed the tape edges, even though the microstructure of the monofilament itself is assumed homogeneous. Thus the fact that this enhanced current flow at the tape edges is found experimentally does not necessarily mean that the microstructure in the tape edges is better, but could be-at least in part-due to the self-field effect. In twisted multifilamentary tapes the current distribution is expected to be homogeneous since the filaments cross over the tape. The self field effect also leads to a reduction of the overall current density for use of stacks of tapes as current leads.         Current and field distribution within multifilamentary Bi2223/Ag tapes    M.D. Johnston, J. Everett, M. Dhalle, A.D. Caplin, C.M. Friend, L. LeLay, T.P. Beales, G. Grasso and R. Flukiger Summary: The magnetic self-flux distribution around high current mono- and multi-core BSCCO 2223 tapes with various filament configurations has been measured with a scanning micro-Hall probe. Using a simple model, the measured field component perpendicular to the tapes was deconvoluted to give an estimate of the way the transport current distributes itself across the width of the tape. From the changes in flux profile as the applied transport current is varied, the current distribution across the width of the tape can be inferred. In the untwisted tapes, the outer filaments tend to screen the inner ones and carry the bulk of the current; in a twisted sample, the current is shared more equally between filaments.         Measurement of current density distribution in high T/sub c/ Ag-sheathed superconducting tapes    P. Usak and F. Chovanec Summary: Flux history and local inhomogeneities in j/sub c/ govern the current distribution in measured Ag-sheathed TlBaCaCuO-2212 and Bi(Pb)SrCaCuO-2223 tapes. The sausage effect and local grain density and coupling fluctuations result in inhomogeneity in j/sub c/ distribution. This is reflected in violation of axial symmetry across the tape as well as longitudinal translation symmetry along the tape. Hall probe mapping of self field component with or without presence of external field was used to achieve the data for inverse calculation of current distribution and its dynamics in response to time variation of flux. To reveal the asymmetry in j/sub c/ distribution across the tape width the method of gradient field scanning/reversing was applied.         Critical current in silver sheathed Bi-2223 tapes    T. Staiger, G. Fuchs, P. Verges, K. Fischer, L. Schultz and A. Gladun Summary: Silver sheathed Bi-2223 tapes have been investigated by transport and magnetization measurements in the temperature range between 4.2 K and 77 K for magnetic fields up to 12 T. The superconducting current through the tape can be explained by assuming a network of platelike grains coupled by weak links. At high temperatures the critical current is governed by flux creep of pancake vortices within the grains. At temperatures below 40 K this intragrain critical current exceeds the intergrain Josephson current leading to a weak link limitation in the tape. In this picture the differences between critical transport and magnetization currents can be explained by a reduction of the geometrical length scale of current loops. An improvement of the weak link current density is observed in multifilamentary wires and tapes with AgCu sheath material.         Analysis of AC loss behavior in BSCCO tapes with different core geometries    R. Mele, G. Crotti, L. Gherardi, D. Morin, L. Bigoni, L. Martini and S. Zannella Summary: AC losses in the transport regime were measured in Ag-sheathed (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ (Ag/2223) tapes at 77 K in the frequency range 35-180 Hz. The samples were multifilamentary, prepared by OPIT (oxide powder in tube) technique, and "concentric" prepared by the wire-in-tube technique, and they had different superconducting core geometries. Measured losses were confirmed to be hysteretic in nature in the examined frequency range. The experimental results are compared with the prediction of the elliptical and thin strip Norris model.         Improved high-field performance in Nb/sub 3/Sn conductor prepared from intermediate compound    K. Tachikawa, Y. Kuroda, H. Tomori and M. Ueda Summary: Nb/sub 3/Sn superconductors have been fabricated using Nb/sub 6/Sn/sub 5/ intermediate compound powder synthesized by a melt diffusion process. The mixed powder of Nb/sub 6/Sn/sub 5/ and Nb was encased in a Ta tube, and then fabricated into a tape without intermediate annealing. A Cu sheath with a Ta barrier was also used for the fabrication. The Nb/sub 3/Sn tape shows a B/sub c1/ of 24.7 T at 4.2 K after the reaction at 900/spl deg/C. In addition the B/sub c2/ increased further by Ti doping. Moreover, the addition of 0.5-1.0 wt% Ge produces appreciable improvements in Tc and Jc at high magnetic fields. A Jc (Nb/sub 3/Sn) of 2.7/spl times/10/sup 4/ A/cm/sup 2/ has been obtained at 21 T and 4.2 K in the Ge-doped specimen. A small amount of Cu addition decreases the optimum reaction temperature to 800-850/spl deg/C. Present Nb/sub 3/Sn conductors seem to be useful for NMR high-field magnets as well as for refrigerator-cooled superconducting magnets.         Fully bonded internal-tin, niobium-tin (Nb/sub 3/Sn) conductor development at Oxford Superconducting Technology    J.C. McKinnell, R. Hentges, J. Tatum, Y.Z. Zhang and S. Hong Summary: Niobium-tin conductors are the class of conductors which allow the fabrication of superconducting magnets that generate over 9 T at 4.2 K and 12 T at 1.8 K, Oxford Superconducting Technology makes a wide range of niobium-tin conductors. One such conductor is a fully bonded internal tin, Nb/sub 3/Sn composite. The process for the manufacture of the fully bonded Nb/sub 3/Sn conductor is described. The process is applicable to conductors for high current applications and applications requiring low AC losses. Results for both classes of conductors are reported.         Development and manufacturing of superconducting cable-in-conduit conductor for ITER    V. Sytnikov, I. Peshkov, A. Taran, P. Dolgosheev, Y. Ipatov, A. Rychagov, G. Svalov and V. Mitrohin Summary: Russia as a member of "Cooperation in the Engineering Design Activities for International Thermonuclear Experimental Reactor" (ITER) takes part in manufacturing of superconducting cable-in-conduit conductor (CICC) for ITER toroidal field (TF) coils. JSC "VNIIKP" is responsible for Cr-plating, cabling and jacketing of TF conductor and develops complex technology for TF CICC production in RFHT. The technology consists of chrome coating, cabling (with compaction and wrapping) and jacketing (with insertion and compaction) operations and quality assurance (QA) procedure performance at every operation and on the finished conductor. There is a technological shop for plating of superconducting and copper wires with metal barrier plates. The shop includes the lines for surface treatment and galvanic chrome-coating, the autonomous system for water supply and regeneration of polluted water. The shop can produce about 100 km Cr-coated strands per week. Large park of tubular and planetary stranders, wrapping machine, compaction devices and other cabling equipment is used for production of sub-cables and cable of CICC. The jacketing line was designed and mounted in a facility 35 km south from Moscow during 1994-1996. The main technological and QA equipment is created, installed and tested. The jacketing line is fitted out with a take-up-pay-off unit, welding equipment, caterpillar, winch, rollgang (up to 1000 m), tube rolling mill, different tools and devices. The main steps of jacketing are assembling of conduit, control of welding joints, pulling cable through the conduit, compaction and conductor quality control. The description of the equipment and results of the trials are presented below.         Analysis of optically and magnetically determined bridging in internal-tin process Nb/sub 3/Sn strands    M.D. Sumption, E.W. Collings, E. Gulko, T. Pyon and E. Gregory Summary: An existing model for bridging induced magnetization and hysteretic loss has been extended to take into account the inhomogeneous morphology of metallurgical bridges. After an appropriate way of calculating the magnetization of a strand with a distribution of filament-bunch sizes had been devised some reasonable conformity between the results of optical image analysis and magnetization measurement was obtained. The previously developed anisotropic continuum model of bridging in multifilamentary (MF) strands led to a description of bridging intensity in terms of a dimensionless parameter /spl gamma//sub 2/ representing the area-fraction of bridged matrix material perpendicular to the filamentary axis. Based on measurements of variously heat treated (HT) internal-Sn ITER strands /spl gamma//sub 2/ was found to have values of 0.2 to 0.7%. At the same time saturation values of the length- and twist-pitch dependent magnetizations of the bridged samples were 3-6 times greater than the estimated un-bridged values. Some attention is also given to the influence of HT time and ramp-rate on the extent of bridging.         Investigation of the multifilamentary (Nb,Ti)/sub 3/Sn conductors with CuNb reinforced stabilizer    A. Shikov, V. Pantsyrnyi, A. Vorobieva, A. Silaev, N. Belyakov, I. Potapenko, K. Mareev, V. Vdovin, A. Nikulin, E. Klimenko, S. Novikov and M. Novikov Summary: Multifilamentary Nb/sub 3/Sn superconducting wires with Cu stabilizer reinforced by Cu-16% Nb circular layer and with the filaments artificially doped by Ti were developed. Microstructure, mechanical properties, superconducting parameters of (Nb,Ti)/sub 3/Sn wires with round and rectangular cross sections were investigated. The influence of heat treatment regimes on the wires critical current density in magnetic fields up to 14 T was examined. The changes of critical current density under the axial strain at 4.2 K were analyzed and distinct shift for a higher strains without diminishing of the critical current was confirmed. The comparison of obtained results with the appropriate values for the similar wires without Cu-Nb reinforcement was made. It was shown that the ultimate tensile strength and yield strength for the developed wires were higher in a factor of 1.5.         Superconducting properties of meter-class multifilamentary Nb/sub 3/Sn fiber-reinforced superconductors    K. Arai, H. Tateishi, M. Umeda, K. Agatsuma and Y. Iwasa Summary: A new type of Nb/sub 3/Sn superconductor, fiber-reinforced superconductor (FRS), has been developed for application in high-field pulsed superconducting magnets. This paper describes the superconducting properties of multifilamentary FRS with a length of one meter made by a sputtering apparatus with spools. The strain versus stress relationship and strain versus critical current properties are compared with those of other samples including a monofilamentary FRS. The index (n) values are examined for the multifilamentary FRS and compared with those of monofilamentary FRS selected from the multifilamentary FRS. A low-J/sub c/ FRS and a high-J/sub c/ FRS prepared by the same process are examined in terms of the critical current distribution.         Manufacture and analysis of internal-tin modified jelly roll cables for the 45 T hybrid magnet    P.D. Jablonski, P.M. O'Larey, M.B. Siddall, P. Morris, J. Vincent, T.A. Painter, L. Summers and J.C. McKinnell Summary: The 45 T hybrid magnet being constructed by the National High Magnetic Field Laboratory will generate the world's highest steady magnetic field. The coil is composed of four sections: A Nb-Ti outsert, two Nb/sub 3/Sn outserts and a water cooled resistive insert. Teledyne Wah Chang produced the wire for the Nb/sub 3/Sn coils (A and B) and oversaw the cabling. The wire design for the 45 T hybrid magnet is a modified version of TWC's Nb diffusion barrier wire. This wire design provides excellent control of the I/sub c/ and hysteresis loss. Coil A is composed of 525, 0.43 mm diameter wires 939 m in length. Coil B is a two piece cable composed of 315, 0.51 mm diameter wires. The lengths of the coil B pieces are 844 m and 623 m. The I/sub c/, "n"-value and hysteresis loss of the wire are shown to be uniform. The variability in RRR for each coil is discussed. The results of triplet test cables are also reported.         Growth conditions of textured YBCO films on a cylindrically curved surface of a YSZ substrate    Sangjun Oh, Doohoon Goo, JunHo Kim and Dojun Youm Summary: A cylindrically textured YBCO film was grown on a cylindrical surface of single crystalline YSZ. The substrate shape was a 60/spl deg/ sector of a cylinder. The substrate surface was pretreated by oxygen ion milling followed by deposition of 15 /spl Aring/ thick CeO/sub 2/ buffer layer. It was confirmed by XRD 2 /spl theta/ and /spl phi/-scan that the c-axes were normal to the surfaces and the a and b-axes were aligned in all regions. T/sub c/ was about 85 K.         Superconducting properties of Nd-Ba-Cu-O thick films prepared by liquid phase epitaxial growth    A. Takagi, U. Mizutani, T. Kitamura, S. Taniguchi, Y. Shiohara, I. Hirabayashi, S. Tanaka and Y. Yamada Summary: C-axis oriented Nd/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub y/ thick films were grown by the liquid phase epitaxy (LPE) technique onto MgO (100) single crystal substrates in Ar gas atmosphere containing 0.5 at.% O/sub 2/. The superconducting transition temperature T/sub c/ was very broad, when the film thickness was 10 /spl mu/m but became very sharp when it was increased to 100 /spl mu/m. The T/sub c/ value for the 100 /spl mu/m thick film could be increased up to 92 K by post-annealing at 300/spl deg/C for 336 hrs in O/sub 2/ atmosphere. Moreover, the peak effect, which is characterized by an increase in magnetisation with increasing magnetic field up to 15000 G at 50 K, was observed in the 100 /spl mu/m thick film. A substantial improvement in the superconducting properties when the film thickness is increased to 100 /spl mu/m, can be attributed to the stable persistence of the steady state growth mode instead of the transient mode responsible for the first 10 /spl mu/m thick deposition.         Introduction of pinning centers in superconducting YBCO thick film prepared by liquid phase epitaxy    T. Kitamura, S. Taniguchi, I. Hirabayashi, S. Tanaka, Y. Sugawara and Y. Ikuhara Summary: YBa/sub 2/Cu/sub 3/O/sub 7-y/ (YBCO) thick films were prepared by liquid phase epitaxy on crystalline substrates. The microstructure of the films is dominated by the misfit of the constant between the YBCO and the substrate. Misfit dislocations are introduced to release the stress due to lattice misfit between the YBCO and the substrate. The residual stress caused other kinds of defects in the YBCO films. The defects introduced to the YBCO films behave as effective pinning centers to enhance the pinning force in the magnetic field.         Formation of edge dislocations in thin epitaxial YBCO films    V. Svetchnikov, V. Pan, C. Traeholt and H. Zandbergen Summary: Transmission electron microscopy (TEM) of thin YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) films on different single-crystalline substrates revealed (by Moire patterns) edge dislocations having non-superconducting cores normal to the substrate. The dislocations are in small-angle boundaries with the average density as high as 10/sup 11/ cm/sup -2/. An extremely high density of dislocations is thought to be the cause of the high critical current density in YBCO epitaxial films. The mechanism for dislocation formation is considered in the framework of a computer model. Computer modeling provided the details of the dislocation arrangement either in domain boundaries or in twist boundaries, depending on the angle of the in-plane misorientation between film and substrate lattices. The model is found to be in goad agreement with experimental data on dislocations in YBCO superconducting films.         Artificially generated bi-epitaxial YBCO grain boundary junctions on SrTiO/sub 3/ and sapphire substrates    S. Nicoletti and J.-C. Villegier Summary: In this work we present the fabrication and characterization of artificially generated bi-epitaxial YBCO grain boundaries on SrTiO/sub 3/ and buffered R-plane sapphire. The grain boundary is obtained by partly interposing a MgO seed layer between a bare or buffered substrate and a CeO/sub 2/ layer. We find that the structural perfection of the YBCO films decrease as the complexity of the stacking sequence increases. By comparing the structural properties of the YBCO film on the different stacking sequences with the transport properties of the fabricated devices, we found a strong correlation between the normalized junction resistance /spl rho//sub N/ and the degree of structural perfection in the superconducting film. The electrical behavior of the obtained junctions can be explained considering the grain boundary as a Josephson structure where the barrier transparency is related with the degree of structural and textural perfection of each superconducting electrode, justifying the correlation between the normalized junction resistance and the disorder in the YBCO films.         Resonant Rutherford backscattering studies of cerium oxide thin films deposited by RF sputtering    C.C. Chin, R.J. Lin, Y.C. Yu, C.W. Wang, E.K. Lin, W.C. Tsai and T.Y. Tseng Summary: We have studied the stoichiometry of cerium oxide films deposited by RF sputtering on sapphire and MgO as a function of deposition conditions using the resonant Rutherford backscattering method. We found that some films have the off-stoichiometry of CeO/sub y/ with y greater than 2.0. Such an off-stoichiometry cannot be due to a mixture of the known phases of bulk cerium oxide samples. This may be due to either cerium vacancies or interstitial oxygen atomic impurities. The cerium ion X-ray photoemission spectra of those films cannot determine the vacancy of the cerium ions. The c-axis YBaCuO thin films deposited by sputtering on the CeO/sub 3.3/ buffer layer on sapphire was found to be epitaxial. The T/sub c/ was 86 K with /spl Delta/ T/sub c/ less than 1 K.         On the phase formation in Ag and AgMg sheathed BSCCO (2223) tapes    W. Goldacker, E. Mossang, M. Quilitz and M. Rikel Summary: BSCCO tapes with dispersion hardened AgMg sheaths possess excellent mechanical properties but reach commonly only about 70-80% of the critical currents of Ag sheathed reference tapes. Investigating the temperature dependence of I/sub c/ and the (2223) phase content for two annealing steps on 19 filamentary Ag and AgMg sheathed tapes, characteristic differences with respect to the reaction kinetics and the resulting final phase content were found. A detailed characterization of the properties of the AgMg envelope, defining the boundary condition during the tape annealing process, gives first indications, that the oxygen exchange between filament and annealing atmosphere is modified with obviously significant influence on the phase formation kinetics and phase diagram shifts.         Influence of the powder calcination temperature on the microstructure in Bi(Pb)-2223 tapes    M.D. Bentzon, Z. Han, L.O. Andersen, J. Goul, P. Bodin and P. Vase Summary: One goal of our research is to be able to manufacture high temperature superconducting cables for power transmission. The key elements is the production of superconducting tapes using the oxide powder in tube process. If quality and critical current density of the tapes can be improved, the quality and capacity of the final cable will also be improved. In this work we have calcinated the powder used in the powder in tube process at different temperatures and the microstructure of ceramic phase has been studied after rolling and after two annealings. It is observed that the powder calcination temperature has a strong influence on the microstructure, that is the arrangement and growth of superconducting phases as well as the secondary phases. It is found that the amount of big secondary particles is lowest for calcination temperatures of 820-830/spl deg/. Better crystal growth and grain sintering during first and second annealing are also observed for these calcination temperatures.         Ramp rate effect in Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10+/spl delta// formation    L.A. Schwartzkopf and D.K. Finnemore Summary: The properties of Ag-sheathed Bi2223 tapes depend strongly on the thermomechanical treatment processing parameters. We have examined the conversion of precursor powders to Bi2223 in heat-treated tapes as a function of ramp-to-temperature rate. Tapes containing precursor powders were ramped at rates from 50/spl deg/C/h to 800/spl deg/C/h to a final temperature of 835/spl deg/C, then held for 50 h, all in 20% O/sub 2/ and 80% N/sub 2/. The composition of the tapes was then determined by X-ray diffraction and by low-temperature magnetization measurements. The heat-treated tapes consisted almost entirely of a mixture of Bi2212 and Bi2223. The volume ratio of Bi2223 to Bi2212 in the tapes depended on the ramp rate in a complicated way; the volume ratio was largest (1.17) at 50/spl deg/C/h, the slowest ramp rate.         Processing and characterization of high T/sub c/ magnetic shields and flux transformers    D. Ponnusamy, N. Tralshawala, J.R. Claycomb, J.H. Miller Jr., K. Ravi-Chandar and K. Salama Summary: The use of high T/sub c/ SQUID (HTSQUID) magnetometers for magnetocardiography (MCG) and nondestructive testing (NDT) requires effective shielding from magnetic noise fields. The authors have investigated the shielding characteristics of high-T/sub c/ superconducting (HTS) material and developed a compact, portable system consisting of several HTS components. A process for fabricating these components out of Bi-Pb-Sr-Ca-Cu-O has been developed. Tubes and disks of various sizes have been formed by cold isostatic pressing (CIP) and sintered at reduced oxygen pressures. The HTS tubes exhibit shielding factors of up to 10/sup 3/ at low frequencies. A novel technique for fabricating superconducting flux transformers (specifically, first-order gradiometers) has also been developed. The flux transfer efficiencies of these first-order gradiometers have been evaluated. The tubes, gradiometers, and flux focusers have been incorporated into an HTSQUID setup. The authors find that the low-frequency noise rejection obtained in their setup is very promising for potential MCG and NDT applications in an unshielded environment.         The effect of wire drawing and cold rolling on the precursor 2212 phase texture and its subsequent influence on the (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ texture in Ag-clad tapes    J.W. Anderson, J.A. Parrell, P.V.P.S.S. Sastry and D.C. Larbalestier Summary: Abstract-We have studied the effect of wire drawing and cold rolling on the texture development of precursor (Bi,Pb)/sub 2/Sr/sub 2/CaCu/sub 2/0/sub x/ (2212) phase and its influence on the subsequent (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/0/sub y/ (2223) phase texture in Ag-clad tapes. A mixture of (Bi,Pb)/sub 2/Cu0/sub 4/ and SrCaCuO/sub 3/ powders having an overall 2223 composition was reacted to form the 2212 phase at different stages of deformation. X-ray diffraction peak height analysis was used to quantify the 2212 texture F/sub 2212/= I(008)/[I(008)+I(115)] at various oxide filament thickness. Wires containing powder reacted to the 2212 phase prior to loading into a Ag tube had F/sub 2212/=0.3 after drawing. This texture increased to F/sub 2212/=0.7 upon rolling. Two other composites reacted to the 2212 phase immediately after drawing, and after being drawn and partially rolled, had worse initial textures, but improved during rolling to F/sub 2212/=0.7. Samples reacted to 2212 after rolling was complete had F/sub 2212/=0.35. The results indicate that the 2212 texture reaches a maximum value of F/sub 2212/=0.7 and remains at that level upon subsequent rolling. Samples of filament thickness =80 /spl mu/m were then reacted to form 2223. For the samples which contained 2212 that had received at least some mechanical deformation, the 2223 phase formed with a texture factor F/sub 2223/ > 0.9, while the tape that contained 2212 formed after rolling developed a 2223 texture of only F/sub 2223/=0.75. The results show that there is a substantial texture enhancement upon reaction to 2223, which could be the result of either the 2223 formation mechanism or geometrically constrained grain growth.         YBaCuO thick films on planar and curved technical substrates    H.C. Freyhardt, J. Hoffmann, J. Wiesmann, J. Dzick, K. Heinemann, A. Isaev, F. Garcia-Moreno, S. Sievers and A. Usoskin Summary: For high-current applications, homogeneous well-textured high-temperature-superconducting Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBaCuO) films on technical ceramic or metallic substrates are required. The ion-beam-assisted deposition (IBAD) of yttria-stabilized zirconia (YSZ) buffer layers, which serve as templates for the YBaCuO, was extended to large planar areas (20 cm/spl times/20 cm) as well as curved or cylindrical (diameter /spl les/15 mm) substrates. For both types of substrates a pronounced in-plane alignment is observed. A deposition equipment is developed to grow high-quality YBaCuO films also on tubes by pulsed laser deposition (PLD), which is characterized by a high long-term stability both of the deposition rate and of the surface temperature of the growing film. Current densities up to 0.9/spl times/10/sup 6/ A cm/sup -2/ at 77 K in self fields are observed in films on planar Ni foils with biaxially aligned YSZ buffers (bi-YSZ). For the coating of long lengths of tubes and tapes a translation and a rotation of the samples are incorporated both in the buffer as well as in the YBaCuO-deposition process. Furthermore, the dependence of the critical transport current densities, J/sub c/, of the HTS layer on magnetic fields and on mechanical stresses are investigated.         The relation between ion damage anisotropy and IBAD YSZ biaxial alignment    K.G. Ressler, N. Sonnenberg and M.J. Cima Summary: Anisotropic damage tolerance is examined in relation to the in-plane orientations of [200] biaxially aligned yttria-stabilized zirconia (YSZ) films fabricated using dual ion beam deposition and ion beam assisted electron beam deposition. It is shown that ion channeling and anisotropic ion etching are not associated with IBAD biaxial alignment. The mechanism of IBAD biaxial alignment is crystallographic orientation change to reduce ion damage. The aggregation of defects leads to the formation of low angle grain boundaries that enable the growth direction change. Damage-tolerant crystalline planes are aligned in the direction of the assisting ion beam through the growth direction change.         Growth of biaxially aligned buffer layers for YBCO tapes by ion-beam assisted laser deposition and in situ RHEED texture analysis    V. Betz, B. Holzapfel and L. Schultz Summary: Biaxially oriented yttria-stabilized zirconia (YSZ) buffer layers were grown at room temperature by Pulsed Laser Deposition (PLD) and Ion-Beam Assisted Laser Deposition (IBALD) on amorphous substrates. Dependent on deposition parameters, IBALD grown films showed in-plane orientations of up to 20° FWHM (full-width at half maximum). Film in-plane alignment increases with film thickness. Film growth at room temperature without assisting ion-beam was polycrystalline with a growth-rate dependent preferred orientation. (011)- and (001)oriented films were obtained for growth rates of 10 /spl Aring//s and 14 /spl Aring//s, respectively. YSZ film growth orientation was monitored in situ with reflection high-energy electron diffraction. A quantitative analysis of the in-plane orientation of the IBALD grown YSZ film surfaces was established.         Transport properties of magnetic field/liquid assisted textured YBa/sub 2/Cu/sub 3/O/sub 7-x/ tape-cast films    J.A. Lewis, A.C. Read and T.K. Holmstrom Summary: Textured YBa/sub 2/Cu/sub 3/O/sub 7-x/ films (thickness=250 /spl mu/m) were fabricated by tape casting in an applied magnetic field (H=6 T). Platinum (1 wt%) was incorporated to induce liquid phase-assisted densification in films fired on silver (Ag) foil to 942/spl deg/C under reduced pO2(g) conditions. The transport critical current densities (J/sub ct/) of such films exhibited nearly field insensitive behavior between H=0-3 T (H/spl par/c-axis) at 77 K, with J/sub ct/>1000 A/cm/sup 2/ at H=3 T.         Preparation of YBa/sub 2/Cu/sub 3/O/sub y/ thick films on Y/sub 2/BaCuO/sub 5/:CeO/sub 2/ substrates by a diffusion process    D. Cha, Jeung Gon Ko, K. Lee and I. Iguchi Summary: High density YBa/sub 2/Cu/sub 3/O/sub y/ thick films were prepared on Y/sub 2/BaCuO/sub 5/(211) substrates with CeO/sub 2/ additions by a surface diffusion process between Ba/sub 3/Cu/sub 5/O/sub y/ composite coating powder and a 211 substrate. It was found that small addition of CeO/sub 2/ from 0 to 0.5 wt% to the 211 substrate had a strong effect on the reaction between the Ba/sub 3/Cu/sub 5/O/sub y/ coating layer and the 211 substrate, which led to the crystallization of YBCO thick film grains without impurity phases such as CuO and unreacted Y/sub 2/O/sub 3/ particles along the grain boundaries. As CeO/sub 2/ additions were increased from 0 to 5 wt%, the density of 211 substrate increased up to 80-90% and the critical temperature and the critical current density of 123 thick films also increased.         Improvement in switching characteristics of HTS power electric device prepared by pulsed laser deposition    Y. Yamagata, K. Shingai, T. Ikegami, K. Ebihara and N. Inoue Summary: High quality YBCO film was prepared on the YSZ buffered Hastelloy substrate by PLD method with an effective in-situ anneal. The T/sub c/(zero) and the J/sub c/ of the YBCO film on YSZ/Hastelloy is 83.4 K and 6.6/spl times/10/sup 3/ A/cm/sup 2/ (at 77 K), respectively. The phase transition between the superconducting state and the normal conducting state of the film showed higher response due to the high thermal conductivity and the small thermal capacity than that of the YBCO film deposited on MgO substrate.         Tensile measurements of the modulus of elasticity of Nb/sub 3/Sn at room temperature and 4 K    S.L. Bray, J.W. Ekin and R. Sesselmann Summary: The critical current of Nb/sub 3/Sn superconductors is highly sensitive to strain. Consequently, accurate mechanical modeling of these conductors is necessary to interpret experimental data and to predict conductor performance in applications such as large magnet systems. A key parameter in these models is the modulus of elasticity (E, Young's modulus); however, there are large discrepancies the available data, and there are no published tensile-test data on E for Nb/sub 3/Sn. Tensile test specimens were prepared from a starting material of Nb tape with 1.4 wt.% ZrO/sub 2/ precipitates. Tensile measurements of unreacted Nb and partially reacted Nb-Nb/sub 3/Sn tapes were made at room temperature (293 K) and at 4 K. A modulus of elasticity of 65/spl plusmn/15 GPa was extrapolated from these measurements for polycrystalline Nb/sub 3/Sn at 4 K, and 150/spl plusmn/15 GPa at room temperature.         Critical current measurements at electric fields in the pV m/sup -1/ regime    D.T. Ryan, H. Jones, W. Timms and N. Killoran Summary: We describe a technique for characterising sample lengths of commercial superconducting wire in closed loop configuration. This enables the measurement of critical current, as a function of applied magnetic field, at electric field criteria in the range 10/sup 6/ to 1 pV m/sup -1/ by detecting the decay of current in the closed loop. How these measurements relate to the more traditional 4 terminal measurements made on short sample coils is discussed and representative data from both NbTi and Nb/sub 3/Sn samples are presented and analysed.         Critical current measurements of NbTi wires in the temperature range 4.2-1.8 K    A.K. Ghosh and W.B. Sampson Summary: The critical currents of several NbTi wires have been measured in boiling helium in the temperature range 4.2-1.8 K and at magnetic fields up to 10T. In some instances, I/sub c/ (defined at a resistivity of 10/sup -14/ ohm) can be measured over the entire temperature range while for other conductors the quench drops below I/sub c/ as the temperature is reduced and the critical current cannot be determined. For most of these strands I/sub c/ can again be measured once the helium bath is in the superfluid state but for some wires it is not possible to measure the effective resistivity even in superfluid. Conductors fabricated by the same manufacturer can exhibit completely different behavior. In general there is a tendency for wires with high intrinsic current density and relatively low copper content to perform erratically at the lower temperature.         Measurement of the critical current and flux creep parameters in thin superconducting films using the single coil technique    J.H. Claassen Summary: A non-contacting method of determining the critical current of a superconducting film has proven useful in several laboratories as a routine indicator of HTS film quality. It consists of a small coil pressed against the film surface and driven with an audio frequency sine wave current (I/sub drive/). The onset of a significant third harmonic voltage component (V/sub 3f/) across the coil indicates that the screening currents in the film have exceeded their critical value. We show in this paper that the quantity V/sub 3f//(f I/sub drive/) should be a universal function of I/sub drive//I/sub sc/ if the Bean critical state model is applicable. Here I/sub sc/ is a scaling that is proportional to J/sub c/d (J/sub c/=critical current density in the film, d is its thickness) and f is the frequency. By varying the temperature of a thin YBCO film between 4.2 K and its transition, this scaling was observed to apply over a range of J/sub c/'s covering more than three decades. The frequency dependent measurements revealed a logarithmic dependence of the critical current on frequency that can be interpreted as a manifestation of flux creep. This data was used to infer the pinning energy within the collective pinning model.         Flux creep and relaxation phenomena in the presence of weak AC magnetic field    A.L. Kasatkin, V.M. Pan, V.V. Vysotskii and H.C. Freyhardt Summary: Evolution of the dynamic vortex response during the relaxation process In a superconducting slab situated in parallel DC magnetic field H/sub 0/ and superimposed weak AC field h/sub AC//spl sim/ exp(i/spl omega/t) is studied theoretically for the nonlinear vortex diffusion coefficient corresponding to the vortex liquid state. The phenomenon of "dynamical melting" of the vortex lattice at high induced current levels and its possible manifestation in relaxation characteristics of the dynamic vortex response are discussed. The flux creep rate and the irreversible magnetisation decay are shown to be enhanced by application of weak AC magnetic field h/sub AC/.         Thermally-induced nonlinearities in the surface impedance of superconducting YBCO thin films    J. Wosik, Lei-Ming Xie, J.H. Miller Jr., S.A. Long and K. Nesteruk Summary: We have measured the microwave power dependence of the surface impedance Z/sub g/ of YBa/sub 2/Cu/sub 3/O/sub x/ (YBCO) thin films up to very high microwave power levels. Experiments have been performed, using both frequency and pulsed time domain techniques, in a 14 GHz TE/sub 011/ dielectric cavity. Our results demonstrate that heating of the superconducting film by the applied RF field contributes significantly to the nonlinearity of the measured surface resistance at high input power levels. Analysis of the electromagnetic response of the cavity to a pulsed input signal has been performed using a dielectric resonator model combined with appropriate thermal balance equations for the film-cavity system. Both the frequency- and time-dependent nonlinear electromagnetic responses of the cavity have been calculated as functions of input power, and are in excellent agreement with our data.         Diagnostics of the high-T/sub c/ superconductive films in a strong electromagnetic field    A.N. Reznik Summary: The method for diagnostics of the nonlinear properties of the high-T/sub c/ superconductive films is proposed. It employs the experimentally obtained nonlinear radiocharacteristics of a superconductive resonator and takes into account the inhomogeneous distribution of the nonlinear surface impedance, caused by inhomogencity of the RF-magnetic field amplitude along a film surface. The last circumstance leads to the integral equation for surface impedance of a superconductor. The proposed method is based on solution of the inverse problem of electrodynamics. The dependences of surface resistance on the RF-magnetic field amplitude, and relationships between precision of the method and a measurement error are obtained.         Optimisation of the properties of high-T/sub c/ thick films    T.C. Shields, J.B. Langhorn, S.C. Watcham, J.S. Abell and T.W. Button Summary: High-T/sub c/ thick films of YBa/sub 2/Cu/sub 3/O/sub 7-/spl part// (YBCO) are potentially useful in various applications; for example in practical fault current limiters in the field of power engineering. The material also shows promise in the fabrication of numerous microwave devices. However it is of paramount importance to optimise their microstructure and properties, with particular respect to the critical current density (J/sub c/) and surface resistance (R/sub s/). Doping and barrier layer technology have been used to improve the characteristics of the films. Enhanced current carrying capacity is achieved as a result of doping with Pt and a Ba/sub 4/Cu/sub 1+x/Pt/sub 2-x/O/sub 9-z/ (0412) compound Exploitation of low dielectric loss and economically attractive alumina substrates has also been achieved, by means of barrier layers. The relation between the processing, microstructure and superconducting behaviour is reported.         Microwave losses and structural properties of large-area YBa/sub 2/Cu/sub 3/O/sub 7/ films on r-cut sapphire buffered with [001]/(111) oriented CeO/sub 2/    A.G. Zaitsev, R. Wordenweber, G. Ockenfuss, R. Kutzner, T. Konigs, C. Zuccaro and N. Klein Summary: YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin films were prepared on 2 inch in diameter (11_02) sapphire substrates buffered with CeO/sub 2/ layer of mixed [001]/(111) orientation. The thickness of the YBa/sub 2/Cu/sub 3/O/sub 7-x/ films was typically /spl sim/250 nm. The YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin films exhibited smooth surfaces (peak-to-valley roughness of less than 20 nm) free of cracks and outgrowths. The critical temperatures of these films were 87-89 K, the critical current densities (2-3).10/sup 6/ A/cm/sup 2/ at 77 K and zero magnetic field. The low field microwave surface resistance (R/sub S/) of the YBa/sub 2/Cu/sub 3/O/sub 7-x/ films was measured at 18.7 GHz. Values of /spl sim/1.4 m/spl Omega/ were obtained at 77 K and <70 /spl mu//spl Omega/ below 20 K. Such low R/sub S/ values are comparable to the lowest reported values for thicker YBa/sub 2/Cu/sub 3/O/sub 7-x/ films grown epitaxially on structurally well-matched substrates, e.g. LaAlO/sub 3/. The elevation of the microwave power produced a weak increase of R/sub S/. No drastic changes in R/sub S/ occur up to the maximum magnetic field of /spl sim/35 Oe at 79 K and /spl sim/63 Oe at 50 K. The properties of the YBa/sub 2/Cu/sub 3/O/sub 7-x/ films do not degrade with time.         Laser processing of YBCO thin films on sapphire for microwave applications    Sang Yeol Lee Summary: Laser ablation has been used to fabricate YBa/sub 2/Cu/sub 3/O/sub 7-x/(YBCO) thin film on sapphire substrates for microwave applications. The Interfaces between the YBCO laser ablated thin films and the r-plane Al/sub 2/O/sub 3/ substrates have been investigated by a transmission electron microscopy (TEM) and an Auger electron spectroscopy (AES) depth profile. The PrBa/sub 2/Cu/sub 3/O7-x (PBCO) buffer layer has been used to prevent the interdiffusion. The interfaces of YBCO/Al/sub 2/O/sub 3/ and YBCO/PBCO/Al/sub 2/O/sub 3/ have been compared. The intermediate diffusion layer in the YBCO film deposited on bare sapphire was visible between the film and the substrate but no diffusion layer between the YBCO/PBCO thin film and the substrate was observed directly by the cross-section image of TEM. The thickness of the diffusion layer on bare sapphire is about 300 /spl Aring/. This result of TEM is consistent with that of AES depth profile. We have fabricated a perturbed superconducting ring resonator on PBCO buffered sapphire for the microwave application. A fundamental resonance peak split was observed in the frequency range of 7.0-8.4 GHz.         Microwave characteristics of Ag-doped YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin films grown on MgO    Jeha Kim, Seok-Kil Han and Kwang-Yong Kang Summary: We prepared the Ag-doped YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (Ag-YBCO) bulk pellets of undoped, 10 wt.%, and 20 wt% and grew high quality thin films on MgO (100) substrates from the pellet targets by pulsed laser deposition. The films are highly c-axis oriented with T/sub c//spl ap/85 K. At T=44 K, the observed critical current density, J/sub c/ was 2.70/spl times/10/sup 6/ A/cm/sup 2/ and 1.17/spl times/10/sup 6/ A/cm/sup 2/ for 10 wt.% and 20 wt.% Ag-YBCO films, respectively. The critical current density, J/sub c/, of the Ag-YBCO/MgO films was improved by 65% with Ag-doing with respect to that of the undoped film. Using meanderline microstrip resonators, we measured the low temperature microwave surface resistance, R/sub s/. The observed R/sub s/ value of the 20 wt.% Ag-YBCO film was as small as 0.71 m/spl Omega/ for at 36 K and 8 GHz. XRD and RBS analysis showed that no silver was in the Ag-YBCO films even for the largest composition of Ag (20 wt.%) in the target pellet.         Relationship between electrical properties and crystallinity of YBa/sub 2/Cu/sub 3/O/sub 7-x/ ultrathin films    Y.N. Drozdov, Y.N. Nozdrin, A.E. Parafin, S.A. Pavlov, V.V. Talanov, A.V. Varganov and E.A. Vopilkin Summary: The X-ray data, DC and microwave properties as functions of the YBaCuO epitaxial films thickness in the range from 5 to 300 nm are investigated. The films were deposited by laser ablation on LaAlO/sub 3/ substrates. Films over 9 nm thickness have T/sub c0/=89 K, J/sub c/(77 K)>3 MA/cm/sup 2/ and the thickness dependence of their effective microwave surface resistance R/sub eff/ at 77 K, 10 GHz is in good agreement with the local electrodynamic theory for the thickness-independent intrinsic surface resistance R/sub s/=0.25 m/spl Omega/ and penetration depth /spl lambda/=250 nm. Decreasing a film thickness to less than a few tens nanometers provides a decrease of orthorhombicity parameter of YBCO cell, and to less than 9 nm - a reduction of transition temperature. The ultrathin films showed no degradation during thermocycling without a protection layer.         Improvements in the properties of internal-tin Nb/sub 3/Sn    E. Gregory, E.A. Gulko and T. Pyon Summary: A review is given of the present status of Stage IV of the strand production at IGC for the Central Solenoid (CS) Model Coil for the International Thermonuclear Experimental Reactor, (ITER). The design of this production strand was essentially frozen more than a year ago but a parallel development program has been carried out to improve the properties of internal-tin processed Nb/sub 3/Sn for fusion and other applications. The H/sub cl/* and T/sub c/* have been raised, the J/sub c/ controlled over a wide range of values, and the losses lowered in a number of different ways. An examination of the microstructure and electrical properties after a series of different thermomechanical treatments has been carried out and some of the preliminary results are described.         Heat treatments, microstructure and properties of internal-tin Nb/sub 3/Sn    R. Taillard, C. Verwaerde, C.E. Bruzek and P. Sulten Summary: The decrease of temperature ramp rate during heat treatments of the internal tin process causes an increase of the critical current density at low and medium magnetic fields (4-16T). This paper investigates the metallurgical origin of this benefit by considering the effects of a change of heating rate on the phase transformations of bronze and on the filament recrystallization. The low temperature formation of Nb/sub 3/Sn is important for the critical current density of this material. This is explained by the composite microstructure evolution.         Repeatability of critical-current measurements on Nb/sub 3/Sn and Nb-Ti wires    L.F. Goodrich, L.T. Medina and T.C. Stauffer Summary: A varying degree of repeatability has been observed in critical-current (I/sub c/) measurements of Nb/sub 3/Sn and Nb-Ti wires as a function of the number of thermal cycles from room temperature to 4 K. The increase of I/sub c/ between the first and second thermal cycle can be 1% to 2% at 12 T for Nb/sub 3/Sn wires. This was observed on Nb/sub 3/Sn wire by all four laboratories that participated in a recent interlaboratory comparison conducted in the International Thermonuclear Experimental Reactor (ITER) project. These data indicate that if I/sub c/ changes beyond the error limits, it increases fairly monotonically with thermal cycling until it eventually saturates. In contrast, the I/sub c/ of a Nb-Ti wire is very repeatable with thermal cycling. This suggests that the effect on the Nb/sub 3/Sn wire is due to its strain sensitivity. Most of these data were taken with the sample on a Ti-6Al-4V measurement mandrel. This study also investigated the repeatability of I/sub c/ measurements using other mandrel materials. The increase in I/sub c/ of Nb/sub 3/Sn wire could enhance the performance of some applications. However, the lack of repeatability in I/sub c/ measurements on Nb/sub 3/Sn wires is a limitation in precise interlaboratory comparisons.         Influence of the field orientation on the critical current density of Nb/sub 3/Sn strands    T. Schild, J.L. Duchateau and D. Ciazynski Summary: In many applications using superconducting cables such as tokamaks for fusion, the angle between the strand axis and the applied field can take values different than 90/spl deg/. Estimating the critical current value for any angles knowing only its value for the well-known perpendicular orientation at a given field, is very useful. A model is presented that could achieve, for a given material, such a result thanks to an intrinsic parameter, called the anisotropy parameter, defined as the ratio of the axial critical current in a perpendicular field to the azimutal critical current In a parallel background field. To check the model for Nb3Sn, this parameter has been measured on Nb/sub 3/Sn untwisted strands. We used two methods: one based on magnetic measurements and the other on critical current measurements with several field orientations and strengths. Unexpectedly an anisotropy of the critical current density as a function of the field orientation has been pointed out in these measurements.         Quantitative image analysis of filament coupling and grain size in ITER Nb(Ti)/sub 3/Sn strand manufactured by the internal Sn process    P.J. Lee, J.R. Ruess and D.C. Larbalestier Summary: Excellent images of Nb/sub 3/Sn filaments and their grain structure can be obtained from high resolution scanning electron microscopy of filamentary Nb/sub 3/Sn strands. Our aim has been to explore the detailed macro- and micro-structural characterization that can been achieved using image analysis of such micrographs. We have quantitatively characterized the filament size, shape and separation by digital image analysis. We have also used fracture surfaces to quantify both grain boundary density and morphology. Grain size and morphology varies not only from filament to filament but within the same filament too. We quantify here, for the first time, clear trends in the variation of both grain size and morphology, as well as local grain boundary density with respect to position within the filaments.         Influence of the tin diffusion process in multifilamentary Nb-Cu-Sn-Mg-Ta wire on Nb/sub 3/Sn inter-filamentary bridging    B.A. Glowacki Summary: An understanding of the correlation between the diffusion of tin from a high tin reservoir to the niobium filaments and the uniform properties of the intermetallic Nb/sub 3/Sn diffusion layers of "high tin" multifilamentary conductors formed during multistage heat treatment is essential for the further improvement of the superconducting electromagnetic properties of advanced conductors. A detailed study has been made of the formation of the A-15 layer in multifilamentary Nb-Cu-Sn-Mg-Ta wire during multistage heat treatment. The importance of the rapid conversion of /spl epsi/-Cu/sub 3/Sn on filament displacement and mechanically induced inter-filamentary bridging within the individual bundles is demonstrated. It is concluded that the architecture of the conductor and phase development in the Cu-Sn-Mg matrix are the two major factors responsible for Nb/sub 3/Sn inter-filamentary bridging.         Flux jump stability in Nb/sub 3/Sn tape    C.G. King, D.A. Grey, A. Mantone, Bu-Xin Xu, M.L. Murray, H.R. Hart Jr. and M.G. Benz Summary: GE manufactured Nb/sub 3/Sn tape was examined to determine the influence of critical temperature, both conductor and coil current density (J/sub c/), and tape width on flux jump stability. The onset of flux jump instability was measured in 3 mm wide, copper stabilized tapes reacted to a range of critical currents (I/sub c/) above and below the normal I/sub c/ in production tape. These tapes were stacked in approximations of coil cross sections with and without Insulating interlayer glass cloth. Production tape, 3 mm wide, was found to be stable above 9 Kelvin (K) with normal quantities of interlayer glass when reacted to yield an I/sub c/ no greater than 482 amps at 5 Tesla (T) and 4.2 K. To evaluate low temperature operation in the range of 4-5 K, consistent with cryocooler advances, narrower width tapes were studied as decreasing tape width will decrease the flux jump stability temperature. Flux jump stability was measured in identically reacted tapes slit to 3.0, 2.5, 2.0 and 1.5 mm. The 1.5 mm tape was found to be stable above 6.5 K. Slitting edge damage in the narrow widths was found to be similar for all widths of tape. The I/sub c/ of the narrower tapes were predictably reduced. Decreasing coil current density also decreased the flux jump stability temperature. Nb/sub 3/Sn tape, 3 mm wide, cowound with copper into a solenoid was tested to evaluate lower temperature operation. The coil was stable during both ramping and operation near the short sample I/sub c/ of the tape at 4.2 K.         Effect of flat-roll forming on critical current density characteristics and microstructure of Nb/sub 3/Al multifilamentary conductors    T. Takeuchi, Y. Iijima, K. Inoue and H. Wada Summary: We have developed a nearly-stoichiometric Nb/sub 3/Al multifilamentary superconductor by exploiting the transformation from bcc supersaturated-solid-solution Nb(Al)/sub ss/. This is a candidate conductor for 1 GHz NMR magnets. Flat-roll forming, an effective way to increase the packing factor of the coil and thereby the coil-current-density, has been carried out on the multifilamentary Nb(Al)/sub ss//Nb wire, and its effects are compared with that of the conventional Nb tube processed conductor. A Nb(Al)/sub ss//Nb wire, 0.74 mm in diameter, was successfully deformed into a tape conductor (the thinnest case: 0.15/sup t//spl times/2.2/sup w/ mm) without mechanical fracture. The flat-roll forming creates very little anisotropy in critical parameters and scarcely degrades the J/sub c/ properties. Excess flat-rolling causes a wide distribution of Nb(Al)/sub ss/ filament areas and thus reduces the n-index in the voltage-current characteristic. However, it is probably possible to retain the high value of the n-index of a wire, by appropriately designing the overall-aspect-ratio of a flattened conductor.         Solid-state high-oxygen-fugacity processing of BSCCO-2212 superconductors    J.J. Gannon Jr. and K.H. Sandhage Summary: Silver-sheathed powder-in-tube processed tapes and thick films of the Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8/spl plusmn//spl delta//-type (Bi-2212) superconductor have been annealed under high temperature, high oxygen fugacity (i.e.fO/sub 2/>0.1 MPa) conditions. At sufficiently high temperatures and oxygen fugacities, the Bi-2212 phase decomposes into a mixture of solid oxides: a Bi/sub 2/(Sr,Ca)/sub 2/Cu/sub 1/O/sub 8/spl plusmn//spl delta//-type (Bi-2201) phase, an alkaline-earth bismuthate Bi/sub 9/Sr/sub 1/1Ca/sub 5/O/sub y/-type (Bi-91_1_5) phase and CuO. Subsequent reformation of Bi-2212 in pure, flowing oxygen at 0.1 MPa and 860/spl deg/C has yielded plate-like grains with enhanced 00l texture (as discerned from X-ray pole figure analyses and electron microscopy). The values of oxygen fugacity leading to sub-solidus decomposition and reformation of Bi-2212 at 500 to 860/spl deg/C are given. XRD and SEM analyses, as well as preliminary critical current measurements of decomposed and reformed Bi-2212 tapes, are presented.         The effect of the maximum processing temperature on the microstructure and electrical properties of melt processed Ag-sheathed Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ tape    M. Polak, W. Zhang, A. Polyanskii, A. Pashitski, E.E. Hellstrom and D.C. Larbalestier Summary: The critical current density (J/sub c/) is very sensitive to the maximum temperature (T/sub m/) used to melt process Ag-sheathed Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ tapes. In this study we have found that the optimum T/sub m/ was 894-896/spl deg/C and that variations of /spl plusmn/2/spl deg/C strongly decreased J/sub c/. We found that the density of the oxide core and its Vickers hardness displayed a maximum in tapes that had been processed at the optimum T/sub m/. In addition, the room temperature electrical resistivity of the core was lowest for the tapes with the maximum J/sub c/ at 4.2 K. A formation of macropores was observed in tapes processed at T/sub m/ above the optimum one. MO imaging and SEM observation showed that the magnetic flux penetrates more easily into tape areas containing macropores. Together these observations show that T/sub m/ exerts a very powerful effect on the macroscopic density of the oxide core, this controlling the connectivity and the effective cross-section of the oxide core. Thus J/sub c/ depends on T/sub m/ primarily because the effective cross-section of the core depends on T/sub m/.         Overpressure processing of Ag-sheathed Bi-2212 tapes    J.L. Reeves, M. Polak, W. Zhang, E.E. Hellstrom, S.E. Babcock, D.C. Larbalestier, N. Inoue and M. Okada Summary: A critical problem for melt-processed silver-sheathed Bi-2212 tapes is gas release during heat treatment which deforms the sheath ("bubbling") and forms voids in the superconducting core. An overpressure furnace is used to study how the extent of bubbling changes with the total pressure (P/sub tot/). By processing in P/sub tot/ up to 9 atmospheres with constant oxygen partial pressure (pO/sub 2/=1 atm), bubbling in coils is eliminated. The critical current density increases with increasing P/sub tot/. Also, the phase assemblage in overpressure-processed tapes is unchanged compared to conventionally processed tapes.         Study of the effect of the Sr/Ca ratio on the microstructure and critical current density of BSCCO 2212 Ag-sheathed tapes    W. Zhang, O.V. Pupysheva, Y. Ma, M. Polak, E.E. Hellstrom and D.C. Larbalestier Summary: The effect of the Sr/Ca ratio and Bi content on the microstructure and J/sub c/ of Ag-sheathed 2212 tapes was studied. Changing the Sr/Ca ratio changed the melting temperature of 2212 phase, the phase assemblage in the melt, and the nonsuperconducting phases in the fully processed tape. In tapes with Sr/Ca=2.75, the 2201 phase crystallizes from the melt before 2212 during cooling, and this 2201 remains in the microstructure. In tapes with Sr/Ca=1.3, there is more liquid left after cooling, and it converts to 2201 as the tape cools to room temperature. Fully processed tape with overall composition 2.1:2:1:2 had the most homogeneous microstructure and highest J/sub c/.         Co-reaction of textured superconducting, conducting and insulating multilayer composites    D.R. Watson, J.E. Evetts and M. Chen Summary: Many applications of superconductors are limited by low values of the engineering critical current density (J/sub cc/). Significant improvements are possible through the merger of green tape and composite reaction texturing technologies. Tape casting and elastomer processing techniques have produced insulating (MgO and Al/sub 2/O/sub 3/), conducting (Ag) and superconducting (Bi-2212+MgO-fibre) tapes with uniform thickness ranging from 0.1-2 mm. Green tapes of the desired thickness can be laminated into multilayer structures and co-reacted; the superconducting layer occupying over 50% of the cross section allows the engineering of an artefact for optimal I/sub c/, and maximum J/sub c/c. The texture observed in the Bi-2212 layer is induced by specifically aligned MgO-fibres. As a necessary step in developing this technology, results are presented on (1) additions of 0-10 %wt Ag to Bi-2212 in order to modify its partial melt behaviour, (2) control of the shrinkage and densification of individual layers which is critical to uniformity and (3) chemical buffering of the Bi-2212 layer from insulating layers of doped MgO and Al/sub 2/O/sub 3/ during co-reaction.         React-wind-and-sinter technique for Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8/ high T/sub c/ coils    S. Boutemy, J. Kessler and J. Schwartz Summary: The fabrication of HTS coils and magnets with critical current densities close to short samples is an important challenge in high field magnet research and development. While wind-and-react suffers from inaccurate temperature control, react-and-wind technique generates strain inside the core during winding. A new technique is being developed at the NHMFL: the react-wind-and-sinter technique. Long lengths of powder-in-tube conductor are reacted uniformly by pulling the tape continuously through a temperature profile in a controlled atmosphere furnace. The precursor is partial-melted and cooled to form large grains. The tape is then wound into the desired coil shape and sintered at constant temperature to repair cracks that developed during winding and achieve high phase purity and grain alignment.         Preparation and properties of nanosize TiO/sub 2/ and MgO-doped Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ tapes    Wangshui Wei, Yangren Sun, J. Schwartz, K. Goretta, U. Balachandran and A. Bhargava Summary: Nanosize MgO and TiO/sub 2/ particles were added to the Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ powder with 20% molar fraction. Powder-in-tube Ag-sheathed tapes were made from the doped powders and heat treated by partial melting processing. Heat treatment optimization was carried out to increase the critical current density. Scanning electron microscopy and energy-dispersive X-ray spectra were used to study the phases present in the tapes. The effect of MgO additions on the flux pinning behavior was investigated by magnetic hysteresis and transport critical current measurements at various temperatures and fields.         Preparation of dispersion-hardened single- and multifilamentary Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ tapes and wires    J. Kessler, S. Boutemy, S. Chen, D. Dimapilis, V. Miller, W. Wei and J. Schwartz Summary: The impact of oxide dispersion-hardening on the mechanical behavior of powder-in-tube Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ tapes is investigated. Single-core tapes and multifilamentary tapes with 19 filaments were prepared from commercially available AgMg tubes and powder. The cold-working process was monitored by observing sample microstructures at intermediate stages. The deformation process was optimized to eliminate bridging in the multifilamentary conductor. Short samples were heat-treated and characterized by critical current measurements (I/sub c/) at 4.2 K and 0 T. The maximum filament critical current density (J/sub c/) obtained was 115,000 A/cm/sup 2/ corresponding to an engineering critical current density (J/sub c/) of 22,000 A/cm/sup 2/.         Improvement of critical current density and residual resistivity on jelly-roll processed Nb/sub 3/Al superconducting wires    N. Ayai, A. Mikumo, Y. Yamada, K. Takahashi, K. Sato, N. Koizumi, T. Ando, M. Sugimoto, H. Tsuji, K. Okuno and N. Mitchell Summary: The residual resistivity of copper stabilizer (/spl rho/), is deteriorated by the diffusion of chromium plated on the strand surface during heating of Nb/sub 3/Al strands. To improve this degradation, the copper stabilizer has been located on the center of the cross-section of the strand rather than near the strand surface. As a result, /spl rho/ is improved to one-sixth of previous value achieving 1.6/spl times/10/sup -10/ /spl Omega/m in a laboratory scale strand. The critical current density (J/sub c/) of this strand was 715 A/mm/sup 2/ at 12 T. This technique was applied to prototype strands to be used in a Nb/sub 3/Al Insert Coil developed in ITER R&D programme resulting in a /spl rho/ of 1.5/spl times/10/sup -10/ /spl Omega/m, which meets ITER specification. In addition, the improvement of J/sub c/ was also studied by two-stage reaction including a continuous heating procedure, which resulted in a J/sub c/ of 1130 A/mm/sup 2/ at 12 T and good longitudinal uniformity.         Dependence of critical current density on temperature and magnetic field in multifilamentary Nb/sub 3/Al strands made by the Jelly roll process    T. Ando, Y. Nunoya, N. Koizumi, M. Sugimoto, H. Tsuji, K. Sato and Y. Yamada Summary: The temperature dependence of critical current in Nb/sub 3/Al/Cu multifilamentary strands fabricated by the Jelly-roll process has been measured to establish a data base for fusion magnet design. The measurements are performed in the temperature range of 4.2 to 16 K and in the magnetic field range of 0 to 16 T. From these data, we have produced empirical formulas available for conductor design work.         Some superconducting characteristics of Nb/sub 3/Al composite wires prepared by rapid-quenching process    K. Fukuda, G. Iwaki, F. Hosono, S. Sakai, Y. Iijima, T. Takeuchi, K. Inoue, N. Kobayashi, K. Watanabe and S. Awaji Summary: Multifilamentary Nb/sub 3/Al superconducting wires for high field magnets above 20 T have been developed by a rapid-quenching process. A long length wire was produced, and a coil was fabricated using the wire. J/sub c/ of this wire was 195A/mm/sup 2/ at 20 T, 4.2 K and 486A/mm/sup 2/ at 20 T, 1.8 K, B/sub c2/ of the coil was 24.6 T at 4.2 K and 26.9 T at 1.8 K and the T/sub c/ was 17.8 K. In addition to investigating the stability, the residual resistance ratio was measured, the value was 16.9. Scattering of J/sub c/ in the longitudinal direction was examined and found to be within /spl plusmn/10%.         Field and temperature dependences of critical current in direct-heated Nb-tube processed Nb/sub 3/Al wires    K. Itoh, T. Kuroda, M. Yuyama, Y. Iijima, H. Wada, Y. Murakami and D. Mao Summary: High-field performance of Nb-tube processed Nb/sub 3/Al conductors is improved and allows these conductors for use above 20 T, when continuous direct-heating is applied before final annealing in the fabrication process. In the present study we prepared 0.74 mm/spl phi/ Nb/sub 3/Al wires containing 121/spl times/121 7-core elementary Nb/Al-Mg composites by this modified method and measured their critical current, magnetization and susceptibility as a function of field and temperature. From these measurements, we have found that the volume pinning force, F/sub p/ of these wires simply follows the Kramer's scaling law, i.e. F/sub p//spl prop/B/sub c2//sup 2.5/b/sup 0.5/(1-b)/sup 2/ w here b=B/B/sub c2/, for the entire range of temperature measured, 4.2/spl sim/16 K. Since A15 phase grains formed are very fine, the most probable pinning source seems to be grain boundaries which are dense compared to other possible sources such as interfaces between Nb-Al alloy phase and Nb/sub 3/Al filaments.         Nb/sub 3/Al thin films made by RF magnetron sputtering process with a single target    K. Agatsuma, H. Tateishi, K. Arai, T. Saitoh, N. Sadakata and M. Nakagawa Summary: We have studied a high field pulsed superconductor with high elastic modulus fiber reinforcement. We call the conductor Fiber Reinforced Superconductor (FRS). We have succeeded in making a sputtering target which consists of reacted Nb/sub 3/Sn single material by powder metallurgy. Nb/sub 3/Al superconductor is well known as a candidate for superconducting magnets for fusion reactors because of good properties of mechanical stress and irradiation toughness. To overcome the difficulty of fabricating into superconducting wire, we have made a single sputtering target of Nb-Al compound by powder metallurgy. Thin Nb/sub 3/Al films on MgO substrate were made using this target. Experimental results for these films are presented.         Electromagnetic properties of high angle [001] twist grain boundaries in Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta// bicrystals    Qiang Li, Y.N. Tsay, Y. Zhu, M. Suenaga, G.D. Gu and N. Koshizuka Summary: Detailed measurement of electrical resistivity and V-I curves as a function of temperature and magnetic field up to 9 T were performed on several superconducting Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta// (Bi-2212) bicrystals with synthetic high angle [001] twist grain boundaries. We found that the resistive onset temperature and field (at level of 10 nV) for all of the measured high angle twist boundaries were similar to those for their constituent single crystals. Furthermore, these boundaries were able to carry critical current as high as the single crystals. Our results suggested absence of weak-link behavior in the high angle [001] twist grain boundaries of Bi-2212 bicrystals.         Vortex transfer mechanisms in C-oriented YBCO films with small-angle-boundaries    A.L. Kasatkin, V.M. Pan and H.C. Freyhardt Summary: The mechanism of vortex depinning and motion along the row of parallel equidistant linear pins in an anisotropic type-II superconductor is considered, The essential role of the surface effects for these processes is emphasized, The activation energy of vortex motion and the critical current value are calculated for the current flow perpendicular to this row. We suppose this model to be applicable for description of resistive properties and the critical current dependence on the azimuthal misorientation angle between neighboring grains for YBCO bicrystals and rather thick c-oriented films with low-angle tilt grain boundaries, containing edge dislocations, which are parallel to the c-axis.         Enhanced vertex pinning in annealed TlBa/sub 2/CaCu/sub 2/O/sub x/ thin films    E.L. Venturini, P.P. Newcomer, M.P. Siegal and D.L. Overmyer Summary: Furnace anneals of TlBa/sub 2/CaCu/sub 2/O/sub x/ thin films at temperatures above 500/spl deg/C cause partial TlO/sub x/ loss. High resolution transmission electron microscopy images reveal nanometer-scale discontinuities (pinched stacking faults) in the microstructure of annealed films. Significant increases in the vortex pinning potential and critical current density at elevated temperatures in strong magnetic fields are observed and are attributed to the presence of these localized defects.         The influence of granularity on dissipation in high temperature superconductor    C.C. Silva and M.E. McHenry Summary: We have investigated AC losses in high temperature superconductors. Granular YBCO samples were prepared by the conventional solid state synthesis process. Individual grains are anisotropic and these polycrystalline samples have randomly oriented c axes. Intrinsic and hysteretic losses were investigated using a Quantum Design PPMS magnetometer. AC susceptibility was measured as a function of magnetic field, frequency and temperature and field history. Three types of temperature dependent loss peaks, T/sub p/'s, were observed. The three peak types (in /spl chi/") are attributed to intrinsic (London theory), intergranular Josephson junction, and intragranular pinning loss mechanisms, respectively. They are observed to change systematically as temperature and magnetic field varies. We suggest physical models for the H, T and /spl omega/ dependence of the loss peaks.         Influence of microstructure on power dissipation in bulk Y-Ba-Cu-O structures    T.R. Askew, M.G. Metzler, M.S. Herron and T.W. Button Summary: The relatively low values of critical current density (J/sub C/) in bulk high T/sub C/ materials are a problem for many applications, but these materials are now ending use in developmental fault current limiters of various design. Intended primarily for AC power applications, these devices rely on materials that transition quickly between a state of effectively lossless conduction and a state which dissipates significant power directly or significantly changes the magnetic coupling between other circuit elements. Most bulk material processes have been adjusted to maximize the value of J/sub C/ rather than to provide the well defined, sharp transition just mentioned. This study compares the dissipative properties of sintered YBCO with equiaxed, unoriented grains to that of two different types of melt-processed thick film material with plate-like grains in c-axis orientation. Dissipative properties are measured under current densities of 10 times J/sub C/ or more. Isothermal conditions are maintained through the use of submillisecond feedback-controlled current pulses. Significant differences are noted in the high-current flux flow properties, with the sintered samples developing Ohmic behavior and the samples with oriented microstructures developing voltages proportional to I/sup 2/. Sharp transitions at J/sub C/ and extreme dependence on applied magnetic field were noted in all cases.         The effect of oxygenation and annealing on the peak effect of the magnetization of melt-grown YBa/sub 2/CU/sub 3/O/sub 7-/spl delta//    Z. Yi, C. Beduz, Y. Yang, R.G. Scurlock and P.A.J. de Groot Summary: The influence of oxygenation and high temperature annealing on the peak effect of the magnetization of melt-grown YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (0         Identification and quantification of phases formed during the processing of (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x//Ag composite conductors    N.N. Merchant, A.K. Fischer, V.A. Maroni, W.L. Carter and R.D. Parrella Summary: Scanning electron microscopy, energy dispersive X-ray analysis (including X-ray dot mapping), X-ray diffraction and computer-based image analysis have been used to study non-superconducting secondary phases that evolve during the processing of (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x//Ag composite conductors. These investigations have provided new information and insights about specific alkaline earth cuprates (AECs) and lead-rich phases, We can conclusively identify (Ca,Sr)/sub 2/CuO/sub 3/, (Ca,Sr)/sub 14/Cu/sub 24/O/sub 41/ (14/24), and CuO phases, the alkaline earth plumbates, and a (Bi,Pb)-Sr-Ca-Cu-O 3221 phase with a wide range of Pb/Bi ratios. These techniques also help in differentiating voids from secondary phases and alkaline earth plumbates from the lead-rich 3221 phase.         Measurement of the penetration depth of superconducting thin films by optoelectronic sampling techniques    Shinho Cho, H. Erlig, Shamino Wang and H.R. Fetterman Summary: The magnetic penetration depth of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) thin films has been determined as a function of temperature by using picosecond optoelectronic sampling techniques. Electrical pulses of 8 ps full width at half maximum were generated on photoconductive switches by a mode-locked Nd:YAG pumped dye laser and propagated on superconducting delay lines which were 250 mm in length. The measured behavior at low temperature (T         Hall effect study of YBCO HTS films implanted with phosphorous ions    H. Kato, A. Kulpa, A. Wong, D. Hui, N.A.F. Jaeger, J.F. Carolan, W.N. Hardy and Q.Y. Ma Summary: The inhibition of superconductivity in YBCO HTS films using ion implantation has shown itself to be a promising method for patterning HTS films for use in the fabrication of electronic devices. In this work we have shown that the carrier concentrations in YBCO films may be reduced in a controlled fashion using ion implantation, while retaining the superconducting properties of the films. YBCO films 100 to 140 nm thick commercially grown on SrTiO/sub 3/, were implanted with phosphorus ions, at 100 keV, with doses ranging from 1/spl times/10/sup 14//cm/sup 2/ to 1/spl times/10/sup 15//cm/sup 2/. Superconducting specimens with carrier concentrations ranging from /spl sim/10x10/sup 21//cm/sup 3/, for an unimplanted sample, to /spl sim/7/spl times/10/sup 20//cm/sup 3/ for a sample receiving an implant dose of 1/spl times/10/sup 15//cm/sup 2/, were obtained. The carrier concentrations were determined from Hall effect measurements.         Optimization of drive coil for inductive measurement of absolute /spl lambda/(T) of superconductor films    Ju Young Lee, Young Hwan Kim, Taek-Sang Hahn and Sang Sam Choi Summary: The drive coil is designed to nullify the screening current density at the film edge in two-coil apparatus which has the drive coil and receive coil coaxially located on the opposite side of a superconducting film in order to obtain /spl lambda/(T). This is achieved by adopting fewer counter winding turns in the top section of drive coil than that of the bottom which is closer to the film. The optimal configuration of drive coil winding is numerically determined for a circular film and corresponding magnetic field at the film edge is parallel to the plane of the film surface. Consequently, the mutual inductance M, which is proportional to the coupled flux to receive coil, is insensitive to small differences in film size and transverse positioning of the film to coil axis. As a result, the accuracy of measurement can be greatly improved by enhancing the precision of the film's vertical positioning.         Magnetic noise in YBCO thin films and its relationship to growth morphology    J. Smithyman, C. Muirhead, M. Aindow, F. Welhofer and P. Woodall Summary: We report preliminary measurements of the magnetic noise from a series of thin YBCO films close to the superconducting transition. This is part of a more extended study of the relationship of flux noise to film thickness and morphology. We find that there are two contributions to the noise, one which is dominant at and above the noise peak and is a function of the temperature dependent resistivity of the film and another which contributes the conventional 1/f noise and is dominant at lower temperatures. The relative contributions are affected by both magnetic field and film morphology.         Infrared characterization of SrTiO/sub 3/ thin films using attenuated total reflectance    C.H. Mueller, D. Galt, R.E. Treece, T.V. Rivkin, J.D. Webb, H.R. Moutinho, M. Dalberth and C.T. Rogers Summary: Attenuated Total Reflectance was used to measure the phonon vibration frequencies over the range 425-800 cm/sup -1/ of SrTiO/sub 3/ thin films deposited either directly on LaAlO/sub 3/, or on YBCO-coated LaAlO/sub 3/ single crystal substrates. In the s-polarized spectra, the transverse optic Ti-O stretching vibration shifted to lower frequencies as the film thickness increased, which was attributed to damping caused by the generation of lower frequency phonon modes. The transverse Ti-O stretching vibration was also observed in the p-polarized spectra, but was more heavily damped, which indicates the damping is more pronounced when the electric field has a component perpendicular to the film surface. Damping of the transverse modes was attributed to coupling of these modes to other phonon modes, and may be a source of the high losses at microwave frequencies.         Photodoping effect in Y-Ba-Cu-O Josephson junctions and thin films    R. Sobolewski, R. Adam, W. Kula, W. Markowitsch, C. Stockinger, W. Gob and W. Lang Summary: We report our studies on the photo doping effect in YBa/sub 2/Cu/sub 3/O/sub x/ (YBCO) grain-boundary weak links and partially oxygen-depleted (T/sub c,mid/ /spl ap/52 K) thin films, We focus our attention on the erasable process, in which persistent photoconductivity (PPC) introduced by light at low temperatures relaxes back above 260 K. In the tested 2-/spl mu/m-wide step-edge grain-boundary junctions, PPC manifested itself as above 30% increase of the critical current, while the illuminated films exhibited up to 2.5 K enhancement of T/sub c/'s. In the case of films, we also observed upon illumination a continuous decrease (no saturation effect) of both the longitudinal and transversal (Hall) resistivities. In-situ Hall effect band model, PPC at low temperatures results in the increase of both the hole mobility and concentration, while at temperatures above 250 K, the mobility is reduced after prolonged illumination, whereas the carrier concentration is enhanced even more than allow temperatures. We have also demonstrated that the T/sub c/ enhancement due to photodoping is a function of the carrier concentration rather than the mobility, Our experimental results indicate that the physical origin of PPC is same in both YBCO grain-boundary junctions and partially oxygen-depleted films, and can be understood as the coexistence of photoassisted oxygen ordering and photoinduced charge transfer.         Resistivity and critical current anisotropy of untwinned a-axis YBCO thin films    Z. Trajanovic, I. Takeuchi, C.J. Lobb, T. Venkatesan and P.A. Warburton Summary: We have pulsed laser deposited untwinned a-axis oriented YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films on (100) LaSrGaO/sub 4/. From resistive measurements, the chain contribution to the total charge carrier density was estimated to be around 60%. Critical current density (J/sub c/) depends on the granular nature of the films and the transport across each grain boundary can be modeled as a collection of multiple parallel narrow conductive paths. Measurements in fields up to 6 T indicate that the behavior of J/sub c/ vs. B along the b- and c- directions is similar to that of standard c-axis films, with no significant weak link effects from the grain boundaries. We have also measured the temperature and magnetic field dependence of the critical current density (J/sub c/) along b- and c- directions of our films. The direction of magnetic field with respect to the crystallographic axes was found to be the dominant factor determining the J/sub c/. For supercurrents flowing along the c- direction, a cross-over from grain boundary pinning to surface and interface pinning was observed as temperatures approached T/sub c/.         Surface morphology, microstructure and electrical properties of Y-Ba-Cu-O thin films    Y.N. Drozdov, S.V. Gaponov, S.A. Gusev, E.B. Kluenkov, Y.N. Nozdrin, V.V. Talanov and A.K. Vorobiev Summary: The relationship between the surface morphology, the microstructure and the electrical properties of "in situ" YBCO thin films deposited by off- axis magnetron sputtering has been investigated in a wide range of deposition temperatures, deposition rate and pressure of gas mixtures. The Cu-rich surface particles formation observed in our experiment can be described using a classical thin film nucleation and growth model based on the concept of capture zones. The films with optimized electrical properties show high critical temperatures, T/sub C/, up to 92 K and high critical current densities, J/sub C/, up to 7/spl middot/10/sup 6/ A/cm/sup 2/ and surface microwave resistance, R/sub S/, less than 0.6 mOhm (at 10 GHz) at 77 K. The films with optimized surface smoothness show T/sub C/ up to 89 K, J/sub C/ up to 2/spl middot/10/sup 6/ A/cm/sup 2/ and they are free of any particles down to a size scale of 100 /spl Aring/.         Modeling of temperature dependent current-voltage curves of YBCO/Ag composites    T.L. Francavilla, M.A. Fisher, L.H. Allen, E.J. Cukauskas and R.J. Soulen Jr. Summary: We have measured the current-voltage (I-V) characteristics of thin film composites made from YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) and Ag. When deposited upon a substrate, this material appears to form arrays of superconducting-normal-superconducting (SNS) junctions. To make these measurements, the films were patterned into microbridges and immersed directly into the cryogen to provide a constant temperature environment and to avoid problems of local heating. The data were fitted by several phenomenological models in an effort to understand the dissipation mechanism appropriate to these materials.         Au/YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin film composites on various substrates    L.H. Allen and E.J. Cukauskas Summary: We have grown a series of composite films of Au with YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// on various substrates using a bilayer deposition technique to study their suitability for flux flow applications. The T/sub c/'s and J/sub c/'s were measured, and results compared with plain YBCO films for the different substrates. The patterning process resulted in some damage to the composites, but an oxygen plasma treatment was effective in restoring T/sub c/'s and resistance ratios, J/sub c/ measurements suggest that Au/YBCO composites behave like SNS-coupled arrays of superconducting grains. Their increased response to small magnetic fields is consistent with Josephson vortices dominating the transport. These findings indicate that Au/YBCO composites are a promising material for flux flow applications.         Off-axis co-sputtered YBCO and CeO/sub 2/ thin films    E.J. Cukauskas, L.H. Allen and J. Pond Summary: We have investigated the properties of off-axis co-sputtered films of YBCO and CeO/sub 2/ having CeO/sub 2/ concentrations up to 43%. Morphology investigations suggest that films with more than 29% CeO/sub 2/ may consist of a new material phase, T/sub c/ and resistance ratio decreased with increasing CeO/sub 2/ concentration. Degradation of T/sub c/, after photoresist processing the films was observed and reversed by a 20 minute oxygen plasma etch. The temperature dependence of the critical current near T/sub c/ showed two power law dependence regions with a crossover near 0.99 T/sub c/ for films having low concentrations of CeO/sub 2/. I/sub C/ 's were decreased by small applied magnetic fields, and for some samples the response was observed to increase at lower temperature. For a sample having 26% CeO/sub 2/, a 40% reduction in critical current was observed for a 2 Gauss applied field. This response indicates that this may be a candidate material for the development of Josephson vortex flow devices.         Thermometric measurements of the self-field losses in silver sheathed PbBi2223 multifilamentary tapes    A.E. Mahdi, T. Hughes, C. Beduz, Y. Yang, R.L. Stoll, J.K. Sykulski, P. Haldar, R.S. Sokolowski and A. Power Summary: Self-field ac losses in Ag sheathed PbBi-2223 tapes were measured using a thermometric method, which determines the losses by measuring the temperature profile of a vacuum insulated sample, with both ends at a fixed temperature. In practice, the samples were placed in a vacuum capsule immersed in LIN bath. By minimizing the bath superheat, thermal emf and heating at the current contacts, a loss induced temperature increase as low as 2 mK was measured using a Si diode thermometer. With a typical sample length of 600 mm, self-held losses between 7/spl times/10/sup -6/ W/m and 4/spl times/10/sup -3/ W/m were measured at different frequencies. The results are in good agreement with both the electric measurement and theoretical calculation. This provides the first independent confirmation that electric measurement with carefully placed voltage loops can give the true losses of the sample.         Connectivity between filaments in BSCCO-2223 multi-filamentary tape    S.P. Ashworth, B.A. Glowacki, M. Ciszek, E.C.L. Chesneau and P. Haldar Summary: Technologically, the most advanced conductor utilising high temperature superconductors is the multifilamentary tape produced by the powder in tube method. Previous investigations have indicated that the filaments in these materials are strongly connected by superconducting paths. This connectivity is of particular importance in, amongst other things, governing the dissipation of the conductors when carrying AC currents or exposed to varying magnetic fields. In this paper we report direct measurements of the transverse (in contrast to the more usual longitudinal) current carrying capability. Measurements of electric field versus current ('E-I characteristics') for transverse and longitudinal transport currents as a function of applied magnetic field and temperature are reported. Our data indicates that the filaments are indeed strongly connected by superconducting paths but also that the E-I characteristics for the transverse and longitudinal connections are different.         AC transport losses of Ag-sheathed Bi2223 multifilamentary twisted tapes    T. Fukunaga, T. Itou, A. Oota, J. Maeda and M. Hiraoka Summary: The ac transport losses are investigated at 77 K on the Ag-sheathed (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/, multifilamentary twisted tapes with filament number N=19 and twist length of 13 mm, through an ac transport method under self-fields. The losses for the twisted tapes are independent of the frequency, so that the main contribution to the losses are the hysteresis loss in the superconductor filaments. The absolute values of the losses agree with the results of Norris theory for an elliptical superconductor with the same critical current. In addition, the resistive voltages on the twisted tapes have a dependence on the potential-taps configurations, which is found in the monofilamentary tape and multifilamentary untwisted tapes. Furthermore, the wave-forms of axial electric fields are similar to the theoretical results for a superconducting cylinder. These results suggest that the distribution of the transport current in the superconductor filaments is not equalized for the twisted tapes and the twisting of filaments causes no notable influence on the at transport properties when the tapes are examined in self-fields.         Effect of twisting on the filaments of multifilamentary BSCC0(2223)/Ag and /AgMg tapes    W. Goldacker, H. Eckelmann, M. Quilitz and B. Ullmann Summary: For reduced AC losses of multifilamentary BSCC0(2223) tapes, it is necessary to apply a twist to the filaments along the tape direction reducing the filament coupling losses. Twists with different twist pitches (10-80 mm) were realized in either Ag sheathed and mechanically reinforced AgMg sheathed 37 filament tapes. Possible reasons for the observed degradations of the transport critical current densities of 22000 Acm/sup -2/ (Ag sheath) and 19000 Acm/sup -2/ (AgMg sheath) down to 50% in the worst case (10 mm twist pitch) for twisted tapes, were investigated analyzing the influence of twisting on the conductor geometry and deformation via quantitative image processing of micrographs. The critical current I/sub C/ of differently twisted tapes was measured in a magnetic field for various tape orientations. From the J/sub C/(B) anisotropy the misalignment angle of the Bi(2223) phase texture was analyzed, and a comparison with rocking angles from X-ray experiments was performed.         Effects of DC transport currents on AC losses by the magnetically induced currents in Ag sheathed Bi(2223) tape    M. Suenaga, Y. Fukumoto, H.J. Wiesmann, P. Haldar and R. Budhani Summary: AC losses at 60 Hz for a Ag sheathed Bi(2223) by a magnetically induced current technique were measured as a function of applied AC field and DC transport current. The results were qualitatively in agreement with the theory, which is based on Bean critical state model, by T. Ogasawara, et al. (Cryogenics, Vol.19, Dec. 1979, pp.236-740). Possible sources for some quantitative disagreements between the results and the theory are discussed.         Development of twisted Bi-2212 and Bi-2223 powder in tube conductors for AC applications    P.F. Herrmann, E. Beghin, G. Duperray, D. Legat, A. Leriche, D. Brouard and P. Manuel Summary: Within Alcatel Alsthom Group, Alcatel Cable and Alcatel Alsthom Recherche Center have undertaken a HTc research program, with support from EDF: the aim was to develop conductors suitable for AC applications, where major market opportunities are expected. For AC applications at 50 Hz low AC loss conductors with a resistive matrix material and a twist length of the superconducting filaments of less than 10 mm are required. Bi-2223 and Bi-2212 conductors are fabricated up to lengths of 200 m of 64 filaments tape by the patented rectangular Alcatel Alsthom route. Recently Bi-2212 conductors for 20 K applications have been tested at liquid helium temperatures. Different Bi-2212 conductors with a twist length of 7 to 9 mm, with a silver-alloy matrix and a cross section of 0.5 mm/spl times/3 mm have been realised. In such conductors transport currents of 400-500 A have been measured at 4 K in self fields with a very good reproducibility. The engineering current density in the wire has reached the threshold value of J/sub C/=30'000 A/cm/sup 2/. The superconducting volume fraction of the conductor is 18% which results in a critical current density in the superconductor of J/sub C/=170'000 A/cm/sup 2/. At liquid nitrogen temperature transport currents of 18 A are carried in this conductor. For this temperature range the development of a Bi-2223 conductor is under progress. For instance, different untwisted conductors with transport currents up to I/sub C/(77 K)=60 A and critical current densities up to are realised.         Transport critical current at 4.2 K of pure and MgO-doped Bi 2212 tapes    L. Zani, M. Menget, P. Regnier, J. Le Bars, T. Dechambre and P. Nicolas Summary: 2/spl times/3.5 /spl mu/m thick Bi 2212 tapes have been prepared by oxidation reaction of precursors deposited electrolytically in a sequential way on both sides of a 50 /spl mu/m thick Ag tape. To try and increase their critical current density MgO doping was attempted. For the sake of making the comparison as differential as possible a sample of Bi 2212 precursors was prepared by electrodeposition. Part of it was directly heat treated, whereas the left was electrolytically plated before with MgO to get the average composition Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/Mg/sub 0.1/. It was found that the transport J/sub c/ at 4.2 K of the MgO-doped specimen was about 1.4 times higher than that of the other in self field conditions and remained still 1.1 times higher in a 7 tesla field applied normally to the tape. The ratio of J/sub c/(B/spl par/(a,b)) to J/sub c/(B/spl perp/(a,b)) starting from 1 for zero applied field was observed to reach 2 in a field. Finally, the pinning potential of the materials were determined accounting silver backing correction (dependence resistivity as a function of magnetic field is incidentally presented too).         Microstructural analysis of BSCCO-2212 wires for magnet application    B. Lehndorff, H. Piel, M. Hortig, G.W. Schulz and R. Theisejans Summary: Short samples of silver-sheathed BSCCO-2212 wires were quenched out of different stages of the sintering process. Microstructural studies of the phase formation have been performed. The development of the superconducting core within these wires exhibit pronounced void formation. In addition it is observed, that silver agglomerates between grains all over the ceramic core. These studies were used to optimize the preparation of BSCCO-2212 wires of medium length. For functional studies of insulation material, small test coils were built from these materials and tested in a Gifford-McMahon-cryocooler. Magnetic fields were determined by a Hall probe measurement in the temperature range of 28 to 77 K.         Characterization of interfacial growth between Bi(2212) and Ag coating    M.J. Breitwisch, D. Kouzoudis, J.E. Ostenson, D.K. Finnemore and U. Balachandran Summary: The growth of hillocks at the interface between Bi(2212) and Ag has been found to occur over a wide range of oxygen partial pressure and in the vicinity of 700/spl deg/C, a temperature far below the Bi(2212)-Bi(2223) conversion temperature. These hillocks have been examined by environmental scanning microscope (ESEM) and regular SEM in secondary and backscattering modes. Definitive chemical analysis is still an open question. The Ag is highly mobile at these temperatures.         An investigation of the characterizations and development of HTS joints in BSCCO 2212/Ag composites    P.V. Shoaff Jr., Y.S. Hascicek, J. Schwartz and S.W. Van Sciver Summary: Superconducting joints are required to provide the long lengths of conductor and the temporal stability necessary in HTS magnets. The Delta B program at the NHMFL has initially developed the joint technology on BSCCO 2212 tapes using a wrap joint technique. Different combinations of stock conductor, including both monocore and multifilament tapes, and fill materials have been investigated in several prototype generations. The transport properties, in-field performance, and microstructure of the most promising prototypes are investigated. This wrap joint technique has produced several joints with critical currents higher than the critical currents of their respective unjoined conductor sections.         Thermal conductivity of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ superconductors in high magnetic fields    S. Nakamae and J. Schwartz Summary: The thermal conductivity of high temperature superconductors provides an understanding of the nature of the charge carriers, phonons, vortices, and the scattering processes between them. Recently, the magnetothermal conductivity has been considered to be a key factor in the understanding of the vortex dynamics. Here we report thermal conductivity measurements of bulk Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ superconductors in an applied magnetic field up to 20 T. The measurements were taken for a wide range of temperatures around T/sub c/. The superconducting parameters were recovered from the obtained data using theoretical model developed by Ausloos et al.         Fabrication and properties of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ multilayer superconducting tapes and coils    T. Hasegawa, Y. Hikichi, T. Koizumi, A. Imai, H. Kumakura, H. Kitaguchi and K. Togano Summary: A flexible 100 m-class Bi-2212 multilayer superconducting tape was fabricated by the continuous heat treatment technique using a Ag-0.2 at% Mg sheath. The sheath material did not change the J/sub c/ value of the multilayer superconducting tape and doubled the tensile stress tolerance compared with pure Ag sheathed Bi-2212 tape. The J/sub c/ value of the Ag-0.2 at% Mg alloy sheathed tape was above 10/sup 5/ A/cm/sup 2/ at 4.2 K, 21 T and 1.3/spl times/10/sup 5/ A/cm/sup 2/ at 20 K, 0 T. A stacked pancake coil fabricated by the "react & wind" technique carried 120 A at 10 K and 90 A at 20 K. The coil could be operated for 24 hours under 18 K with operating current of 75 A.         The effect of oxygen partial pressure during heat treatment on the microstructure of dip-coated Bi-2212/Ag and Ag alloy tapes    H. Fujii, H. Kumakura, H. Kitaguchi, K. Togano, Wei Zhang, Yi Feng and E.E. Hellstrom Summary: The evolution of the microstructure during heat treatment was investigated for dip-coated Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/(Bi-2212)/Ag and Ag alloy tapes as a function of temperature and oxygen partial pressure (P(O/sub 2/)=0.01, 0.21 and 1 atm) using quenched and fully-processed tapes. The microstructures were essentially the same for Bi-2212 on pure Ag and on the Ag alloy, Although the melting temperature of Bi-2212 increased with increasing P(O/sub 2/), the solidification temperature (T/sub sol/) of Bi-2212 for P(O/sub 2/)=0.21 atm was higher than that for P(O/sub 2/)=1 atm. The volume fraction and grain alignment of Bi-2212 processed in P(O/sub 2/)=0.01 atm was smaller than in tapes processed in 0.21 and 1 atm, which were quite similar. HR-TEM studies on grain boundaries and AC susceptibility measurements suggest that the higher critical current density(J/sub c/) for tapes processed in P(O/sub 2/)=1 atm than that for 0.21 atm is due to improved coupling of the grains.         Continuous melt processing of Bi-2212/Ag dip coated tapes    C.G. Morgan, B.M. Henry, C.J. Eastell, M.J. Goringe, C.R.M. Grovenor, J.W. Burgoyne, D. Dew-Hughes, M. Priestnall, R. Storey and H. Jones Summary: Bi-2212/Ag tapes have been produced using a continuous dip coating and partial melt processing technique. The role of the annealing and melt processing temperatures on the microstructure and current-carrying properties of the tapes are reported. In particular, the effect of a pre-anneal heat treatment on the residual carbon content from the organic binder has been investigated, in order to improve critical currents. These results have been used to optimise the temperature profile of a multiple-zone tube furnace through which continuous melt processing of the tape is possible. Multiple metre lengths of superconducting tape have been produced and wound into coils. Critical currents of 8.3 A in statically processed tapes and 1.9 A in continuously processed tapes have been achieved at 77 K, zero field.         Critical current and structure of Bi-2212 bulk oxides prepared by a diffusion process    Y. Yamada, Y. Hishinuma, F. Yamashita, K. Wada and K. Tachikawa Summary: Bi-2212 oxide superconductors have been synthesized by a diffusion process between a Sr-Ca-Cu oxide substrate and a Bi-Cu oxide coating layer. The substrate is formed into a shape of cylindrical rod 3 mm in diameter by CIP, and then sintered. The coating layer with Ag/sub 2/O addition is coated around the surface of the substrate rod. The heat treatment is performed at 820-860/spl deg/C to produce Bi-2212 diffusion phase. The Ag added to the coating layer enhances the diffusion reaction. The Bi-2212 diffusion layer, about 180 /spl mu/m in thickness, shows high density and oriented structure with plate-like grains. The transport I/sub c/ and J/sub c/ of the diffusion layer exceed 300 A and 2/spl times/10/sup 4/ A/cm/sup 2/, respectively, at 25 K and 0 T. The I/sub c/ decreases to about 100 A at 40 K and 0.5 T. Present investigation indicates that the bulk Bi-2212 oxide prepared by the diffusion process may be attractive for a current lead of cryocooler-cooled superconducting magnets.         Microstructure and superconducting properties of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ coatings by plasma spraying    N. Harada, T. Kameyama, H. Kawano, K. Kuroda, K. Osaki and N. Tada Summary: Superconducting coatings of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ were prepared on silver substrates by an atmospheric plasma spraying. The size of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ powders to be used the spraying was 30/spl sim/75 /spl mu/m. The coating samples were 30 mm long and 5 mm wide. The coatings in the thickness range 50/spl sim/100 /spl mu/m was obtained. After annealing at 880/spl sim/845/spl deg/C for 20 hours in the atmosphere, the coatings showed superconductivity at liquid nitrogen temperature. The microstructures of the coatings were analyzed by using X-ray diffractometer and observed by scanning electron microscopy. The superconducting properties of the coatings were discussed on the result of critical current density and AC susceptibility measurements.         Fabrication and characterization of melt-processed YBCO    S. Sengupta, J. Corpus, J.R. Gaines Jr., V.R. Todt, X.F. Zhang, D.J. Miller, C. Varanasi and P.J. McGinn Summary: Large domain YBCO are fabricated by using a melt processing technique for magnetic levitation applications. A Nd/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub y/, seed is used to initiate grain growth and to control the orientation of YBCO grains. Samples as large as 50 mm diameter have been fabricated by utilizing this method. Microstructural studies reveals two distinct regions in these levitators due to different growth mechanisms along the a/b and c axes. Some initial result on the mass production of these; levitators are also reported.         Effects of carbon additions to melt-processed YBa/sub 2/Cu/sub 3/O/sub x/ and Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ compacts    S. Sengupta, V.R. Todt, K.C. Goretta, D.J. Miller, Y.L. Chen and U. Balachandran Summary: YBa/sub 2/Cu/sub 3/O/sub x/ (Y-123) and Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ (Bi-2212) compacts were partial-melt processed. Carbon was introduced into the compacts either by vibratory milling in an organic solution or by heat treating in an atmosphere containing a controlled concentration of CO/sub 2/. The presence of carbon had a strong effect on the melting response of Y-123, but not Bi-2212. For both materials, magnetic-hysteresis width was strongly expanded with added carbon. Transmission electron microscopy revealed nanometer-scale precipitates in specimens exposed to excess carbon. These precipitates are thought to be responsible for enhanced flux pinning.         Precipitation from Gd/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub 7/ superconductor in low oxygen partial pressure    H. Wu, M.J. Kramer, K.W. Dennis and R.W. McCallum Summary: Precipitation behavior of second phases from Gd/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub 7/ solid solution was studied by processing in low oxygen partial pressure. With the decrease of solid solubility in the low oxygen partial pressure, Gd/sub 2/BaCuO/sub 5/ and CuO were precipitated from the solid solution as second phases. This resulted in an increase in the superconducting transition temperature up to that of GdBa/sub 2/Cu/sub 3/O/sub 7/ and an enhancement in the critical current density. The amount and size of the second phases can be controlled by the oxygen partial pressure, processing temperature and the starting composition, thus providing a useful method to introduce flux pinning centers for the improvement of critical current density.         Thermodynamically controlled melt processing to improve bulk materials    G. Krabbes, P. Schatzle, W. Bieger, G. Fuchs, U. Wiesner and G. Stover Summary: High quality melt textured YBCO samples have been prepared on a modified MTG route. A trapped magnetic field of 8.5 T at 51.5 K was measured in the gap of 1 mm in a mini-magnet from two YBCO cylinders (d=26 mm, h=12 mm). At 77 K, each single domain cylinder traps more than 600 mT and the levitation pressure of 15 N/cm/sup 2/ in a distance of 0.5 mm was achieved by a 0.4 T SmCo magnet. The thermodynamic background of the preparation method is outlined. A thermodynamic approach to control growth and stoichiometry y in the alternative material Nd/sub 1+y/Ba/sub 2-y/Cu/sub 3/O/sub x/ is discussed. Critical currents of 46 kA/cm/sup 2/ (77 K) have been achieved by a modified recipe.         Macroscopic and microscopic modeling of the growth of YBaCuO bulk material    M. Seesselberg, G.J. Schmitz, B. Nestler and I. Steinbach Summary: Melt processing of YBaCuO is widely accepted to yield the best superconducting properties in bulk specimens of this material. Modeling of melt processing is a promising tool to optimize the production of bulk YBaCuO material. In a macroscopic simulation, temperature fields in YBaCuO specimen of arbitrary geometry in e. g. Bridgman or VGF furnaces are calculated during solidification. This allows the visualization of the shape of the solidification isotherm and its dependence on cooling rate and the geometries of furnaces and samples. Microscopic modeling of microstructural evolution during YBaCuO growth is of great interest to deepen the understanding of growth kinetics. For this purpose, YBaCuO growth can be simulated numerically using the multiphase field model.         Fabrication and microstructural control of high current ReBa/sub 2/Cu/sub 3/O/sub 7/ current leads (Re=Y, Nd, Sm)    X. Granados, R.Y.B. Martinez, S. Pinol, F. Sandiumenge, N. Vilalta, M. Carrera, V. Gomis and X. Obradors Summary: The potential of YBCO superconductors for the development of current leads has been hindered by the difficulties in the fabrication of long single domain bars which exhibit much higher the critical current density than that for the BSCCO counterpart. In this work we report that very long single domain (10 cm/spl times/0.4 cm) self sustained vertical bars can be directionally solidified by using additives such as CeO/sub 2/. The influence of the processing rate has been investigated and we show that current leads which are able to carry a current higher than 2500 A can be fabricated. Quality factors of these bars such as homogeneity, critical current, thermal conductivity and resistance of ohmic contacts are evaluated. At the same time we report the growth conditions of long bars of ReBa/sub 2/Cu/sub 3/O/sub 7/ (Re=Nd, Sm) in air and we investigate the relationship between microstructure and superconducting properties.         Stability and oscillation of MTG high-T/sub c/ superconductors in inhomogeneous magnetic field    E.V. Postrekhin, L.W. Zhou, C.B. Cai, S.M. Gong, Y.X. Fu and H. Zhang Summary: The dependencies of the oscillation amplitude on the oscillation frequency of high-T/sub c/ superconducting (HTSC) melt-texture growth (MTG) ball-sample suspended or levitated in an inhomogeneous magnetic field have been investigated. The dependence of the oscillation amplitude versus the oscillation frequency has maxima. The rotation of the levitated or suspended MTG ring-sample in the rotating magnetic field have been studied. The curve of the sample rotation frequency versus the magnet rotation frequency has maxima which correlate with maxima of the dependence of the oscillation amplitude of the levitated HTSC MTG ball-sample on the frequency of the external magnetic field.         An investigation of Nb-Ti-Ta alloys and properties of the superconductors based on ternary alloys    G.P. Vedernikov, L.V. Potanina, V.Yu. Korpusov, V.A. Drobishev, V.S. Zurabov, A.S. Zolotarjev, A.D. Nikulin, N.J. Kozlenkova and S.I. Novikov Summary: The vacuum arc melting technique was used to obtain the ingots of Nb-Ti-Ta alloys with 12.3 and 20.4 wt.% Ta. The microhomogeneity of the alloys was investigated by electron probe method and T/sub c/ of the alloys after homogenization was measured in comparison with that of the binary Nb-47.5wt%Ti alloy. Multifilamentary conductors with filament diameter /spl sim/60 /spl mu/m have been fabricated. The characteristics of the wires which have been produced by the regime with 4 intermediate heat treatments are presented.         The effect of Gd doping on the critical current of the Chevrel phase superconductor PbMo/sub 6/S/sub 8/    D.N. Zheng and D.P. Hampshire Summary: A series of samples of Chevrel phase superconductor with nominal composition Pb/sub 1-x/Gd/sub x/Mo/sub 6/S/sub 8/ (0/spl les//spl times//spl les/0.04) have been made using a hot isostatic pressing (HIP) process. DC magnetic measurements have been carried out on the samples. A small increase followed by a decrease of J/sub c/ is observed by increasing the Gd content. The irreversibility field B/sub irr/ also exhibits a similar change. However, despite the change in J/sub c/ and the irreversibility line it was found that the pinning force curves for all samples follow the Kramer scaling relation F/sub p/=J/sub c/,/spl times/B/spl prop/b/sup 1/2/(1-b)/sup 2/ over a wide temperature range. This striking feature indicates that J/sub c/ is limited by one dominant flux pinning mechanism in these samples. A grain boundary pinning mechanism has been proposed previously to account for the scaling relation. In order to test this suggestion further, measurements have been carried out on powdered samples which consist of few grain boundaries. Magneto-resistivity and ac susceptibility measurements have been performed on the samples to investigate the change of B/sub c2/ and other parameters in the Gd doped samples.         Overall critical current density of Chevrel wires at high magnetic field    M. Decroux, N. Cheggour, A. Gupta, O. Fischer, V. Bouquet, R. Chevrel, M. Sergent and J.A.A.J. Perenboom Summary: Wires of Pb/sub 1-x/Sn/sub x/Mo/sub 6/S/sub 8/ (PSMS) using the powder-in-tube process have been carefully drawn and the critical current density J/sub c/ has been measured on small coils wound with wires of 1.5 meter in length in magnetic fields up to 24 tesla. At 1.9 K, we achieved an overall critical current density J/sub co/, exceeding slightly 100 A/mm/sup 2/ at 20 tesla and 63 A/mm/sup 2/ at 24 tesla. Below 18 tesla, we always observed an abrupt occurrence of the resistive state, indicating that in this region J/sub c/ is limited by local defects, generally located at the ends of the coil. Nevertheless, at 15 tesla and 4.2 K, J/sub c/ reaches 550 A/mm/sup 2/. These very good results are the consequence of a better choice of the materials forming the wire and of a full control of the synthesis of the PSMS powder, The analysis of the field dependence of J/sub c/ shows that the grains are well connected, but that the critical field B/sub c2/ is still too low at 4.2 K (31 tesla instead of 50 tesla). An optimization of the annealing conditions is expected to considerably increase J/sub c/ at high magnetic fields.         YBCO thick films for high Q resonators    P.A. Smith, T.W. Button, J. Holmes, G. Dolman, C. Meggs, S.K. Remillard and J.D. Hodge Summary: Three dimensional structures can have high geometric factors and have thus been favoured in applications requiring high Q resonant elements. In this paper the surface resistance of YBCO thick film materials measured in the frequency range 1-10 GHz in a variety of resonant structures is discussed. The power dependence of the materials in the 1 to 2 GHz region is also examined and at these frequencies it is possible to attain Q's of over 150000 using thick film materials.         New substrates for HTSC microwave devices    S.C. Tidrow, A. Tauber, W.D. Wilber, R.T. Lareau, C.D. Brandle, G.W. Berkstresser, A.J. Ven Graitis, D.M. Potrepka, J.I. Budnick and J.Z. Wu Summary: A new substrate material LSAT, a 30/70 mole % solid solution between LaAIO/sub 3/ and Sr/sub 2/AITaO/sub 6/, has been prepared for the purposes of eliminating twinning, strain and non-isotropic microwave properties found in pure LaAIO/sub 3substrates. At 300 K and 30/70 mole %, LSAT is cubic with lattice parameter of 7.737 /spl Aring/. The dielectric properties of single crystal LSAT (30/70 mole %) substrates have been measured at 10 GHz and 300 K and determined to be: dielectric constant /spl epsilon//sub r/=22.5; and, loss tangent tan(/spl delta/) /spl les/ 10/sup -3/. High quality c -axis oriented high critical temperature superconducting (HTSC), YBa/sub 2/Cu/sub 3/O/sub 7//spl middot//spl delta// (YBCO), thin films have been deposited on (001) single crystal LSAT substrates. The crystal quality of these films is excellent as evidenced by the full width half maximum (FWHM) rocking curve widths of typically 300 arc-seconds. Critical current densities (as measured using magnetization) are about 4 x 10/sup 6/ A/cm/sup 2/ at 10 K. Microwave film properties include an onset transition temperature (T/sub c/) higher than 91 K, transition width (/spl tri/T/sub c) less than 5 K, surface resistance R , lower than copper (30 m/spl Omega/) at 85 K and 35 GHz for a film of thickness 2500 /spl Aring/.         Dielectric properties of perovskite antimonates    S.C. Tidrow, A. Tauber, W.D. Wilber, R.D. Finnegan, D.W. Eckart and W.C. Drach Summary: In the search for lower dielectric constant substrates for use in a high critical temperature superconducting (HTSC) microwave technology, the dielectric constants and microwave loss tangents determined from the complex dielectric properties measured at 10 GHz and 300 K are reported for numerous perovskite antimonates like A/sub 2/MeSbO/sub 6/ where A=Ba or Sr, Me=a rare-earth, Y, Sc, Ga or In and A/sub 4/MeSb/sub 3/O/sub 12/ where A=Ba or Sr and Me=Li, Na or K. Using these material properties, the Clausius-Mossotti relationship and a nonlinear regression fitting program, the polarizability of Sb/sup 5+/ has been investigated and determined to be 1.18/spl plusmn/0.49 /spl Aring//sup 3/ which makes it an excellent candidate for use as a constituent in a HTSC microwave substrate technology.         Microwave measurements of superconducting Nb/sub 3/Sn films by a microstrip resonator technique    A. Andreone, A. Cassinese, A. di Chiara, M. Iavarone, F. Palomba, A. Ruosi and R. Vaglio Summary: We report on r.f. measurements of the surface impedance Zs=Rs+iXs of Nb/sub 3/Sn superconducting films deposited on sapphire by planar magnetron sputtering. The measurements are performed by a microstrip resonator technique using a meander line geometry. The power dependence of Zs is studied at different temperatures and frequencies in the range 1-18 GHz. The effects of a d.c. magnetic field applied with different orientations is also studied. The data are analyzed in the context of different models.         Metallurgical analysis and RF losses in superconducting niobium thin film cavities    D. Bloess, C. Durand, E. Mahner, H. Nakai, W. Weingarten, P. Bosland, J. Mayer and L. Van Loyen Summary: Copper cavities with a thin niobium film - as used in the large electron positron collider LEP - would be also attractive for future linear colliders, provided the decrease of the Q-value with the accelerating gradient could be reduced. We aim at extracting the important parameters that govern this decrease. The dependence on the RF frequency is studied by exciting 500 MHz and 1500 MHz cavities in different modes. In addition we combined RF measurements for two 1500 MHz cavities of different RF performance with microscopic tests (AFM,TEM) on samples cut out of the same cavities. Their microstructural characterization in plan-view allows the extraction of the grain size and the defect densities.         Progress in melt processing of Nd-Ba-Cu-O superconductors    S.I. Yoo, N. Sakai, H. Kojo, S. Takebayashi, N. Hayashi, M. Takahashi, K. Sawada, T. Higuchi and M. Murakami Summary: Light rare earth (LRE)-Ba-Cu-O (LREBCO) bulk superconductors melt-processed in a reduced oxygen atmosphere considered to be very promising materials a high field operative with the liquid nitrogen because of their large critical current density (J/sub c/) in high magnetic fields at 77 K, surpassing the limitation of an optimized Y-Ba-Cu-O (YBCO) bulk superconductor. For obtaining further improved J/sub c/ and a large textured domain in the Nd-Ba-Cu-O system (Nd-system), we have applied the oxygen-controlled-melt-growth (OCMG) process to both directional and non-directional solidification techniques. At 77 K and for the field parallel to the (H//c), while J/sub c/ in low field region was apparently enhanced by refining the Nd/sub 4/Ba/sub 2/Cu/sub 2/O/sub 10/(ND422) second phase particles trapped in the NdBa/sub 2/Cu/sub 3/O/sub 7/ (Nd123) matrix, J/sub c/ in high field region principally depended on the location of the fishtail peak (H/sub pk/) which was sensitive to the PO/sub 2/ and thermal processing conditions during the melt growth. Problems related to the NdBCO domain enlargement are also discussed.         Study of superconducting properties in melt textured YBCO levitators    Y.H. Zhang, A. Parikh and K. Salama Summary: A large number of melt-textured Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x/ disk-shaped levitators have been manufactured using a seeding technique. Since DC transport current measurement is only capable of characterizing small samples, we have developed a system for measuring the component of the trapped field perpendicular to the surface of the disk (For simplicity, it will be called "trapped field".) and levitation force. The testing system is capable of measuring the distribution of magnetic field as well as the levitation force at the surface of the levitator in a relatively short time period. The magnetic field mapping can also be used to detect the granular microstructure in the levitators. The trapped magnetic fields of these levitators range between 0.45 and 0.65 T, and levitation forces are from 25 and 35 N. Also, the levitation force and the maximum trapped field values are found to correlate with each other.         P(O/sub 2/)-T phase diagrams and properties of Ln/sub 2/Ba/sub 4/Cu/sub 7/O/sub 15-/spl delta// compounds (Ln=Dy,Er,Eu,Gd,Nd,Pr,Sm,Y and Yb)    V. Manojlovic, M.P. Staines, Wei Gao and J.L. Tallon Summary: Oxygen pressure-temperature phase diagrams for Ln/sub 2/Ba/sub 4/Cu/sub 7/O/sub 15-/spl delta// (Ln-247) compounds (Ln=Er,Eu,Gd,Y and Yb) in the pressure range 2-32 bars of oxygen and temperature range 900-990/spl deg/C were studied. The required pressures for Ln-247 single phase synthesis are much lower than was previously found. In addition, phase-pure Ln-247 (Ln=Dy,Nd,Pr and Sm) samples were prepared at high oxygen pressure. The temperatures of the superconducting transition (T/sub c/) for fully oxygen loaded Ln-247 samples are in the range 63-94 K, except for Pr-247 which is not superconducting at temperatures above 4.2 K. These transition temperatures are, for the wider range of rare earth, considerably higher than previously reported. Evidence is presented for progressive underdoping of carriers with increasing rare earth ionic radius, suggesting that T/sub c/ has not been maximized.         Directional solidification of bulk (Y,Sm,Nd)/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x/    M. Boffa, A. Di Trolio, S. Pace, A. Saggese, A. Vecchione, B. Camarota and N. Sparvieri Summary: Rare Earth (Nd,Sm) elements, having relatively large ionic radius, have been substituted for Yttrium in Y123 superconducting melt textured bulk samples. In (Nd,Sm)123 a wider solidification range and higher recrystallization rate than Y123 significantly increase the solidification rate, making the whole process much faster. A preliminary comparison among directionally solidified (Y,Sm,Nd)/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x/ bulk bars fabricated by the Horizontal Bridgman method has been done. The different microstructural and superconducting features are studied by X-ray, SEM analysis, and ac and dc magnetic measurements. The (Nd,Sm)123 samples, appear comparable to Y123 grown with a pulling rate almost two orders of magnitude lower.         Nucleation and growth of single- and multiple-domain YBa/sub 2/Cu/sub 3/O/sub x/ levitators: influence of seed crystallography    V.R. Todt, X.F. Zhang and D.J. Miller Summary: Large diameter YBa/sub 2/Cu/sub 3/O/sub x/ levitators have been fabricated using seeded melt processing. Two types of levitators have been produced: single-domain, obtained using flat NdBa/sub 2/Cu/sub 3/O/sub x/ seeds, and five-domain, obtained using cubic NdBa/sub 2/Cu/sub 3/O/sub x/ seeds. The difference in these two types of levitators can be attributed to differences in nucleation and solidification processes. In particular, the nucleation of multiple (five) domain levitators may be related directly to the crystallography of the cubic seeding crystals which also exhibit a multiple-domain structure. Single-domain levitators are produced by seeding with plate-like seed crystals which are composed of a single domain. Subsequent growth of the levitator is dominated by anisotropic solidification. Using these types of seeds, we developed a dual-seeded melt textured growth process for the production of bulk bicrystals which are useful for studies of grain boundary transport behavior.         Processing technique for fabrication of advanced YBCO bulk materials for industrial applications    H.J. Bornemann, T. Burghardt, W. Hennig and A. Kaiser Summary: We present a processing technique for fabrication of advanced semi-finished parts and products based on the high-temperature superconductor (HTSC) YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO). High-quality YBCO bulk components are produced powder metallurgically by sintering and partial melting of precursor powders. Depending on size, shape, tolerances and levitation requirements, parts are either die-pressed or precision machined from isostatically pressed blocks. The oxygenation process can be monitored in-situ by a macro-thermogravimetric analyzer. The texture of the bulk of full-size pellets was verified by elastic neutron scattering. Levitation properties under static and dynamic load levels were analyzed using a test bench with a three dimensional force sensor unit. Flux mapping was used to verify the homogeneity of the material, to evaluate macroscopic critical currents and to investigate the field trapping capability. Several HTSC frictionless bearing modules have been built. They are manufactured in various sizes, ranging from O 40 mm to O 140 mm. Lifting forces are up to 200 N per bearing module. Applications for the bearings are seen for mechanical components in high speed rotating machinery, in cryogenic systems, gyroscopes, transportation systems and vibration isolation.         Processing and levitation force in top-seeded YBCO    R. Yu, J. Mora, S. Pinol, F. Sandiumenge, N. Vilalta, V. Gomis, B. Martinez, E. Rodriguez, J. Amoros, M. Carrera X Granados, D. Camacho, J. Fontcuberta and X. Obradors Summary: Bulk cylinders of YBa/sub 2/Cu/sub 3/O/sub 7/-Y/sub 2/BaCuO/sub 5/ composites, up to 35.0 mm in diameter, have been melt-processed using MgO single crystals, Nd123 and Sm123 melt textured ceramics, as seeds. The influence of processing parameters has been examined in order to optimize the growth conditions. Polarized light microscopy, SEM and EDX, have been used to characterize the orientation, size and morphology of the grains, as well as the spatial distribution and size of Y211 particles. An increase of the levitation forces is observed when the top seeding growth is carried out under a temperature gradient. The trapped magnetic and the levitation force of a single domain sample was systematically measured and theoretically simulated by finite element calculations. The deduced J/sub c/ from the different experiments have been compared and analyzed.         Levitation forces and mechanical properties of VGF melt-textured YBCO    M. Ullrich, A. Leenders and H.C. Freyhardt Summary: Thermal cycling reduces the levitation force of melt-textured YBCO. Investigations of the mechanical properties reveal that the fracture toughness, K/sub IC/, and the hardness, H/sub v/, are very low. K/sub IC/ decreases even more after thermal cycling. These poor mechanical properties in combination with nearly no possibility for stress relief due to plastic deformation are thought to be responsible for the generation and propagation of cracks. These cracks reduce the effective radii of the screening currents leading to a decreased magnetic moment and the observed reduction of the levitation force.         Practical high temperature superconductor composites for high energy physics applications    J.M. Seuntjens and G. Snitchler Summary: Next generation High Energy Physics (HEP) applications consider high magnetic fields (>12 T) at liquid helium temperatures as well as low magnetic fields (/spl sim/2 T) and temperatures above 30 K. Multifilament Bi-2223 conductors have achieved the performance to be considered for these applications. In the low temperature, high magnetic field situation, Bi-2223 offers unique advantages over Nb/sub 3/Sn. Issues of Jc, field quality, magnet stability, strain tolerance, and manufacturability are discussed for accessing the merits of Bi-2223 as compared to Bi-2212 and A-15 materials for HEP.         Current connectivity in Bi-2223 silver-sheathed tapes for power cables    C.M. Friend, L. Le Lay and T.P. Beales Summary: The mechanism limiting the transport critical currents of long-length (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ tapes is still debatable. Such knowledge is important for improving the current performance of tapes for their use in superconducting applications. Transport and magnetic measurements have been used to study the current connectivity in tapes fabricated for power cable prototypes. The field dependence does not clearly distinguish between the different mechanisms of connectivity but is a useful parameter for characterising these tapes, even if they may be operated only in very low fields. Future improvements will come from better processing control and for operation at 77 K the intragranular pinning may need to be increased.         Development of Bi-2223/Ag tapes and coils    L. Bigoni, L. Martini, E. Varesi, E. Zampiceni, S. Zannella, A. Baldini, S. Conti, R. Garre, G. Cartegni, D. De Tommaso and L. Rossi Summary: Long high critical current density Bi-2223/Ag tapes are required for the realization of cables and windings to be integrated in electric power devices. A cooperation agreement among CISE SpA, Europa Metalli and INFN, concerns the development of silver-sheathed multifilamentary Bi-2223/Ag tapes, over 100 meters long, produced by means of the Powder-In-Tube (PIT) technique. The Bi-2223/Ag tapes were thermomechanically processed and then wound into double pancakes by the React and Wind method. This article presents and discusses the electrical and magnetic characterization of the tapes, their degradation after winding as well as the performances of the pancakes tested after the final assembling.         Characterization of high-current, high-temperature superconductor current lead elements    R.C. Niemann, D.J. Evans, B.L. Fisher, W.E. Brockenborough, P.R. Roberts and A.J. Rodenbush Summary: A conductor element consisting of laminated stack of high temperature superconductor (HTS) powder-in-tube (PIT) tapes is suitable for incorporation into current leads. The details of an application of such conductor elements to a current lead for a SMES system are presented. The fabrication of the laminated-conductor elements made with BSCCO 2223 PIT tapes is described. The critical current measurement method and results for two such conductor elements are presented. Performance was evaluated with variable temperatures and with variable applied fields.         Advances towards the rolling processing of long BSCCO tapes    H. Miao, F. Lera, A. Larrea, G.F. de la Fuente and R. Navarro Summary: Uniform long length Ag clad mono-filamentary BSCCO tapes have been produced by the powder in tube method making use of drawing, cold rolling and annealing processes. The influence of the starting BSCCO powders, packing method and Ag addition on BSCCO/Ag superconducting tapes have been analyzed using XRD and scanning electron microscopy combined with EDX and Image Analysis. In addition, extensive electrical transport measurements have been carried out. Average values of J/sub c//spl ap/12 kA/cm/sup 2/ with a dispersion of /spl plusmn/5% over a 1 m length have been obtained.         Long-length processing of BSCCO-2223 tapes made by using Ag alloys sheath    Jaimoo Yoo, Hyungsik Chung, Jaewoong Ko and Haidoo Kim Summary: To improve the smoothness of BSCCO/Ag interface as well as to increase strength and resistivity, we have fabricated various compositions of Ag-Mg alloy, Ag-Au alloy, Ag-Pd-Mg alloy, and Ag-Au-Mg alloy. These sheath alloys were evaluated for hardness, resistivity, and microstructure to find out alternative candidate to pure Ag for sheath materials in powder-in-tube (PIT) processing of BSCCO-2223 tapes. For a long-length process, these sheath alloys were extruded into commercial size (OD:12.7 mm, ID:9.5 mm, 200 mm long) of hollow tube, and were investigated for sausaging effect, microstructure, and compatibility (Ic measurement) with 2223 BSCCO superconductor during processing. The alloying of Au and Pd increased resistivity but is not very effective in Increasing hardness. Addition of small quantity of Mg to Ag-Au and Ag-Pd increased hardness significantly due to dispersion hardening. Microstructural studies of BSCCO-2223/Ag-Au-Mg tapes revealed a more dense and aligned BSCCO structure.         Effect on critical current density and irreversibility behaviour of mechanical deformation of Bi-(Pb)-Sr-Ca-Cu-O superconducting tapes    H.K. Liu, J. Horvat, R. Bhasale, Q.Y. Hu, S.X. Dou, K.H. Muller and C. Andrikidis Summary: Comparative studies on the Ag-clad 27-filamentary Bi-2223 tapes deformed under different conditions have been carried out using ac susceptibility and critical current measurements. Hot pressing improves the grain alignment and grain connectivity, resulting in a noticeable improvement in the critical current density in the low field region. However, the irreversibility line for the cold pressed Ag/Bi-2223 tape is positioned at higher temperatures than that for the rolled tape which is in turn positioned at higher temperatures than that for the hot-pressed tape. These results indicate that the hot deformation is only beneficial to the improvement of weak links whereas the cold deformation induces more defects which act as pinning centres in these tapes, responsible for the improvement in flux pinning.         Effect of sintering temperature on phase composition and J/sub c/ of Ag-sheathed Bi-2223 single and multifilamentary tapes    W.G. Wang, H.K. Liu and S.X. Dou Summary: The sintering temperature window of Ag sheathed Bi-2223 tapes was studied by a temperature gradient method for fabrication of tapes. The I/sub c/ of the tapes was found to be very sensitive to the sintering temperature. For the single filament tapes, the I/sub c/ reaches the maximum value at a temperature higher than that at which the 2212 percentage reaches the minimum. Around 6.5% of 2212 still exists in the best single filamentary tapes, while just a half of this 2212 fraction (about 3.5%) remains in the best 19 filamentary tapes. The J/sub c/ was found to be more sensitive to Bi-2212 phase content in the multifilamentary tapes than that in the single core tapes. A J/sub c/ of 4.5/spl times/10/sup 4/ A/cm/sup 2/ (J/sub c/ 1/spl times/10/sup 4/ A/cm/sup 2/) for single core tapes and of 3.3/spl times/10/sup 4/ A/cm/sup 2/ (J/sub c/ 0.65/spl times/10/sup 4/ A/cm/sup 2/) for 19 core multifilament tapes were achieved reproducibly with sintering time of 100 hours and one intermediate pressing. 70% of maximum I/sub c/ can be retained within 4 degrees sintering temperature window for both single and 19 filamentary tapes.         Microstructure and critical current of hot-pressed (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ ceramics    Q.Y. Hu, D. Yu, H.K. Liu, S.X. Dou and M. Apperley Summary: After being sintered for different times, (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ bulk samples were pressed isothermally at 850/spl deg/C under constant pressure of 15 MPa for 1 hour. The samples were examined using SEM, EDS, XRD, and the mass density, critical temperature (T/sub c/) and critical current density (J/sub c/) were measured. As a result of removing voids in the materials under pressure and high temperature. It was found that the mass density significantly increased. In addition to high mass density, grain alignment within the samples was also improved which produced a significant improvement in the J/sub c/. To achieve high J/sub c/, samples require sintering prior to hot-pressing for reasonably long times.         Surface impedance measurements on high-T/sub c/ superconductors using a far-infrared laser    E. Kawate, R. Mossavati, M. Okaji, T. Ito, Y. Ohashi, A.M. Moe and K. Oka Summary: A novel method of absorption measurements is reported through which we have succeeded in measuring directly the absolute absorptivity of a La-based superconductor in the 100 GHz to 500 THz frequency region using different lasers. We have made transmission measurements on free standing single crystals of the La-based superconductor using a laser and a high sensitivity detector, and succeeded in measuring the transmissivity. For the first time, the surface impedance has been analytically derived from the absorptivity and transmissivity at room temperature.         A simple technique for measuring the transition temperature at microwave frequencies    J.M. Pond, L.H. Allen and E.J. Cukauskas Summary: A technique is described which enables contactless measurements at microwave frequencies of the superconducting transition. The approach employs an electrically small microwave loop antenna to sense the change in the reflected microwave signal as flux is expelled, due to the Meissner effect, from the superconductor. Advantages of this technique include the ability to measure small areas of a superconducting thin film after photolithographic patterning into a device geometry. This approach is very sensitive in the frequency range from 0.05 GHz to 5 GHz and for some YBCO films a dependence of the transition temperature width on frequency has been observed. Such frequency-dependent signatures may provide valuable information regarding improvements in film deposition and device processing.         Open resonator mode patterns for characterization of anisotropic dielectric substrates for HTS thin films    T.E. Harrington, J. Wosik and S.A. Long Summary: An open resonator possesses a unique combination of advantages for characterizing the millimeter-wave losses of today's best HTS thin films and substrates. One of the primary advantages is the transverse linearly-polarized electric field of the TEM/sub 00q/ modes, which induces a polarized current in any HTS, dielectric, or semiconductor sample placed inside the resonator. The polarized current flow allows detection and quantification of any material anisotropies. To provide an intuitive understanding of the field and current distributions in an open resonator, mode patterns computed with a finite-difference time-domain model are presented. The theory of open-resonator anisotropic-dielectric testing is reviewed, and measured anisotropic dielectric constants of sapphire, LaAlO/sub 3/, and NdGaO/sub 3/ substrates are listed.         Automated microwave measurements of microstrip ring resonators at low temperatures    B.A. Tonkin and M.W. Hosking Summary: The high frequency properties of both substrates and superconducting materials have been determined from relatively large area microstrip resonator circuits mounted in an automated measurement system. Properties such as dielectric constant and surface resistance are presented for a variety of materials, such as YBa/sub 2/Cu/sub 3/O/sub 7-x/, Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/, Cu and Ag on either yttria-stabilised zirconia, MgO or plastic substrates. The surface resistance of thick film YBa/sub 2/Cu/sub 3/O/sub 7-x/ ring resonators on yttria-stabilised zirconia substrates were found to be limited by the loss tangent of the substrate while the surface resistance of similarly-sized Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ thin film ring resonators on MgO substrates showed a marked power dependence. At 3 GHz the surface resistance of thick film YBa/sub 2/Cu/sub 3/O/sub 7-x/ on yttria-stabilised zirconia at -10 dBm was found to be superior to thin film Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ on MgO below T/sub C//2 as a result of better power handling.         Accuracy considerations in microstrip surface impedance measurements    J.M. O'Callaghan, C. Sans, C. Collado, E. Canet, R. Pous and J. Fontcuberta Summary: An approach is proposed for the design, measurement and data extraction of superconducting microstrip resonators used in determination of surface resistance and penetration depth. Major sources of error are analyzed and procedures to minimize them are given.         Measurement of microwave magnetic properties of superconducting YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin films    Seek Kil Han, J. Kim, Kwang-Yong Kang and Yeon-Su Ha Summary: The magnetic property of high-T/sub c/ superconductors (HTS) at microwave frequency has been of increasing interest since their magnetic behavior is related to microwave vortex dynamics. Thus, we recently designed a cavity perturbation system (CPS) for simultaneous measurement of the resonant frequency (f/sub 0/) and the quality factor (Q). The magnetic susceptibilities (/spl chi/'-j /spl chi/") of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta///MgO thin films at microwave frequencies were investigated and could be analyzed by cavity perturbation theory. We expected that the microwave magnetic susceptibility data as a function of temperature measured using the HTS thin film would explain the phenomenological superconducting dispersion relation. The transition temperature is 91 K and the temperature corresponding maximum imaginary part (/spl chi/") is 85 K. However, the transition temperature and surface resistance (R/sub s/) measured by a conventional transmission-line method were 86 K and 180 /spl mu//spl Omega/ at 40 K, respectively. We found absolute differences between the cavity perturbation method and the transmission line ones, and suggested the CPS is one of the most promising technique for measuring the magnetic susceptibility of HTS thin film with a 0.1/spl sim/1 /spl mu/m thickness.         The microwave surface impedance of DyBa/sub 2/Cu/sub 3/O/sub 7-x/ very thin films    R. Perez, T. Tybell, A. Gupta, J.M. Triscone, M. Decroux and O. Fischer Summary: Measurements of the surface impedance of DyBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (DyBCO) thin films have been made around 6 GHz by using the parallel plate resonator method with sapphire dielectrics. The films were deposited by RF magnetron sputtering on LaAlO/sub 3/ substrates to thicknesses between 20 and 320 nm. The change of the London penetration depth as a function of temperature is deduced from resonance frequency shifts. A generalized two fluid model is used to fit the data in terms of an effective penetration depth /spl lambda//sub eff/(0) at 0 K, taking into account the effect of grain boundary weak links. This analysis give an interpretation of the changes in /spl lambda//sub eff/(0) as a function of the film thickness and yields values for /spl lambda//sub eff/(0) around 160 nm for films thinner than 120 nm.         Importance of thermodynamics and kinetics in the growth of thin film TlBaCaCuO superconductors    M.P. Siegal, D.L. Overmyer, E.L. Venturini, P.P. Newcomer, R. Dunn, F. Dominguez, R.R. Padilla and S.S. Sokolowski Summary: The importance of near-equilibrium thermodynamics in the growth of TlBaCaCuO materials is well-documented; i.e. the independent control of sample temperature, Tl-oxide partial pressure, and oxygen partial pressure. Here we demonstrate how this is accomplished using a simple version of the crucible process. In addition, we report the relevance of growth kinetics. Superconducting thin films are grown in a two-step process. First, /spl sim/2000 /spl Aring/ thick, amorphous Ba/sub 2/CaCu/sub 2/O/sub x/ and Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ precursors are sputter-deposited onto LaAlO/sub 3/(100) substrates. Films are then thallinated and annealed using the crucible-pellet process. With this method, it is possible to grow essentially single-phase Tl-1212, Tl-1223, Tl-2212, and Tl-2223 thin films. Under similar thermodynamic conditions, we find that different phases dominate the film growth as a function of reaction time. For example, the Tl-x212 phases generally nucleate first, and then, depending on growth conditions, convert to the Tl-1223 or Tl-2223 phase with extended annealing times. We demonstrate that knowledge of both the thermodynamics and the kinetics of growth can yield high-quality films of each of the major Tl-superconducting phases.         Microstructural changes in TlBa/sub 2/CaCu/sub 2/O/sub 7-/spl part// thin films after reducing anneals which enhance critical current density    P.P. Newcomer, M.P. Siegal, E.L. Venturini, B. Morosin and D.L. Overmyer Summary: Microstructural changes in TlBa/sub 2/CaCu/sub 2/O/sub 7-/spl part// (Tl-1212) epitaxial thin films resulting from low oxygen partial pressure furnace anneals at 600/spl deg/C are studied using high resolution transmission electron microscopy (TEM). These post-growth anneals have been shown to significantly raise the superconducting transition temperature from 70 to 90 K, and greatly improve the magnetic flux pinning and the critical current density. Changes occur in both the microstructure and the morphology of the films that correlate with changes in J/sub c/. Plan view TEM and high-resolution cross-sectional TEM analysis of the films before and after anneals demonstrates changes in the lattice fringe image, overall contrast modulation, and nanometer-scale discontinuities.         In-situ fabrication of Tl-based superconducting thin films by two-zone RF-sputtering    S.J. Wang, J.Y. Juang, L.C. Shih, C.S. Nee, K.H. Wu, T.M. Uen and Y.S. Gou Summary: Attempts to fabricate Tl-based superconducting thin films in-situ were made using a two-zone off-axis rf-sputtering method. The effects of Tl/sub 2/O partial pressure on the phase formation and growth of various Tl-based superconducting phases were first investigated by an ex-situ two zone post-annealing scheme to simulate the deposition environment of the subsequent in-situ process. The conditions obtained were then used as guidelines for in-situ processes. The rf-sputtering system used for in-situ deposition is equipped with heating facilities capable of controlling the temperatures of the substrates and the Tl/sub 2/O/sub 3/ source separately. Preliminary results indicate that, by varying the substrate temperature and the partial pressure of Tl/sub 2/O in a similar manner, Tl-based superconducting phases can be obtained in-situ with properties comparable to those obtained by two-step annealing processes.         Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub /spl delta// thin films on MgO annealed in a sealed capsule    M. Nemoto, S. Yoshikawa, K. Shimaoka, K. Niki, I. Yoshida and Y. Yoshisato Summary: High-quality c-axis oriented Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub /spl delta// thin films have been prepared on MgO, which is more suitable for high frequency applications than LaAlO/sub 3/ because of its lower dielectric constant (/spl epsi/) and smaller dielectric loss tangent (tan /spl delta/). Annealing of the thin films was carried out in an alumina capsule sealed with a gold gasket. It was revealed that preannealing of the pellets for Tl compensation is effective in improving the structural properties of the thin films. X-ray diffraction (XRD) rocking curve scans of Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub /spl delta// (0 0 12) reflection revealed that a full width of half maximum (FWHM) of thin films annealed with an unpreannealed pellet is 0.89/spl deg/, while that of thin films annealed with a preannealed pellet is 0.22/spl deg/. The highest critical temperature (T/sub c/) is 108 K and the highest critical current density J/sub c/ is 2/spl times/10/sup 6/ A/cm/sup 2/ at 77 K.         Microstructural and microwave characterisation of low temperature processed Tl/sub 2/Ba/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ thin films    J.D. O'Connor, A.P. Jenkins, D. Dew-Hughes, M.J. Goringe and C.R.M. Grovenor Summary: Tl/sub 2/Ba/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ thin films on LaAlO/sub 3/ with excellent alignment suitable for the fabrication of passive microwave devices operating at 77 K are fabricated using an ex-situ anneal step in argon atmospheres at temperatures of 720-740/spl deg/C. In order to understand the factors influencing their microwave and transport properties, the microstructure and compositions of the films have been examined by TEM, HREM and SEM and correlated with R/sub s/ measurements obtained by the partial-end-wall-replacement technique.         Mercury superconductors crystal growth under high pressure and high temperature influenced by crucible composition    A. Morawski, A. Paszewin, T. Lada, H. Marciniak, K. Przybylski, H. Szymczak and A. Wisniewski Summary: We report investigations on chemical reactions among flux containing Hg, Ba, Ca, Cu, O and crucibles made of Al/sub 2/O/sub 3/, Y/sub 2/O/sub 3/ and BaZrO/sub 3/. Our research work on oxide superconductors containing mercury allowed us to compose the first approach of p-T-x conditions of synthesis. We obtain quite large (up to 2/spl times/2 mm/sup 2/), flat single crystals. We present the results of our investigation of the influence of p-T-x conditions on reactions between the batch and the various crucibles. XRD patterns and morphology study by SEM and EDX analysis are shown. We conclude that the BaZrO/sub 3/ crucible is the most neutral for the crystallization process.         Fast temperature ramping Hg-vapor annealing process for fabrication of Hg-based superconducting thin films    J.Z. Wu, S.H. Yun, A. Gapud, B.W. Kang, W.N. Kang, S.C. Tidrow, D. Eckart, X.T. Cui and W.K. Chu Summary: Growth mechanism of superconducting Hg-based cuprate thin films has been studied by changing the sample heating rate in Hg-vapor annealing process. A fast temperature ramping Hg-vapor annealing (FTRA) process has been found to be beneficial to the growth of high quality c-axis oriented epitaxial HgBa/sub 2/CaCu/sub 2/O/sub 6+/spl delta// films with zero-resistance T/sub c/ up to 124 K and HgBa/sub 2/Ca/sub 2/Cu/sub 3/ O/sub 8+/spl delta// films with zero-resistance T/sub c/ up to 130 K on SrTiO/sub 3/ and LaAlO/sub 3/ substrates. The high J/sub c/'s carried by these films makes them promising for many applications.         RF power dependence study of large area YBCO thin films    Zhengxiang Ma, E. De Obaldia, G. Hampel, P. Polakos, P. Mankiewich, B. Batlogg, W. Prusseit, H. Kinder, A. Anderson, D.E. Oates, R. Ono and J. Beall Summary: In an effort to develop HTS superconducting filters with sufficient power handling capability for PCS (Personal Communication Services) base station transmit applications, we have undertaken a study of the power dependence of large area YBCO thin films on LaAlO/sub 3/ substrates. We employed a coplanar-wave-guide (CPW) resonator technique to obtain the changes of loss and inductance versus circulating microwave currents in the films. Data have been collected on uniform large area (2" diameter) films grown by coevaporation and off-axis sputtering techniques under varying deposition conditions. We found correlations between the RF power dependence and other film properties such as penetration depth and crystal structure. The most intrinsic sample, from the coevaporation technique, characterized by the smallest penetration depth, good orthorhombicity and absence of tetragonal phase, shows the least amount of nonlinearity. Such correlations can be used to prescreen films for fabrication and monitor the film production line. However, films from coevaporation and off-axis sputtering show very distinct power dependent behaviors.         Temperature dependence of the surface resistance R(T,/spl omega/) and mean free path l(T) of YBCO-superconductors    T. Jacobs, K. Numssen, R. Schwab, R. Heidinger and J. Halbritter Summary: The surface resistance R(T/spl omega/) at 10 and 145 GHz is obtained experimentally between 4 and 300 K. In the temperature range T/sub a//spl les/T/spl les/T/sub c/ R(T) is quantitatively fitted by the BCS theory with a mean free path l(T) increasing exponentially below T/sub c/. The l(T)-increase is related to diminishing plane-chain scattering and is limited at T/sub a/ by "inelastic surface scattering" at weak or strong links, e.g., at twin boundaries of an average distance a/sub TW/. They dominate scattering for l(T)/spl ges/a/sub TW//2. Below T/sub a/ the enforced energy transfer from YBCO-crystallites to weak links enhances R(T         Surface resistance and morphology of YBCO films as a function of thickness    F.J.B. Stork, K.A. Beall, A. Roshko, D.C. DeGroot, D.A. Rudman, R.H. Ono and J. Krupka Summary: We have examined the thickness dependence of the growth morphology and surface resistance R/sub s/ of laser ablated YBa/sub 2/Cu/sub 3/O/sub 7-x/ films with transition temperatures over 89 K and critical current densities greater than 10/sup 6/ A/cm/sup 2/ at 76 K. The thickness was varied from 50 to 1600 nm while all other deposition conditions were maintained constant. The microstructure has been characterized by scanning electron microscopy and scanning tunneling microscopy continuously decreased with film thickness as a power law with an exponent of -0.5. The surface resistance was measured at 76 K with a dielectric rod resonator. For films less than 300 nm thick, the fields penetrated the superconducting films, causing a rapid increase in the apparent R/sub s/ with decreasing film thickness. Films thicker than 800 nm showed microcracks and the R/sub s/ increased sharply, and no resonance was observed above 1000 nm.         Distribution of critical current density in large YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// grains fabricated using seeded peritectic solidification    C.D. Dewhurst, Wai Lo and D.A. Cardwell Summary: High quality large grain high T/sub c/ superconducting ceramics offer enormous potential as "permanent" magnets and in magnetic screening applications at 77 K. This requires sample dimensions /spl sim/cm with uniform high critical current densities of the order 10/sup 5/ A/cm/sup 2/ in applied magnetic fields of 1T. We report a study of the magnetic characterisation of a typical large YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// grain, prepared by seeded peritectic solidification, and correlate the magnetically determined critical current density, J/sub c/, with microstructural features from different regions of the bulk sample. From this data we extract the temperature, field and positional dependence of the critical current density of the samples and the irreversibility line. We find that whilst the bulk sample exhibits a good J/sub c/ of order 10/sup 4/ A/cm/sup 2/ (77 K, 1T), the local J/sub c/ is strongly correlated with the sample microstructure towards the edge of the sample and more severely at the centre of the sample by the presence of SmBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// seed crystal.         Effect of sample geometry on levitation force in seeded-melt-grown single-domain YBa/sub 2/Cu/sub 3/O/sub x/    S. Sagar, K. Lahiri, D. Shi and J.Z. Yang Summary: Magnetic levitation force is a key factor that influences energy loss in flywheel energy storage applications. Experiments on the relationships between levitation force and YB/sub 2/Cu/sub 3/O/sub x/ sample geometry have been conducted. The levitation force has been conducted. The levitation force has been measured for single-domain YBa/sub 2/Cu/sub 3/O/sub x/ samples with different thicknesses and diameters. It has been found that the thickness dependence agrees well with a current model. However, the measured levitation force that was found only within the linear regime. The levitation force in fact increases as the diameter decreases until a threshold value is reached. As the diameter of HTS sample is reduced smaller than the testing magnet (d=12 mm) the force experiences a rather rapid fall. This behaviour can be qualitatively described by a magnetic dipole model based on Meissner currents. Other factors that dominate levitation force are also discussed.         Development and testing of YBaCuO rings for a gravimeter    V.T. Petrenko, M.A. Tikhonovsky, A.S. Tortika, T.Y. Rudycheva, N.V. Lapina, L.V. Verozub, M.P. Ozerov and V.M. Yemets Summary: YBaCuO rings with an outer diameter of about 20 mm were prepared by the MTG method. The influence of cooling conditions and composition on the structure and critical current density of the rings was investigated. The interaction of the rings with frozen magnetic fluxes was examined using a specially designed device having a force measurement sensitivity of 10/sup -8/ N. The correlation between theoretical calculations and experimental data concerning the interaction of the rings is discussed.         Effects of Sm/sub 2/BaCuO/sub 5/ addition on the melt-textured-growth YBa/sub 2/Cu/sub 3/O/sub y/    H. Zhang, S.M. Gong and C.B. Cai Summary: Effects of Sm/sub 2/BaCuO/sub 5/ addition on the microstructure and superconducting properties of the melt textured-growth YBa/sub 2/Co/sub 3/O/sub y/, have been investigated in this paper. Sm/sub 2/BaCuO/sub 5/ addition decreases the crystal domain size and thickness of plate grains in domains, and increases the intragrain critical current densities. The peak effect in the magnetization curve is observed in the samples with Sm/sub 2/BaCuO/sub 5/ additions. The levitation force and force relaxation with time were measured and compared for bulks with and without the Sm/sub 2/BaCuO/sub 5/ addition.         Microstructural features and fracture resistance of superconductive ceramics    I.A. Parinov, E.V. Rozhkov and C.E. Vassilchenko Summary: Based on the example of the gradient sintered YBa/sub 2/Cu/sub 3/O/sub 7-x/, compositions, a computer microstructural model for crack bridging processes is presented and their effects on the fracture resistance are calculated. Three kinds of restraining bridges are considered namely: elastic connections, frictional ligaments, and tractions due to the thermal expansion anisotropy. Influence of the initial press-powder porosity on the some parameters of crack bridging is evaluated.         Formation mechanism of defects around the Y211 inclusion trapped within the melt-textured Y123 domain    Gye-Won Hong, Ki-Baik Kim, Il-Hyun Kuk, Chan-Joong Kim, Yi-Sung Lee and Hyun-Soon Park Summary: The melt processed Y123 oxide superconductor shows a very high magnetic levitation force and there is lots of research to develop its application technology such as a fly wheel energy storage device. Our recent study on the microstructure of the melt-processed samples showed that oxygenation condition significantly affected the magnetic properties of the YBCO sample. We examined the microstructure around the Y211 inclusion trapped within the melt-textured domain to understand the formation mechanism of the defects such as CuO stacking faults, dislocations and BaCuO platelet boundaries. The microstructures of the YBCO samples were heat-treated in flowing oxygen for various times. No defects were observed around the trapped Y211 inclusions and in the Y123 matrix of the tetragonal sample. Meanwhile, dislocation, transformation twins, the CuO stacking fault and BaCuO platelet structure were observed in the sample transformed into superconducting orthorhombic phase by low temperature heat treatment. The CuO stacking fault and BaCuO platelet structure are developed along the [100] and [010] direction on the a-b plane of the orthorhombic Y123. The formation mechanism of the defects was discussed on the basis of the oxygenation-induced decomposition mechanism.         Melt textured YBCO samples for trapped field magnets and levitating bearings    G. Fuchs, P. Stoye, T. Staiger, G. Krabbes, P. Schatzle, W. Gawalek, P. Gornert and A. Gladun Summary: Bulk melt textured YBCO materials in the shape of disks are being developed for use as trapped field magnets and in superconducting bearings. The trapped field in the gap between two disks of 26 mm in diameter reached maximum values of 1 T at 77 K and of 8.5 T at 51.5 K. A superconducting magnetic bearing has been built up of two YBCO rings and two concentric NdFeB ring magnets between them. A static levitation force of 25 N and values of the axial and radial stiffnesses of 15 N/mm and 10 N/mm, respectively, have been achieved for this bearing in the working position. A high speed motor with two superconducting magnetic bearings of this kind has been tested at 77 K.         Development of Tl-1223 conductors for 77 K HTS applications    V. Selvamanickam, K. Pfaffenbach, D. Kirchoff, K.M. Cardner, D.W. Hazelton and P. Haldar Summary: Tl-1223 conductors have been fabricated by the powder-in-tube (PIT) and surface-coated conductor (thick film) techniques. Current densities (J/sub c/) of 20,000 A/cm/sup 2/ and 12,000 A/cm/sup 2/ have been achieved at 77 K in short monofilament tapes and meter-long 37-filament tapes respectively. A large diameter test pancake coil was successfully fabricated with 17 m long PIT tapes. A new process has been developed to achieve grain alignment in PIT Tl-1223. Critical currents of 18 A and a J/sub c/ of 19000 A/cm/sup 2/ has been achieved at 77 K in surface-coated Tl-1223 conductor fabricated by an industrial process.         Enhanced I/sub c/-B performance in Tl-base high-Te oxides prepared by a diffusion process    K. Tachikana, A. Kikuchi and T. Nakamura Summary: High-T/sub c/ Tl-base oxides can be synthesized by a diffusion reaction within a short reaction time. The F addition apparently promotes the phase transformation from 2223 to 1223. The scanning electron microscope observation reveals that the 1223 phase formed by the F addition shows a dense and homogeneous structure, resulting in an increase in transport I/sub c/ at 77 K. Moreover, F addition significantly improves the I/sub c/ at 77 K under magnetic field, and shifts the irreversibility line to higher temperature. Meanwhile, V addition was found to enhance the diffusion reaction, resulting in the formation of 2223 layer of about 600 pm in thickness after the reaction at 850/spl deg/C for 2 h. The V is pushed out from the diffusion layer and accumulates on the surface of the specimen. The V addition causes almost no degradation in T/sub c/. I/sub c/-B performance is appreciably improved by annealing in O/sub 2/ after the reaction.         Development of a melt processing route for the fabrication of Tl-1223 coils    J.C. Moore, D. Hyland, S. Fox, M.J. Naylor, S. Wivell and C.R.M. Grovenor Summary: Tl-1223 tapes with engineering critical current densities, (E-J/sub c/) values of 2500 Acm/sup -2/ can be routinely fabricated but the magnetic field properties are poor due to weak link effects. We have developed a partial melt processing route which results in increased grain growth with greater potential for achieving grain alignment. We have investigated the effect of Tl-1223 phase composition on the melt process and found that Bi substitutions lead to an increased grain size in tapes made using unreacted powder but a decrease in grain growth in tapes made with reacted powder.         Transport and magnetisation measurements of Tl-1223 tapes-the nature of current paths and the role of grain boundaries at high magnetic fields    J. Everett, M.D. Johnston, G.K. Perkins, A.V. Volkozub, A.D. Caplin, J.C. Moore, S. Fox, D. Hyland and C.R.M. Grovenor Summary: The key factors that make the thallium-based 1223 phase conductors attractive candidates for high field applications are a high transition temperature (/spl sim/ 115 K), and an irreversibility line comparable to YBa/sub 2/Cu/sub 3/O/sub 7/. However, a third important factor is the grain boundary behaviour. We have made detailed transport current-voltage (I-V) and magnetic studies of a Ag-0.1%Hf sheathed Tl-1223 tape. For low fields (B<100 mT) its critical current density J/sub c/ performance displays the "weak-link" signatures well-known for polycrystalline YBa/sub 2/Cu/sub 3/O/sub 7/. At high fields however (B>100 mT) there is a plateau region in its J/sub c/(B) characteristics. Possible scenarios for inter-granular transport current conduction and dissipation in this region are discussed.         Development of buffer layers for high quality Tl-Pb-Sr-Ba-Ca-Cu-O thick films on flexible metal substrates    P.A. Parilla, J.M. McGraw, D.L. Schulz, J. Wendelin, R.N. Bhattacharya, R.D. Blaugher, D.S. Ginley, J.A. Voigt and E.P. Roth Summary: Previous work has demonstrated the ability to grow extremely high quality Tl/sub 0.5/Pb/sub 0.5/Sr/sub 1.6/Ba/sub 0.4/Ca/sub 2/Cu/sub 3/O/sub x/ epitaxial films up to 15 /spl mu/m thick using melt growth techniques on single crystal LaAlO/sub 3/ substrates. This melt growth process is an ideal candidate for producing high quality superconducting films on flexible metal substrates with textured buffer layers; however, the textured buffer layer of choice, cubic yttria stabilized zirconia (YSZ), appears to be incompatible with the melt growth of TI-Pb-Sr-Ba-Ca-Cu-O films. In this work, we investigate textured buffer layers which are compatible with the epitaxial growth of Tl/sub 0.5/Pb/sub 0.5/Sr/sub 1.6/Ba/sub 0.4/Ca/sub 2/Cu/sub 3/O/sub x/ films. Crucial properties for the successful development of a suitable buffer layer are lattice matching, chemical stability and texture. Buffer layer materials investigated are CeO/sub 2/ and LaAlO/sub 3/ grown using a UV (248 nm) pulsed excimer laser deposition system equipped with multiple targets and a controlled ambient. Influence of substrate temperature and ambient gas pressure and flow on buffer growth are analyzed via XRD characterization. Highly textured buffer layers have been fabricated.         Growth of Hg/sub 0.9/Re/sub 0.1/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub 8+x/ on a metallic substrate    K.M. Amm, C. Wolters, D.C. Knoll, S.C. Peterson and J. Schwartz Summary: The large-scale application of any high temperature superconductor will require a metallic sheath to satisfy the mechanical and thermal requirements of superconducting magnets. Thus, an important step in the development of a high temperature superconductor is to study the properties of the superconductor in contact with a metallic surface. Due to the highly corrosive atmosphere necessary for the synthesis of Hg/sub 0.9/Re/sub 0.1/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub 8+x/ ((Hg,Re)1223) the selection of a suitable metal substrate is critical. In this study, we investigate the synthesis of(Hg,Re)1223 samples on Ag, AgHg, Au, and Pt substrates. The samples were prepared by mixing precursor powders in a dry methanol solution which was then pipette dropped or centrifuge coated onto the metal substrates. The samples were encapsulated in quartz and annealed. Microstructural analysis of phase growth and grain alignment at the superconductor/metal interface were carried out on multiple length scales via x-ray diffraction, scanning electron microscopy, and x-ray microanalysis. Magnetic characterization has been carried out in a SQUID magnetometer.         Synthesis of Hg-Re-Ba-Ca-Cu-O superconductors by a two-step method    C. Wolters, K.M. Amm, D.C. Knoll, S.C. Peterson and J. Schwartz Summary: A new two-step method has been developed to synthesize (Hg,Re)Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub y/ with lower annealing temperatures as compared to conventional methods using a precursor which contains the (Hg,Re)Ba/sub 2/CaCu/sub 2/O/sub y/ phase. In the first step, high phase purity (Hg,Re)Ba/sub 2/CaCu/sub 2/O/sub y/ superconductors are prepared from commercially available Ba/sub 2/CaCu/sub 2/O/sub y/ precursors, HgO, and Re/sub 2/O/sub 7/. In the second step, the finely ground (Hg,Re)Ba/sub 2/CaCu/sub 2/O/sub y/ is mixed with Ca-Cu-O and HgO. This precursor mix is encapsulated in evacuated quartz tubes and annealed for 8 to 48 h between 750/spl deg/C and 850/spl deg/C. The resulting samples have (Hg,Re)Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub y/ as a majority phase and exhibit a critical temperature of 133 K as prepared. The superconducting grains are platelike and randomly oriented. The grain sizes depend on the annealing time and temperature and reaches up to 30 /spl mu/m diameter and 5 /spl mu/m thickness. Second phases are mainly unreacted Ba/sub 2/CaCu/sub 2/O/sub y/ and Ca-Hg-O.         High-Tc superconductors synthesis using ferroelectric hosts: barium sodium niobate doped with copper and calcium    A.M. Luiz, J.M. Neto and M.R. Da Silva Summary: From the suggestion that ferroelectric host materials could be used in the search for the synthesis of new high-Tc superconductors, we have synthesized materials derived from barium sodium niobate. Measurements on magnetization, ac susceptibility and resistivity are reported. The materials change from weakly paramagnetic to weakly diamagnetic at low temperatures, when the time of oxygen annealing is reduced, but with high resistivity. With the increase of temperature, a strong decrease in resistivity (of the order of 10/sup 6/ /spl Omega/ cm), with diamagnetism, has been observed for temperatures above 1000 K.         Improvement of critical current density and microstructure of Tl-1223 tapes by a two-powder method    Shiming Wu, B.A. Glowacki, Wei Yao Liang, Xiao-Ming Yang and H.W. Weber Summary: Superconducting tapes of (Tl,R)(Ba,Sr)/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ (R=Bi or Pb) were prepared using a mixture of pre-reacted single phase powder and unreacted precursor of identical or different stoichiometry. The effects of mechanical densification and sintering conditions on critical current (I/sub c/) and microstructure of the tapes were investigated. Compared to the tapes made with entirety unreacted powder or pre-reacted powder, the tapes made with a mixture of the two showed a much improved microstructure, an improved self-field I/sub c/ at 77K, as well as a smaller dependence on sintering conditions and better reproducibility of I/sub c/.         Effects of vortex-vortex interactions on ion-track pinning in high-T/sub c/ superconductors    K.E. Gray, D.G. Steel, J.D. Hettinger, D.J. Miller, B.R. Washburn, M. Ware, J.T. Parkman, M.E. Yoder, C. Moreau and M.M. Eddy Summary: Many superconductor applications rely on the ability to pin vortex lattices. This ability depends on structural defects to pin individual vortices, but vortex-vortex interactions often play an important role in pinning the other vortices. Experimental progress on this complex problem can be made by introducing random arrays of well-defined pinning centers and studying the flux dynamics for a range of vortex densities (i.e., fields). The results of such studies in epitaxial Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub y/ films containing ion tracks show the importance of vortex-vortex interactions. As an example, the effective pinning field of the defects rises to many times the ion-dose field for temperatures well below T/sub c/.         Enhanced critical current density in melt textured YBCO via Au ion surface irradiation    E. Mezzetti, R. Gerbaldo, G. Ghigo, L. Gozzelino, B. Minetti and R. Cherubini Summary: We irradiated both side of bulk melt textured YBCO with 235 MeV Au ions. The thickness of the specimens is significantly larger than the penetration range of the ions so that two surface layers of columnar defects are created. Critical current density enhancements were obtained in temperature and field ranges that are useful for applications. The boundary between reversible and irreversible regime is shifted toward higher temperatures. At higher fields the increase of the relaxation rate with temperature is less steep after irradiation. The general trends are independent of the thickness of the samples, at least in the range from 5% to 13% of volume affected by irradiation.         Effect of heavy-ion irradiation on transport properties of YBa/sub 2/Cu/sub 3/O/sub x/ films    Dong Ho Kim, Seong Yup Shim, Jong Hyeog Park, Young Hwan Kim, Chang Hoon Kim, Jin Wook Jang, Taek Sang Hahn, Sang Sam Choi, J.D. Hettinger, D.G. Steel and K.E. Gray Summary: We have investigated the effect of heavy-ion irradiation on the transport properties of YBa/sub 2/Cu/sub 3/O/sub x/ thin films. Parallel columnar defects to the c axis and crossed columnar defects were introduced into films by heavy-ion irradiation with dose equivalent to 1 or 2 T vortex density. The electrical transport properties including resistivity, critical current density, and the Hall resistivity were measured as a function of temperature, applied magnetic field, and fluence. The irreversibility line defined as an onset of dissipation progressively shifted to higher temperature with increasing dosage and showed its dependence on inclination angle. Critical current also showed a clear enhancement compared to the unirradiated samples. The Hall scaling behavior and the Hall conductivity were modified after heavy-ion irradiation.         Annealing of irradiation induced defects in a LaSrCuO crystal    R.A. Sutton, M.E. McHenry and K.E. Sickafus Summary: Annealing experiments were performed on a LSCO single crystal irradiated with fast neutrons to a fluence of 2.52/spl times/10/sup 18/ n/cm/sup 2/. This fluence increased the critical current density by a factor of 2-3. The sample was annealed for a total of 4.5 hours at 200/spl deg/C and 8 hours at 300/spl deg/C. It was found that annealing of LSCO has a much lesser effect on its critical current density, particularly along the c axis, compared to YBCO. It is hypothesized that the reduced annealing effect is due to the formation of either a more stable interstitial cluster (compared to the Cu-O cluster in YBCO), or clusters which do not act as pinning sites.         Correlations between critical current density and penetration depth in ion irradiated YBa/sub 2/Cu/sub 3/O/sub 7/ thin films    S.H. Moffat, R.A. Hughes, G.D. Poulin, J.S. Preston, D.N. Basov, T. Strach and T. Timusk Summary: Point defects have been introduced into YBa/sub 2/Cu/sub 3/O/sub 7/ through low energy helium ion irradiation in order to probe the origin of dissipation in a current-carrying superconductor. Resistivity, infrared reflectance and x-ray diffraction measurements indicate that the films are not chemically altered and that the induced point defects act as scattering centres. Measured electric field-current density characteristics are found to be well described by a model based on quantum current fluctuations. This description is used to extract the change in the superconducting carrier density with ion damage which agrees well with direct measurements of the same quantity by infrared reflectance. The implications of the relation between dissipation and the superconducting carrier density, or alternatively the magnetic penetration depth, are discussed.         Sensitive measurement of the surface impedance of superconducting single crystals using a sapphire dielectric resonator    J.J. Wingfield, J.R. Powell, C.E. Gough and A. Porch Summary: A highly sensitive system based on a sapphire dielectric resonator has been developed to investigate the microwave properties of superconducting single crystals. The resonator is fabricated from a machined piece of single crystal sapphire, with a hole bored along its axis to accommodate samples. Samples are mounted on a independently heated sapphire rod, which is inserted into the region of high microwave field at the centre of the resonator. Crystals can be mounted with either their c-axis or ab-planes parallel to the microwave field. In the former configuration the predicted smallest detectable change in surface resistance is /spl sim/2.6/spl times/10/sup -4/ /spl Omega/ and is /spl sim/3.7/spl times/10/sup -4/ /spl Omega/ for the latter. Microwave measurements at 10 GHz on high quality YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// single crystals demonstrate the potential of the system for measuring the surface impedance as a function of field (up to 1.75 T parallel and 0.18 T perpendicular to microwave field) and temperature.         Use of a dielectric-loaded cylindrical cavity in measurements of the microwave surface resistances of high-T/sub c/ superconducting thin films    Sang Young Lee, B.J. Soh, J.W. Ahn, J.Y. Cho, B.H. Park, C.S. Jung, V.B. Fedorov, A.G. Denisov, Y.H. Kim, T.S. Hahn, S.S. Choi, B. Oh and S.H. Moon Summary: An analysis of the axially symmetric TM/sub 011/ mode in a dielectric-loaded cavity is presented and a technique of using a TM/sub 011/ mode dielectric-loaded cavity is introduced for measurements of microwave surface resistances of HTS thin films. A dielectric resonator with /spl epsiv//sub r//spl ap/39 is used for this purpose. It turned out that Q of the TM/sub 011/ mode dielectric-loaded cavity is very sensitive to the surface resistance of the material at the bottom plate, especially to the surface resistance of the area under the dielectric resonator, which can be used to investigate local microwave properties of large HTS thin films in a nondestructive, simple way. Experiments on YBCO thin films with the dimensions of /spl sim/2/spl times/2 cm/sup 2/ are performed using this technique, which revealed inhomogeneity in the microwave surface resistance of the thin films at different sites and demonstrated the usefulness of this technique.         Dielectric resonators as microwave characterization tools    E.K. Moser and K. Naishadham Summary: Dielectric resonators, formed by sandwiching a cylindrical piece of polished dielectric material (sapphire) between two planar endplates, offer an attractive platform for microwave testing of HTS films. Each resonator is tested as a two-port system, by exciting and detecting the modal fields with loop-terminated coaxial cables. The observed quality factor of the resonator is a gauge of the surface resistance of the endplates. We discuss utilization of this method as a tool for testing /spl sim/1 cm/sup 2/ areas, at frequencies in the 20-40 GHz range, and at cryogenic temperatures, using field analysis to explore trade-offs involving cylinder geometry, field confinement, and miniaturization. An improved method for analyzing two-port data eases the difficulties associated with testing the resonator in a cryogenic environment.         Magnetic field orientation dependence of J/sub c/ in Bi-2212 round wires    J.O. Willis, T.G. Holesinger, J.Y. Coulter and M.P. Maley Summary: We have performed measurements of the magnetic field dependence of the critical current density J/sub c/ of Bi-2212/Ag round wire produced by isothermal melt processing. In contrast to the case for flat tape, there is very little dependence of J/sub c/ on on the direction of the magnetic field as it is rotated normal to the wire axis which is the direction of the nominal current flow. However, when the angle of the magnetic field direction is rotated from normal to the wire axis to parallel to that axis, J/sub c/ at 64 K and 0.2 T increases by more than a factor of four. Again, this is in contrast to the results observed for Bi-2212/Ag and Bi-2223/Ag flat tapes, which show no anisotropy under similar experimental conditions. We can explain these differences in angular anisotropy by referring to the microstructure of these two conductor types, which have distinctly different types of grain alignment. We discuss the general behaviour of the dependence of J/sub c/ on the orientation of a magnetic field for high temperature superconductors.         Progress in superconducting performance of rolled multifilamentary Bi-2223 HTS composite conductors    Q. Li, G.N. Riley, R.D. Parrella, S. Fleshier, M.W. Rupich, W.L. Carter, J.O. Willis, J.Y. Coulter, J.F. Bingert, V.K. Sikka, J.A. Parrell and D.C. Larbalestier Summary: Significant enhancements in critical current densities in rolled multifilamentary Bi-2223 HTS composite conductors have been achieved using the powder-in-tube (PIT) technique. At 77 K and self field, oxide critical current densities (J/sub c/) of 55 kA/cm/sup 2/, overall or engineering critical current densities (J/sub e/) of 15 kA/cm/sup 2/, and critical currents (I/sub c/) of 125 A have been achieved in different rolled multifilamentary composites. Progress in achieving such high electrical performance is believed to stem in part from an improvement of grain connectivity by reducing weak links. The J/sub c/ dependence on magnetic field (B) and the degree of c-axis texture of these high quality conductors have been investigated at various temperatures. Our results also demonstrate that the critical current retention in magnetic field can be independently controlled from the self field critical current density, suggesting that flux pinning improvements and weak link reductions can be separately engineered into Bi-2223 composites fabricated using manufacturable processes.         Enhanced critical current densities in (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 2/O/sub 10/ silver-sheathed tapes by splayed columnar defects after 600 MeV proton irradiation    B. Hensel, F. Marti, G. Grasso, M. Dhalle, R. Flukiger, F. Paschoud and M. Victoria Summary: Splayed columnar defects are efficient pinning centers for magnetic vortices in high-T/sub c/ superconductors. Irradiation with 600 MeV protons as primary projectiles generates heavy fission fragments in (Bi, Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ via a p-Bi nuclear reaction. The high-Z secondary projectiles are sufficiently energetic to create randomly oriented columnar defects with important effects on the magnetic and transport critical current densities of (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ Ag-sheathed tapes. These effects are discussed on the basis of the splayed defect topology.         Small and repetitive axial strain reducing the critical current in BSCCO/Ag superconductors    B. ten Haken, A. Beuink and H.H.J. Ten Kate Summary: The critical current in two types of axially deformed BSCCO/Ag tape conductors is investigated. An I/sub c/ reduction is observed for small axial strains (ranging from 0 to 0.3%) with a characteristic slope di/sub c//d/spl epsiv/=-5/spl plusmn/1 (relative I/sub c/, change per relative change in length). In the case of an axial compression there is a more pronounced I/sub c/ reduction. For small axial strains (<0.3%) a certain reversible change in I/sub c/ is observed. This reversible behaviour occurs in combination with an irreversible reduction that increases when the number of strain cycles is increased. The reversible part of the I/sub c/ change remains for a large number of strain cycles (>10000) and has a similar negative slope for both compressive and tensile strains. It is proposed that the reversible I/sub c/ change is correlated to a non-hydrostatic lattice deformation. The I/sub c/ versus strain behaviour is in good agreement with an earlier proposed model.         Mechanical properties and strain effects in Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x//AgMg composite conductors    J. Schwartz, B.C. Amm, H. Garmestani, D.K. Hilton and Y. Hascicek Summary: The development of powder-in-tube Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ technology has progressed such that high critical current density (J/sub c/) conductors are produced by many researchers, Prototype systems are being tested to demonstrate engineering feasibility. An important issue that remains, however, is the effect of mechanical strain. While it is evident that large strains induce irreversible damage, applications may be limited by fatigue at low strain values due to crack propagation. Here we report on the development of two devices designed specifically to study strain effects in high temperature superconducting tapes. Preliminary results of the effects of cyclic fatigue on J/sub c/ of AgMg-clad Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/, as measured by electrical transport is shown. Measurements of the constituent and composite mechanical properties are also reported.         Transport critical currents of Bi(2223) tapes at 77 K under mechanical stress    B. Ullmann, A. Gabler, M. Quilitz and W. Goldacker Summary: The transport critical current, j/sub c/, depends on the mechanical stress applied during or before the j/sub c/-determination. Two experiments with different aims were performed : a) bending of the tape tests the resistance against winding (coils, power cables); b) axial strain tests give information on the effect of forces acting on the conductor during operation. Bending of Bi(2223)/Ag tapes from a radius r=/spl infin/ to r=1 cm as well as an axial strain of about 0.2% decreases j/sub c/ by some 80%. For bent as well as for elongated tapes, we find an almost unaffected field dependence of j/sub c/, which is only on a lower j/sub c/ level due to crack formation, i.e. a reduction of the percolation path. The strong j/sub c/ reduction can be avoided by reinforcement of the sheath material by dispersion hardening with 2% Mg. The j/sub c/ decrease after bending in these improved tapes is only some 20%, the maximum axial strain tolerance about 0.8%. The yield of the reinforced tapes is 300-350 MPa, which is more than 5 times the value for Ag sheathed tapes.         Mechanical stabilization of BSCCO-2223 superconducting tapes    C.G. King, D.A. Grey, A. Mantone, K.G. Herd and E.T. Laskaris Summary: A system to provide mechanical stabilization to high temperature BSCCO-2223 superconducting tape by laminating 0.081 mm thick, spring hard, copper foil to both sides with lead-tin eutectic solder has been successfully optimized. This system has been applied as a method to create a strong, windable composite with a minimum of critical current (I/sub c/) degradation. The "as received" conductor is evaluated for physical consistency of width and thickness. Electrical degradation in the strengthened tape as a result of lamination was found to average 24 percent. This was less than the degradation that would have occurred in an unstrengthened tape during subsequent insulation and coil winding processes. The copper can double the ultimate tensile strength of the pure silver tapes. Additionally, pure silver and dispersion strengthened silver matrix tapes are laminated with 0.025 mm thick copper and 304 stainless steel foil to investigate minimization of the cross sectional area of the strengthening component. The stainless steel can increase the UTS of the pure silver tapes sixfold. Mechanical properties and critical currents of these tapes are also reported both before and after strengthening. The I/sub c/ is also measured as a function of strain on the laminated tapes.         Materials basis for a six level epitaxial HTS digital circuit process    J. Talvacchio, M.G. Forrester, B.D. Hunt, J.D. McCambridge, R.M. Young, X.F. Zhang and D.J. Miller Summary: We have developed a process for fabrication of HTS single-flux-quantum logic circuits based on edge SNS junctions which requires six epitaxial film layers and six mask levels. The process was successfully applied to fabrication of small-scale circuits (/spl les/10 junctions). This paper examines the materials properties affecting the reproducibility of YBCO-based SNS junctions, the low inductance provided by an integrated YBCO ground plane, and electrical isolation by SrTiO/sub 3/, or Sr/sub 2/AlTaO/sub 6/, ground-plane and junction insulator layers. Some of the critical processing parameters identified by electrical measurements, TEM, SEM, and AFM were control of second-phase precipitates in YBCO, oxygen diffusion, Ar ion-milling parameters, and preparation of surfaces for subsequent high-temperature depositions.         Characterization and improvement of a YBCO multilayer film process for HTS circuit applications    C.L. Pettiette-Hall, J. Murduck, J.F. Burch, M. Sergant, R. Hu, J. Cordrump, M. Luong and R.K. Ellis Summary: We have developed a 2" multilayer HTS integrated circuit process which contains up to three superconducting YBCO layers, epitaxial dielectric (SrTiO/sub 3/ or SrTiO/sub 3/+Sr/sub 2/AlTaO/sub 6/ combination), Ag wiring, an integrated resistor and non-epitaxial Si/sub x/N/sub y/ dielectric. We have incorporated the use of n-factorial and Taguchi designed experiments to develop and optimize various aspects of this process. This article highlights the designed experiments which addressed fabrication issues for HTS superconducting crossovers, dielectric integrity, and HTS/Ag metal contact resistance.         Epitaxial Sr/sub 2/RuO/sub 4/ heterostructures    S. Madhavan, Ying Liu, D.G. Schlom, A. Dabkowski, H.A. Dabkowska, Y. Suzuki, I. Takeuchi, Z. Trajanovic and R.P. Sharma Summary: Sr/sub 2/RuO/sub 4/ is the only known layered perovskite that is free of copper, yet superconducting. Its low metallic resistivity and excellent lattice match with YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// make it an attractive candidate for use as conductive electrodes to YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta//-based superconducting devices or as a normal metal in YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta//-based SNS junctions. We have determined optimal deposition conditions for growth of single-domain epitaxial films of Sr/sub 2/RuO/sub 4/. Films with excellent crystallinity are readily grown at substrate temperatures exceeding 1000/spl deg/C at low pressures. At lower temperatures and higher pressures, films predominantly consist of the SrRuO/sub 3/ phase. Resistivity versus temperature measurements reveal that the as-grown Sr/sub 2/RuO/sub 4/ films are metallic, but not superconducting. Epitaxial YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta///Sr/sub 2/RuO/sub 4/ heterostructures have also been grown. X-ray and resistivity measurements show that the YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films are of high quality.         Evidence for modification of the superconducting order parameter in YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films by injection of a spin polarized current    D.B. Chrisey, M.S. Osofsky, J.S. Horwitz, R.J. Soulen, B. Woodfield, J. Byers, G.M. Daly, P.C. Dorsey, J.M. Pond, M. Johnson and R.C.Y. Auyeung Summary: We have deposited novel bilayer thin films of a ferromagnetic material and YBa/sub 2/Cu/sub 3/O/sub 7/ separated by a thin Au diffusion barrier to study the effects of a spin polarized nonequilibrium quasiparticle population on the superconducting order parameter. Thin films of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta//, Au, and Permalloy (Ni/sub 0.8/Fe/sub 0.2/) were deposited by pulsed laser deposition onto (100) MgO, SrTiO/sub 3/, or LaAlO/sub 3/ substrates. A thin stripe of YBa/sub 2/Cu/sub 3/,O/sub 7-/spl delta//, was patterned and two pairs of Au cross stripes for current and voltage contact were deposited at each end. Between these contacts a Permalloy and a Au cross stripe was also deposited to serve as the spin polarized and unpolarized quasiparticle injection sources, respectively. Utilizing this pseudo-three terminal device configuration we have in some samples measured reductions in the superconducting order parameter at the ferromagnet contact as compared to the normal metal contact. Details of this experiment, issues for optimized fabrication, and theoretical issues are discussed.         Crystal engineering of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// structures    JiPing Zhou and J.T. McDevitt Summary: In order to produce more stable and processable forms of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// superconductors, a series of cation substitution reactions have been completed. Compounds in the family of Y/sub 1-y/Ca/sub y/Ba/sub 1-y/La/sub y/Cu/sub 3/O/sub 7-/spl delta// display an increased corrosion resistance with increasing substitution level. The composition of Y/sub 0.6/Ca/sub 0.4/Ba/sub 1.6/La/sub 0.4/Cu/sub 3/O/sub 6.96/-(T/sub c/=80 K) is found to be at least 100 times more stable than the parent compound, YBa/sub 2/Cu/sub 3/O/sub 6.94/. In this paper, compositions yielding transition temperature above 83-85 K have been identified in YBa/sub 2-x/Sr/sub x/Cu/sub 3/O/sub 7-/spl delta// and Gd/sub 1-x/Ca/sub x/Ba/sub 2-y/La/sub y/Cu/sub 3/O/sub 7-/spl delta// systems suggesting that the surface reactivity, processability and superconducting properties can be tailored with the use of the appropriate cation compositions. Rational approaches for the systematic tailoring of high-T/sub c/ superconductors based on lattice engineering approaches are thus developed.         Deformation-dominated texturing of superconducting filament in OPIT-fabricated Bi(Pb)SCCO-2223/Ag composite tapes    V. Beilin, A. Goldgirsh and M. Schieber Summary: Texture formation in the ceramic filament of Ag/BiSCCO tapes was studied after cold rolling, uniaxial cold pressing and sintering by XRD /spl theta/-2/spl theta/ and /spl omega/-scan methods. More effective texturing of the outer layers as compared to that of the core interior was observed at the early rolling steps up to about 65% reduction in area. Texture inhomogeneity over the filament cross section is related to the inhomogeneous distribution of plastic deformation. Work hardening due to plastic deformation of non-sintered powder results in the broadening of X-ray peaks and an increase in microhardness. The recovery of these parameters occurs after annealing at the temperatures of 350-600/spl deg/C. The /spl omega/-scan studies revealed an improvement of c-axis texture by intermediate rolling compared to that in the as-sintered and pressed states. Deformation-induced texturing of the 2212-precursor is the main factor responsible for the texture of the final 2223-phase. The influence of Ag during the sintering stage is limited only to the outer layers of the filament; in the case of low preliminary deformation internal layers remained practically non-oriented.         Fabrication of thin-filament Bi-2223/Ag superconducting tapes    D.W.A. Willen, W. Zhu, R. Nadi, A. Paquette and J.R. Cave Summary: The use of high-temperature superconductors (HTS) in some power utility applications requires long lengths of conductors with low AC losses and good mechanical properties. This is typically obtained by making multifilamentary wires with thin filaments. In Powder-In-Tube (OPIT) process, the fabrication of thin filaments is limited by the development of non-uniformities due to "sausaging", shear fracture, and tensile fracture in the oxide core. This work analyses factors that control the uniformity of thin filaments of Bi-2223/Ag superconducting tapes. Some simple theoretical considerations have explained the formation of these types of defects in terms of the stress-dependent mechanical properties of the superconducting powder. Experimental results verify that small roller size and low reduction rates during flat rolling (two factors that reduce die hydrostatic stress component in the powder core) improve the uniformity of these filaments. Tapes with core thicknesses of down to 12-18 /spl mu/m have been manufactured, which exhibit values of critical current density of 31-36 kAcm/sup -2/ (at 77 K and 1 /spl mu/V/cm) for heat treatments of 70-200 h.         Transmission electron microscopy investigation of Bi-based HTS tapes    C.J. Eastell, B.M. Henry, C.G. Morgan, C.R.M. Grovenor, M.J. Goringe, J.W. Burgoyne and D. Dew-Hughes Summary: Bi(Pb)-2223/Ag powder in tube tapes have been examined by TEM. The tapes show good alignment and phase purity in the SEM but TEM investigations revealed a number of fine-scale, current-limiting, features. Such features include variation in grain boundary structure, amorphous phases at twist grain boundaries, residual 2212 layers present at grain boundaries and inside grains, and secondary phases. The Ag/superconductor interface has been shown to be relatively planar with no amorphous phases with the Bi(Pb)-2223 having near perfect c-axis alignment at the interface.         The method of joining of the BSCCO superconductors    M.S. Tseluevskii, N.F. Ladutko, Z.M. Tomilo, N.A. Prytkova, T.M. Golobov and D.M. Turshevich Summary: To lengthen high-T/sub c/ superconducting wares (wires, screens and other) we present a method of joining of BSCCO materials, retaining their initial superconducting properties. The BSCCO original superconducting materials (tubes) were prepared by the melt quenching method with subsequent annealing. The initial superconducting temperature T/sub c//sup 0/ (R=0) of the BSCCO tubes is (85-92) K. For joining of the tubes the BSCCO superconducting material containing additions that decreased the synthesis regimes of BSCCO joining contact (splice) are used. The superconducting property and phase investigations of the original and joined BSCCO tubes are presented.         Investigation of texture formation and phase transition in press-, CIP- and roll-sintered Ag-sheathed Bi(2223) tapes    W. Pachla, H. Marciniak, A. Szulc, M. Wroblewski, P. Kovac, I. Husek and T. Melisek Summary: Observations were made on the Bi(2223) tapes undergoing uniaxial pressing (up to 5.7 GPa), CIPing (up to 2.5 GPa) and rolling combined with sintering. Tapes were fabricated utilizing drawing and flat rolling. They have shown strong textures for press- and roll-sintering modes of working and have indicated that CIPing improves effectively the core density, but if not accompanied by pre-annealing, it is not able itself to improve the core texturing. The FWHM of the rocking curves was measured to evaluate texturing degree and its dependence on the measurement geometry was emphasized.         The effect of deformation regimes on superconducting properties and microstructure of Bi-2223 tapes    A.D. Nikulin, A.K. Shikov, O. Antipova, I.I. Akimov, D.A. Filichev, N.I. Kozlenkova and Yu.N. Belotelova Summary: The rolling process of Bi-2223 tape conductors was optimized through the regressive analysis of experimental data. This procedure ensures the effective densification of the powder precursor in the core and homogeneous distribution of powder density in conductor cross section, thus shortening the rolling process. The Jc values were realized for the monofilament and 19-filament conductors processed by "powder in tube" method with one step intermediate rolling such as 3.1/spl times/10/sup 4/ A/cm/sup 2/ (77 K, OT) and 2.6/spl times/10/sup 4/ A/cm/sup 2/ (77 K, OT) respectively. Characteristics of single pancake coils are presented fabricated from 19-filament conductor: no Jc degradation was observed after 10 steps of thermocycling in the range between 77 and 293 K.         Ceramic core density and homogeneity in BSCCO/Ag tapes    P. Kovac, I. Husek and W. Pachla Summary: The monitoring of density by microhardness profiles (HV 0.01) at transverse cross sections of BSCCO/Ag wires and tapes were done after different deformation processes. The results obtained allow better understanding of deformation process of BSCCO/Ag composite and also show what deformation should be used to obtain homogeneous and dense BSCCO-core by powder-in-tube method. The self field transport currents measurements have indicated that optimal value of core density is needed to reach sufficiently high transport currents. Dense ceramic core is not sufficient to reach high J/sub c/ if texture is not improved as well.         Fabrication and characterization of (Bi,Pb)-Sr-Ca-Cu-O (2223) bars    M.P. Chudzik, J. Polzin, R. Thayer, J.J. Picciolo, B.L. Fisher and M.T. Lanagan Summary: Bulk bars for current lead applications were fabricated from (Bi,Pb)-Sr-Ca-Cu-O (Bi-2223) for low thermal conductivity and high critical current. Bars measuring 17.8 cm in length were made by uniaxially pressing Bi-2223 powder of controlled (1.7/0.34)223 and (1,8/0.4)223 phase composition. The bulk bars were densified by subjecting them to a schedule of alternate liquid-phase sintering and cold isostatic pressing. Liquid-phase sintering temperatures were optimized from differential thermal analysis and microstructure morphology. Phase purity and microstructure were evaluated by X-ray diffraction and scanning electron microscopy. Low-resistance silver contacts were applied to the bars by hot-pressing at 820/spl deg/C and 3 MPa. Critical current densities /spl ap/1000 A/cm/sup 2/ (critical currents of 750 A at 77 K in self-field conditions) were achieved.         Critical current properties of screen-printed Ag-Bi2223 tapes    A. Oota, M. Tanaka and K. Fujikawa Summary: Critical current densities J/sub c/ (T,B,/spl theta/) were investigated on screen-printed, c-axis-oriented Ag-Bi2223 mono-layer tape, at temperatures between 55 and 77 K in fields up to 8T as a function of field angle /spl theta/ between B and c axis. At temperatures T/spl les/30 K, a shift of a peak angle from /spl theta/=90/spl deg/ (i.e., B/spl perp/c axis) occurs in the J/sub c/ vs. /spl theta/ curve accompanied by an additional asymmetry. Such anomalies are explained by the history effect in the field dependence of J/sub c/ for B/spl par/c axis ascribed to the grain-boundary weak links, on the assumption that J/sub c/ is dominated by the field component B/spl par/=Bcos/spl theta/ parallel to the c axis. At elevated temperatures, disappearance of the history effect results in a perfectly symmetrical angular dependence of J/sub c/ with a peak at /spl theta/=90/spl deg/. An increase in the number of ceramic layers for the screen-printed tape does not cause significant influence on critical current properties.         Numerical analysis of AC losses in high T/sub c/ superconductors based on E-j characteristics represented with n-value    N. Amemiya, K. Miyamoto, N. Banno and O. Tsukamoto Summary: A numerical code for the electromagnetic analysis of high T/sub c/ superconductors by finite element method has been developed. The E-j characteristics of superconductor are represented with the n-value. The equivalent conductivity of superconductor is determined as a function of electric field, and Ohm's law is used as the constitutive equation. First, the current and magnetic flux distributions in the infinite slabs of superconductor exposed to a parallel external magnetic field are analyzed. The influence of n-value on AC loss and the frequency dependence of AC loss are studied. The AC loss in the infinitely-long superconductor tapes exposed to the external magnetic field is calculated numerically to study the influence of n-value.         Scaling of current-voltage curves of Bi-2212 tape wire    M. Kiuchi, K. Noguchi, M. Tagomori, T. Matsushita and T. Hasegawa Summary: The current-voltage curves are measured for a dip-coated Bi-2212 tape wire at various temperatures under the magnetic field parallel to the c-axis. It is found that the current-voltage curves are approximately scaled on two master curves by normalizing as predicted in the vortex glass-liquid transition theory. However, the obtained dynamic critical index was about 3 and too small in spite of the two-dimensional flux line system. These results are compared with the theoretical analysis based on the flux creep-flow model taking account of the distribution of pinning strength. It is found that the theoretical result approximately explains the experimental result on the scaling behavior, the critical indices and the transition line.         E-J characteristic and flux pinning in superconducting PbBi alloys    Baorong Ni, T. Wakuda and K. Funaki Summary: The characteristics of electric field E vs. current density J at various magnetic fields and temperatures in superconducting PbBi samples with different pinning strength were measured by using a usual resistive method. The obtained E-J curves show a nonlinear behavior similar to that in high T/sub c/ superconductors (HTSC). With a scaling generally used in HTSC, E-J curves collapse onto one of the two universal branches, with the exponents of /spl nu/ and z similar to those reported in HTSC. It was found that the stronger flux pinning strength leads to the higher transition points of T/sub g/ and B/sub g/ in the E-J characteristic. The nonlinear E-J curves and the enhancement of the transition points were explained and reproduced by using the flux creep and flux flow theory.         Flux-flow resistivity of three high-temperature superconductors    Y.S. Cha, S.Y. Seol, D.J. Evans and J.R. Hull Summary: Results of experiments on flux-flow resistivity (the relationship of voltage to current) of three high-temperature superconductors are described. The superconductors are a melt-cast BSCCO 2212 rod, a single-filament BSCCO powder-in-tube (PIT) tape, and a multifilament PIT tape, The flux-flow resistivity of these superconductors was measured at three temperatures: 77 K (saturated liquid nitrogen), 87 K (saturated liquid argon), and 67 K (subcooled liquid nitrogen). Implications of the present results for practical applications are discussed.         Raman microprobe analysis of patterned Tl-2212 thin films    K.E. Myers, D.J. Walls, C. Wilker, P.S.W. Pang and C.F. Carter Summary: We have used MicroRaman spectroscopy to evaluate the effects of ion-milling on the exposed edges of patterned Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ (Tl-2212) lines. Raman microprobe has previously been used to evaluate oxygen loss at the edges of patterned YBCO lines. The results indicated that appreciable oxygen loss was caused by ion-milling under certain conditions. oxygen loss at the edges will decrease non-uniformly the effective width of the superconducting line. This can, in turn, impact the electrical characteristics of patterned devices. Using the 633 nm lined of a HeNe laser, we have measured the Raman spectrum scanning across patterned and unpatterned regions of several Tl-2212 films with a mapping stage. It is well known that the Raman peak at /spl ap/497 cm/sup -1/ corresponds to the Cu-O(2) stretching mode and is correlated with the superconducting transition temperature of the material. No appreciable variation in the center frequency of the Cu-O(2) peak was observed indicating thallium cuprate films are not degraded by our patterning process, even at the edges. Variations in the power handling of Tl-2212 co-planar lines, as determined by measurement of the Third Order Intercept, were not correlated with the Raman results.         Raman microscopy as a local probe of structural defects and oxygen content in HTS thin films    G. Gibson, J.L. MacManus-Driscoll and L.F. Cohen Summary: Three YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) thin films grown by c-beam evaporation have been studied using Raman microscopy. The films were grown at different temperatures and show different levels of cation disorder as determined from the 'c' axis lattice parameter and certain X-ray peak intensity ratios. We report on how the position of the 115 cm/sup -1/ and 500 cm/sup -1/ Raman peaks change as a function of oxygen, cation disorder and spatial position across the films and relate the results to structural changes which occur in the YBCO unit cell.         Deoxygenation of Y-Ba-Cu-O thin films by reactive ion implantation    A. Wong, A. Kulpa, Ruixing Liang, P. Dosanjh, J.F. Carolan, W.N. Hardy, H. Kato, N.A.F. Jaeger and Q.Y. Ma Summary: Thin films of YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO), grown by pulsed laser deposition, were implanted with Si/sup +/ ions at energies of 30,60, and 90 keV and at doses ranging from 1/spl times/10/sup 13/ cm/sup -2/ to 3/spl times/10/sup 11/ cm/sup -2/. X-ray diffraction techniques were used to investigate the structural dependence on implant parameters and annealing conditions, while d.c. magnetization was measured to characterize superconducting properties. By implanting only the upper portion of the film, implanted Si/sup +/ ions, near the surface, inhibit the superconductivity by removing oxygen from the bottom YBCO lattice which still retains its original crystal structure.         Growth and properties of YSr/sub 2/Cu/sub 2.75/Mo/sub 0.25/O/sub 7-/spl delta// thin films    J.P. Sydow, D. Chamberlain, F. Ronnig, Y. Xu and R.A. Buhrman Summary: We report on the epitaxial growth of YSr/sub 2/Cu/sub 2.75/Mo/sub 0.25/O/sub 7-/spl delta// (YSCMO) thin films by pulsed laser ablation, and discuss the superconducting find normal state transport properties of microbridges patterned from such films. To investigate the dopant oxygen mobility of this material, we have used electrical biases applied at near room temperature to induce long range displacement of chain oxygen vacancies in these microbridges. We find that with electromigration, the T/sub c/ of the microbridges can be raised to |60 K. This transition temperature is higher than any previously achieved for this compound, including the T/sub c/'s achieved. As result of extended very high pressure oxygen anneals, or by high pressure in situ measurements. Micro-Raman spectroscopy measurements have been used to examine and characterize the oxygen order in the film before and After electromigration. These measurements indicate that, as suggested by the final T/sub c/ achieved, a very high degree of oxygenation and chain oxygen order can be induced in the microbridge by this process. Thus the as-grown properties of YSCMO appear to be dominated by the low level of oxygenation and the low degree of oxygen homogeneity obtained by normal annealing processes.         Investigation of critical currents in YBCO tracks over steps in SrTiO/sub 3/ substrates using low temperature SEM beam induced voltage contrast    S.A.L. Foulds, J.S. Abell, Dae-Joon Kang and E.J. Tarte Summary: Electron beam induced voltage contrast has been used to investigate the current flow in thin film YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) tracks, deposited over meanders in SrTiO/sub 3/ substrates. Different film thicknesses and step heights have been studied and related to critical current and atomic force microscopy (AFM) measurements. Tracks with higher critical currents (I/sub c/) exhibited voltage contrast at steps. The contrast along individual step edges and between different step edges was found to be reasonably uniform, AFM measurements indicated that in some tracks step profiles contained two gradients. Such steps were not found to have a major effect on the I/sub c/ of the YBCO track presumably because the extra gradient was very shallow. Tracks with reduced critical currents were limited by one or a few steps and showed non uniform contrast along the steps. AFM measurements indicated a difference in surface roughness between milled and non-milled surfaces. Any such roughness occurring at a step could account for the low I/sub c/'s found in some tracks. One sample exhibited contrast on meander plateaus Rather than at step edges. Critical current measurements prior to and after low temperature scanning electron microscopy (LTSEM) measurements indicated that this sample had become damaged.         Controlling the dopant incorporation in a-axis oriented Co doped YBCO thin films    Z. Trajanovic, R. Shreekala, M. Rajeswari, I. Takeuchi, C.J. Lobb, T. Venkatesan, E. Bauer and F. Bridges Summary: We studied the effects of Co doping on the intrinsic anisotropic properties of aligned a-axis YBa/sub 2/Cu/sub 3-x/Co/sub x/O/sub 7-/spl delta// films pulsed laser deposited on (100) LaSrGaO/sub 4/ substrates We used X-ray-absorption fine structure analysis and resistivity data to determine the quality of Co incorporation. Higher deposition pressures provided with better Co dopant incorporation but smaller grain size. However at lower pressures Co incorporation can still be achieved by down the cooling process. For transport along the c-direction, Co dopant causes reduction interlayer coupling as evidenced by an increase resistive anisotropy (/spl rho//sub c///spl rho//sub b/) with increasing level of Co incorporation, Co doping level of x=0.22 effectively doubles the resistive anisotropy of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films (from -18 to -40 at 100 K).         Diffusion and gettering of implanted ions in YBCO films    S.H. Hong, M.L. Chan, J. Baniecki, Q.Y. Ma, H.A. Wang, R.W. Odom, J. LaGraff, J. Murduck and H. Chan Summary: Ion diffusion and gettering in YBCO oxides were studied, The experiment was carried out by implanting Si or Ni ions into epitaxial YBCO films and subsequently annealing the samples at different temperatures ranging from 450/spl deg/C to 1050/spl deg/C. Secondary ion mass spectroscopy (SIMS) analysis was used to determine ion profiles. At an annealing temperature of 750/spl deg/C, the silicon ions started to getter towards the peak of the silicon concentration, which has the maximum concentration. This gettering process continued annealing temperature was increased and reached the maximum at 850/spl deg/C. Further increases in annealing temperatures caused the ions to outdiffuse and intermix with YBCO. In contrast, nickel ions do not show gettering effect, rather they outdiffuse after annealing. The crystal damage caused by the implantation and chemical reaction between implanted ions and target material seemed to be the main reason of this gettering effect.         Pulsed laser deposition of patterned multilayers for HTS device fabrication    G.M. Daly, J.M. Pond, M.S. Osofsky, J.S. Horwitz, R.J. Soulen, D.B. Chrisey and R.C.Y. Auyeung Summary: Pulsed laser deposition (PLD) has been used to deposit high quality multilayer thin films of Permalloy/Au/YBCO onto (100) oriented substrates of MgO and SrTiO/sub 3/. These multilayer structures are currently being used to investigate the effect of the injection of polarized electrons on the order parameter of high temperature superconducting (HTS) thin films. To observe this effect, thin films with sharp interfaces (to minimize spin scattering) and low contact resistance will be required. The morphology and structure of the deposited films has been investigated using scanning electron microscopy and X-ray diffraction, respectively. The electrical properties (T/sub c/ and J/sub c/ (77 K, B=0)) were measured for both unpatterned and patterned films. Films were patterned using both wet chemical and ion beam (Ar/sup +/, 1 KeV) techniques. Unpatterned films were characterized inductively as having T/sub c/'s>88 K and J/sub c/'s>1 MA/cm/sup 2/. Wet chemical etching resulted in films with slightly reduced T/sub c/'s and J/sub c/'s/spl sim/10/sup 3/-10/sup 4/ A/cm/sup 2/ however, no reduction in T/sub c/ or J/sub c/ was observed for dry etching. A lift off procedure using PMMA/Cu has been explored to define smaller (/spl sim/400 /spl mu/m) features. Extremely low contact resistance's (<10/sup 7/ /spl Omega/ cm/sup 2/) have been measured for Au films deposited by PLD onto YBCO. The low contact resistance is attributed to the high kinetic of the Au particles. These device structures can be used to develop simple HTS based transistors.         Surface study and fabrication of low-resistivity contacts on Cu-1234 superconductor    N. Terada, A. Iyo, H. Ihara, K. Tokiwa and H. Ozawa Summary: The surface nature of CuBa/sub 2/Ca/sub 3/Cu/sub 4/O/sub 12-/spl delta// (Cu-1234) superconducting ceramics has been characterized by photoemission spectroscopy, and an improvement of their surface electronic structure for high performance contacts has been attempted, In photoemission spectra of the specimens which had been scraped by a diamond file in vacuum, a shift of Ba core signals towards the higher binding energy side and reduction of valency of Cu were observed. This indicates that the surfaces of the conventionally treated Cu-1234 should easily lose oxygen from the vicinity of (BaO)/(CuO/sub 2-y/)/(BaO) blocks. Due to this degradation, a high contact resistivity was observed on interfaces between Au and such surfaces. The annealing in ultra-high vacuum at a low temperature below 150/spl deg/C under atomic oxygen or O/sub 3/ beams developed an intrinsic surface-electronic-structure. Due to the treatment, contact resistivity as low as 1/spl times/10/sup 18/ /spl Omega/ cm/sup 2/ was reproducibly achieved.         Development of intrinsic surfaces, and their electronic structures and stability of non-c-axis YBCO epitaxial films    H. Ozawa, N. Terada, S. Kashiwaya, H. Takashima, M. Koyanagi and H. Ihara Summary: Surface-cleaning using 100% ozone beams or atomic oxygen beams has been applied for the fabrication of high quality [110]- and (100)-axis oriented YBCO epitaxial films. The treatment recovers metallic surfaces in spite of the semiconducting properties of the as-received surfaces. High quality [110]- and (100)-oriented films with high T/sub c/ and high orientation were deposited by temperature-gradient self-template method. On both kinds of film clear photoelectron Fermi edges, evidence of a metallic feature, were observed at room temperature. For the [110] films, well-defined photoelectron Fermi edges are observed for the first time, For the (100) surface, the rather high electron density of states Fermi edge is as high as about 15% of Cu 3d signal in valence band, On the other hand, the edge-height of the [110] surface was less than 5% of the Cu 3d and it was reduced as a function of time. Detailed electronic structures and the origin of the difference of the surface-stabilities is discussed.         YBaCuO multilayer structures using CeO/sub 2/ insulating films    H. Sato, H. Akoh, S. Takada and R. Miyagawa Summary: We have fabricated YBaCuO crossover using CeO/sub 2/ insulating film as high-T/sub c/ multilayer structure. The bottom YBaCuO bridges showed good critical temperature T/sub c/ of 87 K and critical current density J/sub c/ of 1.0/spl times/10/sup 5/ A/cm/sup 2/. The top YBaCuO bridges, however, showed lower J/sub c/ than the bottom YBaCuO, since the grain boundaries were formed at the step edges of the bottom bridge. The crossover structures have a resistivity of more than 1/spl times/10/sup 8/ /spl Omega//spl middot/2 cm below 80 K, indicating superior insulating properties of the CeO/sub 2/ layer. In order to improve J/sub c/ of the top YBaCuO bridges, we have also studied the properties of YBaCuO bridges on CeO/sub 2/ film bank. It is found that J/sub c/ of the top bridges was not only dependent on the step height, but also depends on the YBaCuO thickness. In order to improve J/sub c/ of the top bridges, lower step height and thicker YBaCuO films are required.         An improved multi-layer fabrication process for YBa/sub 2/Cu/sub 3/O/sub 7-x/-based circuits    H.Q. Li, R.H. Ono, L.R. Vale, D.A. Rudman, S.H. Liou and W.H. Mallison Summary: Improved via connections in structures of YBa/sub 2/Cu/sub 3/O/sub 7-x//SrTiO/sub 3//YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO/STO/YBCO) multilayers have been made using a combined HF wet-etching and ion-milling process. The critical current density J/sub c/ of the via is as high as 2/spl times/10/sup 6/ A/cm/sup 2/ at 76 K, and is dominated by edge contacts in the ab-plane, YBCO and Sr/sub 2/AlNbO/sub 6/ (SAN) multilayer test circuits were also made with this process. The 4/spl deg/ crossovers in a SAN test chip had a critical temperature T/sub c/ of 88 K and J/sub c/ of 1.5/spl times/10/sup 6/ A/cm/sup 2/ at 81 K, very close to those of the planar film, showing no evidence of weak links in the YBCO crossing low angle SAN steps.         Enhancement of low field magnetoresistance in YBa/sub 2/Cu/sub 3/O/sub 7//Nd/sub 0.7/Sr/sub 0.3/MnO/sub 3/ heterostructures    Z.W. Dong, C.-H. Chen, I. Takeuchi, M. Rajeswari, R.P. Sharma, T. Venkatesan and T. Boettcher Summary: In order to obtain an enhancement of low field magnetoresistance (MR) in Nd/sub 0.7/Sr/sub 0.3/MnO/sub 3/ (NSMO) films, two kinds of superconducting flux focusing devices made of YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) have been fabricated. In the superconducting state, YBCO expels magnetic flux from its interior and focuses the magnetic flux on a bridge of NSMO film. Using such a magnetic "lens", at temperatures below 77 K, /spl sim/900% enhancement in MR was observed. This corresponds to more than 15% change in the MR of NSMO in the presence of a couple of hundred Gauss. In order to successfully integrate high-T/sub c/ superconductivity with the magnetoresistive effect, bilayers of YBCO/NSMO were in situ deposited on (100) LaAlO/sub 3/ substrates by pulsed laser deposition so that the peak resistance temperature (T/sub p/) of NSMO was below the superconducting transition temperature (T/sub c/) of YBCO. X-ray diffraction and Rutherford Backscattering Spectroscopy (RBS) measurements provide evidence of epitaxial growth of YBCO/NSMO heterostructures.         Dielectric functions of common YBCO substrate materials determined by spectroscopic ellipsometry    B.J. Gibbons and S. Trolier-McKinstry Summary: Reference dielectric function data for several common YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) substrate materials have been determined by spectroscopic ellipsometry over the range 250 nm 750 nm. These materials include LaAlO/sub 3/, BaZrO/sub 3/, NdGaO/sub 3/, 9.5 mol% Y/sub 2/O/sub 3/-ZrO/sub 2/ (YSZ), LaSrGaO/sub 4/ (LSGO), and (LaAlO/sub 3/)/sub 0.3/-(Sr/sub 2/AlTaO/sub 6/)/sub 0.7/ (LSAT). The precision of the data was confirmed by comparing SE determined data for SrTiO/sub 3/ to published values, Agreement to the third decimal point was shown. These data have been used to characterize interfaces between YBCO and some of these materials by SE.         On-axis sputter deposition of Sr/sub 2/AlTaO/sub 6/ dielectric thin films for multilayer Y-Ba-Cu-O circuits    R. Hu, J.M. Murduck, C.L. Pettiette-Hall and K.P. Daly Summary: Sr/sub 2/AITaO/sub 6/(SAT) is a desirable dielectric for use in YBCO multilayer circuits due to the close lattice match to YBa/sub 2/Cu/sub 3/O/sub 7/(YBCO), and low dielectric constant, SAT thin films have been deposited using on axis rf magnetron sputtering. Epitaxial growth of SAT has been measured using x-ray diffraction. The electrical isolation of SAT sandwiched between two YBCO layers, and the superconducting critical current of YBCO deposited over SAT crossover structures are measured.         Superconductivity and electric field effect of 90 degree grain boundaries in YBa2Cu/sub 3/O/sub 7-x/ thin films    Jeong Dae Suh, Gun Yong Sung and Do Kyung Kim Summary: A three terminal device was fabricated by depositing YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) thin films containing 90 degree grain boundaries which was covered with a SrTiO/sub 3/ gate layer and an Au gate electrode. YBCO thin films were grown by bi-epitaxial process on LaSrGaO/sub 4/(100) substrate. The resistance versus temperature curve of the YBCO microbridge containing 90 degree grain boundaries showed double resistive transitions. This result was interpreted by the weak link effect of 90 degree grain boundaries in YBCO thin films. A large electric field effect on 90 degree grain boundaries was observed. The superconducting transition temperature of the 90 degree grain boundaries was modulated up to 11.4% by applying an electric field of 4/spl times/10/sup 4/ V/cm.         Dissipation mechanisms in EuBa/sub 2/Cu/sub 3/O/sub 7//SrTiO/sub 3/ and EuBa/sub 2/Cu/sub 3/O/sub 7//PrBa/sub 2/Cu/sub 3/O/sub 7/ multilayers    M. Velez, E.M. Gonzalez, J.I. Martin and J.L. Vicent Summary: Superconducting multilayers of c-axis and a-axis oriented EuBa/sub 2/Cu/sub 3/O/sub 7//PrBa/sub 2/Cu/sub 3/O/sub 7/ and c-axis oriented EuBa/sub 2/Cu/sub 3/O/sub 7//SrTiO/sub 3/ have been grown by dc and rf sputtering on (100) SrTiO/sub 3/ substrates. The critical current densities and the tails of the resistivity transitions (/spl rho/, B) have been used to study the dissipation mechanisms. The activation energy (U) follows a log B law in all the systems and textures. A crossover from U=U/sub 0/ B/sup -/spl alpha// to U=U/sub 0/ log B occurs depending on the superconducting layer thickness, The type of multilayer and texture governs the values of the activation energies U/sub 0/. The former result seems to be related with the competition between the thickness of the superconducting layer and the vortex correlation length, and the latter one (U/sub 0/ values) with the coupling between the superconducting layers.         Fabrication and properties of YBa/sub 2/Cu/sub 3/O/sub 7//RE/sub 1-x/MnO/sub 3-y/ multilayers    P. Przyslupski, S. Kolesnik, E. Dynowska, T. Skoskiewicz and M. Sawicki Summary: The high pressure d.c. sputtering method has been used to fabricate (YBa/sub 2/Cu/sub 3/O/sub 7//Nd/sub 0.67/Sr/sub 0.33/MnO/sub 3-y/)//sub n/ [(YBCO/NSMO)/sub n/] superlattices. X-ray analyses show c-axis epitaxial growth on LaAlO/sub 3/ (100) substrates. Nd/sub 0.67/Sr/sub 0.33/MnO/sub 3-y/ films are strained due to some difference in lattice parameters between substrate and YBCO sublayers. Magnetization measurements done on single NSMO films show ferromagnetic order below 200 K. Magnetic moment measured for the superlattices below superconducting transition show ferromagnetic order and superconductivity. Such a behavior indicates on the co-existence of superconductivity and ferromagnetism in the total volume of heterostructures, where superconductivity is related to the YBCO sublayer and ferromagnetism to the NSMO sublayer.         Manufacturing of HTS composite wire for a superconducting power transmission cable demonstration    M. Buczek, L.J. Masur, P.K. Miles, F. Sivo, D. Marlowe, E.R. Podtburg, D.R. Parker, S. Fleshler, J.D. Scudiere, P. Metra, M. Nassi, M. Rahman and D.W. Von Dollen Summary: American Superconductor Corporation, Pirelli Cable Corporation, and the Electric fewer Research Institute are engaged in a program aimed at developing a commercially viable high temperature superconducting power transmission cable. The first phase of the program has been completed with the fabrication and testing of a 50 meter conductor for a power transmission cable. Over 12,000 meters of wire have been manufactured and thoroughly tested. In this paper, we will present and discuss data of the production wires used in the 50 meter conductor. In addition, we will discuss electrical and mechanical performance data used to qualify a high performance, high strength wire.         Development of Ag-sheathed Bi2223 superconducting wires and their application to magnets    K. Hayashi, S. Hahakura, N. Saga, S. Kobayashi, T. Kato, M. Ueyama, T. Kaneko, T. Hikata, K. Ohkura and K. Sato Summary: Silver-sheathed BiPbSrCaCuO 2223 superconducting wires with long length and high Jc of over 10/sup 4/ A/cm/sup 2/ were developed by using the powder-in-tube method. Future possibilities to obtain much higher Jc's are discussed in relation to crystal alignment, connectivity between grains and flux pinning. High amperage wires and high strength wires were also developed for large scale magnet application. High I/sub c/ of over 300 A at 77 K were obtained for the wire with large cross sectional area. Good stress and strain tolerant characteristics were also obtained for silver alloy sheathed wires. In order to apply the HTS wires for AC use, it is necessary to reduce AC loss. So, the AC loss of the wires are also discussed. As a progress of wire technology, we have fabricated many types of magnets, such as pancake magnets and solenoidal magnets. In the case of 77 K application, it is promising to apply for AC use because of large heat capacity of HTS wires and liquid nitrogen. So, we are developing the 500 kVA transformer and pulse magnet for SMES. A refrigerator cooled magnet operated near 20K was fabricated. This magnet was operated at 21 K and generated 3 T inside a /spl phi/40 mm room temperature bore, stably generated 2.5 T continuously for over 150 hours and could be operated at high ramp rate of over 12 T/min. As for the 4.2 K operation, high field insert magnet for 1 GHz NMR application are developed. Highest magnetic field of 24 T was achieved using the hybrid magnet at MIT and persistent current mode operation was done by using the layer wound coil with persistent current switch.         Processing and characterization of Ag-clad Bi-2223 superconductors    U. Balachandran, A.N. Iyer, R. Jammy, M. Chudzik, M. Lelovic, P. Krishnaraj, N.G. Eror and P. Haldar Summary: Practical applications of high-temperature superconductors will be governed by their current transport and mechanical characteristics. With careful control of the processing parameters high-quality long-length mono- and multifilament Bi-2223 conductors have been fabricated by the powder-in-tube technique. A critical current density (J/sub c/) of up to 1.2/spl times/10/sup 4/ A cm/sup -2/ has been observed at 77 K in a 1260-m-long multifilament conductor containing 37 monocore filaments. A high-temperature superconducting magnet and a prototype transformer were fabricated and characterized from such long-length conductors. Extensive studies on the in-situ strain characteristics of the mono- and multifilament conductors have been conducted. Multilayer silver/superconductor composite tapes, fabricated by a novel chemical etching technique, were also observed to exhibit improved strain tolerance characteristics. To further improve the current characteristics of the Bi-2223 tapes the wire-in-tube technique was adopted. A J/sub c/ value >10/sup 5/ A cm/sup -2/ at 77 K and in self field have been obtained in a Bi-2223 tape fabricated by the wire-in-tube method.         Progress in BSCCO-2212/silver composite tape conductors    K.R. Marken Jr., W. Dai, L. Cowey, S. Ting and S. Hong Summary: Ceramic-silver composite conductors have been fabricated in lengths greater than 200 meters using both powder-in-tube and dip-coated methods. Progress has been made in conductor uniformity through control of process steps including powder packing, tape coating, deformation, and heat treatment. Critical current density (J/sub c/) in lengths up to 100 meters has been evaluated by measuring end to end current in coils, both pancake wound and solenoid wound. These coils were made using a wind-and-react technique. J/sub c/ values greater than 10/sup 5/ A/cm/sup 2/ have been attained over 17 m lengths of conductor in these coils in self field at 4.2 K. The magnetic field dependence of 4.2 K J/sub c/ in fields its high as 17 T will be reported for these coils. Microstructural factors affecting J/sub c/ are discussed.         High critical current densities in long lengths of mono- and multifilamentary Ag-sheathed Bi(2223) tapes    F. Marti, G. Grasso, Y. Huang and R. Flukiger Summary: By optimizing the tape fabrication process, high critical current densities over long length (up to 25 m) of Bi,Pb(2223) Ag-sheathed tapes were reproducibly obtained. The critical current densities of multifilamentary tapes (up to 55 filaments) are typically in the range of 25-30 kA/cm/sup 2/. At 77 K, up to 35 kA/cm/sup 2/ were recently measured for a monofilamentary tape of 0.5 m length. Detailed measurements of the transport properties of these tapes as well as of test pancakes and currents leads will be presented.         Comparative studies on single crystals and superconducting Bi-(Pb)-Sr-Ca-Cu-O tapes    S.X. Dou, J. Horvat, X.L. Wang, M. Ionescu, H.K. Liu, I. Kusevic and E. Babic Summary: Comparative studies on Bi-2212 single crystal, Bi-2212 tape and 2223 tape have been carried out using AC susceptibility, magnetisation and magnetoresistivity measurements. Bi-2212 crystals have been obtained through a spiral growth mechanism using KCl as flux. Magnetisation measurements show an enhanced flux pinning in the spiral grown crystals compared with crystals grown through a layer-by-layer mechanism. The fish tail effect in M-H loop is attributable to the spirals and screw dislocations in spiral grown Bi-2212 crystals. The irreversibility line for the 2223 tape is positioned at higher temperatures than that for the 2212 tape which is in turn positioned at higher temperatures than that for the 2212 crystals. The pinning potential, U/sub o/, for 2212 tape, determined by using resistance measurements in magnetic fields, is smaller than that of Ag/Bi-2223 tapes but larger than that for 2212 single crystals. These results indicate that the defects induced by mechanical deformation or spiral growth act as pinning centers in Bi-based materials, responsible for the improvement in flux pinning.         Evolution of the microstructure in (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x//Ag wires and its influence on the critical current density    K. Fischer, T. Fahr, A. Hutten, E. Muller, M. Schubert, D. Schlafer and R. Wenzel Summary: Mono- and multifilamentary (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/-wire tapes were fabricated by the oxide-powder-in-tube-technique (OPIT) using precursors which were prepared by various methods. In order to get information about the kinetics of the BiPb-2223 phase formation, the microstructure and the phase composition evolution were investigated during annealing by SEM and XRD, respectively. In addition, DTA measurements were performed on precursor powder samples. From the results, it can be concluded that in dependence on the precursor parameters, the formation of BiPb-2223 can proceed by precipitation from a partial melted system as well as by formation from preexisting BiPb-2212 crystals. The microstructure and critical current densities j/sub c/ of the tapes seem to be dependent on its mechanism of formation. Maximum j/sub c/-values of 31 kA/cm/sup 2/ (77 K, 0 T) and about 22 kA/cm/sup 2/ were measured on multifilamentary wires with a length of 5 cm and 90 m, respectively, with precursors made by aerosol spray pyrolysis.         Author Index (1996 - Part 2)    No author information available Summary: Not available

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