Home Welcome Getting Started Conferences Authors

2004 Part 1     Front Cover (2004 - Part 1)    No author information available Summary:         Table of Contents (2004 - Part 1)    No author information available Summary: Not available         Chairperson's Introduction ASC-2004 Proceedings    J. Schwartz, C. Luongo and C. Foley Summary: Not available         Conference organization (2004)    No author information available Summary: Not available         The IEEE Council on Superconductivity Awards in Applied Superconductivity Presented at 2004 Applied Superconductivity Conference    No author information available Summary: Not available         Fabrication process of planarized multi-layer Nb integrated circuits    T. Satoh, K. Hinode, H. Akaike, S. Nagasawa, Y. Kitagawa and M. Hidaka Summary: To improve the operating speed and density of Nb single-flux-quantum integrated circuits, we developed an advanced fabrication process based on NEC's standard process. We fabricated planarized six-Nb-layer circuit structures using this advanced process. This new structure has four Nb wiring layers for greater design flexibility. To shield the magnetic field produced by the DC bias current, the DC bias power supply layer was placed under the groundplane. The critical current density of the Josephson junction was 10 kA/cm/sup 2/. We fabricated and tested more than 10 wafers and demonstrated that the six-layer circuits were successfully planarized. We also confirmed insulation between each Nb layer and the reliability of superconducting contacts. This planarization did not significantly degrade the junction characteristics. We measured small spreads in the critical current of less than 2%. These results demonstrated the effectiveness of this advanced process based on mechanical-polishing planarization.         Six-layer process for the fabrication of Nb/Al-AlO/sub x//Nb Josephson junction devices    R. Cantor and J. Hall Summary: A six-layer process is described for the fabrication of Josephson junction devices and Superconducting QUantum Interference Devices (SQUIDs) on silicon wafers up to 150 mm in diameter. The Nb/Al-AlO/sub x//Nb trilayers are sputter-deposited in a load-locked vacuum chamber with base pressure in the low 10/sup -7/ Pa (10/sup -9/ Torr) range and a very low leak up rate of 5/spl times/10/sup -6/ Pa/min (3.5/spl times/10/sup -5/ mTorr/min). The barrier process is optimized for a critical current density of 100 A/cm/sup 2/, and all resistors are fabricated from palladium with a sheet resistivity of 1 /spl Omega//sq. A charge dissipative dielectric layer is used in order to reduce the probability of damage caused by electrostatic charge build-up and discharge. The trilayer films are wet etched, while the subsequent metal and dielectric films are patterned using fluorine-based reactive ion etch, Ar ion milling, or lift-off techniques. This process is currently being used to fabricate dc SQUIDs for various instrumentation applications, integrated SQUID magnetometers and planar gradiometers, and single tunnel junction detectors.         Direct measurement of the Josephson plasma resonance frequency from I-V Characteristics    A.W. Kleinsasser, M.W. Johnson and K.A. Delin Summary: The speed of Josephson circuits such as those required for rapid single flux quantum logic is limited by the Josephson plasma frequency, /spl omega//sub p/, which (with few exceptions) increases monotonically with increasing critical current density, J/sub c/. Here we describe a new technique for directly measuring /spl omega//sub p/, using the current-voltage characteristics of a simple structure based on externally-shunted, series-connected tunnel junctions. We present both experimental and theoretical demonstrations of the technique and describe its application to the determination of the junction capacitance, a property poorly characterized for high-J/sub c/ junctions.         Characterization of HYPRES' 4.5 kA/cm/sup 2/ & 8 kA/cm/sup 2/ Nb/AlO/sub x//Nb fabrication processes    D. Yohannes, S. Sarwana, S.K. Tolpygo, A. Sahu, Y.A. Polyakov and V.K. Semenov Summary: HYPRES has developed new fabrication processes for higher critical current density Josephson junctions (JJs). These processes incorporate an additional anodization step for junction insulation, which enables fabrication of junctions down to submicron sizes. A set of new processing tools has been employed, including a high density (ICP) plasma etching of niobium and aluminum, and low temperature plasma-enhanced chemical vapor deposition of interlayer dielectric (SiO/sub 2/) from a TEOS source. A set of new parametric control monitor (PCM) test chips has been designed and implemented. Results of electric and SEM characterization of JJ's, wiring, and contact-hole etching are presented. The critical current spreads and shunt resistance uniformity along with the effects of junction shape are discussed. The critical current 1/spl sigma/ spreads of 1.2% have been achieved for the 4.5 kA/cm/sup 2/ process.         Efficient fabrication process for superconducting integrated circuits using photosensitive polyimide insulation layers    K. Kikuchi, M. Goto, H. Nakagawa, S. Segawa, K. Tokoro, T. Taino, H. Myoren, S. Takada and M. Aoyagi Summary: Photosensitive polyimide insulation layers have been introduced to fabricate superconducting integrated circuits. It is shown to simplify the fabrication process, because the photosensitive polyimide insulation layer can be patterned by conventional photolithography process, resulting in the etching process unnecessary in the present new fabrication process. Three kinds of contact hole (junction top electrode contact, junction base electrode contact, and resistor contact) are simultaneously formed in the photolithography process of the polyimide. A minimum contact hole size is designed to be 1.5 /spl mu/m square for a 3 /spl mu/m /spl times/ 3 /spl mu/m squared junction. Superconducting current density of 2.4/spl times/10/sup 6/ A/cm/sup 2/ of the contact hole was measured. Palladium resistors were successfully made with through hole contacts of the photosensitive polyimide insulation layer. We demonstrated superconducting integrated circuits using this new fabrication process including the minimum 3 /spl mu/m /spl times/ 3 /spl mu/m squared Nb/Al-AlO/sub x//Nb Josephson tunnel junction. The circuit operation is also demonstrated in the fabricated superconducting integrated circuits with the photosensitive polyimide insulation layers.         New selective anodization process for Nb Josephson junction with AlO/sub x/ barrier    S. Morohashi, M. Ikuta, T. Miyoshi, D. Matsumoto, S. Ariyoshi, M. Ukibe, M. Ohkubo and H. Matsuo Summary: One of the most important factor of the superconducting tunnel junction for a particle and radiation detection is the sub-gap leakage current. An anodization of a junction edge is an effective method to reduce the sub-gap leakage current. In a new fabrication process of a Nb/Al-AlO/sub x/-Al/Nb junction, the sputtered Al/sub 2/O/sub 3/ layers with 10 nm thickness are used as not only the protection layer for the upper surface of both the base and counter electrodes in the anodization process, but also the etching stop layer for the formation of the contact hole by reactive ion etching process.         Effect of photomask pattern shape for a junction counter-electrode on critical current uniformity and controllability in Nb/AlO/sub x//Nb junctions    H. Akaike, Y. Kitagawa, T. Satoh, K. Hinode, S. Nagasawa and M. Hidaka Summary: The authors evaluated the effect of photomask pattern shape for a counter-electrode on critical current I/sub c/ uniformity and controllability in Nb/AlOx/Nb junctions. Circular, square, and 2 kinds of optical proximity correction (OPC) square patterns were used as the mask pattern shape. Although there was no difference in the I/sub c/ uniformity between square and OPC junctions, the OPC junctions exhibited smaller shrinkage in junction size than the square junction. In addition, the OPC junctions improved the chip-to-chip variation in the shrinkage. The circular junction exhibited the smallest variation in the shrinkage, and had an advantage in I/sub c/ uniformity for smaller than 1.0 /spl mu/m/sup 2/ junctions in comparison with the other junctions. The shrinkage of the circular junction was the largest of all the junctions. This paper describes the recommended choice of the photomask pattern shape for several Nb LSI technologies.         Structural testing of the HYPRES niobium process    A.A. Joseph, J. Sese, J. Flokstra and H.G. Kerkhoff Summary: The HYPRES 3.0 /spl mu/m niobium (Nb) process has proven to be capable of realizing complex low temperature superconductor (LTS) rapid single flux quantum (RSFQ) circuits. In such a mature fabrication process, the importance of the detection of random defects is crucial as they contribute to the majority of the defects occurring while processing the chips. The global low yield in superconductor electronics (SCE) is due to the fact that little is known about the defects and fault mechanisms occurring in Nb technology. This is, however, of crucial importance in realizing the required complex systems with yields required for commercial production. For this purpose, a structural testing approach has been applied to the HYPRES Nb process. As a result, we have developed test structures for the detection of random defects in the process. Test chips were realized in the process and measurements were carried out. Test results on the processed chips leading to defect statistics in the HYPRES Nb process are presented in this paper.         Fabrication and measurement of tall stacked arrays of SNS Josephson junctions    N. Hadacek, P.D. Dresselhaus, Y. Chong, S.P. Benz and J.E. Bonevich Summary: The authors have made tall, uniform stacked Josephson junction arrays by developing an etch process using an inductively coupled plasma etcher. This process produces vertical profiles in thin-film multilayers of alternating superconducting and normal metals. Such a vertical etch is necessary to obtain uniform properties in high-density arrays in order to achieve operating margins for voltage-standard applications. The authors use dry-etchable MoSi/sub 2/ for the normal metal barrier of our niobium Josephson junctions and obtain working series arrays with stacks up to 10 junctions tall. The authors present dc and microwave electrical characteristics of distributed and lumped arrays and discuss the technological improvements needed to fabricate lumped arrays for voltage-standard applications.         RF properties of overdamped SIS junctions    V. Lacquaniti, C. Cagliero, S. Maggi, R. Steni, D. Andreone and A. Sosso Summary: A new type of nonhysteretic Josephson junction suitable for applications in voltage metrology has been developed. These junctions derive from the Nb/Al-AlO/sub x//Nb SIS junctions using a relatively thick Al layer oxidized at a low value of oxygen exposure. This produces junctions with reproducible and spatially homogeneous I-V characteristics, having current densities ranging from 10/sup 3/ to more than 2/spl times/10/sup 4/ A/cm/sup 2/ and characteristic voltages up to 0.40 mV. The authors report here the rf response of these junctions at 70 GHz. The authors have measured the dependence of the rf-induced steps on the microwave power and the stability of the steps, in view of a future application of these junctions to an AC Josephson voltage standard.         A fast turn-around time process for fabrication of qubit circuits    V. Patel, Wei Chen, S. Pottorf and J.E. Lukens Summary: The authors describe a process for fabrication of Nb/AlO/sub x//Nb Josephson junction circuits for quantum computation. The process involves only one etch step and incorporates electron beam lithography and a self-aligned lift-off of the dielectric resulting in a short turn-around time of 4-5 days. Deep submicron junctions of size down to 0.15 /spl times/ 0.15 /spl mu/m/sup 2/ have been fabricated and tested. Results of junction quality measurements will be presented. In particular, a subgap resistance of /spl sim/1 G/spl Omega/ measured at /spl sim/0.4 K indicates that the junction's subgap leakage should not be a limitation for quantum computation.         SINIS junction series arrays for the Josephson arbitrary waveform synthesizer    J. Kohlmann, F. Muller, R. Behr, D. Hagedorn and J. Niemeyer Summary: The Josephson arbitrary waveform synthesizer (JAWS) is based on Josephson junctions operated by short pulses. We describe the development of SINIS Josephson series arrays for applications in this JAWS that were performed within the framework of the EU-funded JAWS project.         Dilute Al-Mn alloys for superconductor tunneling and other devices    S.T. Ruggiero, G.B. Arnold, A. Williams, A.M. Clark, N.A. Miller and J.N. Ullom Summary: The authors present tunneling results for junctions comprising Mn doped Al films produced by sputter deposition, with Mn concentrations in the range of 0-5000 ppm. Our results for S'/I/S', S'/I/S, and N/I/S junctions demonstrate that Al-Mn alloys can serve both as superconductors with critical temperatures reduced from that of Al and as normal metals. The authors find Al-Mn in this doping range to be otherwise identical to pure Al in terms of its BCS-like tunnel characteristics (for superconductors) and its ability to produce high-quality tunnel barriers.         Fabrication and characteristics of multi-terminal SINIS devices    I.P. Nevirkovets, O. Chernyashevskyy and J.B. Ketterson Summary: We fabricated and measured multi-terminal SINIS devices (where S, I, and N denote a superconductor, an insulator, and a normal metal, respectively) with the Nb/Al/AlO/sub x//Al/AlO/sub x//Al/Nb structure. The multilayered SINIS structure was fabricated in-situ using sputter deposition of Nb and Al, and thermal oxidation of the Al layers to grow the tunnel barriers. Devices with a characteristic size of about 10 /spl mu/m were formed via an optical-lithography process that included making an electrical contact to the middle Al layer (16-19 nm thick). Current-voltage characteristics of the devices were measured in different modes (i. e., by feeding the current across the whole device, through each of the junctions, and through the middle Al film) at low temperatures (1.4-4.2 K). Specifically, the devices were tested in a transistor-like configuration to explore the influence of current injection through a SIN junction and the N film on the Josephson critical current and quasiparticle characteristic of the SINIS junction as a whole, and on the characteristics of the second junction.         Proximity effect in NiCu-based Josephson tunnel junctions    R. Latempa, L. Parlato, G. Peluso, G.P. Pepe, A. Ruotolo, A. Barone and A.A. Golubov Summary: We present experimental results concerning both the fabrication and the characterization of superconducting tunnel junctions based on Nb/NiCu superconductor/ferromagnet (S/F) bilayers. Josephson junctions have been characterized down to T=1.4 K in terms of current-voltage I-V characteristics, Josephson critical current vs magnetic field, role of external magnetic field. Proximity parameters of the bilayer, such as the coherence length and the exchange field energy of the F metal, have been estimated by means of a numerical deconvolution of the I-V data the electronic density of states on both sides of the S/F bilayer. Results have been compared with theoretical predictions from a proximity model for S/F bilayers in the dirty limit in the framework of Usadel equations for the S and F layer, respectively.         Transport properties of Nb/yttria-stabilized-zirconia/Nb Josephson junctions    S.K.H. Lam and S. Gnanarajan Summary: Nb/yttria-stabilized zirconia (YSZ)/Nb Josephson junctions have been fabricated. The YSZ interlayer resistivity was found to have values of /spl sim/1 m/spl Omega/ - m and has a weak temperature dependence. The current-voltage characteristics at temperatures from 4.2 K to values close to the Nb critical temperature of /spl sim/8.0 K have been studied. The junction critical current was found to have an exponential relationship with both the YSZ interlayer length and the temperature. These results are consistent with the predicted behavior of a superconductor-normal metal-superconductor junction due to the proximity effect.         Analysis of the barrier in vertically-stacked interface-treated Josephson junctions    M. Inoue, Y. Yoshinaga, K. Wakita, K. Taniike, T. Kimura, A. Fujimaki and H. Hayakawa Summary: The authors have investigated the structure and the composition of the barrier in YBCO vertically-stacked-type interface-treated Josephson junctions by TEM and TEM-EDS. The barrier was formed by the Ar ion milling of the base YBCO electrode surface and the subsequent annealing. For a sample treated with accelerating voltage (V/sub acc/) of 1300 V, we observed Y/sub 2/O/sub 3/ phases in the barrier. In contrast, for a sample with V/sub acc/=700 V, we could observe few Y/sub 2/O/sub 3/ phases. Our TEM observation suggested that junctions with higher J/sub c/ fabricated with lower V/sub acc/ would have thinner and more uniform barriers. In addition, the composition of the barrier was Y-rich and Cu-poor, and such deviation decreased with decreasing V/sub acc/. These tendencies well correspond to the results for ramp-edge-type junctions reported so far.         Vertically-stacked Josephson junctions using YbBa/sub 2/Cu/sub 3/O/sub 7-x/ as a counter electrode for improving uniformity    T. Kimura, K. Wakita, Y. Yoshinaga, K. Taniike, T. Nishitani, M. Inoue, A. Fujimaki and H. Hayakawa Summary: We have fabricated vertically-stacked interface-treated Josephson junctions using YbBa/sub 2/Cu/sub 3/O/sub 7-x/ (YbBCO) as a counter electrode for improving the uniformity. We used YBCO for the base electrode. Most of the junctions fabricated on one chip exhibited resistively-shunted-junction (RSJ) characteristics. The properties of the junctions at 4.2 K were as follows: J/sub c/=1.0/spl times/10/sup 3/ A/cm/sup 2/ with a 1/spl sigma/ spread of 6.9%, and I/sub c/R/sub n/=0.5 mV with a 1/spl sigma/ spread of 5.4%. These spreads were improved compared with those of junctions with YBCO as a counter electrode. Furthermore, the normal conductance G/sub n/ of the junctions with the YbBCO counter electrode was independent of the temperature. Such characteristics have not been obtained for YBCO vertically-stacked interface-treated junctions. We speculate that this difference is attributed to the lattice mismatch between base-and counter-electrodes.         Study of closely spaced YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// Josephson junction pairs    Ke Chen, S.A. Cybart and R.C. Dynes Summary: Using electron beam lithography and ion damage, high quality YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// superconductor-normal metal-superconductor in-plane Josephson junction pairs have been fabricated. These junctions operate at temperatures between 60 and 85 K and have spacing ranging between 150 nm and 800 nm. Central electrodes connecting to the area between the two junctions were made, allowing for simultaneous measurements of the individual junctions as well as the series. Josephson junction pairs with 150 nm spacing were found to have extraordinary properties under microwave radiation with different power. At low power the structure functioned as two independent Josephson junctions in series, while at high power it behaved as one single Josephson junction. A possible origin of this behavior could be that the applied microwave radiation induces weak link behavior in the YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// between the two junctions.         Improvement in reproducibility of multilayer and junction process for HTS SFQ circuits    H. Wakana, S. Adachi, A. Kamitani, K. Nakayama, Y. Ishimaru, Y. Oshikubo, Y. Tarutani and K. Tanabe Summary: We have developed an HTS multilayer structure including a superconducting ground plane and interface-engineered ramp-edge Josephson junctions for single flux quantum (SFQ) circuits, and tried to improve reproducibility in the multilayer and junction process. We found that one of the crucial factors to improve the reproducibility is use of a ground plane with small average surface roughness (R/sub a/) of typically less than 2 nm and a high T/sub c/ above 87 K. By employing La/sub 0.2/-Y/sub 0.9/Ba/sub 1.9/Cu/sub 3/O/sub x/ (La-YBCO) thin films deposited by dc off-axis magnetron sputtering, such high quality was maintained for 3-month successive use of a ceramic target. Use of such a high-quality ground plane reproducibly led to SrSnO/sub 3//La-YBCO/SrSnO/sub 3//La-YBCO //MgO multilayer structures with R/sub a//spl les/2 nm and 100-junction arrays with 1-/spl sigma/I/sub c/ spread of 6-17% at 4.2 K depending on the average I/sub c/ level. The run-to-run reproducibility of average junction I/sub c/ and sheet inductance of both the base- and counter-electrodes for three samples was /spl plusmn/12%, /spl plusmn/3.0%, and /spl plusmn/3.4%, respectively, which are substantially smaller than those previously reported.         Fabrication of high-quality multilayer structure for HTS-SFQ circuits using surface treatments    K. Nakayama, Y. Ishimaru, H. Wakana, S. Adachi, Y. Tarutani and K. Tanabe Summary: Surface treatments have been applied to a multilayer structure in order to improve its surface smoothness and crystallinity for fabricating HTS-SFQ circuits. The surface treatments consist of ion beam etching and annealing in oxygen atmosphere. These surface treatments were applied to a SrSnO/sub 3/ insulating layer on a La-YBCO grandplane as an underlayer for growth of a La-YBCO base layer. From RHEED observation, it was found that a contamination layer or an amorphous layer formed on the SrSnO/sub 3/ surface after the bilayer was exposed to oxygen plasma for removing a photoresist film. The SrSnO/sub 3/ surface structure was observed to be recovered through the ion etching and subsequent annealing procedure. XRD measurement revealed that FWHM of the SrSnO/sub 3/ [200] rocking curve reduced from that of the as-deposited SrSnO/sub 3/ after an annealing at 715/spl deg/C in 120 mTorr oxygen atmosphere, indicating that crystallinity of the SrSnO/sub 3/ layer was also slightly improved. The recovery process for the SrSnO/sub 3/ layer significantly improved the surface roughness Ra and the J/sub c/ at 4.2 K of the La-YBCO base layer.         Thin-film technology for HTSC Josephson devices    P. Seidel, F. Schmidl, H. Wald, M. Mans, K. Peiselt, U. Baldeweg, M. Beck, S. Biering, C. Becker, J. Uhlig and V. Grosse Summary: An overview is given on different thin film preparation methods to produce YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin film Josephson devices on various substrates. Beside laser deposition and ion beam etching techniques the use of inhibit technologies for patterning is discussed for the preparation of large area superconducting structures. For the deposition of large area YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films a heater and dry etching concept is discussed. The quality of the films is compared for all these methods to optimize the crystalline quality, the superconducting properties and the long term stability of the samples. The technology of production of high sensitive and stable Josephson devices like single junctions, dc-SQUIDs and flux transformers is important with respect to applications in nondestructive evaluation and biomagnetism.         Characterization and dynamics of [100]-tilted Y-B-C-O bicrystal junctions on Nd-Ga-O/sub 3/    I.V. Borisenko, I.M. Kotelyanski, A.V. Shadrin, P.V. Komissinski and G.A. Ovsyannikov Summary: We report on the fabrication technique and electrical properties of Basal Plane Tilted YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) superconducting bicrystal Josephson Junctions (BTJ). In order to form the grain boundary in BTJ we apply an inclination of the [001] YBCO basal planes around the direction of {100} YBCO in contrast to the common In-Plane Tilted bicrystal Josephson Junctions (ITJ) where misorientation of the crystallographic axes in the ab-plane of YBCO has been used. Symmetric and asymmetric junctions were fabricated on bicrystal NdGaO/sub 3/ substrates 13-28/spl deg/ tilted from [110] NdGaO/sub 3/. DC and RF properties of the BTJ were investigates at temperatures 4.2-77 K, in magnetic fields up to 100 G, and under influence of electromagnetic radiation of 56 GHz frequency. The experimental dependences of critical current and Shapiro steps from RF current fit the Resistive Shunted model of Josephson junctions (RSJ-model). At T=77 K the BTJ reveal critical current density j/sub C/=0.2-0.5 MA/cm/sup 2/ and characteristic voltage V/sub C/=I/sub C/R/sub N/=0.6-0.9 mV, that makes the junctions promising candidate for practical electronic devices.         Capacitive properties of YBa/sub 2/Cu/sub 3/O/sub 7/ grain boundary Josephson junctions fabricated on 45/spl deg/ [100] tilt asymmetric and 24/spl deg/ [001] tilt symmetric bicrystals    M.A. Navacerrada, M.L. Lucia, L.L. Sanchez-Soto, F. Sanchez-Quesada, E. Sarnelli and G. Testa Summary: We present a comparative study of the electromagnetic parameters, mainly focused in the analysis of the capacitance (C) associated to the barrier, of YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) grain boundary Josephson junctions (GBJJs) fabricated on 24/spl deg/ [001] symmetric and 45/spl deg/ [100] asymmetric tilt bicrystalline substrates. The Swihart velocity (c~) is slightly affected by the nature of the barrier and mainly fixed by the junction width. However, a notable influence of the barrier structure, so of the geometry of the bicrystal substrate, on the relative dielectric constant to the barrier thickness ratio (/spl epsiv//sub r//t) values, so on C, has been found. We have observed that the capacitance values deduced by means of Fiske steps in YBCO 24/spl deg/ [001] symmetric and 45/spl deg/ [100] asymmetric GBJJs scale with junction resistance in opposite direction. This result could reveal the presence of a tunnel barrier in the YBCO 45/spl deg/ [100] asymmetric GBJJs. On the other hand, different capacitance values have been obtained by means of Fiske steps and hysteresis observed in the current-voltage characteristics in 45/spl deg/ [100] asymmetric GBJJs. An interpretation of this result can be made taking into account the contribution of the depleted YBCO layers close to the crystallographic grain boundary.         Misorientation dependence of DC SQUID of YBa/sub 2/Cu/sub 3/O/sub 7-X/ grain boundary junctions on MgO bicrystal substrates    Tung-Wuu Huang and Dow-Chieh Niu Summary: Thermal diffusion-bonded bicrystals of MgO with the configuration of [00l] tilt boundaries were incorporated as substrates to create artificial grain boundaries of epitaxial YBa/sub 2/Cu/sub 3/O/sub 7-X/ (YBCO) thin films. The transport properties of the YBCO grain boundary junctions across various misorientation angles /spl Theta/, /spl Theta/=10/spl deg/, 20/spl deg/, 30/spl deg/, 40/spl deg/, have been studied. The critical current density across the grain boundaries decreased exponentially as the misoriented angle increasing. The current-voltage characteristics of the /spl Theta/=10/spl deg/, 20/spl deg/ grain boundary junctions typically exhibited flux-flow or flux-creep like behavior; and the /spl Theta/=30/spl deg/, 40/spl deg/ grain boundary junctions revealed a resistive shunted junction (RSJ) like I-V characteristics. The transition from strong coupling for low angle grain boundary to weak-link behavior occurred with /spl Theta/>20/spl deg/. The dc SQUIDs made of /spl theta/=30/spl deg/ and 40/spl deg/ misoriented grain boundary showed periodic modulation of voltage-flux characteristics up to 77 K, IcRn = 0.4 mV, with /spl Delta/V=6 /spl mu/V.         Process of fabricating YBCO SQUIDs for 51-channel HTS MCG system    A. Tsukamoto, K. Saitoh, K. Yokosawa, D. Suzuki, Y. Seki, A. Kandori and K. Tsukada Summary: We have constructed a high throughput HTS SQUID fabrication process to develop a 51-channel HTS MCG system. To increase the process throughput of the YBCO deposition, we designed and developed a new deposition system based on a pulsed laser deposition technique. In this deposition system, nine YBCO thin films could be deposited in one deposition sequence by successively depositing the YBCO thin films one by one. In addition to the improvement of the fabrication throughput, the magnetometer pattern was designed to improve the yield of the SQUID fabrication. In our magnetometer design, four SQUIDs were connected with one pickup coil. The yield of good magnetometer chips could be increased by selecting the best SQUID among the four. Using the developed SQUID fabrication process, about one hundred magnetometers were fabricated in a month. The 51-channel HTS MCG system was successfully developed and used for clinical testing.         Comparison of intrinsic Josephson and SIS tunneling spectroscopy of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta//    L. Ozyuzer, C. Kurter, J.F. Zasadzinski, K.E. Gray, D.G. Hinks and N. Miyakawa Summary: Tunneling spectroscopy measurements are reported on optimally-doped and overdoped Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta// single crystals. A novel point contact method is used to obtain superconductor-insulator-normal metal (SIN) and SIS break junctions as well as intrinsic Josephson junctions (IJJ) from nanoscale crystals. Three junction types are obtained on the same crystal to compare the quasiparticle peaks and higher bias dip/hump structures which have also been found in other surface probes such as scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy. However, our IJJ quasiparticle spectra consistently reveal very sharp conductance peaks and no higher bias dip structures. The IJJ conductance peak voltage divided by the number of junctions in the stack consistently leads to a significant underestimate of /spl Delta/ when compared to the single junction values. The comparison of the three methods suggests that the markedly different characteristics of IJJ are a consequence of nonequilibrium effects and are not intrinsic quasiparticle features.         Microwave-induced steps observed in Bi-2212 intrinsic Josephson junctions    T. Tachiki, S. Someya, T. Uchida and Y. Yasuoka Summary: Microwave-induced steps observed in the I-V characteristics of Bi-2212 intrinsic Josephson junctions are investigated and the mechanism producing the zero-crossing steps is discussed. It is found that (1) a junction area smaller than 40 /spl mu/m/sup 2/ shows uniform in-plane distribution of the c-axis dc current and (2) the zero-crossing steps are observed in the uniform distribution. The observation of steps in samples of different sizes under the uniform current condition indicates that the observed steps are produced by the inverse ac Josephson effect.         Characteristic relationship between the maximum Josephson current and the c-axis conductivity observed for intrinsic Josephson junctions in Bi-Sr-Ca-Cu-O    M. Suzuki, T. Hamatani, Y. Yamada, K. Anagawa and T. Watanabe Summary: The maximum Josephson current (MJC) is measured for small mesas fabricated on cleaved surfaces of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta// single crystals. It is found that the MJC increases dramatically with increasing c-axis conductivity. The behavior indicates that the MJC is proportional to the square of the c-axis conductivity. This implies that the superconductivity in high-T/sub c/ superconductors is likely to be inhomogeneous.         Tunneling characteristics for Bi2212 intrinsic Josephson junctions with little influence of self-heating using short pulse technique on 60 ns time scale    K. Anagawa, Y. Yamada, T. Watanabe and M. Suzuki Summary: A small mesa structure (10 /spl mu/m /spl times/ 10 /spl mu/m, 15 nm thick) of intrinsic Josephson junctions in Bi/sub 2/Sr/sub 2/CaCu/sub 2/o/sub 8+/spl delta// is employed to observe the tunneling characteristics and the superconducting gap magnitude by short pulse technique (short pulse interlayer tunneling spectroscopy). In the measurement on 60 ns time scale, the effect of self-heating is almost negligible in the sample, whose resistivity is as small as 10 /spl Omega/cm. In slightly overdoped region, the maximum Josephson current density increases from 0.85 to 2.1 kA/cm/sup 2/ with increasing doping level. The superconducting gap magnitude 2/spl Delta/ decreases from 62 to 37 meV with increasing doping level. The value for 2/spl Delta//k/sub B/T/sub c/ decreases from 8.3 to 5.2 with increasing doping level. These values in slightly overdoped region are smaller than those in optimum and underdoped region.         Realization of a good contact between Au and Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+y/ for HTS ramp-edge junctions    T. Imaizumi, S. Hayase, T. Uchiyama and I. Iguchi Summary: The fabrication process of high-T/sub C/ ramp-edge type junctions with a Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+y/ (Bi-2212) base electrode and a conventional superconducting counter electrode (Nb, Pb or Pb-In alloy) was investigated. An Au film was deposited as a layer between Bi-2212 and Nb (or Pb, Pb-In). Most of thin films were prepared by a pulsed laser deposition (PLD) method. By optimizing the annealing condition for the junction fabrication process, the higher T/sub C/'s (T/sub C//spl sim/80 K) of Bi-2212 thin films were stably available after all processes. Resistivity of Au thin film could be reduced to about 1 /spl mu//spl Omega/cm at 4.2 K by heating the sample at 300-400/spl deg/C during the in-situ Au deposition. There were difficulties to realize Bi-2212/Au/Nb (Pb or Pb-In) junctions. However, in case of Bi-2212/Au junctions, the junction interface was much improved by an interlayer process. Good homogeneous conductivity found to be kept in the fabricated Bi-2212/Au junctions, which was reproducible.         Magnetic field dependence of vortex flow in stacked intrinsic Josephson junctions in Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ single-crystal mesas    G. Oya, T. Hayashi, H. Kaneoya, K. Kanda, A. Irie and N.J. Ali Summary: We have numerically and experimentally studied on the Josephson-vortex flow in stacks of intrinsic Josephson junctions in Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ single crystals. Numerical simulations of static and dynamic behavior of Josephson vortices in such a stack were carried out by using perturbed coupled sine-Gordon equations. The current-voltage characteristics of the stacks in the single-crystal mesas were measured without or with magnetic field B up to 4.5 T parallel to the junction layers at 4.2 K. It has been observed that the vortex flow tends to occur preferably in the highest velocity mode (in-phase mode) only in several junctions in the stack in low B below /spl sim/1 T, in intermediate velocity modes in more junctions in it in intermediately higher B and preferably in the lowest velocity mode (out-of-phase mode) in almost all junctions in it in much higher B above /spl sim/2.5 T, accompanied by a decrease in flow velocity from /spl sim/2.5/spl times/10/sup 6/ to (2-5)/spl times/10/sup 5/ m/s with increasing Bfs. This behavior of vortices can be interpreted to arise from an increase in interaction among vortices in the stack with the increase in B, according to the simulated results.         Investigation of temperature dependence of microwave-induced characteristics of a NbN Josephson junction array    A. Shoji, H. Takashima, M. Murugesan, H. Obara and H. Yamamori Summary: To investigate the temperature dependence of microwave-induced characteristics of a NbN Josephson junction array, the surface resistance, R/sub s/, of NbN films was measured using the dielectric resonator method at 22 GHz and temperatures from 5.8 K to 14.8 K. From the measured R/sub s/ values, the attenuation of 16 GHz microwaves in a NbN coplanar waveguide was calculated and constant-voltage-step amplitude for a NbN junction array biased with a DC current and 16 GHz microwaves was calculated as a function of temperature, resulting in a theoretical temperature dependence of constant-voltage-step amplitude.         Fabrication and characterization of NbN/AlN/NbN junction on MgO(001) and AlN/NbN bilayer on MgO(111) substrates    P.H. Wu, L. Kang, Y.J. Chen, J. Sun, J. Chen and S.Q. Zhao Summary: Using direct current (DC) or radio frequency (RF) magnetron sputtering techniques, NbN/AlN/NbN junctions or AlN/NbN bilayers are prepared on single crystal MgO [001] or MgO (111) substrates respectively, both at ambient substrate temperatures. The crystalline structures of such multilayers are characterized layer-by-layer using X-ray diffraction and transmission electron microscopy (TEM). Interestingly, the AlN barrier in NbN/AlN/NbN/ MgO [001] is amorphous while the NbN/AlN/NbN/MgO (111) is single-crystalline with [001] orientation. The electrical properties of these two structures are compared. Also discussed are the DC and high frequency behavior of NbN/AlN/NbN/ MgO [001] junction.         Correlation between the 1/f noise parameter and the Andreev conductance in epitaxial NbN/AlN/NbN junctions    H. Ishida, K. Okanoue, A. Kawakami, Z. Wang and K. Hamasaki Summary: Low-frequency noise properties of epitaxial NbN/AlN/NbN tunnel junctions have been investigated as a function of the bias voltage. The subharmonic gap structures (SGSs) were clearly observed in the differential resistance dV/dI-V curves. The SGSs were explained with Octavio, Tinkham, Blonder, Klapwijk (OTBK) theory based on the multiple-Andreev reflection (MAR) phenomena. To estimate the amplitude of the voltage noise power spectra S/sub V/(f) in the range 1-10/sup 5/ Hz, we extended Rogers and Buhrman empirical theory. The 1/f noise parameter /spl eta/ in this theory is given as /spl eta/=S/sub V/(f)I/sub b//sup 2/R/sub d//sup 2//fA, where A is the junction area, I/sub b/ is the bias current and R/sub d/ is the dynamic resistance. The /spl eta/ values (/spl eta//sub sg/) biased at the sub-gap voltage were larger than that (/spl eta//sub ag/) of the above-gap voltage. In addition, the /spl eta//sub sg/-V curves in the sub-gap region have dip and peak structures related to the SGSs in the dI/dV-V curves. In contrast, for the above-gap bias voltage, the /spl eta//sub ag/ values did not depend on the bias voltage. We concluded from these results that the excess 1/f noise in the sub-gap bias voltage was caused by the fluctuation of the MAR conductance.         Subharmonic photon-assisted tunneling effect in Superconducting NbN tunnel junctions    Y. Uzawa, M. Takeda, A. Kawakami and Z. Wang Summary: We investigated subharmonic gap structures in the current-voltage (I-V) characteristics of NbN tunnel junctions by observing frequency response using a quasioptical mixer configuration. We chose a 10.5-/spl mu/m-long by 0.6-/spl mu/m-wide junction for the mixer so that the junction behaved as a distributed element at submillimeter-wave frequencies in wideband observations. In the presence of electromagnetic waves, subharmonic photon-assisted tunneling steps with a voltage width of hf/2e could clearly be observed below and above the half-gap voltage in the I-V curves of junctions at measured frequencies from 600 to 950 GHz, where h is Planck's constant, f is frequency, and e is electron charge. This evidence is consistent with a consequence of multiple Andreev reflection at low transmissions or multiparticle tunneling.         Fabrication of superconducting MgB/sub 2/ neutron detectors on Si/sub 3/N/sub 4/ membranes    S. Miki, D. Fujiwara, H. Shimakage, Z. Wang, K. Satoh, T. Yotsuya and T. Ishida Summary: We report a fabrication process for membrane-structured superconducting MgB/sub 2/ neutron detectors and measurement of their dc-characteristics. We prepared /sup 10/B-enriched MgB/sub 2/ thin films on Si/sub 3/N/sub 4/-film-coated Si substrates using a multiple-target sputtering system. The 170 nm thick MgB/sub 2/ thin films were processed to create meandering lines by e-beam lithography, where the line width was 1 /spl mu/m and the total length reached 37.5 cm. After the front side of the device had been fabricated, it was placed into an etching apparatus to protect it. Then, the backside of the device was etched with anisotropic Si etching using ethylene diamine pyrocatechol (EDP) to increase the sensitivity of the device. The membrane-structured MgB/sub 2/ device showed superconductivity, namely, a T/sub C,onset/ of 28.2 K, a T/sub C,offset/ of 27.3 K, and an RRR of 1.18.         Degradation of MgB/sub 2/ thin films in water    Y. Cui, J.E. Jones, A. Beckley, R. Donovan, D. Lishego, E. Maertz, A.V. Pogrebnyakov, P. Orgiani, J.M. Redwing and X.X. Xi Summary: We have studied the degradation of MgB/sub 2/ thin films, grown by hybrid physical-chemical vapor deposition (HPCVD), by submerging MgB/sub 2/ films into de-ionized water at different temperatures. The thickness, room temperature resistance, and superconducting transition were measured as a function of time in water and the temperature of the water. Results show that the films degrade faster at room temperature than at 0/spl deg/C. The room temperature resistance increases with time. The thickness of the MgB/sub 2/ films decreases rapidly initially, but then saturates. The resultant material is amorphous and insulating. Both T/sub c/(onset) and T/sub c/(0) of the MgB/sub 2/ films decrease with time in water, while the superconducting transition become broader. The effects of the exposure to other solvents and photoresist were also studied, and it was found that isopropanol does not cause MgB/sub 2/ films to degrade.         Investigations of MgB/sub 2//MgO and MgB/sub 2//AlN heterostructures for Josephson devices    P. Orgiani, Y. Cui, A.V. Pogrebnyakov, J.M. Redwing, V. Vaithyanathan, D.G. Schlom and X.X. Xi Summary: We report structural and transport proprieties of MgB/sub 2//MgO and MgB/sub 2//AlN multilayers for MgB/sub 2/ Josephson junctions. The MgB/sub 2/ layers were grown by hybrid physical chemical vapor deposition (HPCVD). The epitaxial MgB/sub 2//MgO/MgB/sub 2/ trilayers were grown in situ in the HPCVD system. The AlN layers were grown at room temperature by pulsed laser deposition, and the MgB/sub 2//AlN/MgB/sub 2/ trilayers were deposited ex situ with the deposition of the AlN layer between the depositions of the top and bottom MgB/sub 2/ layers. Although slightly less perfect than in films grown directly on sapphire and SiC substrates, excellent superconducting and transport properties were obtained in the MgB/sub 2/ layers in both heterostructures. The result addressed only the first of many issues about the adequacy of using MgO and AlN as the barrier materials for all-MgB/sub 2/ planar Josephson junctions, i.e. the ability to obtain good structural and superconducting properties in both electrode layers using the trilayer deposition process. It allows us to further investigate the conditions for better wetting and coverage of the insulator layers, as well as other critical issues in the fabrication of all-MgB/sub 2/ planar Josephson junctions.         Exploring the versatility of double-sided fabrication of intrinsic Josephson junctions    H.B. Wang, T. Hatano, S. Urayama, S.M. Kim, K. Inomata, M. Nagao, Y. Takano, A. Ishii, S. Arisawa, M. Tachiki, T. Yamashita, P.H. Wu and P. Muller Summary: After a brief description of the double-sided fabrication process, we give an example to show that a quite large array of intrinsic Josephson junctions (IJJs) can be made by superconductively connecting 256 stacks of junctions together. Each of these stacks contains only 40 junctions which prevents problems causing by heating. We present a detailed discussion on a new structure we have developed in which an extra electrode can be fabricated in the middle of an array by a slight modification of the double-sided process. Using this middle electrode, we can determine further information on the physical processes inside the stack than is possible without such an electrode. Finally we shall discuss terahertz generation in IJJs when an external magnetic field is applied perpendicular to the width of the junctions.         Fabrication and characterization of sub-micron thin film intrinsic Josephson junction arrays    P.A. Warburton, A.R. Kuzhakhmetov, G. Burnell, M.G. Blamire, Y. Koval, A. Franz, P. Muller and H. Schneidewind Summary: We have fabricated intrinsic Josephson junction arrays in thin films of Tl-Ba-Ca-Cu-O. Such arrays are candidates for applications in the sub-millimeter waveband both by virtue of the large gap energy and due to the existence of inductive and capacitive coupling mechanisms between junctions in the array. Characterization of such junctions is complicated by the fact that the transport properties are dominated by Josephson fluxon flow (for junctions whose dimensions exceed the Josephson penetration depth) and premature switching to the voltage state at bias currents less than the critical current (for junctions whose dimensions are less than the Josephson penetration depth). Here we show that the magnetic-field dependence of the switching current is not Fraunhofer-like, although there is clear minimum corresponding to the point at which a single flux quantum is inserted between the cuprate double-planes. Nevertheless a Fraunhofer-like dependence can be obtained if the critical current is experimentally defined by specifying a low-voltage criterion.         Planar YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// ion damage Josephson junctions and arrays    S.A. Cybart, Ke Chen and R.C. Dynes Summary: Reproducible low resistance lumped element Josephson junction arrays are desired for many microwave applications. Using our established process of electron beam lithography and ion damage, we have fabricated and demonstrated high quality YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// superconductor-normal superconductor-superconductor (SS'S) in-plane Josephson junctions. Single junctions and multiple junction arrays with as many as 50 junctions in series have been investigated. These junctions are in close proximity and offer several possible applications. Current-voltage characteristics for single junctions are consistent with the resistively shunted junction model. Junction in pairs have been fabricated which show nearly identical characteristics. Rounding near the critical current occurs for larger number arrays which we attribute to junction nonuniformity. Microwave measurements reveal sharp giant Shapiro steps for junction pairs and 10 junction arrays, rounded steps appear for larger arrays.         Properties of [100] tilt Y-Ba-Cu-O bicrystal grain boundary junctions    E. Sarnelli, G. Testa, D. Crimaldi, A. Monaco, M. Adamo and M.A. Navacerrada Summary: We have fabricated and measured high-quality [100] Y-Ba-Cu-O grain boundary junctions in both symmetric and asymmetric configurations. High values of the critical current times normal resistance I/sub c/R/sub n/ products have been systematically observed. The high I/sub c/R/sub n/ values found in these junctions may be of interest for the fabrication of high-sensitive superconducting quantum interference devices.         Superconductor digital receiver components    A. Kirichenko, S. Sarwana, D. Gupta and D. Yohannes Summary: We have developed and experimentally demonstrated several new RSFQ circuits, designed as components for digital receivers that are being developed by HYPRES. The first circuit is a digital phase generator, which produces a periodic digital signal with a controllable phase shift. This signal is obtained by decimation of an external high frequency signal by a factor of 1024, and provides a controllable phase shift with digital precision of /spl pi//512. The second circuit, a precise digital static frequency divider, is capable of dividing of an input signal frequency by any integer value between 1 and 1024. The third circuit is a digital quadrature mixer performing digital downconversion of bit-stream data. This report presents results of experimental evaluation of these circuits at speeds in excess of 30 GHz.         20 GHz operation of bit-serial handshaking systems using asynchronous SFQ logic circuits    M. Ito, K. Kawasaki, N. Yoshikawa, A. Fujimaki, H. Terai and S. Yorozu Summary: Synchronous design is generally used in SFQ digital systems at present. In large-scale SFQ digital systems, however, the introduction of asynchronous design is required due to the large clock skew in the clock distribution network and complexity in the timing design at high clock rate. We have proposed a hierarchical design approach using asynchronous SFQ circuits with handshaking protocol for asynchronous data transfer. In our asynchronous approach, each circuit module is designed based on a data driven self-timed (DDST) architecture. A handshaking protocol is also used to ensure the logical ordering in data communication between the modules, where we have adopted bit-serial architecture to reduce the communication costs in handshaking. One issues in the bit-serial handshaking (BSHS) system is the synchronization of the input data when the module has multiple input ports. In this study, we have designed an SFQ BSHS system with multiple input ports, where Muller C-elements is used to synchronize the multiple input data. We have designed and implemented a BSHS half adder using NEC 2.5 kA/cm/sup 2/ Nb standard process to demonstrate asynchronous addition of two input data at high speed. We have successfully confirmed its correct operation at about 20 GHz.         Stacked double-flux-quantum output amplifier    Q.P. Herr Summary: A suitable data link from RSFQ to semiconductor electronics remains challenging. We report an output amplifier that uses a new pulse multiplier circuit. The pulse multiplier consists of several stages arranged in series; a double-flux-quantum gate at each stage promotes the SFQ pulse to the next stage. Characteristics of the circuit design are: 1) DC power. As with the DFQ gate, every unshunted Josephson junction in the amplifier is loaded by critically-damped junctions that prevent voltage-state modes. 2) Equal rise and fall times that scale with output amplitude. In our case, 50 ps rise and fall time and 1-2 mV output amplitude can be realized, which is ideal for a data rate of 10 Gb/s. 3) Quantum accurate voltage multiplication independent of bias current. 4) Non-return-to-zero (NRZ) operation. The circuit was designed and successfully tested in our 8 kA/cm/sup 2/ foundry process. A 60 GHz pulse train, generated on-chip, was gated with RSFQ logic to produce a data pattern that was then fed into a pulse multiplier of either ten or twenty stages. Voltage multiplication was observed with operating margins of /spl plusmn/21% on bias current. Fast rise time was directly observed; unfortunately, fall time was spoiled by ringing on a 1 ns time scale. It is plausible that small changes to the physical layout of the circuit would produce desired operation.         A single-clock asynchronous input COSL set-reset flip-flop and SFQ to voltage state interface    C.J. Fourie and W.J. Perold Summary: Although published research in COSL has stagnated, it remains a useful logic family for interfacing the much faster RSFQ family to hot-logic circuits. COSL has always been plagued by the absence of latches, and previous attempts at implementing such latches were clumsy. A new COSL Set-Reset flip-flop is discussed here, and results shown. This asynchronous input latch, which can also be configured as a T flip-flop, can function on a single-phase clock. It was also adapted to convert SFQ output pulses from RSFQ logic circuits to voltage state levels that can be viewed on standard laboratory oscilloscopes. Due to the asynchronous nature of the inputs, the RSFQ-COSL converter is also more reliable than earlier DRO-to-COSL elements.         Characterization of 4 K CMOS devices and circuits for hybrid Josephson-CMOS systems    N. Yoshikawa, T. Tomida, M. Tokuda, Q. Liu, X. Meng, S.R. Whiteley and T. Van Duzer Summary: Characterization and modeling of CMOS devices at 4.2 K are carried out in order to simulate low-temperature operation of CMOS circuits for Josephson-CMOS hybrid systems. CMOS devices examined in this study have been fabricated by using 0.18 /spl mu/m, 0.25 /spl mu/m, and 0.35 /spl mu/m commercial CMOS processes. Their static I-V characteristics and capacitances are measured at 4.2 K to establish the low-temperature device model based on the BSIM3 SPICE model. The propagation delays of CMOS inverters measured by using ring oscillators agree well with the simulation results. The experimental results indicate about 40% speedup from 300 K to 4.2 K. A three-transistor DRAM cell for a Josephson-CMOS hybrid memory is also investigated at low temperature. The temperature dependence of the retention time shows an exponential increase at low temperatures. Based on the low-temperature CMOS device model, we have developed short-delay CMOS amplifiers, which would amplify a 40 mV voltage input to CMOS voltage level with the propagation delay of about 100 ps, assuming the use of a 0.18 /spl mu/m CMOS process. We have measured the propagation delay of the CMOS amplifier by using a single-flux-quantum (SFQ) delay measurement system. This is a complete demonstration of the signal exchanges between SFQ and CMOS circuits at 4.2 K.         RSFQ-asynchronous timing (RSFQ-AT): a new design methodology for implementation in CAD automation    H.R. Gerber, C.J. Fourie and W.J. Perold Summary: Asynchronous timing is very important in the design of large-scale ultra-high speed superconducting digital electronic (SDE) circuits. This paper presents an optimized asynchronous self-timing scheme that will simplify and speed up the design of large digital circuits. Rapid Single Flux Quantum Asynchronous Timing (RSFQ-AT) is compared to other timing schemes by implementing, testing and evaluating a variety of circuits. Further it is shown how the design methodology introduced with this asynchronous self-timing scheme can simplify the design of automated CAD tools for RSFQ-AT.         Influence of the bias supply lines on the performance of RSFQ circuits    E. Tolkacheva, Henrik Engseth, I. Kataeva and A. Kidiyarova-Shevchenko Summary: Two effects of the bias supply line on the performance of RSFQ circuits have been studied: inductive coupling between the bias supply line and circuit inductances; effect of the mirrored current in the ground plane. The following results of the study are presented: 3D calculations and experimental measurements of inductive coupling between parallel and perpendicular microstrips in presence of one and two ground planes; calculated margins dependence on the external magnetic field in RSFQ cell. Bias current density extraction method has been developed and implemented in RSFQ circuit design flow.         Effects of superconducting return currents on RSFQ circuit performance    A.M. Kadin, R.J. Webber and S. Sarwana Summary: Complex RSFQ circuits are typically dc-biased with one or more current bias trees, with current returning through a superconducting ground plane. As the bias currents become larger in more complex circuits, it is increasingly critical to pay attention to the distribution of these return currents, and the effects of the resulting magnetic fields on the performance of the RSFQ circuits. We have modeled the current and field distributions, and found that magnetic field and flux are indeed significant. This has been confirmed by direct measurement using a distribution of SQUIDs. Furthermore, we have measured the performance of several RSFQ circuits, and have found that currents in the ground plane can significantly affect performance margins. Approaches to circuit and system designs that can reduce these problems are discussed.         Tuning of the RSFQ gate speed by different Stewart-McCumber parameters of the Josephson junctions    B. Dimov, M. Khabipov, D. Balashov, C.M. Brandt, F.-Im. Buchholz, J. Niemeyer and F.H. Uhlmann Summary: At the typical operating temperature of 4.2 K, the theoretical upper limit of the clock frequency of the Low-Temperature Superconductive (LTS) Nb based Rapid Single Flux Quantum (RSFQ) digital circuits is several hundred GHz. Nevertheless, the few middle-scale RSFQ circuits reported on up to now operate at only some tens of GHz. An important performance-limiting factor is in this case the clock signal distribution, so nowadays asynchronous RSFQ designs are often considered. Our previous studies have shown that it is an important advantage of a given asynchronous RSFQ cell library to contain gates with tunable delays. We have already shown by simulations that the RSFQ gate delays are best adjusted by changing the Stewart-McCumber parameter /spl beta//sub c/ of the Josephson junctions-this method tunes the delay within a large interval of values while scarcely affecting the margins and the fabrication yield of the RSFQ gates. In order to prove this statement experimentally, we have designed, fabricated, and tested several ring-shaped oscillators with identical topologies but different Stewart-McCumber parameters of the Josephson junctions. Their operating speeds and margins are measured and compared.         Delay analysis of self-timing-aligned clock synchronization technique for superconductive SFQ logic circuits    Gyu Moon, Jungkeun Park, Sangmin Lee, Seongsoo Lee and Jae-Kyung Wee Summary: Delay analysis for superconductive Single Flux Quantum (SFQ) logic is performed for Self-Timing-Aligned Clock Synchronization Technique (STAC). With its pipelined-structure, the SFQ generates and propagates pulses that are to be processed sequentially through serial-connected functional logic blocks, and thus it is critical to acquire a ultra-high-speed and exactly synchronized clock/control signals with a few pico-second resolution. Both passive and Josephson-Junction circuits are investigated for the delay control. These delays, being connected in parallel with input line, and to the clocked-power/control node, produce a self-timing-aligned synchronization. Ways to achieve precision delays are seek by using Mo resistors along with junction inherent capacitors. Both current margins for the bias and critical timing information for the maximum throughput are also investigated. Layouts for the test SFQ circuits, such as D- and RS-flip-flops are done with XIC, and verifications are done through WRSpice with Hypres process parameters.         Superconducting high-order cascaded lowpass sigma-delta modulator    S. Hirano, A. Yoshida, S. Hasuo and K. Tanabe Summary: We propose a superconducting high-order cascaded lowpass sigma-delta modulator. The second-order cascaded modulator consists of two single-loop modulators. A part of an integrating inductor of the first-stage modulator forms a primary coil of a transformer. The secondary coil of the transformer forms an integrating inductor of the second-stage modulator. Output of the first integrator is thus magnetically fed to the second integrator through the transformer. Digital outputs from both modulators are input to a delay and a digital differentiator. The quantization noise of the first-stage modulator is canceled by choosing proper transfer functions for the delay and differentiator. This cascaded type modulator eliminates the difficulty of designing a feedback driver in a double-loop type modulator. Analytical calculation of the transfer function showed that the signal-to-noise ratio is comparable to an ideal second-order lowpass sigma-delta modulator at a given sampling frequency.         High quality on-chip long annular Josephson junction clock source for digital Superconducting electronics    D.E. Kirichenko and I.V. Vernik Summary: We have developed clock sources for rapid single flux quantum (RSFQ) digital circuits using high-quality long Josephson junction (LJJ) resonant oscillators of annular geometry. Being a topologically closed system and unperturbed by reflections from boundaries and collisions among the fluxons (flux quanta), the annular LJJ oscillator has demonstrated a high quality factor. The novel design of an annular junction clock that allows easier interface with RSFQ circuitry has been realized. Magnetic fluxons are inserted into an annular LJJ by local injection of current into the control line of the junction. This technique resolves the long-standing problem of achieving superior stability of the fluxon state for application as a clock source. The linewidth of the phase-locked clock source is measured as low as 24 Hz relative to a reference oscillator at 40 GHz. The cycle-to-cycle jitter was measured to be 9 fs at a frequency of 36 GHz, or 0.04% of the clock period which is in good agreement with theoretical estimation.         Simulated inductance variations in RSFQ circuit structures    C.J. Fourie and W.J. Perold Summary: Manufacturing tolerances influence circuit parameters, and inductance is no exception. A computer application was developed to fully automate inductance calculation as part of a layout extraction suite. InductEx takes a GDSII layout file as input, finds the inductance ports, extracts structures, applies mask-to-wafer offsets and random process tolerances to the circuit structures, builds deck files that can be processed with FastHenry, and manages FastHenry-all autonomously. Results are presented for the simulated variation in inductance-both self and mutual, over hundreds of runs-in several common RSFQ structures in the Hypres 1 kA/cm/sup 2/ process (with the latest tolerance values built in), even with the presence of moats.         Digital SQUID sensor based on SFQ technique    T. Reich, T. Ortlepp and F.H. Uhlmann Summary: For high sensitive measurements of small magnetic fields a Digital SQUID is superior to conventional analog SQUIDs in terms of dynamic properties, but recent realizations as single-flux-quantum (SFQ) circuit suffers from high complexity. A new kind of Digital SQUID as a full digital sensor device with the advantage of a small number of Josephson junctions and a large slew rate was developed. The circuit consists of basic SFQ cells and an internal digital feedback loop. The operation with a bidirectional clock signal ensures a decreased effort on superconducting electronics. The SFQ/dc converter and an additional voltage driver provides a processable digital output signal for hybrid systems including semiconductor electronics. The sensor circuit was simulated, optimized and fabricated in niobium technology. From investigation of dynamic properties of the circuit we expect a flux slew rate in the gigahertz range.         Construction of an RSFQ 4-bit ALU with half adder cells    Jin-Young Kim, Sehoon Kim and Joonhee Kang Summary: As part of the effort to develop a superconductive microprocessor, we constructed a rapid single flux quantum (RSFQ) 4-bit arithmetic and logic unit (ALU) in a pipelined structure. To speed up the circuit, we used a forward clocking scheme. The 4-bit ALU consisted of ten RSFQ Half Adders, four 2 /spl times/ 2 switches, and several D flip-flops. By commutating output ports of the half adder, we were able to produce AND, OR, XOR, and ADD functions. The 4-bit ALU was fabricated using the Korea Photonics Technology Institute's ten-level 1.0 kA/cm/sup 2/ Nb process. The size of the ALU was 3.0 mm /spl times/ 1.5 mm, fitting in a 5 mm /spl times/ 5 mm chip. The fabricated 1-bit ALU block was successfully tested at up to a 40 GHz clock frequency. The complete 4-bit ALU operated correctly at up to a 5 GHz clock frequency.         A 10 gigabit-per-second data collection system for analog to digital converters    C. Lavoie, A.J. Przybysz, A.A. Pesetski and D.L. Miller Summary: A high speed data collection system is designed and built to allow testing of digital devices running at 10 gigabits per second. The system uses commercially available parts and consists of a signal-conditioning front end, a 1-to-16-channel data demultiplexer, an interface board, a 16-channel logic analyzer, and a personal computer. We report on the design and performance of the interface board, and the performance of the complete system whose bit-error rate was found to be 1/spl times/10/sup -7/.         Simulation study of high-T/sub c/ superconducting sampler circuit with bandwidth over 100 GHz    M. Maruyama, H. Suzuki, T. Hato and K. Tanabe Summary: We investigated high-T/sub c/ superconducting sampler circuits by computer simulation and proved that our latest version of sampler circuit can operate with bandwidth over 100 GHz. In our conventional sampler circuit, we found several problems in its circuit design. An improved sampler circuit, which has additional reset junctions in the dc/SFQ and SFQ/dc parts of the circuit and has a Josephson transmission line with an optimized dc bias in front of the comparator, accurately reconstructed signal waveforms with bandwidth above 160 GHz for a typical I/sub c/R/sub n/ product of 1 mV in the simulation.         Design and implementation of stochastic neurosystem using SFQ logic circuits    T. Kondo, M. Kobori, T. Onomi and K. Nakajima Summary: We propose a stochastic neurosystem using SFQ logic circuits and design the main components with the following functions: carrying out the multiplication of an input to a neuron on a synaptic weight value, integrating pulses to generate a membrane potential, and generating the output of a neuron. We simulate some circuits by JSIM and confirm their correct operation. We compare two methods of multipliers: using a comparator and using a divider. The multiplication using the divider is effective with respect to integration, and reduces the accumulation time N/sub a/ required for higher precision operations. We designed a 4-bit up/down counter assuming the NEC 2.5 kA/cm/sup 2/ Nb/AlO/sub X//Nb standard process. We show that it is possible to compose the activation function circuit using a comparator.         Quantitative evaluation of the single-flux- quantum cross/bar switch    T. Yamada, M. Yoshida, T. Hanai, A. Fujimaki, H. Hayakawa, Y. Kameda, S. Yorozu, H. Terai and N. Yoshikawa Summary: We demonstrated the 4 /spl times/ 4-cross/bar-40 Gbps/ch switch which is functionally compatible with a commercial semiconductor one in order to evaluate the current SFQ circuit technology quantitatively in both a operating speed and power consumption. According to our numerical simulations, the SFQ switch has one or two orders of magnitude higher throughput per a single channel than that of the semiconductor, and has much smaller exchanging times between routing paths. In an actual test based on the NEC Nb-2.5 kA/cm/sup 2/ junction technology, correct operation using an on-chip test system made up of 4700 Josephson junctions was confirmed up to 37 Gbps/ch which is about 14 times faster than the semiconductor of 2.7 Gbps/ch speed. We also confirmed that SFQ circuits consumed 1/800 power compared with those of semiconductor. The reason why data rates obtained experimentally did not reach the designed speed of 40 Gbps/ch is due to both the timing error and the influence of magnetic fields caused by large bias currents exceeding 500 mA. These results of quantitative evaluation show that the SFQ technology has much greater potentials than the semiconductor one in both the operating speed and the power consumption, which means it is very effective to apply the SFQ technology to digital applications.         Time-delay optimization of RSFQ cells    S. Intiso, I. Kataeva, E. Tolkacheva, Henrik Engseth, K. Platov and A. Kidiyarova-Shevchenko Summary: This paper presents timing models for RSFQ cells, based on conventional finite-state machines description. Models have been integrated, validated and verified in physical simulations and are suitable for VHDL design. A complete design flow from physical simulation to VHDL simulation, delays optimization, layouting and back-annotation is presented. The correctness of the timing models has been verified in an experiment with 4 /spl times/ 15 shift register.         Double relaxation oscillation SQUID with a 4JL on-chip digital flux locked-loop circuit    H. Myoren, M. Goto, T. Taino, K. Kikuchi, H. Nakagawa, K. Tokoro, M. Aoyagi and S. Takada Summary: Double relaxation oscillation SQUID (DROS) combined with an on-chip superconducting digital flux locked-loop (FLL) circuit has been proposed. In this study, we described superconducting digital FLL circuit which consists of an 8-bit up/down counter and an 8-bit R-2R ladder D/A converter. The circuit was designed using 4-Junction Logic (4JL)-gates which are driven by a two phase power supply. In the up/down counter, we employed binary carry lookahead (BCL) circuits for high-speed operation. Logic simulations for the BCL 8-bit up/down counter showed correct operation up to 4 GHz, assuming a 2.5 kA/cm/sup 2/ Nb/Al-AlO/sub x//Nb junction technology. From simulation results high slew rate of 10/sup 7//spl Phi//sub 0//s and dynamic range of 2.5/spl Phi//sub 0/ can be expected.         Design and operation of a pulse-number multiplier for a high-precision RSFQ D/A converter    M. Suzuki, M. Maezawa, F. Hirayama and M. Ochiai Summary: A pulse-number multiplier (PNM) is a principal subsystem of our rapid single flux quantum digital-to-analog converter for metrology applications. The PNM circuit generates a high-speed pulse train from an input of a precise low-frequency clock signal. We designed, fabricated, and successfully tested a PNM test circuit. The PNM test circuit was implemented by using our standard cell library on 1.6 kA/cm/sup 2/ Nb trilayer technology. Fully functional operation was confirmed by low-speed testing. Experimental bias margins were wider than /spl plusmn/20%, and these results agreed with a simulation. We also tested the circuit by average-voltage measurements for estimating the frequencies of output pulse trains. Results of average-voltage measurements implied that the output frequency of the PNM circuit was tunable from 5 GHz to 17 GHz. The bit error rate (BER) of the PNM circuit was measured, and extrapolation of the error-function fits suggested a sufficiently small BER at the optimum bias point.         Demonstration of the multi-bit sigma-delta A/D converter with the decimation filter    A. Sekiya, K. Okada, Y. Nishido, A. Fujimaki and H. Hayakawa Summary: We have proposed a multi-bit sigma-delta analog-to-digital converter (ADC) in which a modulator is composed of a single quantizer and multiple samplers based on the single-flux-quantum (SFQ) circuits. The quantizer converts analog signals to pulse-density-modulated signals, and the samplers sample the modulated SFQ pulses in every sampling clock. Use of multiple samplers based on delayed-flip-flops (DFFs) increases sampling frequencies virtually, resulting in a multi-bit sigma-delta modulator. We also designed a decimation filter by using the well-established Verilog tools for the SFQ circuits and the Matlab simulator. We prepared an ADC including 4 samplers and a second-order decimation filter with the decimation rate of 1:256 based on the Nb junction technology. We confirmed correct operation of this ADC at 56 GHz clock signals generated by an internal ring oscillator. We experimentally obtained the signal-to-noise ratio of 25 dB and spurious-free dynamic range of 37 dB at the bandwidth of 10 MHz from the upper 7 bits of the outputs of the decimation filter.         Noise induced timing jitter: a general restriction for high speed RSFQ devices    T. Ortlepp and F.H. Uhlmann Summary: All complex devices in rapid single flux quantum (RSFQ) technique work at much lower clock rates than possible for simple cells. New data driven self timed or asynchronous concepts can reduce this gap, but even in this case still a discrepancy between simulation and experiment is shown. It has been pointed out in previous studies, that the influence of thermal fluctuations in RSFQ circuits is divided into static and dynamic switching bit errors as well as timing jitter induced failures. The bit error rate depends exponentially on the temperature and is not the main issue in the low temperature technique. Our last results show for the first time, that the variance of the switching time is much slower decreased by reducing the temperature and is still important at 4.2 K. We describe a general method for calculating the switching time distribution for RSFQ cells. Furthermore, we present detailed results for a timing analysis of a dc/SFQ-converter. The delay between output signal and the input current ramp shows a variation over 1 ps which is more than 10% of the switching time itself. This new understanding of the background of timing jitter enables a goal-oriented improvement in the design process of RSFQ circuits.         An RSFQ DC-resettable latch for building memory and reprogrammable circuits    C.J. Fourie and W.J. Perold Summary: A new RSFQ latch, the DC-Resettable Latch (DCRL), is introduced. The DCRL functions like a standard nondestructive readout register (NDRO), except that it requires a dc current or current pulse to reset. This allows the DCRL to be used as a memory element in large memory blocks, where the entire block can be erased with a current pulse from a single threaded current line instead of unwieldy pulse distribution circuitry. The reset current can be applied by off-chip control logic, or on-chip bipolar current elements such as HUFFLEs. However, the DCRL is most useful as the base building block of complex reprogrammable RSFQ circuitry.         Challenges of Josephson junction arrays for ac voltage generation by microwave pulse power modulation    A.S. Katkov, A.M. Klushin, G.P. Telitchenko, R. Behr and J. Niemeyer Summary: Voltage pulses with a determined amplitude and width might be the basis for high-precision ac voltage measurements in the future. The pulse width modulation technique makes possible the generation of arbitrary waveforms. In this paper, arrays of SINIS Josephson junctions were investigated which produce a 1 V voltage step under irradiation at a frequency of the order of 70 GHz. This step has an amplitude of 1 mA whereof a region of 0.3 mA overlaps with the critical current. This allows the generation of a 1 V voltage pulse by switching the microwave power at constant dc bias current. The results of this investigation will be presented and also the array parameters which are required for obtaining a relative uncertainty of 0.1 ppm in ac voltage measurements.         Implementation of a 4 /spl times/ 4 switch with passive interconnects    Y. Hashimoto, S. Yorozu, Y. Kameda, A. Fujimaki, H. Terai and N. Yoshikawa Summary: We designed and fabricated a 4 /spl times/ 4 switch in which all interconnections were implemented using passive transmission lines (PTLs). The switch consisted of four identical 2 /spl times/ 2 switches connected using PTLs. The 2 /spl times/ 2 switch was designed using gate-to-gate passive interconnections. Using the on-chip testing method, we demonstrated 40-GHz operation of the 4 /spl times/ 4 switch. To verify the effectiveness of passive interconnection, we compared the 4 /spl times/ 4 switch with an identical switch that was designed using Josephson transmission lines (JTLs) for interconnections. The comparison showed that the PTL-version 4 /spl times/ 4 switch had 50% fewer junctions and required 55% less powering current. The latency and the largest jitter in the PTL-version 4 /spl times/ 4 switch were estimated to be 36% and 61%, respectively, of those of the JTL version.         Error detection method for RSFQ voltage multipliers using a SQUID detector    F. Hirayama, M. Maezawa, M. Suzuki and M. Ochiai Summary: The voltage multiplier (VM) is a principal component in high-precision digital-to-analog (D/A) converters based on rapid single flux quantum (RSFQ) circuits. Experimental confirmation of correct operation of the VM is important to guarantee the accuracy of the D/A converter. In this study, a circuit for direct comparison of the output voltages of VMs was designed and demonstrated. An on-chip SQUID sensor was utilized to detect the VM errors. Bit error rates of a single-stage VM were successfully measured down to 10/sup -12/ in the constant-voltage regions. A method of detecting errors during transients was also proposed and carried out.         The relationship between bit-error rate, operating speed and circuit scale of SFQ circuits    H. Terai, Y. Hashimoto, S. Yorozu, A. Fujimaki, N. Yoshikawa and Z. Wang Summary: Timing jitter is an important constraint for the performance of SFQ circuits. We focus on the timing jitter in a Josephson transmission line (JTL) that induces timing errors at logic gates. A proper data analysis of 2-bit shift registers gave a jitter value of about 0.08 ps for a single Josephson junction in a JTL powered at a designed bias current. The variations in timing parameters of logic cells also give rise to timing errors. We experimentally determined the timing parameters in several logic cells and found that the deviations between actual and nominal values are within 2 ps. The relationship between the gray zone and circuit scale was estimated by extrapolating the transition curves observed in 2-bit shift registers. The estimated circuit scale was 20,000-100,000 JJs and 1,000 JJs at an operating clock frequency of 20 GHz and 40 GHz, respectively.         Specification of a technology portable logic cell library for RSFQ: an automated approach    H.R. Gerber, C.J. Fourie and W.J. Perold Summary: Currently, when a new fabrication process becomes available, all logic cells have to be re-designed, re-optimized and laid out from scratch. This is a manual and time intensive process, which hampers the migration of RSFQ circuits to better fabrication processes. The paper investigates the parameters that are required to specify logic gates that are technology and fabrication process independent. Ways of automating the optimization of the logic gates for implementation in new technologies, and automating the layout of logic cells for new design rules or new fabrication processes, are described. Cells can then be characterized for implementation in both LTS and HTS processes. Steps in the development of new logic gates and automation processes are shown.         Modeling of superconducting first- and second-order low-pass sigma-delta modulators    P. Magnusson, P. Lowenborg and A. Kidiyarova-Shevchenko Summary: Here we present our studies of first- and second-order superconducting low-pass sigma-delta modulators with the filtering function realized using an RL-circuit. These modulators have been simulated for different circuit parameters using device level simulations. A linear discrete time model of the first-order modulator has been done. Simulations of the first-order sigma-delta modulator operating at an oversampling ratio of 128 and a bandwidth of 60 MHz give a maximum SNR of 70 dB using a resistance of only 1 m/spl Omega/. The SNR dependence on the parameters of the RL-filter is well predicted by the linear model. Some circuit parameters give however rise to harmonic distortions which can not be predicted by the simple linear model. Under the same conditions, the performance of second-order sigma-delta modulators was found to have a maximum SNR of only 82 dB. We conclude that the estimated upper bound on SNR for superconducting RL-filtered low-pass sigma-delta modulators, is for physical realizable circuits not high enough to give an advantage over other techniques.         Fabrication and logic operation of oxide SFQ-circuit-components    Y. Tarutani, Y. Ishimaru, H. Wakana, S. Adachi, K. Nakayama, Y. Oshikubo, O. Horibe, Y. Morimoto and K. Tanabe Summary: Basic SFQ circuit components, such as SFQ-dc converter, set-reset flip-flop (RS-FF), confluence buffer and splitter, have been fabricated by the YBa/sub 2/Cu/sub 3/O/sub 7-x/-ramp-edge-junction technology and their logic operations were investigated. Circuit parameters were optimized in order to widen the margins of these oxide SFQ circuit components. The SFQ-dc converter that comprised double SQUIDs connected in series showed the output voltage as much as 0.3 mV at 22 K owing to high I/sub c/R/sub n/ value of the ramp-edge junction. Logic operations of the RS-FF, the confluence buffer and the splitter were correctly performed by using the SFQ-dc converter. Finite operating margins were obtainable for these circuits up to the temperature near 30 K.         Advanced design approaches for SFQ logic circuits based on the binary decision diagram    T. Nishigai, M. Ito, N. Yoshikawa, K. Obata, K. Takagai, N. Takagai, A. Fujimaki, H. Terai and S. Yorozu Summary: We have been investigating a design methodology of SFQ logic circuits based on the binary decision diagram (BDD). In the previously proposed BDD SFQ logic circuits, we have used one-to-two binary switches as a node cell in a BDD tree. In this study we will propose a new implementation method of SFQ BDD circuits, in which two nodes are implemented by using a 2-input 2-output switch gate. By employing the new approach, we have designed and implemented a one-bit full adder using the NEC 2.5 kA/cm/sup 2/ Nb standard process and the CONNECT cell library. The maximum operating frequency of the full adder was found to be 40 GHz by circuit simulations and 32.8 GHz by on-chip high-speed tests.         Complete Monte Carlo model description of lumped-element RSFQ logic circuits    C.J. Fourie, W.J. Perold and H.R. Gerber Summary: Over the last decade, Monte Carlo simulations have emerged as the most useful way of predicting the yield of RSFQ circuits, as they consider all manufacturing tolerance effects on a circuit, and are not restricted to bias current variations. Here we finally present a comprehensive definition of layout-extracted Monte Carlo model creation for lumped-element Spice simulations-from the local and global values for inductance, resistance and junction area from statistical models, to the inclusion of parasitics, layer-to-layer variations, variations in the penetration depth, and capacitance and mutual coupling. Finally, the addition of bias current trimming to the simulations to compensate for most global variations is described, and comparative yield results listed.         Possible approach to the driver design based on series SQIF    V.K. Kornev, I.I. Soloviev and O.A. Mukhanov Summary: Possible approach for the design of high-performance driver based on a series Superconducting Quantum Interference Filter (SQIF) is discussed. The main parts of the driver are described in details. The pulse broadening technique is suggested for increase of both the gain and the pulse upper frequency. Basic characteristics of the driver parts and the driver as a whole, as well as the successive pulse transforming have been simulated numerically. The results are presented and discussed in detail.         Demonstration of multiply-accumulate unit for programmable band-pass ADC    P.I. Bunyk, Q.P. Herr and M.W. Johnson Summary: We describe a recent demonstration of a Multiply-Accumulate (MAC) unit, the core of digital signal processor that implements programmable band-pass signal filtering. This MAC unit can be clocked at 20 GHz and is capable of performing 2.5 billion MAC operations per second for 7-bit data samples and 16-bit filter coefficients arriving in bit-serial mode. The unit was designed using VHDL for functional verification and timing optimization and it was implemented in Northrop Grumman Space Technology's (NGST's) 8 kA/cm/sup 2/ J110E Niobium process. We also describe our design approach, which resulted in this successful demonstration, and discuss lessons learned, particularly the risks associated with fringe field magnetic coupling between bias and signal lines.         Investigation of the parasitic coupling effects in densely packaged RSFQ digital circuits    B. Dimov, M. Khabipov, D. Balashov, C.M. Brandt, F.-Im. Buchholz, J. Niemeyer, T. Ortlepp and F.H. Uhlmann Summary: The Rapid Single Flux Quantum (RSFQ) technique is regarded as one of the most promising electronics due to its extremely high operating speed and low power consumption. Middle-scale RSFQ applications operating at multigigahertz frequency have recently been reported on. At such high operating frequencies, the on-chip interconnects start to play a limiting role for the performance of the densely packaged digital circuits. Our previous studies have theoretically investigated the parasitic coupling effects between superconductive microstrip transmission lines and conclusions have been drawn about the critical coupling levels of several typical microstrip geometries. Here, basic RSFQ structures are investigated experimentally, which contain a Josephson transmission line stage with large inductance and can either trap or pass SFQ pulses. These structures are incorporated in critical microstrip layouts, thus being subjected to parasitic coupling. The bias levels are monitored at which the structures start to pass the SFQ pulses with and without coupling influences. Thus, the conclusions of our previous theoretical investigations are verified experimentally.         Demonstration of a single-flux-quantum microprocessor using passive transmission lines    M. Tanaka, T. Kondo, N. Nakajima, T. Kawamoto, Y. Yamanashi, Y. Kamiya, A. Akimoto, A. Fujimaki, H. Hayakawa, N. Yoshikawa, H. Terai, Y. Hashimoto and S. Yorozu Summary: We have successfully demonstrated an 8-bit microprocessor using passive transmission lines based on single-flux-quantum LSI technology. In the microprocessor designed here, called CORE1/spl alpha/6, a simple bit-serial architecture with seven instructions was employed. In the CORE1/spl alpha/6, the floor plan was designed with consideration toward integration of a memory, and superconductive passive transmission lines (PTLs) were used to connect circuit blocks. Utilization of PTLs helped us reduce the propagation delay in long interconnections. The design flexibility of the floor plan was enhanced and the performance of the microprocessor was improved by 20% compared with our previous design. The CORE1/spl alpha/6 was composed of 6319 Josephson junctions and 15 PTLs with power consumption of 2.1 mW. We have confirmed the complete operations of the CORE1/spl alpha/6 by on-chip high-speed tests. The maximum clock frequencies for bit operation and instruction execution have been found to be 18 GHz and 1.2 GHz, respectively, where the performance corresponds to 240 million instructions per second (MIPS).         RSFQ digital signal processor for interference cancellation    I. Kataeva, Hongxia Zhao, Henrik Engseth, E. Tolkacheva and A. Kidiyarova-Shevchenko Summary: RSFQ high performance digital signal processor capable to perform up to 13 13-bit fixed-point GMACS has been designed for use in successive interference canceller in W-CDMA wireless systems. The performance of the processor has been verified by numerical simulations and VHDL simulation using accurate modeling of the RSFQ gates. Components of the processor, 4 /spl times/ 4 and 5 /spl times/ 5 parallel multipliers, 4 /spl times/ 5, 20 /spl times/ 5 and 4 /spl times/ 15 parallel shift registers have been designed and experimentally tested.         Progress of single flux quantum packet switch technology    S. Yorozu, Y. Kameda, Y. Hashimoto, H. Terai, A. Fujimaki and N. Yoshikawa Summary: With regard to sustaining future capacity of network traffic, the current hardware technology has a big bottleneck in terms of power consumption and insufficient operation speed. To overcome this bottleneck, we have developed a single flux quantum (SFQ) packet-switching circuit. We report recent progress in developing the SFQ packet-switching application. First, we demonstrate a 40 GHz, 160 Gb/s, 4 /spl times/ 4 packet switching circuit, which is currently the fastest clock frequency reported packet switch. Then, we describe a currently possible switching module using SFQ technology. Finally, we consider how SFQ technology can be used to scale the packet-switching capacity up to 100 Tbps.         Simulation and measurements on a 64-kbit hybrid Josephson-CMOS memory    Q. Liu, T. Van Duzer, X. Meng, S.R. Whiteley, K. Fujiwara, T. Tomida, K. Tokuda and N. Yoshikawa Summary: A 64-kbit sub-nanosecond Josephson-CMOS hybrid RAM memory is being developed with hybrid high-speed interface circuits. The hybrid memory is designed and fabricated by using commercially available 0.25 /spl mu/m and 0.35 /spl mu/m CMOS processes and the NEC (SRL) 2.5 kA/cm2 and UC Berkeley's 6.5 kA/cm2 Nb processes for Josephson junctions. In order to simulate the low-temperature CMOS circuits, 4 K CMOS device models are established by extracting from experiments. The measurements made at 4 K include static I-V characteristics, gate capacitances and source and drain capacitances. Details of the modeling are found in a companion paper in this issue. Performance of the high-speed interface circuits is optimized by minimizing the parasitic capacitance loading. Both the functional test and high-speed measurement for the interface circuit will be discussed. The whole structure of the memory, including interface circuit, decoder, memory cell, and Josephson read-out circuit is proposed and fabricated. From simulation, a total access time well below 1 ns is expected. The power for the whole system is about 32 mW at 1 GHz. Plans for further power and access time reduction are described.         Integrated millimeter/submillimeter superconducting digital spectrometer    I.V. Vernik, D.E. Kirichenko, S. Sarwana and D.K. Brock Summary: Compact mm/submm integrated spectrometers are required for radio-astronomical research, remote monitoring of the Earth atmosphere and environmental monitoring for hazardous materials of chemical and biological origin. Assembled on a multi-chip module the all superconducting integrated spectrometer offers integration of thin film analog components such as a mixer, superconducting local oscillator and an intermediate frequency SQUID amplifier together with superconducting digital circuitry. A Rapid Single Flux Quantum (RSFQ) 128-bit autocorrelator formed by 16-bit autocorrelator and a 112-bit programmable shift register that adjusts the data delay in increments of 16, is used for digitizing of the down converted signals and real-time digital processing. Experimental results showing both operation of components and the way to their successful integration are presented.         Single-flux-quantum (SFQ) circuit design and test of crossbar switch scheduler    Y. Kameda, S. Yorozu, Y. Hashimoto, H. Terai, A. Fujimaki and N. Yoshikawa Summary: A single-flux-quantum (SFQ) device provides fast operation with low power consumption. As SFQ devices can be applied in network switches requiring high throughput, we have been developing an SFQ network switch system. Not only the switch fabric but also the switch scheduler is a key component for a high-throughput network switch. The switch scheduler orders multiple inputs to a single output at the same time to prevent collisions from occurring in the switch fabric. The scheduling time becomes longer as the number of switch ports increases, because the scheduler must scan requests from all input ports. We designed two types of 4-port arbiters (i.e. switch scheduler sub-circuits) with structures based on serial or parallel processing. We chose to implement and demonstrate the serial arbiter because it has a smaller number of gates. It consisted of about 1800 Josephson junctions, including on-chip test circuitry. We tested a fabricated circuit at high speed and confirmed its correct operation at 40 GHz.         Error rate test of large-scale SFQ digital circuit systems    K. Fujiwara, N. Nakajima, T. Nishigai, M. Ito, N. Yoshikawa, A. Fujimaki, H. Terai and S. Yorozu Summary: We have been developing large-scale SFQ digital circuit systems and have shown the successful demonstration of our prototype SFQ microprocessors and memories. Their circuit scale is now over several thousands of junctions. One question arising in such large SFQ circuits is whether their error rate is low enough for digital applications. In this study, we have examined the error rate of circuit components of our microprocessor. An error rate test system for a program counter (PC) of the CORE1 microprocessor was made using Nb 2.5 kA/cm/sup 2/ process. The system is composed of a clock generator, a comparator and a 16-bit PC under test. It was found from the experiment that the system error rate of the 16-bit PC is lower than 10/sup -8/, which corresponds to a bit-error-rate better than 10/sup -12/. We have also evaluated a timing jitter of the clock generator and an effective temperature of the PC based on the experimental results.         Frequency multiply circuit for superconducting A/D converter    A. Yoshida, S. Hirano, H. Suzuki, S. Hasuo, K. Tanabe, T. Ito, T. Himi and H. Takai Summary: A new frequency multiply circuit generating a 20 GHz sampling clock from an external 5 GHz signal for a lowpass sigma-delta modulator was proposed and designed. The multiply circuit was composed of a ladder circuit, a modified Josephson transmission line (JTL) and T-flip flop (T-FF). We confirmed by numerical simulation that the period jitter of SFQ pulse trains generated by the ladder circuit could be reduced to a value small enough to realize 14-bit resolution for 10 MHz bandwidth by utilizing the repulsion effect between SFQ pulses in the modified JTL. The multiply circuit was fabricated by a 2.5 kA/cm/sup 2/ Nb process, and its correct operation was confirmed.         Limitations on performance of Superconductor oversampling ADCs    V.K. Semenov and A. Inamdar Summary: We discuss several general questions related to the development and optimization of superconductor oversampling modulators. We highlight the importance of specially engineered and parasitic components of the feedback loop. In particular, LR circuits operating as low-pass filters are capable of providing a noticeable SNR improvement and dramatically reducing the dynamic range requirements for used SFQ comparators. On the other hand, the feedback loop delay and time-jitter in timing circuits are able to spoil the potentially extremely high performance of superconductor oversampling ADCs. We also developed a simple formula describing time-jitter in superconductor circuits.         Twelve Giga-sample per second oscillator/counter A/D converter demonstration    M.W. Johnson, Q.P. Herr, B.J. Dalrymple, P. Bunyk and D.J. Durand Summary: We describe recent demonstration of a superconductor oscillator/counter A/D Converter up through 12 GS/s with 3 effective bits of signal-to-noise ratio at that sample rate, along with analysis of its performance. Measurements are described for an A/D converter implemented in Northrop Grumman Space Technology's 4 kA/cm/sup 2/ J110D Niobium process. This A/D Converter incorporates a new technique for defining the aperture using inter-Josephson transmission line SFQ repulsion. This technique is described here.         A study for an improved design of front-end circuit of Superconducting analog-to-digital converter    F. Furuta and K. Saitoh Summary: We have proposed an improved design of the front-end circuit for superconducting analog-to-digital (A/D) converters. The assumed structure of the A/D converter consists of a front-end circuit based on single flux quantum circuitry and a back-end circuit based on semiconductor circuits. To complete the A/D converter, it is necessary to enable synchronous operation between the front-end circuit and assumed back-end circuit. In the present framework, the front-end circuit consists of a ladder-type pulse generator, a modulator, a hybrid DEMUX, shift-registers and stack-type amplifiers. The voltage level of the output data signal is enlarged to about 10 mV by using stack-type amplifiers. Furthermore, the timing margin for synchronization is improved by using a hybrid demultiplexing method. We also have designed a front-end circuit based on the present framework and verified its functionalities at low speed. It was experimentally confirmed that the timing margin in a 1-to-4 hybrid DEMUX was enlarged to three times as large as in the conventional binary-tree DEMUX. A high-voltage output signal of 11 mV was also obtained. From these results, we conclude that functionalities of the designed front-end circuit are correct.         Stacked Nb-MoSi/sub 2/-Nb Josephson junctions for AC voltage standards    P.D. Dresselhaus, Yonuk Chong and S.P. Benz Summary: Superconductor-normal metal-superconductor (SNS) Josephson junctions have proven to be a critical technology for voltage standards. NIST has used SNS junctions for both dc and ac programmable voltage standards. Previous devices have used primarily PdAu as a normal-metal barrier material. In this paper we present measurements of circuits having MoSi/sub 2/ barriers. Stacking enables the junctions to be packed more densely, thus increasing design flexibility and margins for the microwave circuits. In this work, measurements are presented from two- and three-junction stacks for application to ac Josephson voltage standards, which show output voltage and distortion near our best previously published results.         New design and implementation of a fast modulator in NbN technology    E. Baggetta, B. Ebert, N. Hadacek, J.-C. Villegier and M. Maignan Summary: We have designed a band-pass sigma-delta modulator made in niobium nitride technology. The basic components of such a 10 GHz carrier frequency modulator are a band filtering resonator and an SFQ comparator synchronized with a clock frequency up to 200 GHz sampling rate. We describe the clock design including an internal JTL and its testing circuit based on frequency division. The technology involves NbN/Ta/sub x/N/NbN internally shunted Josephson junctions with Jc/spl sim/20kA/cm/sup 2/ and high RnIc product (/spl sim/1 mV) at 4.2 K. Junction parameters are shown to be controlled by the reactive sputtering conditions of the Ta/sub x/N barrier. SiO/sub 2//MgO bi-layers are used as dielectrics associated with NbN wiring layers and ground-plane. All layers are prepared in a way compatible with a full processing at about 350/spl deg/C in order to minimize the London penetration depth of NbN layers and thus to allow circuits operation at about 9 K. High frequency simulations of the modulator's circuits are presented, including the comparator, the DEMUX, and the resonator response.         HTS pulse-stretcher and second order Modulator: design and first results    A. Roussy, S. Karthikeyan, I. Oomen, T. Ortlepp, E.H. Sujiono, A. Brinkman and H. Rogalla Summary: One of the remaining challenges in the application of superconducting electronics is the interfacing between superconducting and semiconducting environments. The voltage and speed mismatch between RSFQ pulses and semiconducting read-out electronics makes it necessary to amplify as well as stretch the RSFQ pulses. Moreover, circuits based on HTS (High Temperature Superconductor) technology are very attractive since they can operate under considerably relaxed cooling effort, which is one of the main problems with LTS (Low Temperature Superconductor) circuits. Within the European project SuperADC, a HTS second order sigma delta modulator and a pulse stretcher, used as an interface between the modulator and the first semi-conducting amplifier stage, have been designed at Twente University and will be presented here.         Practical high-resolution programmable Josephson Voltage standards using double- and triple-stacked MoSi/sub 2/-barrier junctions    Yonuk Chong, C.J. Burroughs, P.D. Dresselhaus, N. Hadacek, H. Yamamori and S.P. Benz Summary: We have developed vertically stacked superconductor normal-metal-superconductor Josephson junction technology for the next-generation quantum voltage standards. Stacked junctions provide a practical way of increasing the output voltage and operating margins. In this paper, we present fully functioning programmable voltage standard chips with double- and triple- stacked MoSi/sub 2/ barrier Josephson junctions with over 100 000 junctions operating simultaneously on a 1 cm /spl times/ 1 cm chip. The maximum output voltages of the double- and triple-stacked chips were 2.6 V and 3.9 V, with respective operating current margins of 2 mA and 1 mA. A new trinary-logic design is used to achieve higher voltage resolution. Thermal transport in these high-density chips will be briefly discussed.         Flexible cryo-packages for Josephson devices    C.J. Burroughs, S.P. Benz, P.D. Dresselhaus, Yonuk Chong and H. Yamamori Summary: We have developed a method of bonding superconductive integrated-circuit chips to interchangeable, microwave-compatible, flexible cryo-packages. This "flip-chip on flex" technology will greatly improve the service life and reliability of our Josephson systems because the present press-contacts to the chip are replaced with directly soldered connections. The new method eliminates the most common failure mode for our Josephson chips, which has been the degradation and variation of the contact resistances of the chip pads due to mechanical wear upon repeated thermal cycles from 4/spl deg/K to room temperature. The superior microwave properties of this packaging provide improved operating margins for our devices. We have demonstrated the reliability of the bonds with repeated thermal cycling for 100% operational chips with 40 connections (67 410 Josephson junctions).         Fabrication of NbN-HEB mixers with fluoride radical etching Process    H. Kataoka, A. Kawakami, Y. Uzawa, Z. Wang and N. Kaya Summary: Hot electron bolometers (HEBs) are expected to be used as low-noise heterodyne mixers for applications in radio astronomy and remote sensing in the terahertz frequency region. We fabricated and tested HEB mixers for these applications; however, those we made with the conventional process easily broke due to thermal stress and electrical surges. To improve their durability, a new process involving fluoride radical etching was developed. In this process, HEB mixers were fabricated using a relatively thick NbN strip (several tens of nm). Finally, the NbN strip was etched that was less than 4-nm thick enough to operate as HEB mixers by using the fluoride radical etching. We confirmed that fluoride radical etching caused no damage to the etched NbN strip. The dc properties of the HEB mixers fabricated with the new process did not change for fourteen 4.2-300 K thermal cycles for 50 days. The receiver noise temperature of the HEB mixer was evaluated and it was about 615 K at 780 GHz.         An investigation of the performance of the superconducting HEB mixer as a function of its RF embedding impedance    D. Loudkov, C.-Y.E. Tong, R. Blundell, N. Kaurova, E. Grishina, B. Voronov and G. Gol'tsman Summary: We have conducted an investigation of the optimal embedding impedance for a waveguide superconducting hot-electron bolometric (HEB) mixer. Three mixer chip designs for 800 GHz, offering nominal embedding resistances of 70 /spl Omega/, 35 /spl Omega/, and 15 /spl Omega/, have been developed. We used both High Frequency Structure Simulator (HFSS) software and scale model impedance measurements in the design process. We subsequently fabricated HEB mixers to these designs using 3-4 nm thick NbN thin film. Receiver noise temperature measurements and Fourier Transform Spectrometer (FTS) scans were performed to determine the optimal combination of embedding impedance and normal-state resistance for a 50 Ohm IF load impedance. A receiver noise temperature of 440 K was measured at a local oscillator frequency 850 GHz for a mixer with normal state resistance of 62 /spl Omega/ incorporated into a circuit offering a nominal embedding impedance of 70 /spl Omega/. We conclude from our data that, for low noise operation, the normal state resistance of the HEB mixer element should be close to the embedding impedance of the mixer mount.         Performance of the NbTiN hot electron bolometer mixer with AlN buffer layer at terahertz frequency range    D. Loudkov, C.-Y.E. Tong, R. Blundell, K.G. Megerian and J.A. Stern Summary: We present recent measurements of receiver noise temperature and intermediate frequency (IF) bandwidth in the frequency range 0.8-1.3 THz for waveguide NbTiN HEB mixers of various dimensions. These devices are fabricated from an NbTiN film deposited on crystalline quartz substrates with AlN buffer layer. The lengths of the mixer elements vary from 0.3 to 0.5 /spl mu/m and their widths vary from 3 to 10 /spl mu/m. Critical temperatures are typically at 8.5 K, and the measured normal state resistance of the devices is about 1000 ohms per square. All the device DC parameters demonstrate a high degree of uniformity. A double side band noise temperature at 0.8 THz as low as 550 K has been measured at an IF frequency of 1.8 GHz, with a conversion loss of around 14 dB. At an IF of 3 GHz, the noise temperature increases to 750 K. We have also made extensive measurements of the IF bandwidth as a function of bias voltages and currents. At the optimal low-noise operation point, a 3-dB IF bandwidth of 1.2 GHz is obtained for a wide variety of device dimensions and bath temperature.         Nanoscale superconducting THz hot electron bolometers fabricated with UV lithography on ultra-thin Si beam lead chips    J.C. Schultz, A.W. Lichtenberger and J.Z. Zhang Summary: While focused E-beam and Focused Ion Beam patterning tools have been shown to be successful methods for defining nanoscale features of superconducting hot electron bolometers (HEBs), there are some drawbacks to these techniques. These serial processes are not widely available and are slow for producing large numbers of HEBs. Although device throughput has not been traditionally emphasized for typical HEB and microwave circuits, HEBs are very vulnerable to ESD damage and low circuit yield. Also, there is growing interest in building high density HEB receiver arrays. As an alternative to high-end nanolithography techniques, we have developed a novel "Suspended Sidewall Nano Patterned Stencil" (SSNaPS) process, which requires conventional I-line contact lithography, sputtering, and RIE tools, which are all commonly available. This method involves a conformal sputtering of Titanium over patterned polyimide steps and a subsequent anisotropic etch of Titanium on the horizontal surfaces. Thin lines of Ti remain on the sidewalls of the polyimide features whose width is determined by the thickness of the initial sputtered layer. These nanoscale Ti-lines, combined with micrometer scale Ti patterns, can be used for the accurate patterning required for superconducting HEB fabrication. This method allows for simplified parallel fabrication of large numbers of HEBs or other nanoscale devices and is available to most fabrication facilities.         NbN hot electron bolometer mixers: sensitivity, LO power, direct detection and stability    J.J.A. Baselmans, M. Hajenius, J.R. Gao, A. Baryshev, J. Kooi, T.M. Klapwijk, B. Voronov, P. de Korte and G. Gol'tsman Summary: We demonstrate that the performance of NbN lattice cooled hot electron bolometer mixers depends strongly on the interface quality between the bolometer and the contact structure. Both the receiver noise temperature and the gain bandwidth can be improved by a factor of 2 by cleaning the interface and adding an additional superconducting interlayer to the contact pad. Using this we obtain a double sideband receiver noise temperature of 950 K at 2.5 THz and 4.3 K, using a 0.4/spl times/4 /spl mu/m HEB mixer with a spiral antenna. At the same bias point, we obtain an IF gain bandwidth of 6 GHz. To comply with current demands on THz mixers for use in space based receivers we reduce the device size to 0.15/spl times/1 /spl mu/m and use a twin slot antenna. We report measurements of the noise temperature, LO power requirement, stability and the direct detection effect, using a mixer with a 1.6 THz twin slot antenna and a 1.462 THz solid state LO source with calibrated output power.         A distributed lumped-element SIS mixer with very wide instantaneous bandwidth    C.-yE. Tong, R. Blundell, K.G. Megerian, J.A. Stern, Shing-Kuo Pan and M. Pospieszalski Summary: A novel type of distributed superconducting mixer with very low output capacitance has been designed for a 330-420 GHz waveguide mixer. In this design, a pair of lumped element Superconductor-Insulator-Superconductor junctions is connected in series to form the unit cell of a composite transmission line. The mixer utilizes two cascaded cells. Using an intermediate frequency (IF) of 5 GHz, we have measured Double-side-band (DSB) receiver noise temperatures of 90-120 K between 360 and 410 GHz. This mixer design offers very wide instantaneous bandwidth. The measured IF bandwidth is in excess of 18 GHz. At a Local Oscillator frequency of 384 GHz, the Y-factor measured at an IF frequency of 18 GHz is 2.1, compared to a Y-factor of 2.2 measured at an IF of 5 GHz. The mixer also has a high dynamic range. The 1-dB input compression point is only reached with an input black body load of 30,000 K.         Local resistivity and the current-voltage characteristics of hot electron bolometer mixers    M. Hajenius, R. Barends, J.R. Gao, T.M. Klapwijk, J.J.A. Baselmans, A. Baryshev, B. Voronov and G. Gol'tsman Summary: Hot-electron bolometer devices, used successfully in low noise heterodyne mixing at frequencies up to 2.5 THz, have been analyzed. A distributed temperature numerical model of the NbN bridge, based on a local electron and a phonon temperature, is used to model pumped IV curves and understand the physical conditions during the mixing process. We argue that the mixing is predominantly due to the strongly temperature dependent local resistivity of the NbN. Experimentally we identify the origins of different transition temperatures in a real HEB device, suggesting the importance of the intrinsic resistive transition of the superconducting bridge in the modeling.         Fabrication of terahertz frequency phonon cooled HEB mixers    J.A. Stern, B. Bumble, J. Kawamura and A. Skalare Summary: We have successfully fabricated NbTiN phonon-cooled, hot-electron bolometers (HEBs) on silicon-on-insulator (SOI) substrates for use in terahertz-frequency waveguide mixers. At these frequencies our technology offers three significant advantages over the more common approach of using thin quartz substrates. Firstly, the SOI chips are more rugged than quartz, which become very fragile at the required thickness (<20 microns). Secondly, the outline of the chips is defined lithographically so that they can be given a nonrectangular shape that may be required for more complicated circuits. Thirdly, freestanding gold beam-leads are used to hold the chip in place in the waveguide block and to make good electrical connections at DC, IF (intermediate frequency) and signal frequencies. The SOI wafer is a 6 /spl mu/m thick Si layer bonded to a 400 /spl mu/m thick oxidized Silicon "handle" wafer. The HEBs and gold beam-leads are fabricated on front side of the SOI wafer. After processing the front side, the handle wafer is removed and the 6 /spl mu/m Si layer is patterned and etched to complete the device. Mixer measurements have been made with such devices at a signal frequency of 19 GHz, giving an IF bandwidth of about 1.4 GHz (under conditions that maximize low-frequency conversion efficiency). This bandwidth is close to that measured with similar devices on thicker silicon and on quartz.         Design and development of SIS mixers for ALMA band 8    W. Shan, T. Noguchi, Shengcai Shi and Y. Sekimoto Summary: In this paper, we report on the design and experimental results of a fix-tuned Superconductor-Insulator-Superconductor (SIS) mixer for Atacama Large Millimeter/submillimeter Array (ALMA) band 8 (385-500 GHz) receivers. Nb-based SIS junctions of a current density of 10 kA/cm/sup 2/ and one micrometer size (fabricated with a two-step lift-off process) are employed to accomplish the ALMA receiver specification, which requires wide frequency coverage as well as low noise temperature. Parallel-connected twin junctions (PCTJ) are designed to resonate at the band center to tune out the junction geometric capacitance. A waveguide-microstrip probe is optimized to have nearly frequency-independent impedance at the probe's feed point, thereby making it much easier to match the low-impedance PCTJ over a wide frequency band. In addition, a superconducting magnet fixed onto the compact mixer block to provide efficient magnetic field coupling is designed. The SIS mixer demonstrates a minimum double-sideband receiver noise temperature of 108 K at the band center and temperatures of less than 167 K over the whole band (for an intermediate-frequency range of 4-8 GHz).         IF gain bandwidth of membrane-based NbN hot electron bolometers for SHAHIRA    J. Baubert, M. Salez, H. Merkel, P. Pons, S. Cherednichenko, B. Lecomte, V. Drakinsky, G. Goltsman and B. Leone Summary: SHAHIRA (Submm Heterodyne Array for HIgh-speed Radio Astronomy) is a project supported by the European Space Agency (ESA) and is designed to fly on the SOFIA observatory. A quasi-optic design has been chosen for 2.5/2.7 THz and 4.7 THz, for hydroxyde radical OH, deuterated hydrogen HD and neutral atomic oxygen OI lines observations. Hot electron bolometers (HEBs) have been processed on 1 /spl mu/m thick SiO/sub 2//Si/sub 3/N/sub 4/ stress-less membranes. In this paper we analyse the intermediate frequency (IF) gain bandwidth from the theoretical point of view, and compare it to measurements.         Characterization of NbN HEB mixers cooled by a close-cycled 4 Kelvin refrigerator    L. Jiang, J. Li, W. Zhang, Q.J. Yao, Z.L. Lin, S.C. Shi, Y.B. Vachtomin, S.V. Antipov, S.I. Svechnikov, B.M. Voronov and G.N. Goltsman Summary: It is quite beneficial to operate superconducting hot-electron-bolometer (HEB) mixers with a close-cycled 4 Kelvin refrigerator for real applications such as astronomy and atmospheric research. In this paper, a phononcooled NbN HEB mixer (quasioptical type) is thoroughly characterized under such a cooling circumstance. The effects of mechanical vibration, electrical interference, and temperature fluctuation of a two-stage Gifford-McMahon 4 Kelvin refrigerator upon the characteristics of the phononcooled NbN HEB mixer are investigated in particular. Detailed measurement results are presented.         Inductive sensor based on nano-scale SQUIDs    L. Hao, J.C. MacFarlane, S.K.H. Lam, C.P. Foley, P. Josephs-Franks and J.C. Gallop Summary: Detectors with sufficient sensitivity to resolve the energy of single photons and particles combined with rapid response times are becoming increasingly important. We describe work in progress on a recently-proposed type of sensor, which we have named the Inductive Superconducting Transition Edge Detector (ISTED). We have theoretically estimated the energy sensitivity of such a sensor, in the case where the heat absorber is incorporated within the sensitive area of a nano-scale SQUID which acts as an inductive readout device. Recent results on the experimental characterization of prototype devices in the temperature range 5-8 K are presented, and ongoing work which is intended to achieve smaller device dimensions together with lower operating temperatures is described.         Noise of a superconducting photon detector    A. Semenov, A. Engel, K. Il'in, M. Siegel and H.-W. Hubers Summary: We have studied electrical noise of photon detectors representing long and narrow superconducting strips. For large bias currents close to the critical current fluctuations lead to localized, temporary transitions into the normal conducting state, which can be detected as voltage transients developing between the strip ends. We present models based on fluctuations of the chemical potential and current-assisted thermal-unbinding of vortex-antivortex pairs, which explain the current and temperature-dependence of the detector noise.         Noise and signal analysis of Ir/Au TES with asymmetrical slits parallel to the electric current    D. Fukuda, H. Takahashi, Y. Kunieda, N. Zen, M. Ohkubo and M. Nakazawa Summary: A multi-pixel TES array is one of the attractive methods to read-out the incident x-ray position, which simplifies a read-out circuit for imaging applications. We fabricated a ten-pixel Ir/Au TES microcalorimeter with asymmetrical slits parallel to the electric current, and analyzed its noise and signal characteristics. The device was successfully operated in a strong electro-thermal feedback (ETF) mode. However, very large excess noise is observed, which cannot be explained by the noise theory for a single pixel TES. We have modeled the multi-pixel TES array as separated thermal group components, and analyzed noise performance theoretically. As a result, the current noise in our theory is well agreed with the measured noise at a low frequency below 3 kHz. From the x-ray irradiation measurements, ten divided signal groups are observed, which will be associated with the incident x-ray position pixel. The best energy resolution was 18 eV (FWHM) for 5.9 keV x-rays at 0.5 /spl mu/V bias voltage.         Fabrication of Mo/Cu multilayer and bilayer transition edge sensors    Z.A. Ali, O.B. Drury, M.F. Cunningham, J.M. Chesser, T.W. Barbee Jr. and S. Friedrich Summary: We are developing cryogenic high-resolution X-ray, Gamma-ray and neutron spectrometers based on superconducting Mo/Cu transition edge sensors. Here we discuss the sensor design for different applications, present the photolithographic fabrication techniques, and outline future detector development to increase the spectrometer sensitivity.         Dynamic range of high temperature superconducting Josephson detecting systems at millimeter-wave band    Jian Chen, Peiheng Wu, K. Nakajima and T. Yamashita Summary: YBCO grain boundary Josephson junctions (GBJJ's), with the normal-state resistance (R/sub N/) around 1 /spl Omega/ and I/sub C/R/sub N/ product of less than 2 mV at 45 K, where I/sub C/ is the critical current of the junction, are used to study the dynamic range of high temperature superconducting (HTS) Josephson detecting systems at millimeter-wave band. A compact pulse tube cryocooler (PTC), or a liquid helium cryostat (LHC), or a liquid nitrogen cryostat (LNC) provides the necessary low temperature environment for the operation, while Gunn oscillators together with doubler generate signals at the frequencies of 50, 98, 196 GHz whose amplitude can be adjusted by a series of calibrated attenuators. By changing the junction parameters, operating frequencies, and the cryocooler or cryostat, we have carefully looked at the dynamic range of the system. For a measuring channel bandwidth of 1 Hz, the dynamic range is around 38 dB which is determined basically by the preamplifier. This indicates that the PTC does not introduce excess noise compared with other kinds of cryostats such as LHC's or LNC's. A measuring channel bandwidth up to 1 MHz can be helpful if fast measurements are needed.         Bandwidth and noise of submillimeter wave cuprate bicrystal Josephson junction detectors    G.A. Ovsyannikov, I.V. Borisenko, K.Y. Constantinian, Y.V. Kislinski, A.A. Hakhoumian, N.G. Pogosyan, T. Zakaryan, N.F. Pedersen, J. Mygind, N. Uzunoglu and E. Karagianni Summary: Detectors made from superconducting cuprate YBa/sub 2/Cu/sub 3/O/sub x/ bicrystal Josephson junctions (BJJs) on sapphire and NdGaO/sub 3/ substrates have been fabricated and characterized in the frequency band 200-900 GHz. Junctions on sapphire substrates had a normal state resistance R/sub N//spl ap/15-60 /spl Omega/, and I/sub C/R/sub N/ product up to 2.5 mV at T=4.2 K. Junctions on NdGaO/sub 3/ substrates had lower R/sub N/=1-5 /spl Omega/ and I/sub C/R/sub N/=0.4-0.9 mV at T=77 K. Three types of detecting devices have been investigated in both the broadband and the frequency-selective detection modes. One type was patterned with log-periodic antenna, and two others with Pt-metal double-slot antenna designed for a central frequency f=300 GHz and f=400 GHz, respectively. Measurements at f=320 GHz of the reception bandwidth /spl Delta/f for a device with double-slot antenna gave a quality factor Q=f//spl Delta/f/spl ap/10. A low-noise cooled 1-2 GHz bandwidth amplifier enables a better sensitivity in the self-pumping frequency mixing mode, avoiding the 1/f noise. The dependence of the spectral density of noise on voltage was compared to the data for the Josephson emission linewidth obtained by the selective detector response method. Also discussed are measurements at 500 GHz of the NEP values carried out at different experimental conditions.         On-chip integrated SQUID readout for Superconducting bolometers    T. May, V. Zakosarenko, E. Kreysa, W. Esch, S. Anders, L. Fritzsch, R. Boucher, R. Stolz, J. Kunert and H.-G. Meyer Summary: We present the first steps toward a 288 pixel sub-millimeter wavelength bolometer camera. We have used bolometers of the transition edge type, choosing a thermometer made of a proximity bilayer of Mo and the alloy Au/Pd with a designed transition temperature of about 500 mK. We have adapted our well-developed niobium based technology for SQUID manufacturing in order to be able to fabricate the current sensor and the bolometer on a common substrate. The function of both devices was successfully tested at the operating temperature of 300 mK.         Antenna coupled niobium bolometers for 10 /spl mu/m wavelength radiation detection    R.H. Hadfield, A.J. Miller, S.W. Nam, R.E. Schwall and E.N. Grossman Summary: We report on the fabrication and testing of antenna-coupled niobium bolometers for 10 /spl mu/m wavelength radiation detection. We use 20 nm thick Nb films on oxidized Si substrates. The bolometer design consists of a 1 /spl mu/m/spl times/1 /spl mu/m Nb microbridge embedded in either a dipole or a spiral Au antenna. We have performed dark dc tests on devices in vacuum at 4.2 K. Current biased dark measurements correspond well to established theory. This result allows us to extract an upper limit for the value of thermal conductance g (340 nWK/sup -1/)-hence an indirect measure of the device bandwidth (0.2 GHz). Measurements under incident black body radiation show that the radiation perturbs the return switching characteristics of the devices.         Origin of dark counts in nanostructured NbN single-photon detectors    J. Kitaygorsky, J. Zhang, A. Verevkin, A. Sergeev, A. Korneev, V. Matvienko, P. Kouminov, K. Smirnov, B. Voronov, G. Gol'tsman and R. Sobolewski Summary: We present our study of dark counts in ultrathin (3.5 to 10 nm thick), narrow (120 to 170 nm wide) NbN superconducting stripes of different lengths. In experiments, where the stripe was completely isolated from the outside world and kept at temperature below the critical temperature T/sub c/, we detected subnanosecond electrical pulses associated with the spontaneous appearance of the temporal resistive state. The resistive state manifested itself as generation of phase-slip centers (PSCs) in our two-dimensional superconducting stripes. Our analysis shows that not far from T/sub c/, PSCs have a thermally activated nature. At lowest temperatures, far below T/sub c/, they are created by quantum fluctuations.         Millimeter-wave sensitivity of YBCO grain boundary Josephson junctions coupled with coplanar waveguide-fed slot dipole antennas    K. Nakajima, N. Ebisawa, H. Sato, Jian Chen, T. Yamashita and Y. Sawaya Summary: Improvements in the coupling efficiency of millimeter wave quasioptically introduced to high-T/sub C/ Josephson junction detectors have been studied. Both increasing of junction resistance and implementation of a lower impedance antenna are required to improve the efficiency. We designed a coplanar waveguide feed slot dipole antenna as a low impedance antenna combined with the Josephson junction detectors. Improvements in the coupling efficiency due to decreasing of antenna impedance have been demonstrated and compared with numerically obtained results by the finite difference time domain method on the slot dipole antenna.         Calculation of the characteristics of coplanar resonators for kinetic inductance detectors    A. Porch, P. Mauskopf, S. Doyle and C. Dunscombe Summary: Photon detectors based on the change of kinetic inductance of a thin superconducting film have a number of applications, particularly in astronomy, owing to their high sensitivity and ease of integration into large arrays. Here we discuss in detail the analysis of kinetic inductance detectors that use thin film microwave coplanar resonators. Photon absorption decreases the electron pair density, increasing the magnetic penetration depth /spl lambda/, which causes a decrease in the resonant frequency (or phase) of an irradiated resonator. To quantify this effect, we first compute the resonator current distribution, from which the /spl lambda/-dependent parameters (such as kinetic inductance) are calculated. Optimum responsivity for phase measurement is achieved by using the thinnest film with the narrowest center conductor width at the lowest possible temperature. However, the responsivity is compromised by extrinsic microwave losses, in particular due to residual surface resistance, which is likely to be significant in the thinnest films.         Measurements and modeling of phonon cooling by electron-tunneling refrigerators    N.A. Miller, A.M. Clark, A. Williams, S.T. Ruggiero, G.C. Hilton, J.A. Beall, K.D. Irwin, L.R. Vale and J.N. Ullom Summary: We demonstrate cooling of the electrons and phonons of a silicon nitride (Si-N) membrane by solid-state refrigerators based on normal metal/insulator/superconductor (NIS) tunnel junctions. We report a temperature reduction of the Si-N membrane from 260 mK to 240 mK, while the electrons in the normal metal of the refrigerator are cooled to 145 mK. We explain the mechanism for cooling an isolated membrane and make quantitative comparisons between experiment and a finite-element thermal model. The model indicates that increasing the thermal conductivity of the cold-fingers, improving the transparency of the tunnel junctions, and reducing the power load through the membrane will make it possible to cool the membrane from 260 mK to below 170 mK. The refrigeration of a membrane makes it possible to integrate other cryogenic devices that require sub-Kelvin temperatures for optimal performance, such as thin-film sensors. We demonstrate this integration by combining NIS refrigerators with an x-ray Transition-Edge-Sensor (TES).         Surface micromachined transition edge sensor microcalorimeters on polyimide membranes    R. Cantor and J. Hall Summary: A surface micromachining process is described for the fabrication of transition edge sensor (TES) microcalorimeters on polyimide membranes. The TES consists of a low-stress superconductor/normal metal bilayer of Mo/Cu. The deposition parameters for the sputter-deposited Mo and Cu films are optimized using a design of experiment and statistical models to obtain a T/sub c/ around 100 mK, bilayer sheet resistance of around 15 to 20 m/spl Omega//sq, and low bilayer film stress of <100 MPa. To fabricate the membranes for the microcalorimeters, a sacrificial poly-Si film is sputter-deposited on a Si wafer with thermal oxide, after which poly-Si mesas are patterned where the membranes are to be formed. Then, a planarizing polyimide film is spin-coated on the wafer. After curing the polyimide, the TES bilayers and wiring layers are deposited and patterned using standard dry etch processes. To release the membranes, windows in the polyimide film above the poly-Si mesas are opened using a dry etch, and the sacrificial poly-Si is removed using a XeF/sub 2/ etch process. Using a polyimide film with low cure temperature (e.g., <200/spl deg/C), wiring and first-stage SQUID readouts for the TES may be deposited underneath the microcalorimeter prior to membrane fabrication, thereby simplifying the design of large, multi-pixel TES microcalorimeter arrays with integrated first-stage SQUID readouts.         Antenna-coupled bolometers for millimeter waves    M.J. Myers, P. Ade, G. Engargiola, W. Holzapfel, A.T. Lee, R. O'Brient, P.L. Richards, A. Smith, H. Spieler and H.T. Tran Summary: We report on the development of antenna-coupled bolometers using Transition-Edge Sensors (TES) for millimeter waves. Our design uses a double-slot dipole antenna which feeds superconducting niobium microstrip. Microstrip filters are used to define the frequency band to which the bolometers are sensitive. The microstrip is terminated with a load resistor and the dissipated power is measured using a TES. We present the results of electrical and optical characterization of single bolometer pixels and discuss the development of a large bolometer array based on this design. This array is being developed for a Cosmic Microwave Background (CMB) polarization anisotropy experiment.         Frequency-domain SQUID multiplexing of transition-edge sensors    T.M. Lanting, Hsiao-Mei Cho, J. Clarke, M.A. Dobbs, W.L. Holzapfel, A.T. Lee, M. Lueker, P.L. Richards, A.D. Smith and H.G. Spieler Summary: We describe our frequency-domain readout multiplexer for transition-edge sensor (TES) bolometers and present measurements of an eight-channel multiplexer. Each sensor is biased with a sinusoidal bias at a distinct frequency. As the sensor absorbs power, it amplitude-modulates its sinusoidal bias. Sensor currents are summed and measured with a single superconducting quantum interference device (SQUID) array. The SQUID array consists of 100 dc-SQUID's in series and is operated with shunt feedback electronics which have a slew rate of 1.210/sup 7/ /spl Phi//sub 0//s. A tuned filter consisting of an inductor and capacitor are placed in series with each sensor to both limit the bandwidth of the Nyquist noise from each sensor and to allow us to bias all multiplexed sensors with a common wire. We place an upper limit on crosstalk between adjacent channels of 0.004, well below our design requirements. Demodulated noise spectra from multiplexed sensors show the expected white noise levels at frequencies above 200 mHz.         Quantum efficiency and noise equivalent power of nanostructured, NbN, single-photon detectors in the wavelength range from visible to infrared    A. Korneev, V. Matvienko, O. Minaeva, I. Milostnaya, I. Rubtsova, G. Chulkova, K. Smirnov, V. Voronov, G. Gol'tsman, W. Slysz, A. Pearlman, A. Verevkin and R. Sobolewski Summary: We present our studies on the quantum efficiency (QE) and the noise equivalent power (NEP) of the latest-generation, nanostructured, superconducting, single-photon detectors (SSPDs) in the wavelength range from 0.5 to 5.6 /spl mu/m, operated at temperatures in the 2.0- to 4.2-K range. Our detectors are designed as 4-nm-thick and 100-nm-wide NbN meander-shaped stripes, patterned by electron-beam lithography and cover a 10/spl times/10-/spl mu/m/sup 2/ active area. The best-achieved QE at 2.0 K for 1.55-/spl mu/m photons is 17%, and QE for 1.3-/spl mu/m infrared photons reaches its saturation value of /spl sim/30%. The SSPD NEP at 2.0 K is as low as 5/spl times/10/sup -21/ W/Hz/sup -1/2/. Our nanostructured SSPDs, operated at 2.0 K, significantly outperform their semiconducting counterparts, and, together with their GHz counting rate and picosecond timing jitter, they are devices-of-choice for practical quantum key distribution systems and free-space (even interplanetary) quantum optical communications.         Performance of photon-number resolving transition-edge sensors with integrated 1550 nm resonant cavities    D. Rosenberg, A.E. Lita, A.J. Miller, S. Nam and R.E. Schwall Summary: Many quantum-information applications require high-efficiency, low-noise, single-photon detectors that operate at visible and near-infrared wavelengths. The tunable superconducting critical temperature and anomalously low electron-phonon coupling of tungsten make it a suitable material for the fabrication of transition-edge sensors (TESs) that meet these requirements. The quantum efficiency of a typical tungsten TES detector, intrinsically around 15% at 1550 nm, can be increased by placing the tungsten detector in a resonant cavity, but the performance of a device embedded in a cavity has not been tested previously. We demonstrate that the presence of the cavity does not adversely affect the sensitivity or response time, and we report on the device characteristics of a new generation of tungsten TESs with greater than 80% quantum efficiency at 1550 nm.         Gigahertz counting rates of NbN single-photon detectors for quantum communications    A. Pearlman, A. Cross, W. Slysz, J. Zhang, A. Verevkin, M. Currie, A. Korneev, P. Kouminov, K. Smirnov, B. Voronov, G. Gol'tsman and R. Sobolewski Summary: We report on the GHz counting rate and jitter of our nanostructured superconducting single-photon detectors (SSPDs). The devices were patterned in 4-nm-thick and about 100-nm-wide NbN meander stripes and covered a 10-/spl mu/m/spl times/10-/spl mu/m area. We were able to count single photons at both the visible and infrared telecommunication wavelengths at rates of over 2 GHz with a timing jitter of below 18 ps. We also present the model for the origin of the SSPD switching dynamics and jitter, based on the time-delay effect in the phase-slip-center formation mechanism during the detector photoresponse process. With further improvements in our readout electronics, we expect that our SSPDs will reach counting rates of up to 10 GHz. An integrated quantum communications receiver based on two fiber-coupled SSPDs and operating at 1550-nm wavelength is also presented.         Numerical Simulation of multi-junction bias circuits for superconducting detectors    K. Segall, J.J. Mazo and T.P. Orlando Summary: We present numerical simulations of a new biasing circuit for single photon detectors based on superconducting tunnel junctions. A single detector junction is replaced with a circuit of three junctions to achieve biasing of a detector junction at subgap currents without the use of an external magnetic field. The biasing occurs through the nonlinear interaction of the three junctions. We show nonlinear numerical simulation for different values of junction parameters and demonstrate that the biasing state is numerically stable against external fluctuations. The elimination of the external magnetic field potentially increases the capability of these types of photon detectors and eases constraints involved in the fabrication of large detector arrays.         Tantalum STJ for photon counting detectors    C. Jorel, P. Feautrier and J.-C. Villegier Summary: Superconducting Tunnel Junctions (STJ's) are currently being developed as photon detectors for a wide range of applications. These detectors are used because they are energy resolving photon counters, and they can be used from the infrared (2 /spl mu/m) to X-ray wavelengths with good quantum efficiency (80%). At visible wavelengths, the spectral resolution of STJ's can exceed one part in ten. The goal of this work is to develop STJ's for use in low-light astronomical applications in the near infrared. This work emphasizes two points: improvement of the epitaxial tantalum absorber and the development of a new fabrication process for Ta/Al-AlOx-Al/Ta STJ's. The main features of this process are that pixels have aligned electrodes and vias patterned through a protecting SiO/sub 2/ layer. These vias are used to contact the top electrode layer of the STJ. The AlOx tunnel barrier has symmetric Al-Ta trap layers on either side. The 150 nm thick Ta absorber is epitaxially grown on top of a thin Nb seed layer. Photon counting experiments with theses devices are presented at /spl lambda/=0.78 /spl mu/m. Digital filtering methods are used to compute the photon counting data in order to minimize noise.         A broad-band THz radiation detector using a Nb-based superconducting tunnel junction    C. Otani, T. Taino, R. Nakano, K. Hoshino, T. Shibuya, H. Myoren, S. Ariyoshi, H. Sato, H.M. Shimizu, S. Takada and K. Kawase Summary: We have proposed and been developing a new broad-band terahertz (THz) radiation detector using a Nb-based superconducting tunnel junction (STJ). The STJ's were fabricated on LiNbO/sub 3/ and LiTaO/sub 3/ mono-crystal substrates. We radiated monochromatic THz pulses in the range 1-2 THz with the pulse repetition rate of 49 Hz, and successfully detected the corresponding periodic signals via a charge-sensitive preamplifier. The current signal obtained by the derivative of the output signal gave the time response of about 15-20 microseconds. The frequency response was compared with that of a conventional pyro-electric sensor. We found their frequency response showed the similar shape in frequency, demonstrating the flat response of the STJ detector in 1-2 THz. These results show that the detector can be used as a broad-band THz and far-infrared radiation detector above the frequency corresponding to the energy gap of the superconductor used for the base electrode.         Characteristics of Superconducting series array tunnel junctions for heavy ions    H. Sato, M. Kurakado, Y. Takizawa, S. Shiki, M. Ohno, H.M. Shimizu, K. Morita, K. Morimoto, D. Kaji and T. Akiyama Summary: Heavy ion detection experiments were carried out with superconducting series array tunnel junctions. /sup 40/Ar beam from linear accelerator was introduced to a cryostat and stopped in a substrate on which series array tunnel junctions were fabricated. An energy resolution of 4.2% was obtained for 191 MeV /sup 40/Ar, but linearity proved poor for energy ranges from 136 MeV to 191 MeV.         The effect of X-ray irradiating superconducting tunnel junctions on Al/sub 2/O/sub 3/ and LiNbO/sub 3/ substrates    T. Taino, K. Hoshino, R. Nakano, C. Otani, H. Myoren, K. Kawase, H. Sato, H.M. Shimizu and S. Takada Summary: We have developed a phononmediated radiation detector using Nb-based superconducting tunnel junctions (STJs). The STJs are fabricated on a substrate as an absorber of the radiation, and a substantial amount of emergent phonons with an energy above the energy gap are detected. The performance of the detector depends on the collection efficiency of the phonons. A selection of an appropriate substrate is required for optimizing the detector performance. We fabricated Nb-based STJs on a Al/sub 2/O/sub 3/ and a LiNbO/sub 3/ substrates, and compared the pulse heights of substrate phonon events due to X-ray irradiation to the substrates. We found that the maximum pulse height of the phonon events for the LiNbO/sub 3/ substrate was about twice of that for the Al/sub 2/O/sub 3/ substrate, so that these spectra which was obtained from two STJs showed different shapes, especially the peak due to phonon events.         The responsivity of Ta-based STJ devices as a function of temperature and bias    I. Jerjen, E.C. Kirk, P. Lerch, A. Zehnder and H.R. Ott Summary: The potential of superconducting tunneling junctions (STJ) as energy resolving photon counters was proved in the range of 1 eV to 6 keV. In our laboratory we are producing and studying Ta/Al1/AlOx/Al2/Ta STJs. The responsivity of a STJ depends on the energy of the photon, the geometry of the STJ, the temperature and the bias point. We measured the dependence of the responsivity on the bias and the temperature. We model our devices with four quasiparticle populations coupled by the usual Rothwarf-Taylor balance equations. This simple approach appears to explain some of the observed features and doesn't require the introduction of local traps in the quasiparticle dynamics.         X-ray detection using superconducting tunnel junctions with polyimide insulation Layer    M. Yoshida, K. Hoshino, T. Taino, H. Myoren, S. Takada, K. Kikuchi, H. Nakagawa, M. Aoyagi, H. Sato and H.M. Shimizu Summary: We have fabricated Nb-based superconducting tunnel junctions (STJs) with Al trapping layers using the photosensitive polyimide insulation layer for X-ray detector. It is possible to simplify the fabrication process of the STJs, because the photosensitive polyimide is used as the insulation layer instead of conventional inorganic insulation films without an etching process in a vacuum chamber. The polyimide insulation layer expects to be stable for thermal cycling between 0.3 K and room temperature. The preliminary experiments of 5.9 keV radiation shows the energy resolution of 86 eV.         Diffusion-engineered quasiparticle multiplication for STJ single photon detectors    V.A. Savu, C.M. Wilson, L. Frunzio, D.E. Prober and R.J. Schoelkopf Summary: We have designed a diffusion-engineered, single-photon spectrometer in the optical-UV range using a superconducting tunnel junction. The optical photon is absorbed in a Ta film and creates excess quasiparticles. These trap into an Al tunnel junction. Internal charge multiplication is achieved with backtunneling, which occurs when the residence time of the quasiparticles near the junction is longer than the tunneling time. The collected charge is a multiple of the initially created charge. We implement backtunneling by geometrically constricting the outflow of quasiparticles, with a narrow lead. The outdiffusion time is set by the geometry of the narrow lead. Our geometry optimizes the energy resolution and count rate, while reducing the heating and noise seen with much longer confinement time. Long confinement times produce excess heating and noise, as we observed previously with quasiparticle confinement achieved via bandgap engineering.         Sensitivity and S/N-ratio of superconducting high-resolution X-ray spectrometers    O.B. Drury and S. Friedrich Summary: Superconducting tunnel junction (STJ) X-ray spectrometers have been developed for synchrotron-based high-resolution soft X-ray spectroscopy. We are quantifying the improvements in sensitivity and signal-to-noise ratio that STJ spectrometers can offer for the analysis of dilute specimens over conventional semiconductor and grating spectrometers. We present analytical equations to quantify the improvements in terms of spectrometer resolution, detection efficiency and count rate capabilities as a function of line separation and spectral background. We discuss the implications of this analysis for L-edge spectroscopy of first-row transition metals.         THz hot-electron photon counter    B.S. Karasik and A.V. Sergeev Summary: We discuss an implementation of a hot-electron transition-edge sensor (TES) capable of counting THz photons. The main need for such a THz calorimeter is spectroscopy on future space telescopes with a background limited NEP/spl sim/10/sup -20/ W/Hz/sup 1/2/. The micromachined bolometers will unlikely reach such sensitivity at temperatures above 10 mK. The hot-electron TES with sufficient sensitivity will still have a time constant /spl sim/0.1-1.0 ms that is too short for integrating a flux of THz background photons arriving at a rate of <100 s/sup -1/. The Hot-Electron Photon Counter based on a submicron-size superconducting Ti bridge with Nb Andreev contacts will be able to detect individual photons above 170 GHz due to its very low heat capacity. A discrimination of the low energy fluctuations with a threshold device would allow for realization of an NEP/spl sim/10/sup -20/ W/Hz/sup 1/2/ at /spl ges/1 THz while operating at 300 mK. With the sensor time constant of a few microseconds, the dynamic range is /spl sim/30-40 dB. A compact array of the antenna-coupled counters can be fabricated on a silicon wafer without membranes.         Time-resolved carrier dynamics in Hg-based high-temperature Superconducting photodetectors    X. Li, Y. Xu, S. Chromik, V. Strbik, P. Odier, D. De Barros and R. Sobolewski Summary: We present fabrication and optical time-resolved photoresponse characterization of Hg-based high-temperature superconducting (HTS) thin films. The films were prepared from RF-magnetron-sputtered precursor films by an ex-situ mercuration process. Femtosecond, time-resolved, optical pump-probe spectroscopy measurements gave insight into the details of the Cooper-pair breaking and formation processes in our Hg-based films at temperatures far below the material's critical temperature. We observed that the Cooper-pair dynamics is not limited by the phonon bottleneck, which makes this HTS compound the material-of-choice for ultrafast optoelectronics applications.         Fabrication development for nanowire GHz-counting-rate single-photon detectors    J.K.W. Yang, E. Dauler, A. Ferri, A. Pearlman, A. Verevkin, G. Gol'tsman, B. Voronov, R. Sobolewski, W.E. Keicher and K.K. Berggren Summary: We have developed a fabrication process for GHz-counting-rate, single-photon, high-detection-efficiency, NbN, nanowire detectors. We have demonstrated two processes for the device patterning, one based on the standard polymethylmethacrylate (PMMA) organic positive-tone electron-beam resist, and the other based on the newer hydrogen silsesquioxane (HSQ) negative-tone spin-on-glass resist. The HSQ-based process is simple and robust, providing high resolution and the prospect of high fill-factors. Initial testing results show superconductivity in the films, and suggest that the devices exhibit photosensitivity.         Multi-channel HTS rf SQUID gradiometer system recording fetal and adult magnetocardiograms    Yi Zhang, N. Wolters, D. Lomparski, W. Zander, M. Banzet, J. Schubert, H.-J. Krause and P. van Leeuwen Summary: We report on experiments with a multi-channel HTS radio-frequency (rf) SQUID gradiometer for recording fetal and adult magnetocardiograms. Four sensing SQUID magnetometers and two common reference SQUID magnetometers form a 4 channel electronic gradiometer system of either first or second order. The magnetometers consist of HTS step edge SQUIDs and flux concentrators fabricated from YBaCuO thin films, with dielectric substrate resonators serving as tank circuits. With a washer area of 18 mm in diameter, all six magnetometers reached a field sensitivity of 20-30 fT//spl radic/Hz. Each gradiometer channel is formed using two or three such magnetometers with individual readouts in electronic difference. The dc and rf crosstalk between any channel pair was measured. In ordinary operation we did not find any noise contribution from neighboring channels, even though the resonant frequencies of the resonators are closely spaced. In a standard magnetically shielded room, using a first-order gradiometer configuration with an ultra-long baseline of about 20 cm, we demonstrated 4 channel real-time heart signal recordings of a fetus in the 33rd week of gestation.         SQUID-based simultaneous detection of NMR and biomagnetic signals at ultra-low magnetic fields    M.A. Espy, A.N. Matlachov, P.L. Volegov, J.C. Mosher and R.H. Kraus Jr. Summary: Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) at ultra-low magnetic fields (ULF, fields of /spl sim//spl mu/T) have several advantages over their counterparts at higher magnetic fields. These include narrow line widths, the possibility of novel imaging schemes such as T/sub 1/ weighted images, and reduced system cost and complexity. In addition, ULF NMR/MRI with superconducting quantum interference devices (SQUIDs) is compatible with simultaneous measurements of biomagnetic signals, a capability conventional systems cannot offer. SQUID-based ULF MRI has already been demonstrated, as have measurements of simultaneous MEG and NMR at ULF. In this paper we will show simultaneous magnetocardiography (MCG) and magnetomyography (MMG) with NMR are also possible. Another compelling application of NMR/MRI at ULF is the possibility of directly measuring magnetic resonance consequences of neuronal signals. In this paper we explore simultaneous MMG/NMR and MCG/NMR for an effect on the NMR signal, in T/sub 2//sup */, that might be associated with the effects of bioelectric currents.         Development of mice biomagnetic measurement system using dc-SQUID magnetometer    Y. Ono, A. Ishiyama, N. Kasai and A. Odawara Summary: A biomagnetic measurement system on mice using a dc superconducting quantum interference device magnetometer has been developed. We are going to use it for comparative magnetoencephalogram (MEG) and magnetocardiogram (MCG) studies of transgenic mice to clarify the functional influence of gene modification in a living body. The system has a low-T/sub c/ direct coupled dc SQUID. A focuser type pickup coil whose outside/inside diameter is 1 mm/100 /spl mu/m was adopted for detailed functional mapping of the brain or the heart of mice. The minimum lift-off distance was reduced to 700 /spl mu/m to achieve the sufficient spatial resolution and magnetic field sensitivity. The field sensitivity of this system is 1.3 pT/Hz/sup 1/2/ in the white-noise region (10 Hz-10 kHz). The MCG of a wild mouse at 9-months of age was measured and compared with the data of 3-month old mice. The spatial and time changes of MCG signals were similar in both ages of mice, while the amplitude of MCG signals of 9-month mice was less than 40% of that of 3-month mice. This decrease in MCG amplitude may be due to aging. The result suggested the capability of our system in evaluating the mice MCG signals.         Compact readout electronics for 62-channel DROS magnetocardiogram system    Jin-Mok Kim, Yong-Ho Lee, Kiwoong Kim, Hyukchan Kwon, Yong-Ki Park and I. Sasada Summary: Compact and low-cost SQUID electronics to operate double relaxation oscillation SQUIDs (DROSs) has been constructed for detecting magnetocardiogram (MCG) fields. SQUID electronics consists of low-noise preamplifier with a white noise of 0.6 nV//spl radic/Hz, flux-locked loop (FLL) circuit with auto-reset, and interface circuit to control FLL using 3 digital lines from a computer. The automatic control software adjusts SQUID parameters to the optimum operating condition within 15 seconds for 62 channels. Outputs of FLL circuits are passed through the hardware filter box to the 64-channel data acquisition board. Each SQUID electronics for FLL and digital control is built together on a printed circuit board of 45 mm /spl times/ 95 mm. When SQUID electronics is connected to DROS gradiometer with typical flux-to-voltage transfers of 1 mV//spl Phi//sub o/, the noise contribution of FLL circuit is about 0.6 /spl mu//spl Phi//sub o///spl radic/Hz or 0.6 fT//spl radic/Hz at 100 Hz, low enough to measure MCG fields.         Tangential cardiomagnetic field measurement system based on double relaxation oscillation SQUID planar gradiometers    Yong-Ho Lee, Jin-Mok Kim, Kiwoong Kim, Hyukchan Kwon, In-Seon Kim, Yong-Ki Park, Young-Guk Ko and N. Chung Summary: We present a 62-channel double relaxation oscillation SQUID (DROS) planar gradiometer system to measure magnetocardiogram (MCG) signals tangential to the chest surface. The DROSs were fabricated using Nb/Al-oxide/Nb junctions, and provided flux-to-voltage transfers of larger than 1 mV//spl Phi//sub 0/ typically, which is large enough for direct readout by room-temperature flux-locked loop (FLL) circuits. The analog FLL circuits and digital control circuits are made in a single printed circuit board. The planar gradiometers are integrated, series-connected first-order pickup coils with a baseline of 4 cm. White noise level of the planar gradiometer is about 1.5 (fT/cm)//spl radic/Hz or 6 fT//spl radic/Hz, operated inside a magnetically shielded room. The planar gradiometers were arranged to measure dB/sub x//dz and dB/sub y//dz simultaneously. The covering area of the 62 channel system is 162 mm /spl times/ 162 mm, which is smaller than the sensor coverage area of vertical measurement systems, but large enough to measure the essential MCG field distribution in a single position measurement.         High-T/sub c/ SQUID magnetometers for low noise measurements of magnetocardiograms    I.-S. Kim, K.K. Yu, Y.H. Lee, K.W. Kim and Y.K. Park Summary: YBCO dc superconducting quantum interference device (SQUID) magnetometers based on bicrystal junctions have been fabricated for magnetocardiograph measurements. The pickup coil of the device was designed employing 16 parallel loops with 50-/spl mu/m-wide lines. Noise performance was improved by applying a modification in the coupling line between pickup loop and SQUID washer. We could obtain optimized SQUID magnetometer design having magnetic field noise of about 38 fT/Hz/sup 1/2/ at 1 Hz and about 20 fT/Hz/sup 1/2/ at 100 Hz with an 1/f corner frequency of 2 Hz, measured inside a magnetically-shielded room. Demonstration of magnetocardiograph measurements showed quite promising results with high signal-to-noise ratio of 82 with a moderate magnetic shielding.         Development of multisample biological immunoassay system using HTSSQUID and magnetic nanoparticles    A. Tsukamoto, K. Saitoh, D. Suzuki, N. Sugita, Y. Seki, A. Kandori, K. Tsukada, Y. Sugiura, S. Hamaoka, H. Kuma, N. Hamasaki and K. Enpuku Summary: We developed a prototype magnetic immunoassay system using a high temperature superconductor (HTS) superconducting quantum interference device (SQUID) to investigate the performance and usability of the magnetic immunoassay. The system is designed to measure multiple samples and liquid samples, and it can work in an unshielded environment at a medical facility. To reduce the disturbance from environmental noise, the SQUID and samples are covered with three-layers of permalloy magnetic shield. The SQUID and magnetic shield are set in an aluminum box which acts as an RF shield. A gradiometer with a 5 /spl times/ 10 mm pickup coil, which is cooled by liquid nitrogen through a sapphire/Cu rod, is used as a sensor. We also developed a nonmagnetic sample disk with 12 reaction cells and examined 12 samples in one measurement sequence. The measurement process is controlled by a computer, which perform data averaging. Fe/sub 3/O/sub 4/ nanoparticles with a 25-nm diameter were used as test samples. After applying a magnetic field of about 0.1 T, we measured the remanent magnetic field from the Fe/sub 3/O/sub 4/ nanoparticles. The present system could detect 30 pg of Fe/sub 3/O/sub 4/ nanoparticles. This result was obtained by averaging 100 trials under an unshielded laboratory environment. The measurement time for 100 trials was only 100 s.         Magnetic immunoassays utilizing magnetic markers and a high-T/sub c/ SQUID    K. Enpuku, K. Inoue, K. Soejima, K. Yoshinaga, H. Kuma and N. Hamasaki Summary: Magnetic immunoassays utilizing magnetic markers and a high-T/sub c/ SQUID have been performed. We first showed a design of the SQUID for the sensitive detection of the magnetic signal from the marker, where the spatial distribution of the signal field was taken into account. Using the design, we can obtain the relationship between the magnetization of the maker and the signal flux detected with the SQUID. This relationship is important for quantitative evaluation of the immunoassay. Next, we detected biological materials called IgE with a remanence measurement method, where a marker made of Fe/sub 3/O/sub 4/ particles with diameter of 25 nm was used. We showed that 2 atto-mol of IgE can be detected, which shows high sensitivity of the present method.         A DNA detection system based upon a high Tc SQUID and ultra-small magnetic particles    S. Tanaka, Z. Aspanut, H. Kurita, C. Toriyabe, Y. Hatsukade and S. Katsura Summary: A high Tc SQUID system for biological molecules (DNA) detection is developed. This system is based on a hybridization process. Two strands in a DNA molecule are held together by hydrogen bonds between base pairs like a ladder. The two strands are referred to as being complementary each other. HPVB 33 (Human Papillomavirus Probes 33) was prepared as a DNA. One strand (Sample DNA) was labeled with Fe/sub 3/O/sub 4/ ultra-small magnetic particles and the other (probe DNA) was anchored on a glass slide. Then they were hybridized each other on the slide. After washing the excess sample DNA, the hybridized DNA was evaluated in the presence of excitation ac field by high Tc SQUID. The signal was initially proportional to the concentration of the sample DNA and then saturated. It means that the hybridization occurred successfully between the sample DNA and the probe DNA.         Nanomagnetic particles for SQUID-based magnetically labeled immunoassay    H.E. Horng, S.Y. Yang, Y.W. Huang, W.Q. Jiang, C.-Y. Hong and H.C. Yang Summary: With the increasing importance of SQUID-based magnetically labeled immunoassay, the study on the synthesis of controllable sizes of magnetic nanoparticles plays a role to promote the accuracy of the immunoassay. In this work, Fe/sub 3/O/sub 4/ nano-particles coated with a suitable bio-probe (biotin) are synthesized through chemical co-precipitation process to probe the bio-target (avidin). Through the synthesis developed here, the particle hydrodynamic diameter can be adjusted from 30 to 90 nm, which provide candidates for probing various bio-targets in the future. The amount of the magnetically labeled avidin is then analyzed via measuring the saturated magnetization or the remanence of the sample by using a SQUID magnetometer.         A 30-channel SQUID vector biomagnetometer system optimized for reclining subjects    Y. Adachi, J. Kawai, M. Miyamoto, S. Kawabata, H. Okubo, Y. Fukuoka, H. Komori and G. Uehara Summary: We propose an LTS-SQUID biomagnetometer system equipped with vector magnetometers for the purpose of measuring the evoked magnetic field from the spinal cord. In case of measurement around the neck, the number of sensors to be arranged is inevitably limited by the small observation area. To acquire more information on the magnetic field distribution in a limited area, we introduced a vector magnetometer, which has an axial-type gradiometric pick-up coil and two planar-type gradiometric pick-up coils located orthogonal to each other, which detects not only the magnetic field component radial to the body but also the tangential components. The cryostat was designed to put the SQUID sensors close to the back or back of the neck of the subject sitting in a reclining position, so that the subject can relax and hold the position throughout a long-time measurement. The fluctuation caused by the subject's movement can be suppressed. We installed 10 vector magnetometers arranged in a zigzag pattern in the cryostat and successfully detected the biomagnetic signals from the neck of the subject.         Instrumentation for simultaneous detection of low field NMR and biomagnetic signals    A.N. Matlachov, P.L. Volegov, M.A. Espy, R. Stolz, L. Fritzsch, V. Zakosarenko, H.-G. Meyer and R.H. Kraus Jr. Summary: We have built and demonstrated a simple system with open geometry that measures biomagnetic signals such as magnetoencephalogram (MEG), magnetocardiogram (MCG) and magnetomyogram (MMG) simultaneously with low field nuclear magnetic resonance (NMR) free induction decay signals (FID). The system employs LT/sub C/ SQUID gradiometers and can operate with proton Larmor frequency in the 80 Hz-10 kHz range. A pre-polarizing field of up to 60 mT is generated by resistive coils. Two different types of SQUID gradiometers were used: a tangential thin-film planar first-order gradiometer and an axial second-order gradiometer. The gradiometers were placed inside a fiberglass dewar at about 1 cm distance from a subject. All measurements were performed inside a single-layer magnetic shielded room. This system is the prototype for a system that will ultimately be capable of measuring biomagnetic signals together with magnetic resonance images (MRI).         High-T/sub c/ SQUID-based impedance magnetocardiography    V. Vajrala, D. Nawarathna, J.R. Claycomb and J.H. Miller Jr. Summary: We report impedance magnetocardiography (I-MCG) measurements carried out in a partially shielded environment. In these measurements, a small-amplitude ac current is injected through the torso via outer electrodes and the ac magnetic fields are probed with a high-Tc SQUID magnetometer. We have also performed simulations using an axisymmetric finite element method (FEM) model in order to predict the SQUID response to changes in tissue conductivity and blood volume during the cardiac cycle. The heart is modeled as a nested sphere inside an idealized conducting thorax. The current density and resulting magnetic field are calculated during two phases of the cardiac cycle. Calculated field values are compared to experimental results. FEM simulations are extended to model the induced current density and SQUID response during noncontacting I-MCG.         Examination of relationship between resistivity and photocurrent induced magnetic field in silicon wafers using laser SQUID    M. Daibo and D. Kamiwano Summary: Using the laser SQUID method, we examined the relationship between silicon wafer resistivity and magnetic field. By irradiating the wafer with a 3.2 W high-power laser beam, we were able to generate a measurable magnetic field perpendicular to the wafer, even for the wafers without p-n junctions. For samples having resistivities of 130 /spl Omega//spl middot/cm or less, we observed magnetic field distributions in the form of concentric circles. Histogram analysis showed that as resistivity decreases, mean value of magnetic field and standard deviation increase. For p-type wafers having resistivities of up to 300 /spl Omega//spl middot/cm, both mean value of magnetic field and standard deviation vary as a power law with respect to resistivity. However, for samples having resistivities of 300 /spl Omega//spl middot/cm or higher, the relationship was saturated, and determining resistivity was difficult. Since the laser SQUID method can be used to measure resistivity without electrical contact, it works well even for wafers with surface oxide films, and does not cause contamination.         Sampling method to extend bandwidth of scanning SQUID microscopes    J. Matthews, C.P. Vlahacos, S.P. Kwon and F.C. Wellstood Summary: We present preliminary results on the development of a 4.2 K scanning SQUID microscope with a bandwidth in the GHz range. We have overcome the bandwidth limitations of traditional scanning SQUID microscopes, which use a flux-locked loop, by using a hysteretic SQUID and a pulsed sampling technique. We describe the overall design and operation of our measurement system, and present high-speed measurement results.         A new software for the processing of SQUID-microscopy images    S.A. Andreenko, O.V. Snigirev, A.G. Maresov, M. Muck and F. Scholz Summary: We have developed a program running on the Windows platform which enhances the quality of two-dimensional images acquired by a scanning SQUID microscope. The program can also be used for image processing of data from other SQUID based systems, such as eddy current SQUID NDE systems. A general description of the program and the incorporated additional digital filters for removing image artifacts in the Fourier space is given. The user interface is presented as well as several examples of this software applications to real images.         Vortex imaging in microscopic superconductors with a scanning SQUID microscope    S. Okayasu, T. Nishio, Y. Hata, J. Suzuki, I. Kakeya, K. Kadowaki and V.V. Moshchalkov Summary: Direct observation of vortex arrangement in microscopic superconductors is achieved with a scanning SQUID microscope. Newly 2 /spl mu/m diameter sensing pickup coil is developed for the observation of giant vortex state. Vortex arrangements in 10 /spl mu/m triangles is investigated with the new pickup device. No giant vortex state, however, can be seen under this experimental condition. Further investigation is needed.         Portable SQUID NDE system for practical application    S. Nakayama, M. Ikeda, K. Chinone, K. Isawa, S. Takagi and S. Tosaka Summary: A portable SQUID NDE system was developed for practical use in industrial applications. The system consists of a high order DC-SQUID gradiometer, a downsized liquid helium cryostat, battery-operated electronics and a computer for data acquisition and controlling the system by customized software. Experiments confirmed that the system was quite useful in practical applications due to its rapid moving (as high as 100 mm/s) and free movability in the Earth's magnetic field without the need for magnetic shielding.         Electronic axial HTS dc SQUID gradiometer cooled by pulse-tube cooler    D.F. He, M. Yoshizawa, M. Nakamura and H. Itozaki Summary: An electronic axial high-T/sub c/ dc SQUID gradiometer cooled by pulse-tube cooler was developed. In order to extend the operating times, a method of temperature control was used to stabilize the operating temperature of the SQUID. We used the SQUID gradiometer cooled by pulse-tube cooler to perform eddy-current nondestructive evaluation and corrosion signal detection in an unshielded environment.         NDE of defects in Superconducting wires using SQUID microscopy    Su-Young Lee, V. Viswanathan, J. Huckans, J. Matthews and F.C. Wellstood Summary: Using a scanning Superconducting Quantum Interference Device (SQUID) microscope we have examined small samples of Nb-Ti wire with known defects and a sample with artificial defects. We orient the SQUID to measure the field parallel to the wire, which is near zero unless a defect is present. We also have examined known defects using a multi-channel scanning SQUID microscope. In addition, we have modified the nose cone of our SQUID microscope to enable fast NDE of long wires by positioning a thin tube immediately beneath the SQUID chip, while feeding the wire through the tube.         Electromagnetic non-destructive evaluation of fiberglass/aluminum laminates using HTS SQUID magnetometers    C. Bonavolonta, G.P. Pepe, G. Peluso, M. Valentino, G. Caprino and V. Lopresto Summary: The aerospace and aeronautical industries pay much attention to improve flight safety of the airlines. In aircraft design it is important to couple low structural weight with high damage tolerance. For this reason, a new class of advanced composite materials, named Fiber/Metal Laminates (FML), which combine the best features of organic matrix composites and metals, are used. In this work, a nondestructive evaluation of FML specimens based on an eddy-current technique that uses an HTS SQUID (Superconductive QUantum Interference Device) magnetometer is proposed. The aim is to demonstrate that this technique is capable of detecting the presence of damage hidden by plastic deformation after impact events.         Practical scanning SQUID system for nondestructive evaluation    K. Isawa, S. Takagi, S. Tosaka, S. Nakayama, M. Ikeda and K. Chinone Summary: An advanced scanning Superconducting Quantum Interference Device (SQUID) system called a "Traveling SQUID-NDE" was developed for nondestructive evaluation (NDE). The traveling SQUID-NDE can continuously "travel" back and forth over the surface of an object during testing without the need for magnetic shielding. Such movement by the SQUID sensor itself enables the SQUID-NDE to scan objects of unlimited size. In this work, the traveling SQUID-NDE system was combined with a manipulator used by conventional robots (either rectangular-type or articulated-type) used in industry, to manipulate the SQUID sensor for travel across an object. The effectiveness of this robotic traveling SQUID-NDE system was demonstrated by using it to detect artificial damage in stainless steel samples. This robotic traveling SQUID-NDE system proved useful for measuring two-dimensional magnetic images of fixed objects.         Characterization of stainless steel inertia welds using HTS SQUID NDE    C. Carr, M.A. Espy, T.G. Abeln and R.H. Kraus Jr. Summary: Inertia welding has become one of the key joining technologies in the aerospace industry with, at present, no reliable and reproducible nondestructive technique to evaluate weld quality. We previously reported on the preliminary studies of solid-state inertia welds in stainless steel using HTS SQUID magnetometers. A comparison of the SQUID data with that obtained from destructive metallurgical analyses of the welds was not conclusive, due mainly to the limited range in perceived weld quality of the sample set investigated. In this paper we report on eddy current-based measurements carried out on a set of stainless steel samples fabricated using parameters designed to create a wider range of weld qualities.         Mobile cryocooler-based SQUID NDE system utilizing active magnetic shielding    Y. Hatsukade, T. Inaba, Y. Maruno and S. Tanaka Summary: A mobile cryocooler-based SQUID NDE system was developed for realization of NDE of fixed targets that can't be moved or rotated. In order to move the SQUID in an ambient field, an active magnetic shielding technique employing a compensation coil and feedback circuit including a band elimination filter was introduced in a SQUID NDE system. The HTS SQUID gradiometer was cooled by a coaxial pulse tube cryocooler to 74 K /spl plusmn/ 0.04 K. The flux noise caused by moving the SQUID at 32 mm/s was well suppressed. Unlocking of the flux-locked loop (FLL) circuit or a significant increase in noise did not occur during the motion. Detection of hidden slots in fixed single and double-layered carbon/carbon composites in ambient field was demonstrated by moving the HTS SQUID gradiometer.         Detection of magnetic contaminations in industrial products using HTS SQUIDs    H.-J. Krause, G.I. Panaitov, N. Wolters, D. Lomparski, W. Zander, Yi Zhang, E. Oberdoerffer, D. Wollersheim and W. Wilke Summary: Many products in the pharmaceutical and food industry are packaged in metallized wrappings. With standard high-frequency search coil metal detectors, they can only be tested for metal contaminations before they are wrapped. However, a key requirement of industrial quality control is the inspection of the products at the end of the production line. We have developed an inspection system for detecting the magnetic remanence of the contaminants. The system utilizes two HTS rf SQUID magnetometers with step edge junctions immersed in liquid nitrogen. The SQUIDs are arranged such that they cover the product channel in a rotated planar electronic gradiometer configuration. In order to suppress the low-frequency magnetic disturbances typically found in industrial environment, the product channel and the SQUID system were mounted inside a coaxial three-layer Mumetal shield. In combination with the gradiometric suppression, homogeneous low-frequency disturbance fields were attenuated by a factor of 400,000. The sensitivity of the system for small magnetic particles was determined experimentally, using numerous steel balls and splinters. A stainless steel particle of 3 /spl mu/g, corresponding to a sphere diameter of 0.09 mm, was detected with and without aluminized wrapping.         Nondestructive evaluation of various materials using a SQUID-based eddy-current system    M. Muck, M. Korn, C. Welzel, S. Grawunder and F. Scholz Summary: We have investigated the applicability of SQUIDs for nondestructive evaluation of various materials from industrial production. For this purpose, we tested production samples and compared the results with other NDE methods such as conventional eddy-current or ultrasonic testing. The materials investigated included niobium sheets for superconducting resonators and indium-tin-oxide sputtering targets for solar panels. Especially for the case of thick, highly conductive or ferromagnetic materials, as well as sintered materials, we found that the SQUID-based systems show a much higher sensitivity compared to conventional eddy-current NDE and ultrasonic testing. In addition, the SQUID systems have the advantage that the sample does not need to be immersed in water (which is necessary for ultrasonic testing), which can lead to serious degradation of sample quality.         SQUID probe microscope with through-hole SQUID    T. Hayashi and H. Itozaki Summary: We have developed a high T/sub C/ SQUID probe microscope for investigation of samples at room temperature in air. A high permeability probe needle was used as a flux guide to improve the spatial resolution. A directly coupled DC SQUID with a through-hole in the pickup loop was prepared to improve the coupling of magnetic flux between the probe and the SQUID. By adjusting the position of the SQUID head, the probe could be made to penetrate through the hole in the pickup loop. We observed the magnetic fields emanating from a Japanese thousand yen bill and a current carrying meander line. We also investigated the coupling efficiency of the magnetic flux for various depths of penetration of the probe through the pickup loop of the SQUID by both experiment and numerical simulation.         Study of a multi-channel RF Amplifier Based on DC SQUID for 3-5 GHz band    G.V. Prokopenko, S.V. Shitov, I.L. Lapitskaya, S. Kohjiro, M. Maezawa and A. Shoji Summary: A low-noise rf amplifier based on a dc SQUID (SQA) is developed and tested within frequency range 3.0-4.5 GHz. The 4-channel chips are designed using proven balanced output configuration; they employ special damping filters. Each channel is tested separately demonstrating the following parameters at 3.95 GHz central frequency: gain (9.5 /spl plusmn/ 1.0) dB, 3-dB bandwidth 300 MHz and noise temperature (1.0 /spl plusmn/ 0.5) K. The 1-dB gain compression estimate is 50 K*GHz for bias voltage 80 /spl mu/V and characteristic voltage 285 /spl mu/V.         Appearance of sign reversal in geophysical transient electromagnetics with a SQUID due to stacking    H.-J. Krause, G.I. Panaitov, Yi Zhang and M. Bick Summary: In geophysical transient electromagnetics (TEM) measurements with HTS SQUID magnetometers, a so-called 'frequency dependence' of the stacked time transients on the repetition frequency of the transmitter, and the appearance of so-called 'sign reversals', the crossover of the stacked time transients to negative values, have been observed frequently. Recently, we have shown that both of these effects can be attributed to the summing of remnant responses from earlier transmitted pulses of the repetitive transmitter waveform. Although the step function inductive response for many TEM targets decays monotonically and is positive at all times, instances of sign reversal do occur. We postulate that this sign reversal is due to the typical bipolar waveform of the TEM transmitter and the stacking procedure. In this contribution, we systematically extend our analysis to binary and ternary power-law expressions for the step function response, modeling measured responses for typical ground structures. The conditions are determined under which sign reversals appear. It is shown that the effect occurs mainly in the case where a shallow slope response is followed by a rapidly decaying response at late times. Such a signal is typically measured on a resistive overburden over a conducting medium. As an example, data are presented from a location where a sign reversal was measured with a SQUID whereas none was found in the coil data. A deconvolution procedure for determining the single pulse response from measured SQUID data is proposed.         High Tc SQUID system for transient electromagnetic geophysical exploration    T. Nagaishi, H. Ota, E. Arai, T. Hayashi and H. Itozaki Summary: Transient electromagnetic (TEM) method using high temperature SQUID (HTS SQUID) for geophysical exploration has been developed. In terms of high sensitivity, wide bandwidth and its easy handling, HTS SQUIDs are anticipated for use with the coolant of the liquid nitrogen. The development was focused on high magnetic field sensitivity and high slew rate for better resolution and deeper depth of exploration. A highly sensitive large direct couple SQUID is made with step-edge junctions on a 20 mm by 20 mm substrate. The effective area is 0.52 mm/sup 2/ and the typical magnetic field noise is 50-100 fT/Hz/sup 1/2/. The flux locked loop circuit is a direct-readout type for the purpose of high frequency response up to 100 kHz and has low amplifier noise of 0.5 nV/Hz/sup 1/2/. The system achieved noise level of 200 fT/Hz/sup 1/2/ under the magnetic field environment and the slew rate of 7.3 mT/sec. We conducted field trials at several sites in Japan with the successful operation of the system. It was confirmed that the system has up to two orders improved sensitivity than the conventional system which enables the exploration of deeper regions. The reconstructed resistivity profile by 1-D inversion of the SQUID data agrees well with the results of the drilling survey.         Detection of mobile targets from a moving platform using an actively shielded, adaptively balanced SQUID gradiometer    K.P. Humphrey, T.J. Horton and M.N. Keene Summary: Tests have been performed with a moving HTS dc SQUID gradiometer mounted on a nonmetal motion table. The system operated with sensitivity of 80 pT/m//spl radic/Hz (1 Hz) and 1 pT/m//spl radic/Hz (white) whilst undergoing pitch, roll and yaw motions of /spl plusmn/5/spl deg/ in an outside environment. Gradient anomalies of /spl ges/ 1 nT/m were detected with 12 dB signal-to-noise ratio and a measurement bandwidth of 1 kHz. In this paper, we describe the performance of the gradiometer at measuring remote moving ferromagnetic targets whilst it is in motion. These measurements have an important bearing on understanding the viability of SQUID-based systems as magnetic anomaly detectors, when mounted on airborne or seaborne platforms. In one early test, a target of approximately 300 Am/sup 2/ travelling at 2-5 m/s was detected at 25 m range with a signal to noise ratio of 4:1, whilst the gradiometer was undergoing motions of /spl plusmn/5/spl deg/ in pitch roll and heading.         SQUID-detected in vivo MRI at microtesla magnetic fields    M. Mossle, W.R. Myers, Seung-Kyun Lee, N. Kelso, M. Hatridge, A. Pines and J. Clarke Summary: We use a low transition temperature (T/sub c/) Super-conducting Quantum Interference Device (SQUID) to perform in vivo magnetic resonance imaging (MRI) at magnetic fields around 100 microtesla, corresponding to proton Larmor frequencies of about 5 kHz. In such low fields, broadening of the nuclear magnetic resonance lines due to inhomogeneous magnetic fields and susceptibility variations of the sample are minimized, enabling us to obtain high quality images. To reduce environmental noise the signal is detected by a second-order gradiometer, coupled to the SQUID, and the experiment is surrounded by a 3-mm thick Al shield. To increase the signal-to-noise ratio (SNR), we prepolarize the samples in a field up to 100 mT. Three-dimensional images are acquired in less than 6 minutes with a standard spin-echo phase-encoding sequence. Using encoding gradients of /spl sim/100 /spl mu/T/m we obtain three-dimensional images of bell peppers with a resolution of 2/spl times/2/spl times/8 mm/sup 3/. Our system is ideally suited to acquiring images of small, peripheral parts of the human body such as hands and arms. In vivo images of an arm, acquired at 132 /spl mu/T, show 24-mm sections of the forearm with a resolution of 3/spl times/3 mm/sup 2/ and a SNR of 10. We discuss possible applications of MRI at these low magnetic fields.         Actively shielded, adaptively balanced SQUID gradiometer system for operation aboard moving platforms    M.N. Keene, K.P. Humphrey and T.J. Horton Summary: Extremely high dynamic range is required if magnetometer SQUIDs are to be operated while in motion in the earth's field. We have developed an HTS SQUID gradiometer system that uses active shielding and an adaptive signal processing algorithm to achieve the necessary dynamic range. An array of four thin-film SQUIDs with flux transformers is configured to form two orthogonal magnetometers and a single-axis gradiometer with a baseline of 10 cm. External field changes are cancelled by a three-axis Helmholtz coil set, driven by integral feedback from the SQUIDs, which surrounds the array. A real time adaptive balancing algorithm corrects for gradient offset, electronics scaling errors, sensor misalignments and uniformity errors in the Helmholtz coils. For outside use, light RF shielding is provided by thin layers of Al foil. In laboratory tests, intrinsic noise levels of 20 pT/m//spl radic/Hz (1 Hz) and 0.3 pT/m//spl radic/Hz (white) were measured. In field trials, the Helmholtz coils provided a shielding factor, for uniform fields, of 50-60 dB (0.1-10 Hz) during roll, pitch and yaw rotations of up to /spl plusmn/5/spl deg/. Adaptive balancing reduced gradient noise to the ambient background level of 80 pT/m//spl radic/Hz (1 Hz) and 1 pT/m//spl radic/Hz (white), whilst in motion.         Highly balanced long-baseline axial gradiometer based on high-T/sub c/ superconducting tape    M. Bick, K.E. Leslie, R. Binks, D.L. Tilbrook, S.K.H. Lam, S. Gnanarajan, Jia Du and C.P. Foley Summary: The improving quality of high-T/sub c/ superconducting (HTS) tape with critical current densities larger than 1 MA/cm/sup 2/ creates the possibility to construct high quality flexible superconducting electronics operating at liquid nitrogen temperatures. We patterned a symmetric flux transformer into a 700 nm thick YBa/sub 2/Cu/sub 3/O/sub 7-x/ film on a 70 /spl mu/m thick, 85 mm long Hastelloy tape. The center loop of the transformer was coupled to the pickup loop of a SQUID magnetometer in a flip-chip configuration. The two outer pickup loops of the transformer were bent such that they were facing each other perpendicular to the magnetometer plane. The resulting axial gradiometer has a long baseline of 35 mm and a gradient sensitivity of 7.3 nT/(cm/spl Phi//sub 0/). A superconducting shield was used to reduce uniform magnetic fields applied perpendicular to the magnetometer plane. Common-mode rejection ratios less than 10/sup -4/ were achieved in the best case. The noise-limited gradient field resolution was approximately 330 fT/(cm/spl radic/Hz) at a frequency of 10 Hz. This resolution was mainly limited by the flux noise level of our dc-SQUID magnetometer of approximately 45 /spl mu//spl Phi//sub 0///spl radic/Hz. In an unshielded laboratory environment, external noise contributions at 50 Hz were reduced by a factor of approximately 10/sup 3/.         Single sensor high-temperature superconducting axial gradiometer with thick film pick-up loops    S. Haining, E.J. Romans, C.M. Pegrum, G.B. Donaldson, L. Hao and J.C. MacFarlane Summary: A high-temperature superconducting first-order axial gradiometer with thick film YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// pick-up loops inductively coupled to a thin film YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// superconducting quantum interference device magnetometer has been designed, fabricated and characterized. The gradiometer has a baseline of 79 mm, an estimated intrinsic system balance of 1:480 for uniform axial magnetic fields and an estimated axial magnetic field gradient sensitivity of 70 fT/(cm/spl radic/Hz) at 1 kHz, in magnetic shielding.         SQUID-gradiometers for arrays of integrated low temperature magnetic micro-calorimeters    R. Stolz, V. Zakosarenko, L. Fritzsch, H.-G. Meyer, A. Fleischmann and C. Enns Summary: We designed first-order integrated planar SQUID gradiometers especially for readout of signals from magnetic micro-calorimeters used for the detection of single x-ray quanta. These SQUIDs must operate in magnetic fields up to 5 mT and at temperatures down to 10 mK. Various new designs of eight-pixel gradiometer SQUID arrays on one chip were developed. The dimensions of the gradiometers are adapted to the magnetic thermometer of the micro-calorimeter. The intrinsic noise of the SQUID gradiometers measured at 4.2 K is lower than 2.5/spl mu//spl Phi//sub 0//Hz/sup 1/2/. They withstand external magnetic fields up to 7 mT without degradation of their performance. A new concept for thermal contact of the detector to the environment based on normal-conducting metallic wiring on the chip is introduced. Field coils with a persistent current switch were integrated on chip to produce the necessary magnetizing field. Appropriate changes in niobium technology compared to our previous work were introduced to achieve necessary critical current of the coil. Thermal coupling between the switch heater and the superconducting short was optimized. A persistent current of up to 80 mA can be injected in the field coil using a heater power of 4 mW. This current corresponds to magnetizing field of 6 mT at the paramagnetic sensor. During the heat pulse the SQUID remains superconducting.         dc SQUID readout electronics with up to 100 MHz closed-loop bandwidth    D. Drung, C. Assmann, J. Beyer, M. Peters, F. Ruede and T. Schurig Summary: High-speed readout electronics for sensors based on dc superconducting quantum interference devices (SQUIDs) are presented. The SQUID sensor involves a series array of 16dc SQUIDs and an intermediate transformer to enhance its current sensitivity. By using a highly gradiometric design and /spl les/5 /spl mu/m linewidth for the SQUID array, the device can be cooled down in fields of up to 85 /spl mu/T and be operated magnetically unshielded. A special feedback coil design minimizes the parasitic coupling between feedback and input coil. The SQUID sensor is directly connected to the room temperature electronics. A composite preamplifier is used consisting of a slow dc amplifier in parallel with a fast ac amplifier. A virtual 50 /spl Omega/ input resistance with negligible excess noise is realized by active shunting. Two types of high-speed readout electronics were developed. The first was designed for optimum dc performance, high flexibility, and user-friendliness. It is fully computer controlled. The white voltage and current noise levels are 0.3 nV//spl radic/Hz and 3 pA//spl radic/Hz, respectively, resulting in an overall system noise level of 0.4 /spl mu//spl Phi//sub 0///spl radic/Hz or a coupled energy sensitivity around 500h (/spl Phi//sub 0/ is the flux quantum and h is Planck's constant). The maximum flux-locked loop (FLL) and open-loop bandwidths are about 20 MHz and 50 MHz, respectively. The second readout electronics is an ultra-high-speed prototype which was designed for maximum speed at the expense of dc performance. A very low intrinsic signal delay of 1.7 ns and a high open-loop bandwidth of 300 MHz were measured. Using a novel FLL scheme, a very high signal bandwidth of 130 MHz was achieved with 0.8 m distance between SQUID and electronics.         Superconducting quantum interference filters consisting of Josephson junctions with unconventional current-phase relation    M. Seifried, C. Haussler, J. Oppenlander and N. Schopohl Summary: Superconducting quantum interference filters (SQIFs) are parallel or serial Josephson junction arrays with a unique DC voltage output around vanishing magnetic field B = 0. Certain features of the voltage output also depend on the current-phase relation of the individual junctions in the array. Taking into account the first two harmonics I/sub c1/ and I/sub c2/ of the supercurrent we investigate the DC voltage output of the array. In particular we describe a characteristic magnetic field asymmetry of the voltage output. Applications of the theory include the design of SQIFs with novel flux to voltage transfer functions using high-T/sub c/ superconductors on bi- or tri-crystal substrates.         Development of a SQUID readout system for the MiniGRAIL    M. Podt, L. Gottardi, Arlette de Waard, G. Frossati and J. Flokstra Summary: The MiniGRAIL is one of the three similar spherical gravitational wave detectors that are currently being developed. The detector has a resonant frequency of about 3 kHz and will be operated at 20 mK. The ultimate goal is to use a readout system consisting of six transducers coupled to nearly quantum limited two-stage SQUIDs. The two-stage SQUIDs are based on double relaxation oscillation SQUIDs, which enables a direct voltage readout scheme. We have developed nonintegrated two-stage SQUIDs and experimentally verified the proper operation of the system coupled to a capacitive transducer. Based on the results that were achieved, integrated two-stage SQUIDs were designed. Special attention has been paid to the sensor SQUID, the back action of the SQUID and the feedback scheme that is used for linearizing the SQUID output.         Investigation of YBCO SQUIDs with gold damping resistors    D.S. Pinker, L.K. Sahoo, D.A. Ansell, G. Burnell, S.H. Mennema, U. Sinha and E.J. Tarte Summary: It has been previously shown that resistively damping the inductances of YBCO SQUIDs reduces the degradation of their output voltage by large values of the screening parameter. This paper reports on the viability of using gold damping resistors with YBCO dc SQUIDs, connected via in situ gold/YBCO contacts deposited by laser ablation on 24/spl deg/ STO bicrystal substrates. It is shown that for SQUIDs of our design that this technique enhances their normalized voltage modulation, compared to their undamped counterparts at 77 K. The amount of enhancement agrees well with that predicted by Enpuku's theory. The SQUID behavior was studied over a wide range of values of the effective screening parameter, /spl beta//sub eff/, which was achieved by measuring the SQUIDs over a temperature range of 20-77 K. These measurements confirmed that the behavior of this SQUID design is inline with established theory.         Flux-to-Voltage transfer function of the series-SQUID array with grain-boundary Josephson junctions    J.T. Jeng, H.C. Hung, C.R. Lin, C.H. Wu, K.L. Chen, J.-C. Chen, H.C. Yang, S.H. Liao and H.E. Horng Summary: The factors affecting the flux-to-voltage transfer function of the series-SQUID array with grain-boundary Josephson junctions were investigated. By using the proposed critical-current-modulation model, it is found that the voltage swing of the series-SQUID array is suppressed greatly by the spread in critical currents of Josephson junctions. For the inductance L = 80 pH and the logarithmic average critical current 2I/sub ave/ = 20 /spl mu/A of the component SQUID, the allowed spread in critical currents of Josephson junctions is 0.4I/sub ave/ to 2.2I/sub ave/ for achieving the low flux noise with the series SQUID array.         Digital control of high-performance dc SQUID readout electronics    S. Bechstein, D. Drung, F. Petsche, M. Scheiner, C. Hinnrichs, H.-J. Barthelmess and T. Schurig Summary: We have developed analog superconducting quantum interference device (SQUID) readout electronics for diverse applications. To improve their user-friendliness and flexibility, these analog circuits are embedded into a digitally-controlled system including an in-system programmable microcontroller on the electronics board and a user interface which runs on a personal computer. In this paper, we present the concept of software and hardware and discuss the achieved improvements.         Magnetocardiographic performance of single-layer second-order YBCO SQUID gradiometers    Soon-Gul Lee, Seung Moon Park, Chan Seok Kang and In-Seon Kim Summary: We have studied noise properties and magnetocardiographic performance of single-layer second-order YBCO SQUID gradiometers made on STO substrates. A three-loop pickup coil is directly coupled to a step-edge junction SQUID with the coupling polarity of the center loop opposite to that of two side loops. Optimized device parameters for balancing were obtained from 8.8 mm /spl times/ 3.0 mm devices on 10 mm /spl times/ 10 mm substrates and scaled up to the larger devices for use in cardiomagnetic measurements. A 17.6 mm /spl times/ 6 mm gradiometer with a 5.8 mm baseline showed an unshielded gradient noise of 0.84 pT/cm/sup 2//Hz/sup 1/2/ at 1 Hz, which corresponds to an equivalent field noise of 280 fT/Hz/sup 1/2/. A large balancing factor of 10/sup 3/ allowed us to record magnetocardiogram of a human subject.         High-T/sub c/ electronic planar gradiometer constructed from magnetometers on a chip    Kuen-Lin Chen, Jau-Han Chen, Chuan-Chin Lin, Chiu-Hsien Wu, Ji-Cheng Chen, Herng-Er Horng and Hong-Chang Yang Summary: We have fabricated a high-T/sub c/ electronic planar gradiometer composed of dc SQUIDs on a 10 mm /spl times/ 10 mm SrTiO/sub 3/ bicrystal substrate. The SQUIDs were patterned in a single-layer YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin film which is prepared by pulsed laser deposition. The outputs of the magnetometers are added and subtracted by analog electronic circuits to form the gradiometer. These magnetometers could be used to construct two sets electronic planar first-order gradiometers or an electronic planar second-order gradiometer, which could measure the elements /spl part/B/sub z///spl part/x and /spl part/B/sub z///spl part/y or /spl part//sup 2/B/sub z///spl part/x/spl part/y, respectively. The noise spectra of each magnetometer and a first-order electronic planar gradiometer were measured.         A new figure of merit for planar SQUID gradiometers and magnetometers    E.A. Lima and A.C. Bruno Summary: There has recently been significant progress in the sensitivity of SQUID planar gradiometers and magnetometers. Usually, their performance is expressed in terms of the associated field noise spectrum together with a description of the geometry of the device. This is not a straightforward combination and poses a difficult task if one wants to assess the overall performance of the device and to compare different designs. To address these issues, we propose a new figure of merit based on spatial frequency features of the gradiometer. It consists of obtaining its spatial frequency response and extracting from it relevant parameters such as magnitude and bandwidth. An assessment of different gradiometer designs is made.         Fabrication of DC SQUIDs based on Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ intrinsic Josephson junctions    A. Irie and G. Oya Summary: We report on the first observation of clear voltage modulation in dc SQUID based on intrinsic Josephson junctions of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/. Stacked series array of intrinsic Josephson junctions and dc SQUID based on it have been made from Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ single crystals using a double-side etching process. The number of junctions in the stack is rather controllable by monitoring the junction resistance at room temperature. The current-voltage characteristics of the SQUIDs with stacks of 20-50 IJJs at 4.2 K exhibit additional closely spaced branches together with typical multiple quasi-particle branches with voltage spacing of /spl sim/20 mV. On applying magnetic field clear periodic modulation of the lowest critical current and voltage of the SQUID are observed and the flux period obtained from the voltage-flux characteristics agrees with one flux quantum. The maximum voltage modulation and transfer function are about 80 /spl mu/V and 0.75 mV//spl Phi//sub 0/ at 26 K, respectively. The property of dc SQUID with shunt resistances is also discussed.         Fabrication of magnetometers with multiple-SQUID arrays    M. Matsuda, K. Nakamura, H. Mikami and S. Kuriki Summary: We have designed and fabricated magnetometers with multiple-SQUID arrays to achieve higher signal to noise ratio compared to that for a single SQUID. In our directly coupled scheme, ten SQUIDs are connected in parallel with the same pickup coil composed of four parallel rectangular loops. Each SQUID having inductance of 70 pH and junctions of 1.5 /spl mu/m width was fabricated from an Au/YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin film on a SrTiO/sub 3/ bicrystal substrate with 30/spl deg/ misorientation angle. To avoid forming superconducting loops between junctions of adjoining SQUIDs, a Au wiring layer interrupts a current bias line. The obtained critical current of 20I/sub c/ and normal resistance of R/sub n//20 including contact resistance for the Au wiring layer are 350 /spl mu/A and 0.4 /spl Omega/, respectively. The modulation voltage of 25 /spl mu/V for multiple-SQUIDs is the same level as for a single SQUID. On the other hand, the modulation current of 40 /spl mu/A is several times larger than that for a single SQUID, but rather smaller than the expected value when all SQUIDs have equal parameters. A flux noise level of 15 /spl mu//spl Phi//sub 0//Hz/sup 1/2/ at 100 Hz, including preamplifier noise, was observed by using flux-locked loop electronics in a magnetically shielded room.         Fabrication and characterization of an integrated 9-channel Superconducting quantum interference device magnetometer array    J. Kawai, T. Shimozu, M. Kawabata, G. Uehara, Y. Adachi, M. Miyamoto and H. Ogata Summary: We have fabricated and characterized nine Superconducting Quantum Interference Device (SQUID) magnetometers, which were integrated on a single chip. The magnetometers are based on a directly-coupled multiloop SQUID with Nb/Al-AlO/sub x//Nb junctions, and are arranged in a 3 /spl times/ 3 matrix in the area of 10 mm /spl times/ 10 mm. The diameter of the circular pick-up loop of each magnetometer is 2.5 mm and the distance between neighboring magnetometers is 2.75 mm. In the operation with a flux locked loop (FLL) with direct voltage readout, typical flux-locked noise level of less than 3/spl times/10/sup -6/ /spl Phi//sub 0///spl radic/Hz in the white region were obtained with the magnetometer in a superconductive shield. From the calibration of the sensitivity, typical field noise was measured to be 7 fT//spl radic/Hz. In combination with a small cryostat, we expect that this magnetometer will be useful for multi-channel measurement of magnetic fields requiring highly spatial resolution in various applications.         New fabrication process for superconducting quantum interference devices with Nb/AlAlOx/Nb junctions by using photosensitive polyimide insulation layers    J. Kawai, T. Shimozu, K. Kikuchi, M. Kawabata, H. Nakagawa, M. Aoyagi and G. Uehara Summary: We propose a new fabrication process for Superconducting Quantum Interference Devices (SQUIDs) with Nb/Al/AlOx/Nb junctions by using photosensitive polyimide insulation layers. The photosensitive polyimide, which is synthesized by multi-block copolymerization, can be formed into a thin layer with spin-coating, and patterned with conventional photolithography. Compared to forming a SiO/sub 2/ insulation layer with a sputtering and etching process, the fabrication is simplified and the coverage over the edge of the patterns can be improved due to planarization. SQUIDs with a flux transformer having two insulation layers were successfully fabricated with this process and were characterized. The critical current of the flux transformer was more than 20 mA, and a flux noise of less than 1/spl times/10/sup -6/ /spl Phi//sub 0///spl radic/Hz was obtained in the white region. With an axial gradiometer in combination with this SQUID, a field resolution of 1.5 fT//spl radic/Hz was achieved.         A cross-type SNS junction array for a quantum-based arbitrary waveform synthesizer    M. Schubert, T. May, G. Wende and H.-G. Meyer Summary: Central to quantum-based arbitrary waveform synthesizers is a Josephson junction array driven by short pulses. Its linear dimensions should be small compared to the line wavelength in order to generate an ac voltage with quantum accuracy. Therefore, we use coplanar strip transmission lines to integrate a large number of cross-type SNS Josephson junctions into multiple parallel arrays. First measurements show that a circuit with 1,760 junctions exhibits Shapiro steps over a large frequency range. By using pulse driving the chip generates unipolar voltages up to 6.4 mV at a clock frequency of 3.5 GHz, the maximum frequency of the available pulse pattern generator.         Quantum entanglement and controlled logical gates using coupled SQUID flux qubits    Zhongyuan Zhou, Shih-I Chu and Siyuan Han Summary: We present an approach to realize universal two-bit quantum gates using two SQUID flux qubits. In this approach the basic unit consists of two inductively coupled SQUIDs with realistic device parameters. Quantum logical gates are implemented by applying resonant microwave pulse to the qubits. This procedure is demonstrated by realizing a controlled-NOT (CNOT) gate and the maximally entangled states of the coupled qubits through highly accurate numerical solution of the time-dependent Schrodinger equation of the system. This coupling scheme is simple and can be readily extended to many-qubit circuits required for scalable quantum information processing.         Picosecond on-chip qubit control circuitry    T.A. Ohki, M. Wulf and M.F. Bocko Summary: Fast on-chip control of superconducting qubits has engaged complex and power consuming RSFQ circuits that currently pose more of an experimental burden than an asset. Measurements of quantum coherent oscillations of qubits require dilution refrigerator temperatures. The motivation of this design is to minimize the necessary bias leads and power dissipation for an SFQ based control circuit. Elimination of redundant circuit elements by innovative use of fundamental elements allows small-scale control circuitry.         Resonant readout of a persistent current qubit    J.C. Lee, W.D. Oliver, T.P. Orlando and K.K. Berggren Summary: We have implemented a resonant circuit that uses a SQUID as a flux-sensitive Josephson inductor for qubit readout. In contrast to the conventional switching current measurement that generates undesired quasiparticles when the SQUID switches to the voltage state, our approach keeps the readout SQUID biased along the supercurrent branch during the measurement. By incorporating the SQUID inductor in a high-Q resonant circuit, we can distinguish the two flux states of a niobium persistent-current (PC) qubit by observing a shift in the resonant frequency of both the magnitude and the phase spectra. The readout circuit was also characterized in the nonlinear regime to investigate its potential use as a nonlinear amplifier.         Energy relaxation times in a Nb persistent current qubit    Yang Yu, W.D. Oliver, D. Nakada, J.C. Lee, K.K. Berggren and T.P. Orlando Summary: We measured the energy relaxation time in a Nb superconducting persistent current qubit using a time-resolved fast measurement scheme. The energy relaxation time is longer than 10/spl mu/s, showing a strong potential of realizing quantum computation with Nb-based superconducting qubits.         A new flux/phase qubit with integrated readout    M.G. Castellano, F. Chiarello, R. Leoni, G. Torrioli, P. Carelli, C. Cosmelli, M. Di Bucchianico, F. Mattioli, S. Poletto and D. Simeone Summary: We propose a new scheme for a flux/phase qubit, based on a double-SQUID modified to achieve a direct readout of the flux state. The readout is performed by inserting a large Josephson junction in the SQUID loop; the junction is biased by an external current and switches from the zero-voltage to the running state depending on the flux state of the qubit. We report recent results concerning the theoretical behavior and the experimental characterization at 4.2 K of the device, which has been realized with Nb/AlOx/Nb trilayer technology.         Unconventional Josephson junction arrays for qubit devices    G. Rotoli Summary: The presence of spontaneous currents in unconventional Josephson junctions gives rise to the possibility of using zero magnetic field magnetization states in an unconventional loop as qubit states in a Josephson quantum computing device. However, the advantage of zero field may be insufficient to overcome the problems arising in the design and fabrication of low-noise, low-dissipation, reproducible devices. On the other hand, low-T/sub c/ "flux" devices suffer the same problems though their perspectives are more promising. The solution could be an increase in the device complexity, but with the gain of an effective advantage on the external noise rejection of the system during quantum evolution. Using advanced fabrication techniques it is now possible to build Josephson junction arrays made of superconducting unconventional loops. On this basis, a new qubit device can be designed as a ring array of unconventional loops. From a theoretical point of view this device is analogous to an annular Josephson junction, but with a "built in" natural degeneracy. For their topological and energetical properties, such arrays could be excellent devices for the qubit circuitry usable as the basic building blocks for quantum computing devices. In this work, we show how some of the principles of qubit design could be implemented in such devices.         Dressed States of Josephson phase qubit coupled to an LC circuit    M. Wulf, T.A. Ohki, Xingxiang Zhou and M.J. Feldman Summary: We study the dynamics of a current biased Josephson phase qubit capacitively coupled to an LC circuit. We find that the eigenstates of this system are dressed states that are entangled states between the phase qubit and the LC resonator. We demonstrate that these dressed states can be probed by measuring the avoided crossing in the spectrum of the system. We present our experimental setup to investigate them. This system is interesting not only in demonstrating entanglement, the essential element for quantum information processing (QIP), but also in serving as a first step toward a solid-state analog of cavity QED.         Fabrication and characterization of superconducting circuit QED devices for quantum computation    L. Frunzio, A. Wallraff, D. Schuster, J. Majer and R. Schoelkopf Summary: We present fabrication and characterization procedures of devices for circuit quantum electrodynamics (cQED). We have made 3-GHz cavities with quality factors in the range 10/sup 4/-10/sup 6/, which allow access to the strong coupling regime of cQED. The cavities are transmission line resonators made by photolithography. They are coupled to the input and output ports via gap capacitors. An Al-based Cooper pair box is made by e-beam lithography and Dolan bridge double-angle evaporation in superconducting resonators with high quality factor. An important issue is to characterize the quality factor of the resonators. We present an RF-characterization of superconducting resonators as a function of temperature and magnetic field. We have realized different versions of the system with different box-cavity couplings by using different dielectrics and by changing the box geometry. Moreover, the cQED approach can be used as a diagnostic tool of qubit internal losses.         Observation of quantized energy levels in a Josephson junction using SFQ circuits    Y. Yamanashi, M. Ito, A. Tagami and N. Yoshikawa Summary: A single flux quantum (SFQ) circuit to measure quantized energy levels in a Josephson junction has been proposed and implemented, which allows us to perform high-speed and low-noise measurements of the escape rate in Josephson junctions. By using this technique, the measurement of escape rate has been carried out at 4.2 K, the temperature three times higher than the crossover temperature. The test results show periodic dependence of the escape rate on the junction bias current, which is caused by the energy quantization effect in the Josephson junction.         Thermometry using thermal activation of Josephson junctions at MilliKelvin temperatures    T.A. Ohki, M. Wulf, J.P. Steinman, M.J. Feldman and M.F. Bocko Summary: We use the thermal activation of Josephson junctions as a thermometer to investigate heat flow from a hot resistor at milliKelvin temperatures on a silicon chip used for superconducting qubit experiments. The experiments are compared to computer simulations and agree well. These results indicate that on-chip resistors can be used below a certain power level, but not above that level.         Measurements of a persistent-current qubit driven by an on-chip radiation source    J.L. Habif, B. Singh, D.S. Crankshaw and T.P. Orlando Summary: Monolithic integration of control electronics with superconducting qubits will facilitate scalability of a superconducting quantum computer by reducing the room temperature electronics necessary for performing quantum state manipulation. We report the experimental results of the monolithic integration of an on-chip radiation source with a persistent-current (PC) qubit and dc SQUID measurement device. The devices were fabricated at MIT Lincoln Laboratory in a Nb/Al/AlOx/Nb trilayer process. The two PC qubit states were detected by measuring the switching current of an underdamped dc SQUID magnetometer inductively coupled to the qubit. The radiation source comprised an overdamped dc SQUID operating in the voltage state and inductively coupled to the qubit and measurement SQUID through a low-Q RLC filter. The oscillator was designed to have tunable amplitude and frequency to satisfy the requirements for coherent quantum manipulation of a superconducting PC qubit. We will discuss the measurements in the millikelvin regime and the effects of the oscillator noise on the state of the qubit.         Quantum dynamics of the Interferometer-type charge qubit under microwave irradiation    W. Krech, D. Born, V. Shnyrkov, T. Wagner, M. Grajcar, E. Il'ichev, H.-G. Meyer and Y. Greenberg Summary: We study theoretically dynamic properties of an interferometer-type Josephson charge qubit consisting of a single-Cooper-pair transistor (with capacitive gate) closed by a superconducting inductive loop. Analyzing the radio frequency response of the device to microwave fields within a two-band model, we present basic features of a method for observation of various Rabi oscillation modes. For this purpose, we apply the dressed-state approach in conjunction with the rotating-wave approximation to the strongly driven quantum bit. We demonstrate the existence of multiphoton excitations and Rabi frequency transitions between quantum levels connected with them. The resulting oscillations of the supercurrent in the interferometer modify the spectral loop susceptibility. This effect may be detected via the coil of a high-quality tank circuit inductively coupled to the qubit by measuring the tank-qubit impedance variations belonging to it.         Backaction effects of a SSET measuring a qubit spectroscopy and ground State measurement    B. Turek, J. Majer, A. Clerk, S. Girvin, A. Wallraff, K. Bladh, D. Gunnarsson, T. Duty, P. Delsing and R. Schoelkopf Summary: We investigate the backaction of superconducting single-electron transistor (SSET) continuously measuring a Cooper-pair box. Due to the minimized backaction of the SSET, we observe a 2e periodic Coulomb staircase according to the two-level system Hamiltonian of the Cooper-pair box. We demonstrate that we can control the quantum broadening of the ground state in-situ. We perform spectroscopy measurements and demonstrate that we have full control over the Cooper-pair box Hamiltonian. The ability to reduce the backaction is a necessary condition to use the SSET as a quantum state readout for the CPB as a qubit.         Cooper-pair box as a variable capacitor    H. Paik, F.W. Strauch, R.C. Ramos Jr., A.J. Berkley, H. Xu, S.K. Dutta, P.R. Johnson, A.J. Dragt, J.R. Anderson, C.J. Lobb and F.C. Wellstood Summary: We calculate the effective capacitance of a Cooper-pair box and demonstrate that the Cooper-pair box can be used as a variable capacitor. The gate voltage modulates the charge transfer through the small junction in the Cooper-pair box, leading to a gate-dependent capacitance. We describe ongoing experiments to use an Al/AlO/sub x//Al Cooper-pair box as a tunable circuit element at milli-Kelvin temperatures and discuss possible applications to quantum computing as a variable coupling element between two Josephson junction qubits.         Fabrication and properties of ac-dc superconducting rectifier    E.M. Gonzalez, J.E. Villegas, M.P. Gonzalez, J.V. Anguita and J.L. Vicent Summary: Magnetron sputtering, electron beam lithography and etching techniques allow us to fabricate Nb thin films on array of periodic nonsuperconducting nanometric triangles. These asymmetric pinning potentials induce a ratchet effect on the vortex lattice motion: injecting an ac current on the sample yields a dc voltage. This rectification effect does not depend on the ac frequency in the kHz range. The effect occurs for magnetic as well as nonmagnetic pinning centers. The rectification is enhanced at lower temperatures.         Ultra-sensitive field sensors - an alternative to SQUIDs    M. Pannetier, C. Fermon, G. Legoff, J. Simola, E. Kerr, M. Welling and R.J. Wijngaarden Summary: Very low magnetic fields are detected up to now using SQUID-based devices. In the femtotesla range, only low-T/sub c/ SQUIDs have a sufficiently low level of noise to measure extremely low signals, as for instance induced fields of the neural activity of the brain, for magneto-encephalography (MEG). An alternative to SQUIDs is to combine a superconducting flux-to-field transformer with a high-sensitivity giant magnetoresistive sensor (GMR). We have fabricated and performed experiments on such an integrated YBCO-based mixed sensor. It is comprised of a GMR stack separated from a YBCO thin film by an insulating layer. The induced supercurrent in the YBCO is forced through a narrow constriction, thereby creating a local field much larger than the external field. This large local field is detected by the GMR. Effective noise levels are down to 30 fT/sqrtHz, which is in the range of high-Tc Squids. Performance of this device is shown from liquid helium temperature (4.2 K) up to liquid nitrogen temperature (77K). By replacing the GMR by a Tunneling Magneto Resistance (TMR) or a Colossal Magneto Resistance (CMR) sensor, and by adjusting the dimensions to optimize the local enhancement effect, the sensitivity should reach the subfemtotesla range at low frequency. A large number of applications could be investigated by this sensor, especially in the biomagnetism area, as well as in various other fields, from earth mapping to fundamental physics (vortex motion in superconductors, magnetic interactions...).         Use of a generalized thouless energy in describing transport properties of Josephson junctions    J.K. Freericks, A.N. Tahvildar-Zadeh and B.K. Nikolic Summary: The concept of a Thouless energy, introduced originally in the context of Anderson localization (as the inverse diffusion time through a finite-size disordered conductor), has turned out to be an essential energy scale for understanding proximity-induced superconductivity in a normal metal connected to a superconductor; in particular, it has had significant success in the quasiclassical description of phenomena in superconductor-normal-metal-superconductor Josephson junctions. We generalize the concept of a Thouless energy to include transport through strongly correlated insulators, and show how it provides a unified description of transport and indicates how the quasiclassical picture breaks down as we turn on electron-electron correlations in the normal metal layer of a Josephson junction to tune it through the Mott metal-insulator transition.         Superconducting maser    A.N. Lykov Summary: A new approach to designing active superconducting elements is developed. The mixed state in the superconducting films is influenced by an alternative magnetic field directed perpendicular to the film surface. The field slowly varies in time, and sets up the vortex structure in the film. The interaction of the vortices with planar pinning centers leads to a metastable mixed state, which can bring into the ground state. Such a transition synchronized by an external resonant circuit causes the generation of the electromagnetic radiation. Coherent microwave radiation has been directly detected from superconducting thin films thus excited. Moreover, it is found that the radiation depresses the noise radiation, so that low-frequency noise is transformed into the coherent radiation. Harmonic mixing and amplification of the electromagnetic radiation are also detected. The system resembles a maser in which the energy two-level structure is formed by Abricosov vortices.         Giant-magnetoresistive/Superconducting contacts and Josephson junction devices    G. Burnell, Chi-Wah Leung, C. Bell and M.G. Blamire Summary: We have been investigating superconductor-normal metal-superconductor (SNS) (Proximity-Effect) Josephson Junctions in which the normal metal is a magnetic heterostructure in which the magnetic character can be actively controlled. As part of this program we have investigated the use of giant magnetoresistive (GMR) Cu-Py multilayers as the barrier in variable thickness planar bridge SNS junctions in addition to in-plane S-GMR contacts. In this paper we report on the latest results from our devices which have been fabricated using our established focussed ion beam (FIB) processes.         Spin valve Josephson junctions    C. Bell, G. Burnell, Chi-Wah Leung, E.J. Tarte and M.G. Blamire Summary: We are currently researching Nb-based Josephson junctions with magnetic barriers in which the magnetic character can be actively changed, with the final aim of producing a magnetically controllable /spl pi/-junction. Pseudo-spin-valve Nb/Fe/sub 20/Ni/sub 80//Cu/Co/Nb Josephson junctions have been grown by d.c. magnetron sputtering. As we have previously reported, the spin-valve magnetoresistance could be measured at high bias at 4.2 K. The zero field critical current of the junction could also be varied by preparing the spin valve in different remanent states. Jumps and smooth changes in the critical current were observed, in line with the changes in magnetoresistance. In this work we discuss the effect of varying the total barrier thicknesses on the change in the critical current, as well as varying the Co:Fe/sub 20/Ni/sub 80/ ratio.         Oscillations of Josephson-vortex flow resistance in narrow intrinsic Josephson junctions    T. Hatano, Huabing Wang, Sunmi Kim, S. Urayama, S. Kawakami, Sang-Jae Kim, M. Nagao, K. Inomata, Y. Takano, T. Yamashita and M. Tachiki Summary: Oscillations of Josephson vortex-flow resistance have been studied in narrow (L/spl sim/2-4/spl lambda//sub J/) Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta// intrinsic Josephson junctions as a function of magnetic field applied parallel to junction edges. Lengths of junctions fabricated are /spl sim/1 /spl mu/m in order to enhance pinning effects of Josephson vortex lattice to the junction edges and thus to enhance formation of rectangular vortex lattice which would lead an in-phase mode of the junctions as a necessary condition for the THz generator application. The observed Josephson vortex flow resistance showed a periodic oscillation with a period (H/sub p/) corresponding to one flux quantum enters per junction, namely, corresponding to the rectangular vortex lattice. Observed strong oscillation was a result of collective behavior of the entry and escape of vortices in a form of rectangular vortex lattice. Peaks in the oscillations were found at the fields H=nH/sub p/, here n shows an integer number. Here, Josephson vortex lattice flow speed shows a local maximum. With this magnetic field, outermost vortex rows geometrically match to the edges of junctions. Contrary to this, a minimum of flow speed, namely pinned state of the vortex lattice, was observed at H=(n+1/2)H/sub p/.         Characterization of Josephson-vortex flow device as a magnetic sensor    K. Hirata, S. Ooi, E.H. Sadki, Shan Yu and T. Mochiku Summary: We have found periodic oscillations in the Josephson-vortex flow resistance of the intrinsic Josephson junctions of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta// single crystal under the parallel magnetic fields from a few kOe to more than 70 kOe. The oscillations indicate a precise and an absolute measurement at higher fields. To demonstrate the characteristics of the magnetic sensor, we have performed modulation measurements with small coils producing a few Oe in Tesla order magnetic fields and have studied details on the flow resistance in the magnetic field and temperature cycles. The results show a high performance as a magnetic sensor.         Characterization of an STJ-based direct detector of submillimeter waves    S. Ariyoshi, H. Matsuo, C. Otani, H. Sato, H.M. Shimizu, K. Kawase and T. Noguchi Summary: We have developed submillimeter-wave direct detectors employing niobium-based superconducting tunnel junctions (STJs), with broadband spectral response, high sensitivity and imaging capability. Spectral response peaked at 650 GHz with a fractional bandwidth of 14 percent, which fits one of the important atmospheric windows for an astronomical project. We also confirmed the linearity of the detector response in the dynamic range greater than 10/sup 6/. The measured coupling efficiency was about 0.2, which was lower than the expected value of 0.5. The measured noise current of the detector was 10 fA//spl radic/Hz, which agreed with the shot noise from the residual leakage current of 100 pA at 0.3 K. Resultant noise equivalent power (NEP) is 1.6/spl times/10/sup -16/ W//spl radic/Hz, that is less than the background photon fluctuation limit for ground-based submillimeter-wave observations.         Performance projection of electro-optical Modulators for radio-over-fiber in 2 GHz cryogenic front-end receivers    O. Menendez, C. Collado, J. Mateu, M.C. Santos and J.M. O'Callaghan Summary: We present the design of a Y-Ba-Cu-O on LiNbO/sub 3/ cryogenic electro-optical modulator for analog 2 GHz applications. A resonant configuration of coplanar electrodes is considered, showing improvements with respect to both resonant Au electrodes and to traveling-wave electrodes, even beyond the traveling-wave theoretical maximum performance limit. The optimized layout is presented featuring a reduced length of 8.26 mm.         Fabrication and characterization of niobium diffusion-cooled hot-electron bolometers on silicon nitride membranes    A.M. Datesman, J.C. Schultz, A.W. Lichtenberger, D. Golish, C.K. Walker and J. Kooi Summary: We have successfully fabricated niobium diffusion-cooled hot-electron bolometer (HEB) mixers on membranes of silicon nitride less than one micron thick. This advance has allowed us to construct a 1 /spl times/ 5 HEB receiver array intended for operation at 1.45 THz. This article provides an overview of the integration of the HEB array chip with silicon micromachined backshorts and feedhorns, discusses materials issues surrounding the device fabrication, reports resistance and I-V measurements, and compares HEBs fabricated on silicon nitride to similar devices on quartz substrates.         Effects of spatial nonuniformity of superconducting-tunnel-junction ion detectors on mass spectroscopy    M. Ohkubo, M. Ukibe, N. Saito, A. Kushino, S. Ichimura and S. Friedrich Summary: Spatial uniformity of superconducting tunnel junction detectors with a size of 200 /spl mu/m is improved by increasing Al thickness of the Nb/Al proximized electrodes in an energy range of 5-10 keV. which is in the same order as an acceleration energy in time-of-flight mass spectroscopy (TOF-MS). It has been confirmed in the TOF experiments with Ta ions and Ta clusters that the proximized junction detectors clearly separate different ionic states and multi-hit events in impact energy spectra, and moreover can reveal the difference in ion species or ion-surface collision dynamics. However, a better spatial uniformity is not always good for TOF-MS, possibly because a detector with the thicker Al layers has a lower superconducting energy gap, which results in an improper detector operation because of a temperature rise due to heat radiation, or the states of the detector surfaces are different.         Superconducting quantum interference filters operated in commercial miniature cryocoolers    J. Oppenlaender, C. Haeussler, A. Friesch, J. Tomes, P. Caputo, T. Traeuble and N. Schopohl Summary: Superconducting Quantum Interference Filters (SQIF's) are multi-loop arrays of Josephson junctions possessing unconventional grating structures. The flux-to-voltage transfer function of SQIF's is unique and has a single delta-peak like characteristics at zero applied magnetic field. The fault tolerance of SQIF's allows them to be realized in standard high-temperature grain boundary Josephson junction technology. We have successfully designed high-temperature YBCO SQIF's with voltage swings of more than 3 mV and a rather large dynamical range. This large dynamical range allows high-Tc SQIF's to be operated in commercial miniature cryocoolers at 50 K-80 K without any significant problems. Typical parasitic oscillations which are induced by the 55 Hz driven compressor of the cryocooler do not degrade the performance of SQIF's. Even if SQIF's are operated fully unshielded no significant degradation of the performance has been observed.         Kinetic inductance detectors for mass spectroscopy    S. Pagano, E. Esposito, M. Ejrnaes, C. Nappi and R. Cristiano Summary: Mass Spectroscopy (MS) is a powerful analysis tool used for the study of DNA and Proteins. Recently, Time of Flight (ToF) MS instrumentation based on superconductive detectors, namely Transition Edge Sensors (TES) or Superconducting Tunnel Junctions (STJ), have been proposed because they feature a good efficiency even for high masses molecules, which have very low speed. This is due to the fact that both STJ and TES provide a signal that is proportional to the kinetic energy rather than the speed. However, TES and STJ require a low operating temperature (0.1 K) and are relatively slow, which in a ToF-MS translates directly to degraded mass resolution. We propose a different type of detector: the Kinetic Inductance Detector, which has been successfully investigated as an ultra-fast and ultra-sensitive optical detector. This detector has a very fast time response (sub ns), thus providing a very good mass resolution, and shares with the other superconductive detectors the independence on the mass value. Moreover, it could operate at higher temperature (in the 2-4 K range). We have investigated different configurations of kinetic inductance detectors for MS, alone and in combination with Josephson devices, and report on the expected performances.         A particle detector based on a double barrier Josephson junction    S.E. Shafranjuk, J.B. Ketterson and I.P. Nevirkovets Summary: We analyze the performance of a particle detector based on a double-barrier Nb/Al/AlOx/Al/AlOx/Al/Nb junction where the Al trapping layer is embedded between two insulating AlO/sub x/ barriers. Within this layer, a very sharp Andreev bound state (ABS) level E/sub 0/ is formed. Because of a very long recombination time, the charge amplification factor is expected to be 10-100 times larger in the double-barrier detector compared to ordinary single-barrier devices. The double barrier detector also has much higher idle-state subgap resistance at low temperatures. Because the middle Al quasiparticle trap layer is separated from the adjacent layers by two insulating tunneling barriers, the proximity effect is minimized. This provides much better alignment between the maximum of nonequilibrium quasiparticle distribution function and the maximum in the electron density of states. All the factors listed result in much higher sensitivity and the energy resolution of the double barrier Nb-based STJ as compared to their single-barrier analogs.         Microwave oscillator based on an intrinsic BSCCO-type Josephson junction    N.F. Pedersen and S. Madsen Summary: The electrical behavior of anisotropic BSCCO single crystals is modeled by mutually coupled long Josephson junctions. For the basic fluxon modes with one fluxon per layer, the fluxons will arrange themselves in an anti phase configuration (triangular lattice) because of the mutual repulsion. We are interested in the in-phase modes (square lattice) desired for many potential applications. We consider two mechanisms (i) intrinsic locking by out of phase oscillations at the trailing edge and (ii) locking by an external high-Q resonator with a resonance frequency corresponding to fluxon in-phase motion. The resulting model is a set of coupled nonlinear partial differential equations. By direct numerical simulations we have demonstrated that the qualitative behavior of the combined intrinsic Josephson junction and cavity system can be understood on the basis of general concepts of nonlinear oscillators interacting with a resonator. For some region of the parameter space it is possible to reach the desired synchronous state, making the system potentially suitable for applications. We also consider the system in the flux flow mode under a high magnetic field.         Effect of temperature on impedance behavior of insulation layer in a HTS MEMS switch for RF applications    Y. Hijazi, A. Bogozi, M. Brzhezinskaya, J. Martinez, J. Burke, J. Noel, Y.A. Vlassov and G.L. Larkins Jr. Summary: We have successfully developed High Temperature Superconducting (HTS) MicroElectroMechanical (MEM) switches for RF applications. A typical switch is composed of a superconducting Yttrium Barium Copper Oxide (YBa/sub 2/Cu/sub 3/O/sub 7/) coplanar waveguide structure with a gold bridge membrane suspended above an area of the center conductor covered with Barium Titinate (BaTiO/sub 3/) ferroelectric. A control voltage applied between the membrane and transmission line causes the membrane to collapse on top of the dielectric layer by electrostatically induced force; this in turn allows the RF signal to capacitively shunt to ground. Initial testing of switches showed very promising RF behavior with insertion losses less than 0.1dB with 30 dB isolation at 3 GHz. These switches rely on the "ON/OFF" impedance ratio to achieve switching; this is determined by the dielectric constant of the BaTiO/sub 3/ ferroelectric. These switches will be operated at cryogenic temperatures; we have investigated the impedance behavior vs. temperature of the HTS/ferroelectric/metal heterostructure to better understand the behavior of the insulating layer at cryogenic temperatures.         Highly-selective electronically-tunable cryogenic filters using monolithic, discretely-switchable MEMS capacitor arrays    E.M. Prophet, J. Musolf, B.F. Zuck, S. Jimenez, K.E. Kihlstrom and B.A. Willemsen Summary: A low loss electronically tunable filter was demonstrated using HTS/Au MEMS switched capacitor arrays. The two-pole filter was tuned by simultaneously varying the capacitance of each resonator by equal amounts. A K factor of between 3,500 and 5,000 was demonstrated for single pole resonators. The total tuning range was about 25% with an average Q of 7,000 at 77 K.         Superconducting integrated receiver for TELIS    V.P. Koshelets, S.V. Shitov, A.B. Ermakov, L.V. Filippenko, O.V. Koryukin, A.V. Khudchenko, M.Yu. Torgashin, P.A. Yagoubov, R.W.M. Hoogeveen and O.M. Pylypenko Summary: TELIS (Terahertz and submm Limb Sounder) is a cooperative European project to develop a three-channel heterodyne balloon-based spectrometer for measuring a variety of atmospheric constituents within the lower stratosphere. The 600-650GHz channel is based on a phase-locked Superconducting Integrated Receiver (SIR). SIR is the on-chip combination of a low-noise SIS mixer with quasioptical antenna, a superconducting Flux Flow Oscillator (FFO) acting as Local Oscillator (LO) and an SIS harmonic mixer (HM) for FFO phase locking. A number of new solutions was implemented in the new generation of SIR chips. To achieve the wide-band performance of the spectrometer, a side-feed twin-SIS mixer with 0.8 /spl mu/m/sup 2/ junctions integrated with a double-dipole (or double-slot) antenna is used. A Fourier transform spectrometer (FTS) test demonstrated a possibility to obtain the required instantaneous bandwidth for the SIS mixer. To ensure the autonomous operation of the phase-locked SIR on the balloon a number of approaches for the PLL SIR automatic control have been developed.         Optimization of the phase-locked flux-flow oscillator for the submm integrated receiver    V.P. Koshelets, P.N. Dmitriev, A.B. Ermakov, A.S. Sobolev, M.Yu. Torgashin, V.V. Kurin, A.L. Pankratov and J. Mygind Summary: The Superconducting Integrated Receiver (SIR) comprises in one chip a planar antenna integrated with an SIS mixer, a superconducting Flux Flow Oscillator (FFO) acting as Local Oscillator (LO) and a second SIS harmonic mixer (HM) for FFO phase locking. Free-running FFO linewidth well below 10 MHz is required to ensure phase-locked operation of an SIR. Comprehensive experimental study of the Nb-AlOx-Nb FFO linewidth and other main parameters has been carried out in order to achieve this goal. Essential dependence of the FFO linewidth on its width and idle region dimension has been found. It makes possible an optimization of the FFO design and selection of the best FFO parameters for practical operation of the SIR.         The submm wave Josephson flux flow oscillator; linewidth measurements and simple theory    J. Mygind, V.P. Koshelets, M.R. Samuelsen and A.S. Sobolev Summary: The Flux Flow Oscillator (FFO) is a long Josephson junction in which a DC bias current and a DC magnetic field maintain a unidirectional viscous flow of magnetic flux quanta. The theoretical linewidth of the electromagnetic radiation generated at the end boundary is due to internal current fluctuations as given by the usual expression for the lumped junction. Experimentally, however, the linewidth deviates significantly both in magnitude and functional dependence. We suggest a simple solution based on the assumption that the bias current creates an additional magnetic field in the junction. This is supported by linewidth measurements on FFO's subjected to different bias configurations.         Mechanical tuning of Superconducting lumped element filter    S. Hontsu, K. Iguchi, K. Agemura, H. Nishikawa and M. Kusunoki Summary: The tunable filter has variable center frequency (f/sub 0/) and variable bandwidth (BW) that can be adapted to software defined radio. In our mechanical tunable filter, capacitance of each element is changed by motion of dielectric plate that is located above the capacitive elements. The dielectric plates are moved by piezoelectric bimorph actuators. Tuning test of the f/sub 0/ in a cryocooler is performed using an actual superconducting filter fabricated with YBa/sub 2/Cu/sub 3/O/sub y/ thin film deposited on an MgO (100) substrate. Taking into account of the effective change of parallel capacitance to ground plane by movement of dielectric plates above the element, we choose the coplanar wave guide type filter that has the ground plane on top side of the substrate. Suitable design of the mechanically tunable superconducting lumped element filter is discussed.         Nonlinear model of coupled Superconducting lines    J. Mateu, C. Collado and J.M. O'Callaghan Summary: High Temperature Superconductor materials are known to produce intermodulation and other nonlinear effects. In planar structures, these nonlinearities depend on the field configuration on the strip, which in turn strongly depends on the device structure and therefore on the coupling between the strips. In this work we present an equivalent circuit that models the linear and nonlinear effects in coupled transmission lines. Numerical techniques based on Harmonic Balance are used to solve the equivalent circuit. We validate the equivalent circuit model by fitting measurements of a superconducting hairpin notch resonator. Examples of several coupled transmission line structures are given.         Elastic modulus study of gold thin film for use as an actuated membrane in a Superconducting RF MEM switch    A. Bogozi, A.V. Datye, M. Brzhezinskaya, Y.S. Hijazi, J. Martinez, J. Noel, K.H. Wu, Y.A. Vlasov and G.L. Larkins Jr. Summary: In earlier work a capacitively shunted superconducting MicroElectroMechanical (MEM) switch was designed and fabricated. The switch is composed of a superconducting YBa/sub 2/Cu/sub 3/O/sub 7/ coplanar waveguide structure with a Au bridge membrane suspended above an area of the center conductor covered with BaTiO/sub 3/ dielectric. The Au membrane is actuated by the electrostatic attractive force acting between transmission line and the membrane when voltage is applied. The value of the actuation force will greatly depend on the geometry and mechanical properties of the bridge material. Since Young's modulus characterizes the elastic properties of a material which is temperature dependent, it is important to find the effect of low temperature especially below the transition temperature of the superconductor in order to better understand the switch operation. Our results show that the elastic modulus for Au thin film at cryogenic temperature is 470 times bigger than it is at room temperature.         Fabrication of epitaxial NbN devices with TiN resistors    A. Kawakami, R. Terajima, S. Imai and Z. Wang Summary: To extend the application range of epitaxial NbN devices, we developed epitaxial TiN thin-film resistors. TiN has approximately the same lattice constant and crystalline structure as NbN and MgO. However, high quality TiN thin films show superconductivity at the liquid helium temperature. We attempted to remove this superconductivity using TiO impurity. The ratio of Ar and N/sub 2/ was fixed at 5:1 and the O/sub 2/ flow ratio varied from 0 to 1.6% in relation to the total gas flow. When O/sub 2/ ranged from 0.5 to 1.6%, superconductivity vanished and the resistivity obtained was about 50-145 /spl mu//spl Omega/cm at 4.2 K. X-ray analysis showed that the TiN films grew epitaxially on the MgO substrate as did the NbN films on the TiN films. Using the TiN resistor, a fully epitaxial NbN Josephson array oscillator was fabricated and tested. The oscillator was formed with 10 TiN-shunted NbN/MgO/NbN tunnel junctions and NbN microstrip resonators. At around 1.0THz, Shapiro steps induced by the Josephson oscillation were observed in the detector I-V characteristics.         Design and development of a prototype of hybrid superconducting receiver front-end for UMTS wireless network: first results and application perspectives    F. Ricci, V. Boffa, Guojun Dai, G. Grassano, R. Mele, R. Tebano, D. Arena, G. Bertin, N.P. Magnani, G. Zarba, A. Andreone, A. Cassinese and R. Vaglio Summary: In this paper we will describe the main results of the activity aimed to develop a prototype of superconducting receiver front-end (HTS RFE) for specific application in UMTS network. The system has been specifically designed to reach very low noise figure on the receiving channel to exploit the best performance in terms of sensitivity of the up-link channel.         Nonlinear distortion in a 8-pole quasi-elliptic bandpass HTS filter for CDMA system    C. Collado, J. Mateu, O. Menendez and J.M. O'Callaghan Summary: High Temperature Superconductor materials are known to produce intermodulation and other nonlinear effects which may restrict their use in wireless communication systems. Quantifying this degradation is crucial in determining if the use of HTS filters in the receiver is beneficial. In this work we use an approach for representing the HTS filter nonlinear equivalent circuit and simulating its performance. We have tested the approach on a planar, 8-pole quasielliptic (QE) filter, showing agreement between simulations and measurements of intermodulation products (IMD). The nonlinear equivalent circuit is then used to predict the nonlinear behavior of the filter and its effects on system parameters when it is subject to broadband signals like those used in wireless communication systems.         Analysis and design of Superconducting left-handed transmission lines    H. Salehi, A.H. Majedi and R.R. Mansour Summary: In this paper, for the first time, we study the properties of a superconductive-based left-handed transmission line (SLHTL). The effect of the kinetic inductance on the propagation constant of the left-handed transmission line is analyzed. It is shown that increasing the kinetic inductance decreases both the bragg frequency and the negative index frequency band of a distributed LHTL. A Coplanar waveguide structure is proposed to realize the LHTL. It is shown that the CPW structure has the capability of increasing the kinetic inductance of the TL by narrowing the spacing between the line and the ground plane because they are deposited on the same side of the substrate. This was not possible in a microstrip line as the spacing between the line and the ground is equal to the substrate thickness and is usually fixed. Furthermore, the dependency of the kinetic inductance to the bias current has been employed to design a tunable SLHTL. Possible applications of the tunable SLHTL in the design of miniaturized tunable resonators and filters are discussed.         Phase-sensitive measurements of nonlinearity in high-temperature superconductor thin films    J.C. Booth, K. Leong, S.A. Schima, J.A. Jargon, D.C. DeGroot and R. Schwall Summary: We present new frequency-dependent measurements of both the magnitude and phase of the nonlinear response in superconducting thin films at microwave frequencies obtained using a large-signal network analyzer. Our measurements show that the nonlinear inductance dominates the nonlinear response in thin YBCO films at 76 K, and our analysis yields two current-density scales corresponding to the real and imaginary components of the nonlinear response. The current-density scale associated with the dominant inductive response likely results from intrinsic pair-breaking, while the current-density scale associated with the nonlinear resistive term is smaller than the expected value due to pair-breaking, and could originate from vortex motion or other extrinsic effects.         HTS narrow band filters at UHF band for radio astronomy applications    Jiafeng Zhou, M.J. Lancaster, Frederick Huang, N. Roddis and D. Glynn Summary: High performance narrow-band High-Temperature Superconductor (HTS) filters at 610 MHz with very sharp cut-off response and low loss are needed for improving the observation of pulsars at the Jodrell Bank Observatory, UK. An eight-pole quasi-elliptic HTS filter using compact resonators has been designed for this purpose. The measured response of filter has an insertion loss of 0.3 dB (including a 0.2 dB ripple), and a return loss of 15 dB in the passband. Two transmission zeroes are realized to improve the steepness of the cut-off. The lowest harmonic is designed to appear at 1.79 GHz, about three times the center frequency. The out-of-band rejection is better than 85 dB up to this harmonic. The filter has been tested in the observatory with excellent results.         An X-band front-end module using HTS technique for a commercial dual mode radar    Dow-Chih Niu, Tung-Wuu Huang, Hao-Jung Lee and Chi-Yang Chang Summary: A front end module of receiver has been designed to eliminate the interference between the tracking and searching radar used in commercial radar application. The module is located at the receiving path of the searching radar. The proposed module includes two parts, the HTS superconducting filter and cryogenic low noise amplifier. The bandwidth of the eight-resonator HTS hairpin filter is 2% at the X-band frequency. Low insertion loss (below1 dB) and good skirt rejection (down to 60 dB at 50 MHz from the pass-band edge) are obtained. The two-stage low noise amplifier is designed by commercial low noise HEMT devices, NE321000. Two Lange couplers are located at output and input port of each amplifier stage to improve the return loss and to make LNA easily match to optimal low noise impedence. The cryogenic amplifier shows 30 dB gain and 0.4 dB NF at 77 K in X-band. A very high rejection is necessary for the elimination of unwanted spurious signals. The acceptable specification is 110 dB down at 500 MHz away from the band-edge of the filter. In general, the skirt rejection of a hairpin HTS filter is pretty good near the pass-band edge, but may become worse far from the pass-band edge. To meet the requirement of this commercial radar application, a high rejection suspended stripline filter is put after the low noise amplifier. The whole module shows an maximal NF of 1.5 dB, a gain of 25 dB around pass-band frequencies, and a rejection of better than 110 dB at 500 MHz away from the band edge of the filter. It totally solves the interference problem in this dual mode radar.         Thermal noise of microwave superconducting filter-amplifier combinations    W. Jutzi, S. Wuensch, H. Mattes, F. Schaefer and O. Lochner Summary: Superconducting filters in radioastronomical receiver frontends at cm-wavelengths may eliminate nearby terrestrial interference signals since they offer very high frequency selectivity and extremely small insertion loss. Moreover, power in unwanted intermodulation signals is sufficiently small at the expected input levels. On the other hand thermal noise outside the passband of a filter-amplifier combination may affect the receiver performance. The overall thermal noise of superconducting filters with Butterworth or quasi-elliptic characteristic connected via a 50 /spl Omega/ transmission line of finite length with a low noise amplifier is investigated. Arrangements with very low noise outside the passband are described. Simulated and measured thermal noise spectra are in reasonable agreement.         Design and performance of miniaturized quarter-wavelength resonator bandpass filters with attenuation poles    H. Kanaya, K. Kawakami, F. Koga, Y. Kanda and K. Yoshida Summary: For more size reduction of the high temperature superconducting coplanar waveguide (CPW) bandpass filter (BPF), we introduce the design method of the meanderline quarter-wavelength resonator BPF. The admittance and impedance inverters (J- and K-inverters) are realized by using interdigital gaps and meanderline short stubs. Also, we estimate the slope parameter of the meanderline resonator by using EM-simulator. In order to control the attenuation poles, we adjust the meanderline intervals and shapes of the cross-coupling section, so that we can design the frequency and number of the attenuation poles. The size of the 6-pole CPW quarter-wavelength resonator with two attenuation poles (center frequency = 2 GHz) was 3.5 /spl times/ 8 mm.         Design and performance of an electrically small slot loop antenna with a miniaturized superconducting matching circuit    Y. Tsutsumi, H. Kanaya and K. Yoshida Summary: In order to realize a small superconducting receiver, we designed an electrically small slot loop antenna with a miniaturized impedance matching circuit. The area of the slot loop antenna is 4 mm /spl times/ 4 mm on MgO substrate at a frequency of 2.4 GHz. By applying 2-pole bandpass filter technique, we propose a design theory of the miniaturized impedance matching circuit that consists of coplanar waveguide (CPW) quarter and half wavelength transmission lines of meandering geometry and the impedance inverting circuits (J inverters). By using electromagnetic field simulator, we realized the circuit which matches the small radiation resistance R/sub a/=0.776 /spl Omega/ of the electrically small slot loop antenna to the feeder impedance Z/sub 0/=50 /spl Omega/, and attained the normalized bandwidth of 3%. We also made a preliminary experiment on this miniaturized antenna using a YBCO thin film on MgO substrate.         RF power dependence of microstrip disk resonators with YBCO films for 4 GHz band    K. Yamanaka, A. Akasegawa, M. Kai and T. Nakanishi Summary: High-Tc superconducting (HTS) power filters have an attractive possibility of being applied to the base stations of the- future mobile-communication systems. In the microstrip structure, disk-shape-patterned HTS resonators are considered potential candidates for the HTS power filters. In order to research the application feasibility of disk resonators, the resonator samples were fabricated with different quality YBCO thin-films, and the power handling and third intermodulation-distortion (IMD3) of the samples were then examined for the incident continuous wave power of up to about 10 W around 4 GHz at cryogenic temperatures. We discuss the results on the relationship between the RF power dependence and the YBCO film qualities.         Shapiro step responses in the flux-flow state of bi-2212 intrinsic Josephson junctions with cooperation of pancake vortices    Y. Yamada, K. Nakajima, T. Yasuda and T. Yamashita Summary: Flux-flow properties of one-dimensionally long Bi-2212 intrinsic Josephson junction stacks are studied. Quasioptically irradiated millimeter waves drives Josephson vortices and reveals current steps in equal voltage intervals corresponding to the Josephson relation. Differential conductance properties and the power dependence of the current step height are also measured. The experimental results indicate that the responses are consistent with the Shapiro step. Periodic potentials produced by pancake vortices are considered to be effective to realize the in-phase collective motion of the Josephson vortices.         Influence of parameters of fabrication on quality and performance of Superconducting MEM switches    M. Brzhezinskaya, J. Noel, J. Martinez, Y. Hijazi, Y.A. Vlasov and G.L. Larkins Jr. Summary: In earlier work a capacitively shunted superconducting MicroElectroMechanical (MEM) switch has been designed and fabricated. The switch is composed of high temperature superconducting (HTS) YBa/sub 2/Cu/sub 3/O/sub 7/ coplanar waveguide structure with a gold bridge membrane suspended above an area of the center conductor covered with BaTiO/sub 3/ dielectric. The switch demonstrated an insertion loss of less than 0.007 dB with 30 dB isolation at 3 GHz. These switches have been shown to be viable, however, issues of the dielectric material deposition and gold bridge release process posed limitations on the yield and switch cycling. In this work we report on the issues encountered and improvements made in the development of HTS MEMS switches for use in tunable RF devices.         Multi-tapped micro-strip "T" resonator using MEM switch for tuning    L.G. Lawrence, J. Burke, M. Brzhezinskaya, Y. Hijazi, J. Martinez, D. Fairweather, Y.A. Vlasov and G.L. Larkins Jr. Summary: In this work we have fabricated multiple MEM (micro-electro-mechanical) switches using a high-T/sub c/ superconductor to change the tap positions (open circuit termination to grounded termination) on a micro-strip "T"-resonator structure. MEM switches at different positions along the base of the "T's" resonator line introduce notches for different operating frequencies. This design has its lowest resonant frequency of approximately 3.5 GHz with the first tap position at the base of the "T"-resonator. The tap positions are changed with three MEM switches placed at the base of the "T"-resonator and separated by 1/8 of the fundamental wavelength. The performance, fabrication details and recent test results will be presented along with simulation data.         Cross-coupled narrow-band filter for the frequency range of 2.1 GHz using YBCO resonators with artificial magnetic pinning lattices    L.M. Wang, Chang-Hao Hsieh and Chih-Chang Chang Summary: Narrow-band microstrip cross-coupled band-pass filters based on the quadruplet geometry are designed for wireless-communication applications. We have fabricated the high-T/sub c/ superconducting filters by pattering YBa/sub 2/Cu/sub 3/O/sub y/ (YBCO) films deposited on LaAlO/sub 3/ substrates. The flux pinning in YBCO resonators is increased with an artificial magnetic lattice of Nd/sub 0.2/Sr/sub 0.8/MnO/sub 3/ (NSMO) pinning dots. The 4-pole 15-mm-square filter has a pair of transmission zeros near the pass-band edge, a 2.18-GHz center frequency with a 9.8-MHz bandwidth and a 1.48-dB minimum insertion loss at 77 K. The results are discussed and compared with that of an identical YBCO filter without NSMO pinning dots. The influences of the flux pinning on filter performance are discussed.         Superconducting quantum interference filters as absolute magnetic field sensors    P. Caputo, J. Tomes, J. Oppenlander, C. Haussler, A. Friesch, T. Trauble and N. Schopohl Summary: We propose Superconducting Quantum Interference Filters (SQIFs) as high sensitive magnetic field detectors. The SQIF is made of high critical temperature grain boundary Josephson junctions, and it is surrounded by an on chip superconducting pick-up loop which enhances the magnetic field sensitivity of about 10 times with respect to the same SQIF without pick-up loop. The devices are operated in Stirling microcoolers, at a temperature of about 70 K. In the presence of an applied magnetic field B, SQIFs show the typical magnetic field dependent voltage response V(B), which is sharp delta-like dip in the vicinity of zero magnetic field. When the SQIF is cooled with magnetic shield, and then the shield is removed, the presence of the ambient magnetic field induces a shift of the dip position from B/sub 0/ /spl ap/ 0 to a value B /spl ap/ B/sub 1/, which is about the average value of the Earth magnetic field, at our latitude. The low hysteresis observed in the sequence of experiments makes SQIFs suitable for high precision measurements of the absolute magnetic field. Typical magnetic flux noise spectra of SQIFs show a white noise level of about 0.6 /spl mu/T//spl radic/Hz. Comparative measurements of the direct spectra with the spectra measured by using noise reduction techniques reveal a significant decrease of the 1/f noise levels. The experimental results are discussed in view of potential applications of high critical temperature SQIFs in magnetometry.         HTS microstrip antenna array for circular polarization with cryostat    Dong-Chul Chung, Chang-Hun Yun, Kay-Hyeok An, Sung-Hun Lim, Sung-Yul Choi, Byoung-Sung Han, Je-Ha Oh, Min-Hwan Kwak, Sung-Hae Jung, Kwang-Yong Kang, Seok-Kil Han, Jong-Sun Hwang, Tae-Hyun Sung and Hyo-Sang Choi Summary: We report the comparison results of an HTS antenna array for circular polarization with a self cryostat and comparison with a gold counterpart. The HTS antenna array designed in this work was fabricated using a YBCO superconducting thin film on an MgO substrate, and the designed resonant frequency was 11.85 GHz. We used square patches with truncated corners for circular polarization and employed a corporate feed network using sequential rotation techniques for enhancement of axial ratio. A cryostat was constructed for the measurement of each antenna, and liquid nitrogen was used as a coolant. Measurements from HTS antennas, including return loss, bandwidth, gain, efficiency and axial ratio are presented and compared with those of gold counterparts. The measured results show that useful antennas can be made using the proposed architecture for satellite communication systems.         Author Index (2004 - Part 1)    No author information available Summary: Not available         Upcoming Special Conference Issues (2004 - Part 1)    No author information available Summary: Not available

© Copyright 2009 All Rights Reserved. Developed for IEEE Applied Superconductivity Conference by InControl Productions, Inc..