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We investigate theoretically the effect of the coupling radius on the transfer function in 1D parallel and 2D SQUID arrays with different number of Josephson junctions in parallel and series at 77 K. Our results show a plateauing of the array maximum transfer function with the number of junctions in parallel. The plateauing defines the array coupling radius which we show increases with decreasing the normalised inductive reactance of the SQUID loop. The coupling radius is found to be independent of the number of junctions in series. Finally, we investigate the voltage versus magnetic field response and maximum transfer function of one 1D and two 2D SQIF arrays with different SQUID loop area distributions. [ABSTRACT FROM AUTHOR]

We compare the potential of SQUID arrays and Josephson junction arrays as magnetic field detectors in an open-loop configuration, accounting for such limitations as technological parameter fluctuations, current density distribution and self-field effects originating from the bias current. Because of the simplicity of its single layer process, the ion-damaged barrier technology is used to fabricate the Josephson junctions (JJ) and to make the evaluations by extrapolation to larger area detectors. From preliminary experimental results on series arrays of Josephson junctions, we expect a less detrimental effect of self-flux and parameter dispersion, which is particularly important with high critical temperature technologies. [ABSTRACT FROM AUTHOR]

We developed a fabrication process to establish large arrays of up to 5-stacked Josephson junctions for the Josephson Arbitrary Waveform Synthesizer (JAWS). SNS-type Josephson junctions with NbxSi1-x barriers are used for this application. By modifying our standard window process, e.g. to add a CMP (chemical mechanical polishing) and an ALD (atomic layer deposition) step, the yield of this process was increased. An output voltage of 1 V RMS could be achieved by using 4 JAWS arrays in series with a total number of 60,000 5-stacked junctions. The investigation of the current-voltage characteristics (IVC) showed an interesting and potentially useful feature. The required pulse amplitude per junction for getting the maximum Shapiro step width reduces for higher junction stacks. We found that the pulse power linearly reduces with the square of the junction number in the array. The origin of this effect might be a strong neighbour-neighbour interaction of the junctions, which are closely arranged within the stacked configuration. This might generate a strong self-synchronization of the junctions. [ABSTRACT FROM AUTHOR]

Superconducting electronics often require high-density microwave interconnects capable of transporting signals between temperature stages with minimal loss, cross talk, and heat conduction. We report the design and fabrication of superconducting 53 wt% Nb-47 wt% Ti (Nb47Ti) FLexible coAXial ribbon cables (FLAX). The ten traces each consist of a ${\oslash}$ 0.076 mm NbTi inner conductor insulated with PFA (${ \oslash }$ 0.28 mm) and sheathed in a shared 0.025 mm thick Nb47Ti outer conductor. The cable is terminated with G3PO coaxial push-on connectors via stainless steel capillary tubing (${ \oslash }$ 1.6 mm, 0.13 mm thick) soldered to a coplanar wave guide transition board. The 30 cm long cable has 1 dB of loss at 8 GHz with $-$ 60 dB nearest neighbor forward cross talk. The loss is 0.5 dB more than commercially available superconducting coax likely due to impedance mismatches caused by manufacturing imperfections in the cable. The reported cross talk is 30 dB lower than previously developed laminated NbTi-on-Kapton microstrip cables. We estimate the heat load from 1 K to 90 mK to be 20 nW per trace, approximately half the computed load from the smallest commercially available superconducting coax from CryoCoax. [ABSTRACT FROM AUTHOR]

We have developed large-format, close-packed X-ray microcalorimeter arrays fabricated on solid substrates, designed to achieve high energy resolution with count rates up to a few hundred counts per second per pixel for X-ray photon energies up to 8 keV. Our most recent arrays feature 31-micron absorbers on a 35-micron pitch, reducing the size of pixels by about a factor of two. This change will enable an instrument with significantly higher angular resolution. In order to wire out large format arrays with an increased density of smaller pixels, we have reduced the lateral size of both the microstrip wiring and the Mo/Au transition-edge sensors (TES). We report on the key physical properties of these small TESs and the fine Nb leads attached, including the critical currents and weak-link properties associated with the longitudinal proximity effect. [ABSTRACT FROM PUBLISHER]

We develop superconducting transition-edge sensor (TES) microcalorimeter focal planes for versatility in meeting the specifications of X-ray imaging spectrometers, including high count rate, high energy resolution, and large field of view. In particular, a focal plane composed of two subarrays: one of fine pitch, high count-rate devices and the other of slower, larger pixels with similar energy resolution, offers promise for the next generation of astrophysics instruments, such as the X-ray Integral Field Unit Instrument on the European Space Agency's ATHENA mission. We have based the subarrays of our current design on successful pixel designs that have been demonstrated separately. Pixels with an all-gold X-ray absorber on 50 and 75 μm pitch, where the Mo/Au TES sits atop a thick metal heatsinking layer, have shown high resolution and can accommodate high count rates. The demonstrated larger pixels use a silicon nitride membrane for thermal isolation, thinner Au, and an added bismuth layer in a 250-μm2 absorber. To tune the parameters of each subarray requires merging the fabrication processes of the two detector types. We present the fabrication process for dual production of different X-ray absorbers on the same substrate, thick Au on the small pixels and thinner Au with a Bi capping layer on the larger pixels to tune their heat capacities. The process requires multiple electroplating and etching steps, but the absorbers are defined in a single-ion milling step. We demonstrate methods for integrating the heatsinking of the two types of pixel into the same focal plane consistent with the requirements for each subarray, including the limiting of thermal crosstalk. We also discuss fabrication process modifications for tuning the intrinsic transition temperature ( Tc) of the bilayers for the different device types through variation of the bilayer thicknesses. The latest results on these “hybrid” arrays will be presented. [ABSTRACT FROM PUBLISHER]

This paper presents the design and modeling of a second-generation (2G) high-temperature superconducting (HTS) magnet, which is suitable for Lorentz force electrical impedance tomography (LFEIT). The concept of constructing a superconducting magnet using the configuration of a Halbach array is proposed, which can achieve a favorable thin geometry for the LFEIT system, and is able to build a homogeneous magnetic field with high intensity. The modeling of this superconducting Halbach array magnet has been executed by COMSOL Multiphysics. \boldsymbolH-formulation together with \boldsymbolB-dependent critical current density and bulk approximation are used as the basic tools for modeling. Results reveal that this magnet can achieve over 1-T magnetic field in the cross section required. The optimization of HTS coils' location and different numbers of coils are carried out to balance the strength and homogeneity of magnetic field. [ABSTRACT FROM PUBLISHER]

The capability of an all-niobium superconducting quantum interference device (SQUID) array to operate as an electrically small antenna capable of detecting radio frequency from distant sources was demonstrated. The measurements were performed in three different arrays, with each array consisting of 2400 identical cells. The intrinsic broadband characteristics of the device were confirmed by the flat frequency response of the ratio of the output and input voltages (the S21 parameter) of the array between 300 kHz and 1 GHz. Setting the device to its optimal operating parameters allowed the detection of signals from local frequency-modulation stations. [ABSTRACT FROM PUBLISHER]

A design of a galactic RF distance measuring system based on a Josephson junction array is presented. The system can be used to measure the approximate distance to the origin of a radio burst in space, by measuring the frequency dispersion of the burst radiation and calculating the dispersion measure, which is then used to calculate the approximate distance to the source. The designed system can be used to nominally measure signals lasting a minimum duration of 10 ms or greater, within an RF range of 1–3 GHz. [ABSTRACT FROM PUBLISHER]

Using numerical simulation, we investigate the output power and loading tradeoffs for Superconducting Quantum Arrays (SQAs) suggested for the implementation of broadband radio-frequency systems, including active electrically small antennas capable of providing highly linear transfer characteristics with a high dynamic range. Standard matching loads used for linear microwave networks, including passive antennas, are not applicable for the active SQA-based circuits generally due to the strong shunting effect restricting the attainable linearity. At the same time, the output power of an active device can be increased by a power supply even for the impedance-mismatched circuits. Both the optimum achievable balance of the shunt effects and getting the required output power are analyzed and discussed in detail. [ABSTRACT FROM PUBLISHER]

New superconductor single flux quantum logics with no static power dissipation in bias resistors, such as Reciprocal Quantum Logic (RQL), offer opportunities to create energy-efficient superconductor processors operating at high frequencies with ultra-low power consumption. This paper discusses the results of our work on the cell-level design and analysis of a benchmark set of 32-/64-bit RQL processor integer and floating-point units such as adders, multipliers, an arithmetic-logic unit, and an array shifter, as well as small 1–4 Kbit RQL on-chip storage components such as register files, on-chip memory, and the top level caches. Our layout-aware design process includes the complete cell-level design and approximate physical layout of the circuits followed by the VHDL simulation, verification, and energy profiling using our RQL VHDL cell library tuned to the future MIT Lincoln Laboratory 10 \kA/cm^2 248 nm process with 10 Nb metal layers and the minimum JJ critical current of 38 \mu\A. Our designs have the energy efficiency of $\sim$1.0 single-precision TFLOPS/W and $\sim$0.5 double-precision TFLOPS/W for floating-point units, and $\sim$1–24 TOPS/W for 32-bit integer units at room temperature using the cryocooling efficiency of 0.1 $\%$ (1000 W/W). The 1–4 Kbit 32-/64-bit multi-ported scratchpad memory, register files, write-through and write-back caches designed with RQL Non-Destructive Read-Out storage cells have the average energy consumption of 3.0–9.5 fJ/bit/operation at room temperature using the cryocooling efficiency of 0.1 $\%$. While these results are very promising, more work is needed to evaluate the contribution of the energy costs of instruction scheduling and off-chip main memory access to the energy efficiency of RQL computing across a whole system. [ABSTRACT FROM PUBLISHER]

Mixers comprising series-connected distributed Superconductor–Insulator–Superconductor tunnel junctions (SDJ) are analyzed. Compared to mixers consisting of parallel-connected distributed junctions (PDJ), SDJ mixers offer wider instantaneous bandwidth and higher dynamic range as well as easier magnetic field tuning. However, SDJ mixers are more complex in operation and in design as well. The reason lies in the fact that the large-signal nonlinear equations containing 3N unknowns, with N the junction number, are difficult to be solved. We propose a fixed-point iterative method to solve the nonlinear equations. This method is verified to be effective and efficient and a case study is done to clarify the uniqueness of SDJ mixers in operation. [ABSTRACT FROM PUBLISHER]

A quantum-accurate waveform with an rms output amplitude of 1 V has been synthesized for the first time. This fourfold increase in voltage over previous systems was achieved through developments and improvements in bias electronics, pulse-bias techniques, Josephson junction array circuit fabrication, and packaging. A recently described ac-coupled bipolar pulse-bias technique was used to bias a superconducting integrated circuit with 25 600 junctions, which are equally divided into four series-connected arrays, into the second quantum state. We describe these advancements and present the measured 1 V spectra for 2 Hz and 10 Hz sine waves that remained quantized over a 0.4 mA current range. We also demonstrate a 2 kHz sine wave produced with another bias technique that requires no compensation current and remains quantized at an rms voltage of 128 mV over a 1 mA current range. Increasing the clock frequency to 19 GHz also allowed us to achieve a maximum rms output voltage for a single array of 330 mV. [ABSTRACT FROM PUBLISHER]

Bulk high-temperature superconductors with a rectangular shape are easy to realize a compact assembly, which is promising for maglev applications. In order to find a reasonable array pattern, we have studied the levitation force of four multiseeded rectangular YBaCuO blocks with three possible arrays above two different permanent-magnet guideways (PMGs). Experimental results show that the levitation force can be improved by optimizing the array pattern of the bulk superconductors. An effective method to improve the utilization rate of the applied magnetic field is to avoid the joint air gaps between bulks located in a strong magnetic field area of the PMG. The optimal array pattern is able to enhance the levitation performance of the present superconducting maglev vehicle. [ABSTRACT FROM PUBLISHER]

The fabrication of high-Tc YBa2Cu3Oy (YBCO) superconducting quantum interference devices (SQUIDs) that produce low flux noise while maintaining a high fabrication yield continues to challenge scientists. In this paper, we report the characterization of low-noise serial high-Tc SQUIDs for biomagnetic applications. Epitaxial high-Tc YBCO thin films with a root-mean-square surface roughness less than 5 nm are optimized for the low-noise serial SQUID coupled to a common pickup coil to form magnetometers and gradiometers. Current-voltage curves, voltage-flux curves, and flux noise of SQUID devices are characterized. A smooth surface morphology across the bicrystal line is essential for SQUIDs to show good characteristics. The field sensitivity is improved by a factor of (2)1/2 with the designed serial SQUID array, which is coupled to a common pickup loop. This is demonstrated, and its fabrication yield is higher than 80% for devices with peak-to-peak voltage VPP ≥ 15 μV. The challenges and perspectives of the high-Tc serial SQUID array for biomagnetic applications are addressed and discussed. [ABSTRACT FROM PUBLISHER]

The fabrication of high- Tc \YBa2\Cu3\Oy (YBCO) superconducting quantum interference devices (SQUIDs) that produce low flux noise while maintaining a high fabrication yield continues to challenge scientists. In this paper, we report the characterization of low-noise serial high- Tc SQUIDs for biomagnetic applications. Epitaxial high- Tc YBCO thin films with a root-mean-square surface roughness less than 5 nm are optimized for the low-noise serial SQUID coupled to a common pickup coil to form magnetometers and gradiometers. Current–voltage curves, voltage–flux curves, and flux noise of SQUID devices are characterized. A smooth surface morphology across the bicrystal line is essential for SQUIDs to show good characteristics. The field sensitivity is improved by a factor of (2)^1/2 with the designed serial SQUID array, which is coupled to a common pickup loop. This is demonstrated, and its fabrication yield is higher than 80% for devices with peak-to-peak voltage VPP\geq 15\ \mu\V. The challenges and perspectives of the high- Tc serial SQUID array for biomagnetic applications are addressed and discussed. [ABSTRACT FROM PUBLISHER]

Bulk high-temperature superconductors with a rectangular shape are easy to realize a compact assembly, which is promising for maglev applications. In order to find a reasonable array pattern, we have studied the levitation force of four multiseeded rectangular YBaCuO blocks with three possible arrays above two different permanent-magnet guideways (PMGs). Experimental results show that the levitation force can be improved by optimizing the array pattern of the bulk superconductors. An effective method to improve the utilization rate of the applied magnetic field is to avoid the joint air gaps between bulks located in a strong magnetic field area of the PMG. The optimal array pattern is able to enhance the levitation performance of the present superconducting maglev vehicle. [ABSTRACT FROM PUBLISHER]

Cold-electron bolometers (CEBs) integrated with twin-slot antennas have been designed and fabricated. Optical response was measured at bath temperatures of 0.06 to 3 K using blackbody radiation source at temperatures of 3 to 15 K. The responsivity of 0.3 \ast 10^9\ \V/W was measured at 2.7-K blackbody temperature that is close to the temperature of the cosmic microwave background. Optical measurements indicate quasi-optical coupling efficiency of up to 60% at low phonon temperature and low signal level. Estimations for bolometer responsivity were made for practical range of bath temperatures and blackbody radiation temperatures. The estimated ultimate dark responsivity at 100-mK bath temperature can approach SV =\break 10^{10}\ \V/W and reduces down to 1.1 \ast 10^8\ \V/W at 300 mK for a device with absorber volume of 5 \ast 10^-20\ \m^3. [ABSTRACT FROM PUBLISHER]

The ITER tokamak includes 18 superconducting D-shaped toroidal field (TF) coils. Unavoidable shape deformations as well as assembly errors will lead to field errors, which can be modeled with the knowledge of the current center line (CCL). Accurate survey during the entire manufacturing and assembly process, including transfer of survey points, is complex. In order to increase the level of confidence, a room temperature magnetic measurement of the CCL on assembled and closed winding packs is foreseen, prior to insertion into their cold case. In this contribution, we discuss the principle of the CCL determination and present a low frequency ac measurement system under development at PSI, within an ITER framework contract. The largest current allowed to flow in the TF coil at room temperature and the precision requirements for the determination of the CCL loci of the coil are hard boundaries. Eddy currents in the radial plates, the winding pack enclosures, and possibly from iron in the reinforced concrete floor of the assembly hall are more subtle to bring under control quantitatively, and will limit the highest frequency that can be used to measure reliable values of the field gradients. Our objective is to measure the CCL loci by combining magnetic data obtained with printed circuit board flux coils and survey data gathered around the perimeter of the D-shaped coil. [ABSTRACT FROM PUBLISHER]

We have constructed a niobium multiloop SQUID current sensor and a 60-SQUID series array as a mix-and-match fabrication experiment utilizing our in-house projection stepper. The multiloop SQUID includes an input coil with a linewidth of 0.8 \mu\m and a pitch of 1.6 \mu\m, resulting in the mutual inductance M^ -1 = 1.8 \ \mu\A/\Phi0. The SQUID array is built on the same chip as the second-stage amplifier. The array and the multiloop showed white flux noise of 0.2 and 0.8 \mu\Phi0 \ \Hz^{-1/2} at 4.2 K, respectively. Owing to the well-balanced gradiometric narrow-line construction, the two-SQUID system can be cooled down in the Earth's magnetic field and can be operated without superconducting or mu-metal shields. Excess low frequency noise was observed, whose possible origin in Josephson dynamics has been briefly studied with numerical simulation. [ABSTRACT FROM PUBLISHER]

The magnetic design of a pair of elliptically polarized undulators with APPLE-II type which will be used in a soft X-ray beam line for ARPES and PEEM at SSRF is presented. The undulators will cover the energy range from 20 eV to 2000 eV of arbitrary polarized light including the horizontal, vertical, elliptical and circular polarization. The quasi-periodic design to minimize the contributions of the higher harmonics of the low energy undulator is also described. [ABSTRACT FROM PUBLISHER]

The correction of the magnetic field of an elliptically polarized undulator (EPU) decreases the phase errors, the RMS trajectory and multipole magnetic components. The conventional method to correct the field involves tedious work with much trial and error. Based on field-shimming procedures and a field-shimming simulator proposed in National Synchrotron Radiation Research Center, the duration of field correction of EPU46 becomes decreased. The first field integral and the kicker value at each magnet pole determine the amount of adjustment of vertical and horizontal positions of the magnet. The final result of correcting a single pair of a magnet array shows a phase error less than 5^\circ and a variation of the RMS trajectory less than 5 \mum, in both circular and linear polarization modes for single pair of magnet array. [ABSTRACT FROM PUBLISHER]

Motivated by the needs of Cornell High Energy Synchrotron Source (CHESS), we developed and are now constructing a novel type of planar undulator magnet called CHESS Compact Undulator. The device consists of two pure permanent magnet (PPM) arrays mounted inside of a rectangular box-like frame on linear bearings providing magnet array motion along the beam axis. The outside frame dimensions are 156 mm \times 148 mm. Undulator is 1 meter long. It has 5 mm constant gap. The magnetic field strength is controlled by the array longitudinal motion (adjustable phase scheme). Magnetic structure has 24.4 mm period and maximum peak field 1.1 Tesla. The PM material is Nd-Fe-B of 40UH grade. [ABSTRACT FROM PUBLISHER]

A use of bulk high-temperature superconductors (HTSs) for an undulator is attractive since a high magnetic field can be generated at low-temperatures. While potential for generation of the high magnetic field is high, in-situ magnetization of the bulk HTSs for periodic field generation is challenging issue. Recently, we proposed a new type of undulator using bulk high-Tc superconductors (HTS) and a solenoid magnet. The undulator, named Bulk HTSC staggered array undulator (Bulk HTSC SAU), consists of a stacked array of bulk HTSs and copper insulators and a solenoid magnet. A proof of principle experiment at 77 K using liquid nitrogen has been carried out. The estimated performance at about 30 K was estimated using results of property measurements for the HTS used for the Bulk HTSC SAU. The expected undulator peak field reaches to 1.08 T for undulator period length of 9.9 mm for the undulator gap of 4.0 mm. This performance is about 2 times higher than that of existing technologies. [ABSTRACT FROM PUBLISHER]

Two series/parallel arrays of ten cold-electron bolometers with superconductor–insulator–normal tunnel junctions were integrated in orthogonal ports of a cross-slot antenna. To increase the dynamic range of the receiver, all single bolometers in an array are connected in parallel for the microwave signal by capacitive coupling. To increase the output response, bolometers are connected in series for dc bias. With the measured voltage-to-temperature response of 8.8 \mu\V/mK, absorber volume of 0.08 \mu\m^3, and output noise of about 10 \nV/Hz^1/2, we estimated the dark electrical noise equivalent power (NEP) as \NEP = 6 \ast 10^-18\ \W/Hz^1/2. The optical response down to \NEP = 2 \ast 10^-17\ \W/Hz^1/2 was measured using a hot/cold load as a radiation source and a sample temperature down to 100 mK. The fluctuation sensitivity to the radiation source temperature is 1.3 \ast 10^-4\ \K/Hz^1/2. A dynamic range over 43 dB was measured using a backward-wave oscillator, a variable polarization grid attenuator, and cold filters/attenuators. [ABSTRACT FROM AUTHOR]

Arrays of nanometric Ni dots embedded in amorphous Mo3Si (a-Mo3Si) or crystalline Nb superconducting films modify the vortex lattice dynamics and the dissipation mechanisms, close to critical temperatures. The vortex lattice force vs. velocity characteristics have been measured in both hybrids. The velocities of the ordered and synchronized vortices are the same in both systems (hybrids based on Nb films or a-Mo3Si films), but remarkably the needed driving forces are one order of magnitude smaller in a-Mo3Si hybrids than in Nb based hybrids. This experimental behavior points out magnetic/superconducting hybrids, based on amorphous superconductors films, could be a promising material for controlling vortex motion with very low driving forces. [ABSTRACT FROM AUTHOR]

With the aim of clarifying the origin of local defects in coated conductors (CCs) and feeding back to the fabrication process, we have examined the distribution of defects in each layer of a CC which has \ Ag/GdBCO/CeO2/LaMnO3(LMO)/IBAD -MgO/ \break Gd2Zr2O7(GZO)/Hastelloy structure by means of a high-speed scanning laser observation system. The system detects anomalies in height of the surface and reflectivity due to existence of local defects such as depressions, precipitates, scratches, dust, and inhomogeneous physical properties at the maximum speed of 100 m/h. Distribution of local defects in superconducting layer has been examined by means of various evaluation systems with a Hall sensor array, a SQUID gradiometer array, and magneto-optical imaging. By comparing the data of defects evaluated by these testing systems, we found one of the main origins of the delamination defects was the anomaly at the surface of the Hastelloy substrate. It is possible to decrease the number of times and kinds of evaluation processes for low cost CCs with a higher yield by finding the key point of evaluation in the process of CCs with the laser observation system. [ABSTRACT FROM AUTHOR]

Superconducting YBCO thin films have been prepared by the pulsed laser deposition (PLD) technique. YBCO films have been patterned by kagomé antidot lattice. The optical lithography technique has been used to get the required pattern. We have studied the variation of the critical current with magnetic field in kagomé patterned YBCO films. The longitudinal critical current exhibits jumps which are found to be asymmetrically positioned in magnetic field. These steps are found mainly at nonmatching fields. Around the zero field limit the critical current remains independent of magnetic field. The impact of the DC current and ac-superposition in controlling the vortex motion in patterned film has been discussed. [ABSTRACT FROM AUTHOR]

There is an intense research in maglev technology for providing convenient and safe transportation. In particular, several projects are being carried out worldwide -particularly in Germany, Brazil, and China- for constructing full-scale maglev trains. They are based on the levitation of superconducting pellets over magnetic guideways. The optimization of their geometrical parameters and the properties of both superconducting and magnetic parts become very important. Theoretical simulations capturing the essential physics of the superconducting levitation become a very useful tool for understanding and improving the devices. In this work, we extend previous numerical models to incorporate new features in order to simulate closer to actual maglev designs. In particular, we analyse how the levitation and guidance forces are modified when the superconducting part is composed of several superconductors as compared with a single one. [ABSTRACT FROM AUTHOR]

To improve the response performance of superconducting infrared detectors, we have developed a fabrication process for nano-antennas. A nano-antenna consists of a dipole antenna, and a superconducting thin film strip placed in the antenna's center. By measuring the transition temperature of the superconducting strips, we confirmed that their superconductivity maintained a good condition after the nano-antenna fabrication process. We also evaluated nano-antenna characteristics using Fourier transform infrared spectroscopy. The evaluated antenna length and width were respectively set at around 2400 nm and 400 nm, and the antennas were placed at intervals of several micrometers around the area of 1 mm^2. In an evaluation of spectral transmission characteristics, clear absorption caused by antenna effects was observed at around 1400 cm^-1. High polarization dependencies were also observed. [ABSTRACT FROM AUTHOR]

The characteristics of the voltage-biased superconducting quantum interference device (SQUID) were investigated. Under the proper bias conditions, the flux-to-current transfer coefficient in a voltage-bias mode is the same as that in a current bias mode. To enhance the flux-to-current transfer coefficient, we proposed the parallel SQUID array connected by wire bonding. The enhancement in current modulation amplitude with the parallel array is verified experimentally. The probabilities of finding successful SQUIDs to form the array are also calculated. According to the theoretical analysis, the field noise of the two-stage directly-coupled SQUID magnetometer is less than that of the conventional directly-coupled SQUID magnetometer. The proposed design can be implemented by using the high-Tc junction technologies. [ABSTRACT FROM AUTHOR]

We have designed a 2-bit Booth encoder with Josephson Transmission Lines (JTLs) and Passive Transmission Lines (PTLs) by using cell-based techniques and tools. The Booth encoding method is one of the algorithms to obtain partial products. With this method, the number of partial products decreases down to the half compared to the AND array method. We have fabricated a test chip for a multiplier with a 2-bit Booth encoder with JTLs and PTLs. It has a processing frequency of 20 GHz with the bias margin \pm25%. The frequency of this circuit increases up to 45 GHz with the bias voltage by 25% increased from the design voltage. The circuit area of the multiplier designed with the Booth encoder method is compared to that designed with the AND array method. [ABSTRACT FROM AUTHOR]

We describe the transition-edge-sensor (TES) focal plane arrays used for three cosmic microwave background (CMB) polarimetry projects. The first is BICEP2. The focal plane array for BICEP2 has been delivered and the instrument is now taking data at the South Pole. Second is the Keck Array. The focal planes for Keck will be nearly identical to those of BICEP2, but will cover multiples frequencies (96, 150 and 225 GHz). The scheduled deployment of Keck is late 2010. Finally, there is Spider, a high-altitude balloon observatory, which will also cover 96, 150, and 225 GHz and will be deployed in 2012. The goal of all three experiment is detecting B modes in the polarization of the CMB. [ABSTRACT FROM AUTHOR]

We are developing a detection system based on a NbSi Transition Edge Sensor (TES) bolometer array. A thermo-mechanical architecture accomodates the array and the cryogenic stage of the readout. We model the coupling of the TES bolometer to the radiation by means of twin slot antenna. We present the latest design of the cryogenic readout which includes a BiCMOS SiGe integrated circuit at 4 K controlling a Superconducting Quantum Interference Device (SQUID) amplifier. [ABSTRACT FROM AUTHOR]

The SWIFTS integrated waveguide device (Stationary Wave Integrated Transform Spectrometer) has been designed on top of a 1D parallel array of 50-nm-width single stripe Superconducting Nanowire Single Photon Detectors (SNSPD). Colored light, around 1.55-\mum wavelengths, is introduced inside PE-CVD deposited and patterned Si3N4 monomode rib waveguides, in order to produce a counter-propagative stationary wave over the Nanowire array. Optical power losses are reported, mainly due to waveguide sidewall roughness scattering, end-fire fiber coupling and mode coupling mismatch. Simulations and measurements over waveguide bending, coupling and roughness quantify the loss contributions of the different factors. E-beam lithography has been re-optimized on 4-inch sapphire and NbN passivating nano-layers added for elaborating SWIFTS devices with 24 Nanowires each of 50-nm widths, capable of directly sampling the stationary wave profile. Process compatibility has been demonstrated, thanks to the MgO layer protecting NbN Nanowires before SiN deposition. Each SNSPD should operate separately at 4K in the single photon counting regime for sampling the guided standing wave, introduced by the high precision mechanical alignment of a fiber in the test set-up. [ABSTRACT FROM AUTHOR]

We report here a real-time pulse processing algorithm for superconducting transition-edge sensor (TES) based x-ray microcalorimeters. TES-based microcalorimeters offer ultra-high energy resolutions, but the small volume of each pixel requires that large arrays of identical microcalorimeter pixels be built to achieve sufficient detection efficiency. That in turn requires as much pulse processing as possible must be performed at the front end of readout electronics to avoid transferring large amounts of data to a host computer for post-processing. Therefore, a real-time pulse processing algorithm that not only can be implemented in the readout electronics but also achieve satisfactory energy resolutions is desired. We have developed an algorithm that can be easily implemented in hardware. We then tested the algorithm offline using several data sets acquired with an 8\times8 Goddard TES x-ray calorimeter array and 2\times16 NIST time-division SQUID multiplexer. We obtained an average energy resolution of close to 3.0 eV at 6 keV for the multiplexed pixels while preserving over 99% of the events in the data sets. [ABSTRACT FROM AUTHOR]

Enhancement of detection efficiency of Low Temperature Detectors (LTDs) is quite important for biomolecular mass spectrometry. One solution to realize efficient analysing tools is to produce large-scale array detectors. In this case the wiring configuration in cryostats gets much more complex. For the purpose of detecting macromolecules efficiently, we are developing spectrometer systems with 100 pixel array Superconducting Tunnel Junction detectors (STJs), infrared-blocking filters, and cryogen-free cryostats. Considering thermal leakage and signal attenuation through signal wires at each stage of a cryostat, the optimal combination of wiring cables and infrared-blocking filters was deter- mined. Furthermore, from the point of view of cryostat handling, an easy exchange of detectors and simple maintenance are necessary for practical use of the spectrometers. In this study, the configuration of a cryogen-free cryostat and its cooling performance is presented. [ABSTRACT FROM AUTHOR]

We successfully exploit the parabolic shape of the dc voltage output dip around B = 0 of a Superconducting Quantum Interference Filter (SQIF) to mix weak external rf signals. The two-tone response of weak time harmonic electromagnetic fields has been detected on the spectral voltage output of the SQIF at frequency f0 = f1 - f2, for various frequencies f1 and f2 ranging from few MHz up to 29 GHz. The two-tone response is a characteristic function of static magnetic field B and of bias current Ib, related to the second derivative of the dc voltage output. [ABSTRACT FROM AUTHOR]

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 YBa2Cu3O7-δ 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. [ABSTRACT FROM AUTHOR]

UV and X-ray astronomy need hyperspectral imaging devices, i.e. large format (1000/spl times/1000) arrays of pixels in which each single-photon event is tagged with spectral information. Such devices permit multicolor imagery and surveys to be obtained with a single camera. Here we discuss the first-stage of development of a new generation of UV/X-ray detectors that will provide 0.1-0.01% energy resolution in an array format. [ABSTRACT FROM PUBLISHER]