A five-year project for Nb-based single flux quantum (SFQ) circuits supported by Japan's Ministry of Economy Trade and Industry (METI) in Japan was started in September 2002. Since April 2003, the New Energy and Industrial Technology Development Organization (NEDO) has supported this Superconductor Network Device Project. The aim of the project is to improve the integration level of Nb-based SFQ circuits to several ten thousand Josephson junctions, in comparison with their starting integration level of only a few thousand junctions. Actual targets are a 20 GHz dual processor module for the servers and a 0.96 Tbps switch module for the routers. Starting in April 2003, the Nb project was merged with SFQ circuit research using a high-T$_{c}$ superconductor (HTS). The HTS research targets are a wide-band AD converter for mobile-phone base stations and a sampling oscilloscope for wide-band waveform measurements.

We studied the effect of spin injection on tunneling conduction properties of intrinsic Josephson junctions formed in $Bi_2$$Sr_2$$CaCu_2$$O_{ 8＋x}$ single crystals. properties of an identical stack (10${\times}$5.0${\times}$0.030 $\mu\textrm{m}^3$) of intrinsic Josephson junctions were compared for the bias current injected through Au and Co electrodes. The suppression of the superconducting gap in the $_2$ double layers and the interlayer Josephson critical current was manifested in the tunneling current-voltage characteristics of the stacks. This effect appears to be caused by the pair breaking associated with spin-polarized carriers injected from the Co electrode into the $Bi_2$$Sr_2$$_2$O$CaCu_{ 8＋x}$ single crystal. This study may provide valuable information on clarifying the mechanism of high- $T_{c}$ superconductivity.y.y.

We observed the splitting of the fluxon-flow branches in the current-voltage characteristics of serially stacked intrinsic Josephson junctions (IJJs) formed in $Bi_2$$Sr_2$$CaCu_2$$O_{ 8＋x}$ single crystals in the long-junction limit. Stacks of IJJs were sandwiched between two Au electrodes deposited on the top and the bottom of the stack using the ‘double-side cleaving technique’. In all the samples studied, the branch splitting started occurring for a dense fluxon configuration around 2 T and became more distinct in a higher magnetic field range. This observation can be explained in terms of switching between different Josephson fluxon modes in resonance with the collective plasma oscillations induced by both inductive and capacitive coupling between stacked IJJs. This is the first detailed and quantitative identification of the coherent flux-flow modes in stacked..

In this work, we have studied about an RSFQ (Rapid Single Flux Quantum) switch element. The circuit was designed, simulated, and laid out for mask fabrication. The switch cell was composed of a D flip-flop, a splitter, a confluence buffer, and a switch core. The switch core determined if the input data could pass to the output. “On” and o“off” controls in the switch core could be possible by utilizing an RS flip-flop. When a control pulse was input to the “on” port, the RS flip-flop was in the set state and passed the input pulses to the output port. When a pulse was input to the “off” port, the RS flip-flop was in the reset state and prevented the input pulses from transferring to the output port. We simulated and optimized the switch element circuit by using Xic, WRspice, and Julia. The minimum circuit margins in simulations were more than $\pm$20%. We also performed the mask layout of the circuit by using Xic and Lmeter.

We have designed and measured a SFQ(Single Flux Quantum) DFFC and an Inverter(NOT) for superconducting ALU(Arithmetic Logic Unit) development. To optimize the circuit, we used Julia, XIC, and L meter for circuit simulations and circuit layouts. The Inverter was consisted of a D Flip-Flop, a data input, a clock input and a data output. If a data pulse arrives at the inverter, then the output reads ‘0’ (no output pulse is produced) at the next clock period. If there is no input data pulse, it reads out ‘1’(output pulse is produced). The DFFC was consisted of a D flip-Flop, an Inverter, a Data in, a Clock in and two outputs. If a data pulse arrives at the DFFC circuit, then the output2 reads ‘1’ at the next clock period, otherwise it reads out ‘1’ to output1. Operation of the fabricated chip was performed at the liquid helium temperature and at the frequencies of 1KHz.

We have designed and simulated an 1-bit ALU (Arithmetic Logic Unit) by using a half adder. An ALU is the part of a computer processor that carries out arithmetic and logic operations on the operands in computer instruction words. The designed ALU had limited operation functions of OR, AND, XOR, and ADD. It had a pipeline structure. We constructed an 1-bit ALU by using only one half adder and three control switches. We designed the control switches in two ways, dc switch and NDRO (Non Destructive Read Out) switch. We used dc switches because they were simple to use. NDRO pulse switches were used because they can be easily controlled by control signals of SET and RESET and show fast response time. The simulation results showed that designed circuits operate correctly and the circuit minimum margins were ＋/-27%. In this work, we used simulation tools of XIC and WRSPICE. The circuit layouts were also performed. The circuits are being fabricated.

Magneto-cardiogram(MCG) signals may be highly distorted by the environmental noise, such as power-line interference, broadband white noise, surrounding magnetic noise, and baseline wondering. Several kinds of digital filters and noise cancellation methods have been designed and realized by many researchers, but these methods gave some problems that the original signal may be distorted by digital filter due to the wideband characteristics of background noise. To eliminate noise effectively without distortion of MCG signals, we performed multi-level frequency decomposition using wavelet packets and local adaptive noise cancellation in each local frequency range. In addition to the proposed wavelet filter to eliminate these various non-stationary noise elements, the local adaptive filter using the least mean square(LMS) algorithm and the soft threshold do-noising method are introduced in this paper. The signal to noise ratio(SNR) and the reconstruction square error(RSE) are calculated to evaluate the performance of the proposed method and compared with the results of the conventional wavelet filter and adaptive filter. The experimental results show that the proposed local adaptive filtering method is better than the conventional methods.

Wide-bandwidth SQUID current amplifier and its control electronics have been constructed for detecting pulse outputs of a superconducting microcalorimeter. The current amplifier made of a double relaxation oscillation SQUID (DROS) has a bandwidth of 1.2 MHz and typical white noise level of about 6 pA/(equation omitted) Hz. To increase the dynamic range of the current amplifier, the flux-locked loop (FLL) has additional circuits to reset the integrator and to count reset numbers which present the number of passed flux quanta. In this system, dynamic range covers from -65 mA to +65 mA. SQUID electronics are controlled by software to get the optimum FLL condition, and to control the current to bias the transition edge sensor (TES). The electronics are shielded from the outside electromagnetic noises by using an aluminum case of 66 mm ${\times}$ 25 mm ${\times}$ 100 mm, and consist of 2 separate printed-circuit-boards for the current amplifier and the control electronics, respectively. The SQUID current amplifier and its control electronics will be used in TESs for detecting photons such as UV and X-ray with high energy resolution.

The aim of this study is to confirm clinical usefulness of magnetocardiogram (MCG) by analyzing MCG data of health subjects and patients with Wolff-Parkinson-White (WPW) syndrome and dilated cardiomyopathy (DCM). Measurement of MCG signals was done with a home-made 40-channel SQUID system. MCG signals of 30 healthy subjects were measured as the reference of MCG signals. Among the DCM patients, 7 patients showed abnormal the direction of T wave vector. For a WPW syndrome patient, we measured the MCG signals before and after the surgery. and compared the difference. From the measured magnetic field distribution, current vector map was obtained to show the myocardium current activity. By comparing the MCG signals and current maps, we showed the differences in the analysis results between the healthy subjects and patients with heart diseases.

We have designed and fabricated the single-layer high $T_{c}$ SQUID magnetometer consisting of a directly coupled grain boundary junction SQUID with an inductance of 100 pH and 16 nested parallel pickup coils with the outermost dimension of 8.8 mm ${\times}$ 8.8 mm. The magnetometer was formed from a YBCO thin film deposited on an STO(100) bicrystal substrate with a misorientation angle of $30^{\circ}$. The SQUID magnetometer was further improved by optimizing the multi-loop pickup coil design for use in unshielded environments. Typical characteristics of the dc SQUID magnetometer had a modulation voltage of 40 $\mu\textrm{V}$ and a white noise of $30fT/Hz^{1}$2/. The SQUID magnetometer exhibited a 1/f noise level at 10 Hz reduced by a factor of about 3 compared with that of the conventional solid type pickup coil magnetometers and a very stable flux locked loop operation in magnetically disturbed environments.s.

We have fabricated $∂^2$$B_{z}$ /$∂x^2$ type planar gradiometers and studied their properties in operation under various field conditions. $YBa_2$$Cu_3$$O_{7}$ film was deposited on $SrTiO_3$ (100) substrate by a pulsed laser deposition (PLD) system and patterned into a device by the photolithography with ion milling technique. The device consists of 3 pickup loops designed symmetrically Inner dimension and the width of the square side loops are 3.6 mm and 1.2 mm, respectively, and the corresponding dimensions of the center loop are 2.0 mm and 1.13 mm. The length of baseline gradiometer is 5.8 mm. Step-edge junction width is 3.0 $\mu\textrm{m}$ and the hole size of the SQUID loop is 3 $\mu\textrm{m}$ ${\times}$ 52 $\mu\textrm{m}$. The SQUID inductance is estimated to be 35 pH. The device was formed on a 20 mm ${\times}$ 10 mm substrate. We have tested the behavior of the device in various field conditions. The unshielded gradiometer was stable under extremely hostile conditions on a laboratory bench. Noise level 0.45 pT/$\textrm{cm}^2$/(equation omitted)Hz and 0.84 pT/$\textrm{cm}^2$/(equation omitted)Hz at 1 Hz for the shielded and the unshielded cases, which correspond to equivalent field noises of 150 fT/(equation omitted)Hz and 280 fT/(equation omitted)Hz, respectively. In spite of the short baseline of 5.8 mm, the high common-mode-rejection-ratio of the gradiometer, $10^3$, allowed us to successfully record magnetocardiogram of a human subject, which demonstrates the feasibility of the design in biomagnetic studies.

We designed and constructed integrated 3-channel flux-locked-loop (FLL) electronic system for the control and readout of high-T$_{c}$ SQUIDs. This system consists of low noise preamplifiers, integrators, interface circuits, and software. FLL operation was carried out with biased signals of 19 KHz modulated current and 150 KHz modulated flux, which are reconstructed as detected signals by preamplifier and demodulator. Computer controlled interface circuits regulate FLL circuit and adjust SQUID parameters to the optimum operating condition. The software regulates interface circuits to make an auto-tuning for the control of SQUIDs, and displays readout data from FLL circuit. 3-channel SQUID electronic system was assembled with 3 FLL-interface circuit boards and a power supply board in the aluminum case of 56 mm ${\times}$ 53 mm${\times}$ 150 mm. Overall noise of the system was around 150 fT/(equation omitted)Hz when measured in the shielded room, 200 fT/(equation omitted)Hz in a weakly shielded room, respectively.y.

In HTS transformer with double pancake windings, the perpendicular component of leakage magnetic flux density ($B_{r}$ ) applied to HTS tapes of double pancake windings of HTS transformer acts as a cause to decrease the critical current in HTS tape. So, in this paper, HTS transformer with reciprocal arrangement winding is designed. And in order to investigate the$ B_{r}$ applied to HTS windings, the 2-D non-linear electromagnetic analysis of HTS transformer is performed by using the OPERA 2D. The maximum $B_{r}$ applied to winding of HTS transformer is 0.112 T and the characteristics of HTS transformer were also obtained. But in this type of winding arrangement, reciprocal arrangement, the generated ac-loss to the HTS windings is very high because of the applied $B_{r}$ to HTS windings. Therefore, in order to reduce the generated ac-loss to the HTS windings, the new design of HTS transformer with concentric winding arrangement is presented in this paper and the 2-D non-linear electromagnetic analysis and the ac-loss for HTS transformer with the concentric winding arrangement is also carried out.

Many researches on fabrication process for BSCCO precursor powders have been developed for high J$_{c}$ BSCCO-2223 tape. Spray pyrolysis method for fabrication of precursor powder has many advantages, such as high purity, fine particle size and low carbon content of BSCCO precursor powder. Fine, spherical powders were prepared by ultrasonic spray pyrolysis from the aqueous solution of metal nitrates. BSCCO precursor powders were synthesized with various solutes concentration and heat treatment conditions. Average particle size for spray pyrolysis powders was $1.5∼3\mu\textrm{m}$. Bi-2223/Ag tape was prepared by PIT method and followed by various sintering conditions. BSCCO precursor powders were characterized by XRD, SEM, EDS, Carbon content and particle size analysis.s.

We fabricated cube textured Ni substrate for YBCO coated conductor and evaluated the effects of processing parameters on microstructural evolution and texture formation. Ni-rods as an initial specimen were prepared by two different methods, i.e., powder metallurgy(PM) and plasma arc melting(PAM). Subsequently, the rods were cold rolled to 100 $\mu\textrm{m}$ thick substrate and annealed at temperatures of $700∼1200^{\circ}C$. The texture of the substrate was characterized by pole-figure. It was observed that the texture of substrate made by P/M did not significantly varied with annealing temperature of 600∼$l100^{\circ}C$ and the full-width at half-maximums (FWHM) of both in-plane and out-of-plane were 9$^{\circ}$∼$10^{\circ}$. On the other hand, the texture of substrate made by PAM was more dependent on the annealing temperature and the corresponding values were $9^{\circ}$ ∼$13^{\circ}$ at the temperature range. In addition, recrystallization twin texture, (221)＜221＞, was formed as the temperature increased further. OM profiles showed that the grain size of substrate made by P/M was smaller than that made by PAM and this difference was correlated to the microstructure of initial specimens.

YBCO films were deposited with various thicknesses from 100nm to 1.6$\mu\textrm{m}$ on single crystal $SrTiO_3$ substrates by pulsed laser deposition (PLD). The effects of different deposition conditions, especially different deposition rates by means of changing the pulsed laser frequency up to 200Hz, on the J$_{c}$ value were studied. For YBCO film with the thickness of 200nm, the $J_{c}$ value of $2.1MA/\textrm{cm}^2$ has been achieved under the high deposition rate of 3.2nm/s (190nm/min). The $J_{c}$ can be maintained greater than $1M/\textrm{cm}^2$ with the thickness less than 1$\mu\textrm{m}$. The X-ray analysis was used to examine the texture, crystallization and surface quality. The SEM was employed to analyze the surface of YBCO, and it was shown the surface of YBCO film became rougher with increasing the thickness. There were many large singular outgrowths and networks of outgrowths on the surface of YBCO films which lowered the density of thick YBCO film. The outgrowth network was probably the a-axis YBCO corresponding to XRD $\theta$-2$\theta$scan and $\chi$-scan which were used to characterize a-axis orientation of YBCO film. The reason for J$_{c}$ declining with increasing the thickness was studied and discussed.sed.

Superconducting YBCO thin films are fabricated on single-crystalline substrates by Metallo-organic Depostion process employing Trifluoroacetic acid as a chelating agent (MOD-TFA). (100)-oriented single crystalline LaAlO$_3$ substrates were employed to grow superconducting film with high crystallinity. The fully processed YBCO thin films were characterized with XRD, SEM, EDS, etc. The microstructures of YBCO thin films show labyrinth-like patterns. The origin of this microstructure was delineated by compositional inhomogeneity during the MOD process and it was shown that the microstructure may be modified by additives. In this work, effects of additives on the microstructures and electrical properties of YBCO thin films have been investigated.

$YBa_2$$Cu_3$$O_{7-x}$ (YBCO) thin films were fabricated by MOD-TFA process via dip-coating method on LaAlO$_3$, (LAO) single crystalline substrates. In this study, we investigated effect of annealing temperature and solvent on the microstructure and texture of YBCO thin films. The precursor films were annealed at various temperature to improve surface morphologies and phase purities. It was shown that the films annealed at relatively lower and higher temperature exhibit low phase purity and crystallinity. The effect of various solvents on surface morphologies and second phase has been investigated.