Keiichi Tanabe's research while affiliated with Remote Sensing Technology Center of Japan (RESTEC) and other places

Publications (167)

Article
Full-text available
We developed a hybrid cooling system consisting of a liquid-nitrogen Dewar and a cryocooler with the aim of cooling HTS-SQUIDs fast at operation sites, extending cooling period time, and avoiding noise increase caused by the cryocooler. Liquid nitrogen is evaporated mainly by thermal inflow into the Dewar. Thus, we tried reducing the thermal inflow...
Article
We have developed a three-channel HTS-SQUID eddy current testing (ECT) system for detection of a fatigue crack which occurs in a steel deck plate used in expressway bridges. To avoid physical interference between adjacent channels, a dipole coil with compact design is employed. A field test using the three channel ECT system was performed on an exp...
Article
We have developed ultrasonic guided wave testing system for pipes utilizing magnetostrictive method and high temperature superconductor (HTS) superconducting quantum interference device (SQUID) gradiometer. Two pre-magnetized nickel thin plates were adhered on an aluminium pipe. One of them with a field coil was used as a magnetostriction-based T (...
Article
To perform an early stage detection of the deteriora-tion of steel parts used in infrastructures, a nondestructive testing method is required, which is capable of evaluating hidden parts, such as a steel deck covered with an asphalt pavement. To achieve this, a magnetic field detector should be sufficiently large to detect magnetic fields over a wi...
Article
We are developing an Ultra-Low Field (ULF) Magnetic Resonance Imaging (MRI) system with a high-temperature superconductor superconducting quantum interference device (HTS-SQUID) for the purpose of food contaminant inspection. Our previous ULF SQUID-MRI system for food inspection used a resonant circuit to detect a magnetic field, which was tuned at...
Article
Full-text available
We propose an HTS-SQUID vector magnetometer with a new configuration reducing the crosstalk between a pickup coil of one SQUID and feedback coils of other SQUIDs. The new configuration is designed to mount three SQUIDs at symmetric positions where the crosstalk should be ideally zero while keeping minimal height of a probe head. In an actual HTS-SQ...
Article
We examined a portable cryostat utilizing liquid nitrogen with temperature control function for operation of high-temperature superconducting quantum interference devices (HTS-SQUIDs) to have a higher slew rate. To operate a non-destructive evaluation system with HTS-SQUID in city areas with serious environmental electromagnetic noise, we often nee...
Article
In this paper, multipoint measurements of ultrasonic guided waves on an aluminum sample pipe were performed using a high-temperature superconductor superconducting quantum interference device (HTS-SQUID) gradiometer. Two magnetized thin nickel plates were glued on the pipe with circumferential defects. One of them was used as a magnetostrictive tra...
Article
We examined the design method of a glass Dewar for liquid nitrogen as a cooling apparatus of an HTS-SQUID system for field use. Cooling technique without stressing operators is very important. Though cooling technique using liquid nitrogen is suitable to cool HTS-SQUIDs fast at an operation site and operate them without additional noise, the operat...
Article
We have been developing an HTS-SQUID eddy current testing (ECT) system using an HTS-SQUID module and external pickup coil made of Bi-2223 tape to investigate the feasibility of non-destructive evaluation of a steel plate paved with asphalt. In this work, a new excitation coil intended as a current dipole source is designed and evaluated. The curren...
Article
We fabricated HTS-SQUID magnetometers with ramp-edge-type Josephson junctions and measured their noise properties using dc/ac biasing mode. Some exhibited lowered low-frequency noise by ac biasing and others did not. We compared various parameters to find correlative ones with effectiveness of ac biasing. We found that the junction width and the cr...
Article
Our research group reported successful observation of “co-faulting” Earth’s magnetic field changes because of piezomagnetic effects caused by earthquake tremors during the 2008 Iwate-Miyagi Nairiku earthquake of M7.2 using a geomagnetic observation system with flux-gate magnetometers. This is an important finding: electromagnetic fields propagate f...
Article
We have tried to develop an induction logging system for oil fields utilizing a high-temperature superconducting quantum interference device (HTS-SQUID). Enhanced oil recovery (EOR) technology utilizing carbon dioxide (CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) is a promising techniqu...
Article
We have developed an HTS-SQUID eddy current testing (ECT) system using an HTS-SQUID module and external pickup coil made of Bi-2223 tape to investigate the feasibility of non-destructive evaluation of a steel plate paved with asphalt. Steel plates with simulated cracks were measured by using the system with a liftoff of 80 mm which corresponds to a...
Conference Paper
For accurate and stable monitoring of the oil/gas and fluid distributions in the reservoir during the EOR (Enhanced Oil Recovery) operation even if the well distance exceeds a thousand meter, JOGMEC (Japan Oil, Gas and Metals National Corporation) is developing a crosswell electromagnetic survey system with applying a super-sensitive magnetic senso...
Article
Magnetic sensing techniques have been recently developed to detect biomarkers using magnetic nanoparticles (MNPs) in liquid-phase assays. In the case of alternating current (ac) magnetic susceptibility when detecting a low number of MNPs, the diamagnetic signal of water becomes a major problem at a low signal-to-noise ratio. Therefore, we developed...
Article
We have developed high-T-c superconducting quantum interference devices (SQUIDs) containing ramp-edge-type Josephson junctions and oxide multilayer structures. In this work, we propose a new design for a small biaxial gradiometric SQUID and report its successful fabrication. It is comprised of two gradiometric SQUIDs with a baseline length of 30 mi...
Article
Full-text available
This paper reviews the highlights of a 4-years-long research project supported by the Japanese Government to explore new superconducting materials and relevant functional materials. The project found several tens of new superconductors by examining ~1000 materials, each of which was chosen by Japanese team member experts with a background in solid...
Article
Full-text available
We propose a high-Tc superconducting quantum interference device ultralow-field magnetic resonance imaging (ULF MRI) system for food inspection. Although the ULF MRI is compact and low cost, compared with a conventional high-field MRI, the detected signal is extremely weak. Thus, a nuclear magnetic resonance (NMR) system was constructed and optimiz...
Article
We have tried to develop crosshole electromagnetics for oil fields utilizing a high-temperature superconducting quantum interference device (HTS-SQUID). Enhanced Oil Recovery (EOR) technology utilizing CO2 is an epoch-making technique for efficient production of oil. Recently, a new technique of changing CO2 to CH4 based on biotechnology has also a...
Article
Direct detection of magnetic fields generated by the ion currents in electrolytic cells was performed and the ion currents were mapped during a cyclic voltammetry experiment. A high-TC superconducting quantum interference device (SQUID) gradiometer with ramp-edge Josephson junctions was used as the detector and thus the first derivative of the magn...
Article
We developed a highly sensitive HTS SQUID system for liquid-phase detection of biological targets using magnetic markers. The SQUID consists of a ramp-edge Josephson junction made using an RE123-based multilayer process, and it showed a flux noise of 7.5 $muPhi_{0}/hbox{Hz}^{1/2}$ in the white noise region. The $1/f$ noise was 14 $muPhi_{0}/hbox{Hz...
Patent
Full-text available
A high-temperature superconducting magnetic sensor having a superconducting layer formed on a substrate and a plurality of superconducting quantum interference devices fabricated on the superconducting layer, which includes: a plurality of input coils that are formed on the superconducting layer and connected to or magnetically coupled with each of...
Article
Full-text available
Solar panels are expected to play a major role as a source of sustainable energy. In order to evaluate solar panels, non-destructive tests, such as defect inspections and response property evaluations, are necessary. We developed a DC current distribution mapping system of the solar panels using a High Critical Temperature Superconductor Supercondu...
Conference Paper
To clarify the relationship of the crystal structure, the critical temperature (Tc) and the gap structure in iron pnictide superconductors, the studies on 1111-type iron pnictides with the highest Tc are important. However itis well known that the single crystal growth of 1111-compounds is difficult. In this work, we have established a method for r...
Article
Full-text available
The high upper critical field and low anisotropy of the iron-based superconductor BaFe2As2 make it promising for its use in the construction of superconducting magnets. However, its critical current density in high magnetic fields needs to be improved. Here we demonstrate a simple, one-step and industrially scalable means of achieving just this. We...
Article
We studied the anisotropy and superconducting properties of BaFe2(As1-xPx)(2) films with various phosphorus contents x (= 0.19-0.45) fabricated on MgO by pulsed laser deposition. We demonstrated that the x = 0.28 film with optimal critical temperature (T-c,T-zero = 26.5 K) has the lowest anisotropy of upper critical field (gamma(H) = 1.54), as well...
Article
A magneto-electrical cyclic voltammetry has been proposed and developed. This measurement method utilized three electrodes: a counter, a working, and a reference electrode, as the conventional voltammetry uses and the magnetic field by the currents were detected. Thus, the current distribution in the electrolyte cells during the voltammetry measure...
Article
To improve the field resolution of a magnetometer for use in the Earth's field, we have developed a new magnetometer using a hybrid superconducting quantum interference device (SQUID). A multi-turn input coil (Ni turns) is inserted between a directly-coupled SQUID and a pickup coil in series in the hybrid SQUID. Screening current couples with the S...
Article
The key point of this presentation is that we successfully develop the high-temperature-superconductor based superconducting-quantum-interference-device (HTS-SQUID) magnetometer system for super-sensitive observation of geomagnetic field changes. Electromagnetic changes associated with earthquakes have been investigated previously. Our research gr...
Article
We have investigated the fabrication of a high-temperature superconducting (HTS) gradiometer with long baseline for geophysical applications. The proof-of-concept gradiometer using a 1-turn pickup coil made of a GdBa2Cu3Oy coated conductor (GCC) and 5.5-turn input coil integrated on a SQUID was fabricated in our previous work. In this study, we hav...
Article
We have developed a new fabrication method for a high-Tc superconducting quantum interference device (SQUID) with an integrated multiturn input coil to improve the fabrication yield. The method consists of a new multi-SQUID layout and an additional patterning process. In this layout, each input coil is shunted by a shunt inductor to avoid an increa...
Article
Using a scanning Hall-probe microscopy, we have developed a noncontact characterization method for multifilamentary coated conductors. In-plane distributions of sheet current density in a multifilamentary coated conductor were visualized at different conditions of external magnetic field. From these results, we could extract local critical current...
Article
Relationships between microstructure and transport properties of bicrystal grain boundary (BGB) junctions were studied in cobalt-doped BaFe2As2 (BaFe2As2:Co) epitaxial films grown on [0 0 1]-tilt bicrystal substrates of MgO and (La, Sr)(Al, Ta)O3 with misorientation angles θGB = 3–45°. The θGB of BaFe2As2:Co BGBs were exactly transferred from those...
Article
We developed a compact moving-sample magnetometer that uses a high-temperature superconductor--superconducting quantum interference device (high-Tc SQUID) to directly measure the flux coupled to a normal detection coil from a sample's magnetic moment in the presence of an external DC magnetic field. The moving-sample method is employed by inserting...
Article
Recent developments of electronic devices containing Josephson junctions (JJ) with high-Tc superconductors (HTS) are reported. In particular, the fabrication process and the properties of superconducting quantum interference devices (SQUIDs) with a multilayer structure and ramp-edge-type JJs are described. The JJs were fabricated by re-crystallizat...
Article
The recent discovery of iron-based superconductors has evoked enthusiasm for extensive research on these materials because they form the second high-temperature superconductor family after the copper oxide superconductors and impart an expectation for materials with a higher transition temperature (Tc). It has also been clarified that they have pec...
Article
Full-text available
High critical temperature superconductors have zero power consumption and could be used to produce ideal electric power lines. The principal obstacle in fabricating superconducting wires and tapes is grain boundaries-the misalignment of crystalline orientations at grain boundaries, which is unavoidable for polycrystals, largely deteriorates critica...
Article
Full-text available
High critical current densities (J<sub> c </sub>)>1 MA / cm <sup>2</sup> were realized in cobalt-doped BaFe <sub>2</sub> As <sub>2</sub> ( BaFe <sub>2</sub> As <sub>2</sub>: Co ) films on flexible metal substrates with biaxially textured MgO base-layers fabricated by an ion-beam assisted deposition technique. The BaFe <sub>2</sub> As <sub>2</sub>:...
Article
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/CeO<sub>2</sub>/LaMnO<sub>3</sub>(LMO)/IBAD -MgO/Gd<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub>(GZO)/Hastelloy structure by means of a high-sp...
Article
We have fabricated a two-axis high-T<sub>c</sub> planar gradiometer. Two gradiometers with planar gradiometric pickup coils lie diagonally on a square substrate. Therefore, they can measure field gradients, dBz/dx and dBz/dy at the same site. The two-axis gradiometer was fabricated on a 15 × 15 mm MgO (100) substrate using an HTS multilayer process...
Article
We have fabricated a large high-temperature superconducting gradiometer for geophysical application such as a Transient Electro-Magnetic (TEM) method. The seamless gradiometric pickup coil was made of a commercially available GdBCO coated conductor formed on a Hastelloy tape. Two pickup loops with a diameter of 100 mm and an integrated input coil o...
Article
We have studied the fabrication process of HTS-SQUIDs with ramp-edge Josephson junctions (JJs). SmBa<sub>2</sub>Cu<sub>3</sub>O<sub>y</sub> (SmBCO) and Er<sub>0.95</sub>La<sub>0.1</sub>Ba<sub>1.95</sub>Cu<sub>3</sub>O<sub>y</sub> (L1ErBCO) having T <sub>c</sub>'s around 90 K were used for base- and counter-electrodes, respectively. SrSnO<sub>3</sub...
Article
Effect of an addition of a cooled step-up transformer to a flux locked loop (FLL) circuit was studied to reduce indirect rf interference to HTS-dc-SQUID. First, we demonstrated that a noise level of an HTS-dc-SQUID system using the FLL circuit with single room-temperature transformer could be easily degraded by radiation of rf electromagnetic wave...
Article
We have studied the magnetization behavior of iron-pnictide superconductor, Ba(Fe1-xCox)2As2 (Co-doped Fe122) with various Co doping and BaFe2(As0.65P0.35)2 (P-doped Fe122) single crystals. All of the Co-doped Fe122 crystals showed a very pronounced "peak effect" in all the temperature range, irrespective of doping state. It is important to mention...
Article
La-doped YBCO (Y0.9La0.2Ba1.9Cu3Oy) superconducting films were deposited by an off-axis DC magnetron sputtering method. We investigated the relationship between the film characteristics and the deposition conditions, and drew systematical maps in terms of composition, surface morphology, crystal structure and superconducting properties for the film...
Article
Full-text available
DC superconducting quantum interference devices (dc-SQUIDs) were fabricated in Co-doped BaFe2As2 epitaxial films on (La, Sr)(Al, Ta)O3 bicrystal substrates with 30deg misorientation angles. The 18 x 8 micro-meter^2 SQUID loop with an estimated inductance of 13 pH contained two 3 micro-meter wide grain boundary junctions. The voltage-flux character...
Article
Full-text available
Josephson junctions were fabricated in epitaxial films of cobalt-doped BaFe2As2 on [001]-tilt (La,Sr)(Al,Ta)O3 bicrystal substrates. 10m-wide microbridges spanning a 30-degrees-tilted bicrystal grain boundary (BGB bridge) exhibited resistively-shunted-junction (RSJ)-like current-voltage characteristics up to 17 K, and the critical current was suppr...
Article
A high-T<sub>c</sub> superconducting (HTS) single-flux-quantum (SFQ) logic family including an and gate, an or gate, and an inverter was designed. The circuit parameters were optimized for a Josephson junction's critical current density, which may change due to a temperature change or insufficient run-to-run reproducibility of the fabrication proce...
Article
We have fabricated high-temperature superconductor (HTS) dc superconducting quantum interference devices (SQUIDs) with a multilayer structure and ramp-edge Josephson junctions. For stable operation at 77 K, SmBa<sub>2</sub>Cu<sub>3</sub>O<sub>y</sub> (SmBCO) and La<sub>0.1</sub>-Er<sub>0.95</sub>Ba<sub>1.95</sub>Cu<sub>3</sub>O<sub>y</sub> (La-ErBC...
Article
A novel HTS-SQUID gradiometer with ramp-edge Josephson junctions (JJs) composed of SmBa<sub>2</sub>Cu<sub>3</sub>O<sub>y</sub> base-electrode and La<sub>01</sub>Er<sub>0.95</sub>Ba<sub>1.95</sub>Cu<sub>3</sub>O<sub>y</sub> counter-electrode was developed. The robustness of the gradiometer in AC field perpendicular to the device plane was investigat...
Article
We developed a non-destructive testing (NDT) system utilizing multi-channel high-temperature superconductor (HTS) SQUID gradiometers in order to examine rare earth (RE)-123 coated conductors striated into multi-filamentary lines. The 5-channel HTS SQUID gradiometer array was composed of ramp-edge junctions with LaErBaCuO and SmBaCuO electrode layer...
Article
We have fabricated the F-doped LaFeAsO superconductors via three fabrication process; (1) solid-state sintering, (2) high pressure (HP) synthesis and (3) crystallization from flux solution. Samples prepared by these processes have unique features depending on the process such as a large volume and uniformity of the sintered pellet, variety of the c...
Article
The d-dot device is composed of a square shaped d-wave superconductor buried into a s-wave superconductor thin film. The internal phase difference at neighboring square side junction causes a half-quantum-flux at each corner of square of d-wave superconductor. We have developed the method for preparing the d-dot with YBCO thin film by PLD method pr...
Article
We have developed the fabrication process, the circuit design technology, and the cryopackaging technology for high-Tc single flux quantum (SFQ) devices with the aim of application to an analog-to-digital (A/D) converter circuit for future wireless communication and a sampler system for high-speed measurements. Reproducibility of fabricating ramped...
Article
Ramp-edge Josephson junctions using LnBCO (Ln=Yb, Y and Sm) superconductors and a SrSnO3 (SSO) insulator were successfully fabricated. La-doped YbBCO and YBCO superconductors, i.e. La-YbBCO and La-YBCO, were used for counter and base-electrodes, respectively. Junctions were formed on a SmBCO ground plane (GP). The layer sequence was La-YbBCO/SSO/La...
Article
We have developed a new fabrication process for monolithic integrated high-Tc dc superconducting quantum interference devices (SQUIDs) that enables us to prevent a degradation of the junction Tc. In the new process, bicrystal junctions are fabricated simultaneously with a flux transformer by using the top superconducting layer. The junctions in YBa...
Article
Recent progress in single flux quantum (SFQ) device technologies in Japan is described, mainly focusing on those developed in the NEDO "Superconductors Network Device Project" which includes developments of both LTS and HTS devices. The advanced Nb process which consists of a planarized structure with nine Nb layers and 10 kA/cm<sup>2</sup> Josephs...
Article
We are developing waveform measurement systems using a high- superconducting (HTS) sampler. As one of the methods for introducing high-frequency signals into the sampler chip, we are testing optical input systems. A uni-traveling-carrier photodiode (UTC-PD), which has potential bandwidth of over 300 GHz, is used in the systems for converting optica...
Article
We have fabricated ramp-edge Josephson junctions using a Cu-poor oxide layer as a precursor of the barrier. La<sub>0.2</sub> - Y<sub>0.9</sub>Ba<sub>1.9</sub>Cu<sub>3</sub>O<sub>x</sub>(La-YBCO) and La<sub>0.2</sub> - Yb<sub>0.9</sub>Ba<sub>1.9</sub>Cu<sub>3</sub>O<sub>x</sub> (La-YbBCO) were used for the base-electrode and the counter-electrode, r...
Article
We have developed a fabrication process for single flux quantum (SFQ) circuits including a superconducting ground plane and interface-modified ramp-edge Josephson junctions. We found that the critical current density (J<sub>c</sub>) for individual junctions in a circuit was influenced by the circuit pattern layout. The dependence of the I<sub>c</su...
Article
A Single flux quantum (SFQ) one-to-two (1:2) switch circuit was designed and fabricated by using YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-delta</sub> ramp-edge junction technology, and the logic operations were investigated. The circuit parameters were optimized by taking account of an I<sub>c</sub> spread and a global I<sub>c</sub> shift due to an ope...
Article
Full-text available
Single flux quantum (SFQ) circuit elements have been designed and fabricated using the YBa 2 Cu 3 O 7−δ ramp-edge junction technology. Logic operations of SFQ circuit elements, such as a toggle flip-flop (T-FF), a set-reset flip-flop (RS-FF), and a 96-junction Josephson transmission line (JTL), were successfully demonstrated, and dc supply current...
Article
This paper reviews our progress on the high- T c superconducting (HTS) sampler development, covering from the circuit design to the latest experimental data in the sinusoidal and pulse waveform measurements. A computer simulation has revealed that our sampler circuit with an improved design enables waveform measurement with the bandwidth over 100 G...
Article
Toggle-flip-flop (T-FF) is one of the most important high-T<sub>c </sub> superconducting single-flux quantum (HTS SFQ) circuit components and has been designed and fabricated by using YBa<sub>2</sub>Cu<sub>3 </sub>O<sub>7-delta</sub> ramp-edge junction technology. The circuit layout of the T-FF was improved to suppress the junction critical current...
Article
We have studied the effect of thermal noise and trigger jitter on the bandwidth of a high-T<sub>c</sub> superconducting sampler by computer simulation and analytical calculation. Simulation results showed that the minimum I<sub>c</sub>R<sub>n</sub> product of the junctions required to obtain 100-GHz bandwidth is raised from 0.63 to 0.75 mV under th...
Article
The properties of YbBCO and LuBCO thin films were examined with the aim of applying them to an upper wiring layer for HTS SFQ circuit. c-Axis oriented films could be prepared for both the materials at a relatively low temperature of 640 °C. However, there was a little difference in their superconducting properties, and YbBCO films exhibited better...
Article
Multilayer structures consisting of (Hg0.9Re0.1)Ba2CaCu2Oy [(Hg,Re)-1212] superconducting layers and CeO2 insulating layers have been successfully fabricated. A CeO2 film could be epitaxially grown on a (Hg,Re)-1212 film at a relatively low temperature of 500°C without deterioration of crystallinity and superconductivity for (Hg,Re)-1212. Moreover,...
Article
We have investigated the distribution of critical current density (Jc) for interface-modified ramp-edge Josephson junctions in high-Tc single flux quantum (SFQ) circuits. The 1sigma spread of Jc in a toggle flip-flop test circuit with a conventional layout is 26.7% and much larger than typical values obtained for junction series-arrays. It is found...
Article
Single flux quantum (SFQ) circuit components such as an SFQ-dc converter and a confluence buffer have been fabricated by using an YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> ramp-edge junction technology and their logic operations at temperatures up to near 60 K were investigated. The SFQ-dc converter was correctly operated in a wide temperature r...
Article
This paper reports selected recent topics in high-Tc superconductive electronics. Improved process technology for high-Tc digital electronics, the development of a sampling oscilloscope, magnetic immunoassay using a high-Tc superconducting quantum interference device (SQUID), scanning laser-SQUID for integrated circuits testing, terahertz radiation...