A low-temperature diffusion jointing technique based on citric-acid surface activation was applied to directly connect the Cu stabilizing layers of REBCO tapes, and its electrical characteristics were systematically investigated. The effects of joining conditions, such as, pressure, heating time, and joint length on interfacial resistivity were examined to identify the optimal jointing condition, which produced uniform and low-resistance Cu–Cu interfaces. I–V measurements confirmed that the critical current (Ic) and n-value of the jointed tapes showed no significant degradation compared with non-jointed conductors. When applied to two-tape stacked REBCO conductor, the Ic increased by about 1.7 times, indicating efficient current transfer through the joint region. These results demonstrate that the proposed citric-acid-assisted diffusion jointing method enables reliable electrical connections suitable for multi-tape REBCO conductors and provides a promising approach for practical high-temperature superconducting applications.
{"title":"Direct Joining Method of Y-based high-Temperature Superconducting Tapes for Application to High-Current Conductors","authors":"Daisuke Ohkura;Noriko Chikumoto;Michihiko Watanabe;Naoki Hirano;Yuta Onodera;Ryosuke Kodama","doi":"10.1109/TASC.2026.3651234","DOIUrl":"https://doi.org/10.1109/TASC.2026.3651234","url":null,"abstract":"A low-temperature diffusion jointing technique based on citric-acid surface activation was applied to directly connect the Cu stabilizing layers of REBCO tapes, and its electrical characteristics were systematically investigated. The effects of joining conditions, such as, pressure, heating time, and joint length on interfacial resistivity were examined to identify the optimal jointing condition, which produced uniform and low-resistance Cu–Cu interfaces. <italic>I–V</i> measurements confirmed that the critical current (<italic>I</i><sub>c</sub>) and <italic>n</i>-value of the jointed tapes showed no significant degradation compared with non-jointed conductors. When applied to two-tape stacked REBCO conductor, the <italic>I</i><sub>c</sub> increased by about 1.7 times, indicating efficient current transfer through the joint region. These results demonstrate that the proposed citric-acid-assisted diffusion jointing method enables reliable electrical connections suitable for multi-tape REBCO conductors and provides a promising approach for practical high-temperature superconducting applications.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2026-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146175796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A superconducting transition edge sensor (TES), a type of photon-number-resolving detector, is essential for quantum information applications that utilize highly nonclassical quantum states. For these applications, TES devices must simultaneously achieve high detection efficiency and high energy resolution. Matching the mode field diameter of optical fibers requires a sufficiently large sensitive area, which introduces an alignment tolerance. However, the increased heat capacity associated with a larger area degrades the energy resolution and consequently reduces the accuracy of the photon-number discrimination. Thus, developing a TES with both a large sensitive area and high energy resolution remains highly challenging. To address this issue, we developed a Ti/Au/Ti/Au four-layer structure TES. Theoretically, stacking metal materials with different Debye temperatures confines high-energy phonon within the TES. This suppression of high-energy phonon loss during energy down-conversion improves the energy collection efficiency, thereby enhancing the energy resolution. Furthermore, lowering the transition temperature through the proximity effect provides additional improvement. Consequently, we evaluated the enhancement of energy resolution resulting from phonon confinement and the reduction in transition temperature. As a result, in contrast to conventional Ti/Au bilayer TESs, the four-layer TES with a size of 21 $mathrm{mu }$m × 21 $mathrm{mu }$m exhibited photon-number-resolving ability at 1550 nm, achieving an energy resolution of 0.32eV. While the bilayer TES showed a transition temperature of around 320 mK, the four-layer TES achieved a significantly lower value of 179 mK. Moreover, the energy collection efficiency exhibits no dependence on incident photon wavelengths, resulting in an average value of 97.4 $pm$ 1.0% over all measured data points, compared with approximately 80% for the bilayer TES. These results demonstrate that multilayer TES structures with different Debye temperatures can effectively reduce the transition temperature and confine phonons, thereby improving energy resolution.
{"title":"High Energy Collection Efficiency in a Ti/Au/Ti/Au Four-Layer Transition Edge Sensor","authors":"Takeshi Jodoi;Tetsuya Tsuruta;Takahiro Kikuchi;Nao Kominato;Koki Shirota;Daiji Fukuda","doi":"10.1109/TASC.2026.3656513","DOIUrl":"https://doi.org/10.1109/TASC.2026.3656513","url":null,"abstract":"A superconducting transition edge sensor (TES), a type of photon-number-resolving detector, is essential for quantum information applications that utilize highly nonclassical quantum states. For these applications, TES devices must simultaneously achieve high detection efficiency and high energy resolution. Matching the mode field diameter of optical fibers requires a sufficiently large sensitive area, which introduces an alignment tolerance. However, the increased heat capacity associated with a larger area degrades the energy resolution and consequently reduces the accuracy of the photon-number discrimination. Thus, developing a TES with both a large sensitive area and high energy resolution remains highly challenging. To address this issue, we developed a Ti/Au/Ti/Au four-layer structure TES. Theoretically, stacking metal materials with different Debye temperatures confines high-energy phonon within the TES. This suppression of high-energy phonon loss during energy down-conversion improves the energy collection efficiency, thereby enhancing the energy resolution. Furthermore, lowering the transition temperature through the proximity effect provides additional improvement. Consequently, we evaluated the enhancement of energy resolution resulting from phonon confinement and the reduction in transition temperature. As a result, in contrast to conventional Ti/Au bilayer TESs, the four-layer TES with a size of 21 <inline-formula><tex-math>$mathrm{mu }$</tex-math></inline-formula>m × 21 <inline-formula><tex-math>$mathrm{mu }$</tex-math></inline-formula>m exhibited photon-number-resolving ability at 1550 nm, achieving an energy resolution of 0.32eV. While the bilayer TES showed a transition temperature of around 320 mK, the four-layer TES achieved a significantly lower value of 179 mK. Moreover, the energy collection efficiency exhibits no dependence on incident photon wavelengths, resulting in an average value of 97.4 <inline-formula><tex-math>$pm$</tex-math></inline-formula> 1.0% over all measured data points, compared with approximately 80% for the bilayer TES. These results demonstrate that multilayer TES structures with different Debye temperatures can effectively reduce the transition temperature and confine phonons, thereby improving energy resolution.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 6","pages":"1-7"},"PeriodicalIF":1.8,"publicationDate":"2026-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146175895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A smart-insulation (SI) approach employing a metal–insulator transition (MIT) material has been investigated for improving the thermal stability and charging characteristics of REBCO coils. In this study, we investigated a coating method for REBCO tapes using a material (Pr0.8Sm0.2)0.6Ca0.4CoO3 (PSCCO) which exhibits a MIT around 74 K. PSCCO powder, synthesized by the sol–gel method and then ball-milled, was dispersed in N-methyl-2-pyrrolidone (NMP) to form a slurry, which was subsequently coated onto the REBCO tape. The contact resistivity (ρct) between REBCO tapes was measured from 10 K to 270 K under uniaxial pressures. The ρct decreased monotonically from 1.9 × 108 μΩ·cm2 at 10 K to 7.0 × 103 μΩ·cm2 at 270 K. However, the ρct did not show a sharp MIT-like transition as observed in bulk PSCCO. Magnetization measurements confirmed that the transition became significantly broadened in the coated layer. Finally, the temperature rise of a coil employing the PSCCO coating was estimated based on the previous reported theory, suggesting that a temperature increase up to around 90 K can be expected during magnet operation. These results suggest that PSCCO is a promising turn-to-turn insulation material for realizing SI coils.
{"title":"Contact Resistivity Between REBCO Tapes With (Pr0.8Sm0.2)0.6Ca0.4CoO3 Smart-Insulation Layer","authors":"Kyosuke Sakurai;Yuji Tsuchiya;Masahiro Tahashi;Hideo Goto;Satoshi Awaji","doi":"10.1109/TASC.2026.3655248","DOIUrl":"https://doi.org/10.1109/TASC.2026.3655248","url":null,"abstract":"A smart-insulation (SI) approach employing a metal–insulator transition (MIT) material has been investigated for improving the thermal stability and charging characteristics of REBCO coils. In this study, we investigated a coating method for REBCO tapes using a material (Pr<sub>0.8</sub>Sm<sub>0.2</sub>)<sub>0.6</sub>Ca<sub>0.4</sub>CoO<sub>3</sub> (PSCCO) which exhibits a MIT around 74 K. PSCCO powder, synthesized by the sol–gel method and then ball-milled, was dispersed in N-methyl-2-pyrrolidone (NMP) to form a slurry, which was subsequently coated onto the REBCO tape. The contact resistivity (<italic>ρ</i><sub>ct</sub>) between REBCO tapes was measured from 10 K to 270 K under uniaxial pressures. The <italic>ρ</i><sub>ct</sub> decreased monotonically from 1.9 × 10<sup>8</sup> μΩ·cm<sup>2</sup> at 10 K to 7.0 × 10<sup>3</sup> μΩ·cm<sup>2</sup> at 270 K. However, the <italic>ρ</i><sub>ct</sub> did not show a sharp MIT-like transition as observed in bulk PSCCO. Magnetization measurements confirmed that the transition became significantly broadened in the coated layer. Finally, the temperature rise of a coil employing the PSCCO coating was estimated based on the previous reported theory, suggesting that a temperature increase up to around 90 K can be expected during magnet operation. These results suggest that PSCCO is a promising turn-to-turn insulation material for realizing SI coils.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146082057","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-19DOI: 10.1109/TASC.2026.3652669
Timo Muscheid;Daniel Crovo;Robert Gartmann;Eduardo Gerlein;Oliver Sander;Sebastian Kempf;Luis E. Ardila-Perez
Simultaneous readout of large-scale cryogenic detector arrays relies on multiplexing schemes such as frequency-division multiplexing (FDM) with microwave superconducting quantum interference device (SQUID) multiplexers and highly customized readout electronics. In traditional detector systems, where mixed-signal application-specific integrated circuit (ASIC)s are used in detector front ends and typically provide a digital interface, hardware-in-the-loop (HIL) testing can be readily implemented by reusing the existing digital logic of the front end for emulation purposes. Such straightforward emulation is not possible for FDM low-temperature detectors, where the sensor signal is encoded in a high-frequency microwave carrier via a two-stage modulation scheme depending on the cryogenic resonators and the SQUID response. To address this challenge, we present CryoDE, a digital cryogenic detector emulator for microwave SQUID multiplexed detector systems. CryoDE generates the encoded detector signals, including realistic pulse responses, enabling full HIL testing of the room temperature data acquisition (DAQ) system without requiring the cryogenic hardware. This resource-efficient detector twin integrates seamlessly into the field-programmable-gate-array (FPGA) firmware of existing DAQ systems and allows experiment-specific adjustment of detector signal parameters. We describe the internal architecture and capabilities of CryoDE within our custom HIL framework and demonstrate its use in evaluating the performance of real-time signal processing firmware optimized for different microwave SQUID multiplexed cryogenic detector experiments.
{"title":"CryoDE: A Digital Cryogenic Detector Emulator for Microwave SQUID Multiplexed Systems","authors":"Timo Muscheid;Daniel Crovo;Robert Gartmann;Eduardo Gerlein;Oliver Sander;Sebastian Kempf;Luis E. Ardila-Perez","doi":"10.1109/TASC.2026.3652669","DOIUrl":"https://doi.org/10.1109/TASC.2026.3652669","url":null,"abstract":"Simultaneous readout of large-scale cryogenic detector arrays relies on multiplexing schemes such as frequency-division multiplexing (FDM) with microwave superconducting quantum interference device (SQUID) multiplexers and highly customized readout electronics. In traditional detector systems, where mixed-signal application-specific integrated circuit (ASIC)s are used in detector front ends and typically provide a digital interface, hardware-in-the-loop (HIL) testing can be readily implemented by reusing the existing digital logic of the front end for emulation purposes. Such straightforward emulation is not possible for FDM low-temperature detectors, where the sensor signal is encoded in a high-frequency microwave carrier via a two-stage modulation scheme depending on the cryogenic resonators and the SQUID response. To address this challenge, we present CryoDE, a digital cryogenic detector emulator for microwave SQUID multiplexed detector systems. CryoDE generates the encoded detector signals, including realistic pulse responses, enabling full HIL testing of the room temperature data acquisition (DAQ) system without requiring the cryogenic hardware. This resource-efficient detector twin integrates seamlessly into the field-programmable-gate-array (FPGA) firmware of existing DAQ systems and allows experiment-specific adjustment of detector signal parameters. We describe the internal architecture and capabilities of CryoDE within our custom HIL framework and demonstrate its use in evaluating the performance of real-time signal processing firmware optimized for different microwave SQUID multiplexed cryogenic detector experiments.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 6","pages":"1-6"},"PeriodicalIF":1.8,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146175893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In a recently developed multilayer (ML) scheme, two or more 10-nm thick Ca0.3Y0.7Ba2Cu3O7-x spacers were inserted into BaZrO3-doped YBa2Cu3O7-x (BZO/YBCO) films to enable dynamic diffusion of Ca ions from the spacers to BZO/YBCO layers. In these ML BZO/YBCO nanocomposite films, significantly enhanced pinning has been attributed to Ca/Cu substitution on the Cu-O planes of YBCO, leading to reduced lattice mismatch and hence defects at the BZO/YBCO interface. In this work, we further probe the Ca diffusion in the five-layer ML films by varying the thickness of the two Ca0.3Y0.7Ba2Cu3O7-x spacers in the range of 1 nm-10 nm and also the thickness of the three BZO/YBCO layers in the range of 50–330 nm. Ca diffusion has been found highly effective if the spacer layer thickness exceeds 2 nm and can diffuse through large BZO/YBCO thicknesses up to 330 nm (total film thickness ∼ 1 µm) along the BZO/YBCO interface. The critical current density exhibits enhanced and almost thickness-independent trends in the ML BZO/YBCO nanocomposite films. Significantly enhanced pinning is illustrated in up to 5 folds enhancement of Jc at 65 K and 9.0 T. At lower temperatures, the enhanced pinning extends to a broad range of the orientations of magnetic field (B). At 20 K and 9.0 T, the Ic is up to 654 A/cm-width at B//c, which is close to 753 A/cm-width at B//ab due to the intrinsic pinning, has been achieved. This result suggests that the ML scheme provides an interesting approach to improve pinning in nanocomposite films.
{"title":"Achieving High and Isotropic Pinning in Multilayer BaZrO3/YBa2Cu3O7-x Films","authors":"Aafiya;Victor Ogunjimi;Mary Ann Sebastian;Mohan Panth;Benson Tsai;Abhijeet Chowdhury;Jialong Huang;Timothy Haugan;Haiyan Wang;Judy Wu","doi":"10.1109/TASC.2026.3651418","DOIUrl":"https://doi.org/10.1109/TASC.2026.3651418","url":null,"abstract":"In a recently developed multilayer (ML) scheme, two or more 10-nm thick Ca<sub>0.3</sub>Y<sub>0.7</sub>Ba<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> spacers were inserted into BaZrO<sub>3</sub>-doped YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> (BZO/YBCO) films to enable dynamic diffusion of Ca ions from the spacers to BZO/YBCO layers. In these ML BZO/YBCO nanocomposite films, significantly enhanced pinning has been attributed to Ca/Cu substitution on the Cu-O planes of YBCO, leading to reduced lattice mismatch and hence defects at the BZO/YBCO interface. In this work, we further probe the Ca diffusion in the five-layer ML films by varying the thickness of the two Ca<sub>0.3</sub>Y<sub>0.7</sub>Ba<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> spacers in the range of 1 nm-10 nm and also the thickness of the three BZO/YBCO layers in the range of 50–330 nm. Ca diffusion has been found highly effective if the spacer layer thickness exceeds 2 nm and can diffuse through large BZO/YBCO thicknesses up to 330 nm (total film thickness ∼ 1 µm) along the BZO/YBCO interface. The critical current density exhibits enhanced and almost thickness-independent trends in the ML BZO/YBCO nanocomposite films. Significantly enhanced pinning is illustrated in up to 5 folds enhancement of <italic>J</i><sub>c</sub> at 65 K and 9.0 T. At lower temperatures, the enhanced pinning extends to a broad range of the orientations of magnetic field (B). At 20 K and 9.0 T, the <italic>I<sub>c</sub></i> is up to 654 A/cm-width at B//c, which is close to 753 A/cm-width at B//ab due to the intrinsic pinning, has been achieved. This result suggests that the ML scheme provides an interesting approach to improve pinning in nanocomposite films.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146026322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MgB2 superconducting wires made with internal magnesium diffusion (IMD) process have reached an excellent performance than other routes. However, the incomplete Mg/B reaction has been the core problem of IMD process. In this study, MgB2/Ni IMD superconducting monofilament wires were prepared using the improved IMD process. By exploring annealing processes during fabrication, we improved the ductility of the wires and ensured the uniform continuity of the central Mg core filaments. The optimal heat treatment process for MgB2/Ni IMD wires was ascertained by micro structural morphology analysis, phase structure analysis, superconducting property analysis. The study demonstrates that this processing technique leads to a more complete reaction between Mg and B after heat treatment. The critical current density of MgB2/Ni super-conducting wires was measured at 4.2 K, demonstrating high current-carrying capabilities, particularly at high magnetic fields. This research provides valuable insights for the processing and heat treatment of MgB2/Ni multi-core superconducting wires in the future.
{"title":"Preparation and Properties of High Performance MgB2/Ni Superconducting Wire With Improved Internal Magnesium Diffusion Process","authors":"Yiming Wang;Qingyang Wang;Zhenyu Chen;Dan Xi;Hongli Hou;Shengnan Zhang;Jianqing Feng;Jianfeng Li;Pingxiang Zhang","doi":"10.1109/TASC.2026.3654478","DOIUrl":"https://doi.org/10.1109/TASC.2026.3654478","url":null,"abstract":"MgB<sub>2</sub> superconducting wires made with internal magnesium diffusion (IMD) process have reached an excellent performance than other routes. However, the incomplete Mg/B reaction has been the core problem of IMD process. In this study, MgB<sub>2</sub>/Ni IMD superconducting monofilament wires were prepared using the improved IMD process. By exploring annealing processes during fabrication, we improved the ductility of the wires and ensured the uniform continuity of the central Mg core filaments. The optimal heat treatment process for MgB<sub>2</sub>/Ni IMD wires was ascertained by micro structural morphology analysis, phase structure analysis, superconducting property analysis. The study demonstrates that this processing technique leads to a more complete reaction between Mg and B after heat treatment. The critical current density of MgB<sub>2</sub>/Ni super-conducting wires was measured at 4.2 K, demonstrating high current-carrying capabilities, particularly at high magnetic fields. This research provides valuable insights for the processing and heat treatment of MgB<sub>2</sub>/Ni multi-core superconducting wires in the future.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-4"},"PeriodicalIF":1.8,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146026427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-16DOI: 10.1109/TASC.2026.3655165
Avirup Roy;Robinjeet Singh;Joel C. Weber;William B. Doriese;Johnathon Gard;Mark W. Keller;John A. B. Mates;Kelsey M. Morgan;Nathan J. Ortiz;Daniel S. Swetz;Daniel R. Schmidt;Joel N. Ullom;Evan P. Jahrman;Thomas C. Allison;Sasawat Jamnuch;John Vinson;Charles J. Titus;Cherno Jaye;Daniel A. Fischer;Galen C. O’Neil
We present the electrothermal characterization of transition-edge sensor (TES) detectors suspended on Si membranes fabricated using a silicon-on-insulator wafer. The use of an all-silicon fabrication platform, in contrast to the more commonly used silicon nitride membranes, is compatible with monolithic fabrication of integrated TES and SQUID circuits. The all-silicon architecture additionally allows the efficient use of focal plane area; the readout circuitry may be positioned out of the focal plane by bending a thinned portion of the chip. Compatibility with integrated fabrication and the efficient use of focal plane area provide a path to an efficient soft X-ray spectrometer. This work is motivated by our goal to develop a 10 000-pixel TES spectrometer to overcome critical measurement limitations in catalysis research. The characterization of fragile, carbon-based intermediates via techniques, such as resonant inelastic X-ray scattering (RIXS), is often precluded by the slow, high-flux nature of existing technologies. The new instrument will allow for fast RIXS measurements to be made without causing sample damage. We verify the detector models and measure the energy resolution using a pulsed optical laser, demonstrating the viability of this approach for the final instrument to be deployed at the National Synchrotron Light Source II.
{"title":"Characterization of Silicon-Membrane TES Microcalorimeters for Large-Format X-Ray Spectrometers With Integrated Microwave SQUID Readout","authors":"Avirup Roy;Robinjeet Singh;Joel C. Weber;William B. Doriese;Johnathon Gard;Mark W. Keller;John A. B. Mates;Kelsey M. Morgan;Nathan J. Ortiz;Daniel S. Swetz;Daniel R. Schmidt;Joel N. Ullom;Evan P. Jahrman;Thomas C. Allison;Sasawat Jamnuch;John Vinson;Charles J. Titus;Cherno Jaye;Daniel A. Fischer;Galen C. O’Neil","doi":"10.1109/TASC.2026.3655165","DOIUrl":"https://doi.org/10.1109/TASC.2026.3655165","url":null,"abstract":"We present the electrothermal characterization of transition-edge sensor (TES) detectors suspended on Si membranes fabricated using a silicon-on-insulator wafer. The use of an all-silicon fabrication platform, in contrast to the more commonly used silicon nitride membranes, is compatible with monolithic fabrication of integrated TES and SQUID circuits. The all-silicon architecture additionally allows the efficient use of focal plane area; the readout circuitry may be positioned out of the focal plane by bending a thinned portion of the chip. Compatibility with integrated fabrication and the efficient use of focal plane area provide a path to an efficient soft X-ray spectrometer. This work is motivated by our goal to develop a 10 000-pixel TES spectrometer to overcome critical measurement limitations in catalysis research. The characterization of fragile, carbon-based intermediates via techniques, such as resonant inelastic X-ray scattering (RIXS), is often precluded by the slow, high-flux nature of existing technologies. The new instrument will allow for fast RIXS measurements to be made without causing sample damage. We verify the detector models and measure the energy resolution using a pulsed optical laser, demonstrating the viability of this approach for the final instrument to be deployed at the National Synchrotron Light Source II.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 6","pages":"1-8"},"PeriodicalIF":1.8,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146175927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-14DOI: 10.1109/TASC.2025.3650523
Dai Oikawa;Hirokazu Komatsu;Keita Tsuzuki;Hiroya Andoh
The configuration of a robust, high-security system has become increasingly important because, as computer processing speeds continue to improve, the vulnerabilities of cryptographic systems that rely on conventional pseudo-random-numbers have raised concerns regarding potential leaks of confidential information. To establish such a secure system, high-quality and high-speed random numbers are essential. Here, high-quality random-numbers are defined as statistically unbiased, non-reproducible, and unpredictable values. One approach to generating such numbers is to exploit physical random phenomena, such as chaos. In particular, chaos in Josephson junctions (JJs) under radio-frequency (RF) irradiation has been identified as a suitable mechanism for random-number generation. In this study, we considered RF-biased intrinsic Josephson junctions (IJJs) in a mesa-type Bi $_{2}$ Sr$_{2}$CaCu $_{2}$ O$_{8+delta }$ single crystal. Since the interactions among stacked IJJs must be considered, it is insufficient to evaluate their properties using the conventional resistively and capacitively shunted junction (RCSJ) circuit model. Instead, we numerically investigated the chaotic voltage of an IJJ stack irradiated with higher frequencies than those typically used in conventional RF systems, employing the capacitively coupled JJ model with diffusion current, which incorporates interlayer interactions. Based on the time-series output voltage of the IJJ, we then generated random-numbers and evaluated their quality using statistical tests.
{"title":"Random-Number Generation Using Chaos in RF-Irradiated Stacked Intrinsic Josephson Junction","authors":"Dai Oikawa;Hirokazu Komatsu;Keita Tsuzuki;Hiroya Andoh","doi":"10.1109/TASC.2025.3650523","DOIUrl":"https://doi.org/10.1109/TASC.2025.3650523","url":null,"abstract":"The configuration of a robust, high-security system has become increasingly important because, as computer processing speeds continue to improve, the vulnerabilities of cryptographic systems that rely on conventional pseudo-random-numbers have raised concerns regarding potential leaks of confidential information. To establish such a secure system, high-quality and high-speed random numbers are essential. Here, high-quality random-numbers are defined as statistically unbiased, non-reproducible, and unpredictable values. One approach to generating such numbers is to exploit physical random phenomena, such as chaos. In particular, chaos in Josephson junctions (JJs) under radio-frequency (RF) irradiation has been identified as a suitable mechanism for random-number generation. In this study, we considered RF-biased intrinsic Josephson junctions (IJJs) in a mesa-type Bi <inline-formula><tex-math>$_{2}$</tex-math></inline-formula> Sr<inline-formula><tex-math>$_{2}$</tex-math></inline-formula>CaCu <inline-formula><tex-math>$_{2}$</tex-math></inline-formula> O<inline-formula><tex-math>$_{8+delta }$</tex-math></inline-formula> single crystal. Since the interactions among stacked IJJs must be considered, it is insufficient to evaluate their properties using the conventional resistively and capacitively shunted junction (RCSJ) circuit model. Instead, we numerically investigated the chaotic voltage of an IJJ stack irradiated with higher frequencies than those typically used in conventional RF systems, employing the capacitively coupled JJ model with diffusion current, which incorporates interlayer interactions. Based on the time-series output voltage of the IJJ, we then generated random-numbers and evaluated their quality using statistical tests.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145982231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Optimizing various fabrication parameters is one of the major challenges in the development of superconducting wires, often resulting in prolonged transition periods from fundamental research to practical applications. Additionally, escalating costs for essential resources such as liquid helium have amplified the difficulty of experimental work, further underscoring the importance of data-driven research approaches. In this study, we focus on magnesium diboride (MgB2) wires and demonstrate the effectiveness of Bayesian optimization in efficiently searching complex parameter spaces to identify optimal fabrication conditions. Specifically, we investigate the internal magnesium diffusion (IMD) process, employing Bayesian optimization and the BOXVIA visualization tool to explore key heat-treatment parameters—namely, heat-treatment time and temperature—with the aim of maximizing the engineering critical current density ($J_{mathrm{e}}$). Our results show that, under conventional conditions, the highest Je was achieved at approximately 700 °C with a short holding time of less than one hour. Moreover, our process informatics approach enabled the discovery of optimal conditions even under unconventional parameter settings. This methodology substantially reduces the number of experimental iterations required and enhances the performance of superconducting wires. Overall, our data-driven optimization strategy offers a promising route for faster, more efficient wire fabrication and the accelerated commercialization of superconducting technologies.
{"title":"Development of Premix Internal-Magnesium-Diffusion MgB2 Wire Using a Data-Driven Approach","authors":"Akiyoshi Matsumoto;Akimitsu Ishii;Rei Kawasaki;Takahiro Hosokawa;Akiyasu Yamamoto","doi":"10.1109/TASC.2026.3652546","DOIUrl":"https://doi.org/10.1109/TASC.2026.3652546","url":null,"abstract":"Optimizing various fabrication parameters is one of the major challenges in the development of superconducting wires, often resulting in prolonged transition periods from fundamental research to practical applications. Additionally, escalating costs for essential resources such as liquid helium have amplified the difficulty of experimental work, further underscoring the importance of data-driven research approaches. In this study, we focus on magnesium diboride (MgB<sub>2</sub>) wires and demonstrate the effectiveness of Bayesian optimization in efficiently searching complex parameter spaces to identify optimal fabrication conditions. Specifically, we investigate the internal magnesium diffusion (IMD) process, employing Bayesian optimization and the BOXVIA visualization tool to explore key heat-treatment parameters—namely, heat-treatment time and temperature—with the aim of maximizing the engineering critical current density (<inline-formula><tex-math>$J_{mathrm{e}}$</tex-math></inline-formula>). Our results show that, under conventional conditions, the highest Je was achieved at approximately 700 °C with a short holding time of less than one hour. Moreover, our process informatics approach enabled the discovery of optimal conditions even under unconventional parameter settings. This methodology substantially reduces the number of experimental iterations required and enhances the performance of superconducting wires. Overall, our data-driven optimization strategy offers a promising route for faster, more efficient wire fabrication and the accelerated commercialization of superconducting technologies.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-4"},"PeriodicalIF":1.8,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146026356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As the only high-temperature superconducting material that can be prepared into isotropic round wires, Bi-2212 has important application value in the high magnetic field domain. This study investigates the manufacturing process of connection joints between a Bi-2212 round wire and other superconducting materials. First, pure tin is used to dissolve the sheath materials of the outer layers of each superconducting material, and then the superconducting solder PbBi alloy is used to replace the nonsuperconducting tin. During this process, the influence of time on the dissolution of different metal sheath by the solder was compared and analyzed, and the more appropriate soldering temperature and time are preliminarily given. Second, joints between Bi-2212 and NbTi, Nb3Sn, as well as Bi-2223 were successfully prepared by applying this process, and the current-carrying capacity test was carried out at 4.2 K and 0–1.2 T. Finally, elemental analysis of the joints was performed by using a scanning electron microscope (SEM), confirming the good bonding performance between the PbBi alloy and the base metal.
{"title":"Research on Solder Joints Process between Bi-2212 Round Wire and Other Superconducting Materials","authors":"Lei Yu;Zhen Fang;Qingbin Hao;Hang Zhao;Zhipeng Jiang;Jianyuan Xu;Hangwei Ding;Yuyang Shi;Pengcheng Huang;Zhiyou Chen;Wenge Chen","doi":"10.1109/TASC.2026.3653561","DOIUrl":"https://doi.org/10.1109/TASC.2026.3653561","url":null,"abstract":"As the only high-temperature superconducting material that can be prepared into isotropic round wires, Bi-2212 has important application value in the high magnetic field domain. This study investigates the manufacturing process of connection joints between a Bi-2212 round wire and other superconducting materials. First, pure tin is used to dissolve the sheath materials of the outer layers of each superconducting material, and then the superconducting solder PbBi alloy is used to replace the nonsuperconducting tin. During this process, the influence of time on the dissolution of different metal sheath by the solder was compared and analyzed, and the more appropriate soldering temperature and time are preliminarily given. Second, joints between Bi-2212 and NbTi, Nb<sub>3</sub>Sn, as well as Bi-2223 were successfully prepared by applying this process, and the current-carrying capacity test was carried out at 4.2 K and 0–1.2 T. Finally, elemental analysis of the joints was performed by using a scanning electron microscope (SEM), confirming the good bonding performance between the PbBi alloy and the base metal.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 2","pages":"1-6"},"PeriodicalIF":1.8,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146026618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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