Equivalent contact resistivity is a key parameter that affects the dynamic process and overcurrent characteristic of the non-insulation (NI) high-temperature superconducting coil. Adding stainless steel material between turns of a parallel-wound NI coil results in the formation of various types of internal contact interfaces. Therefore, describing the shunt behavior of the coil, i.e., the parallel-wound metal-insulation (PWMI) coil, requires more than one equivalent contact resistivity, which makes it difficult to determine their specific values only through coil inductance and time constant. To handle this problem, we propose a method to acquire distinct equivalent contact resistivities of the PWMI coil. In this method, the equivalent contact resistivities are inverted based on the measured coil voltage or magnetic field. The bridge to connect the experimental data and equivalent contact resistivities is the streamlined field–circuit coupling model based on the T–A formulation, which can reflect the complex electromagnetic topology and the distribution of equivalent contact resistivities of the PWMI coil. After obtaining the measurement results, the least-squares method is used to optimize the equivalent contact resistivities until the simulation curve is sufficiently consistent with the experimental curve. In order to improve the efficiency of the optimization, we construct the lumped circuit model of the PWMI coil. Before the optimization process begins, the initial values of equivalent contact resistivities can be obtained based on this model, which can reduce the search scope of the optimization. The results of multiprocess testing indicate that using the equivalent contact resistivities obtained by the proposed method can effectively predict the transient behavior of the coil.
{"title":"Inversion of Equivalent Contact Resistivities of Parallel-Wound Metal-Insulation HTS Coil Based on Experimental Data and Multilevel Simulation","authors":"Hongzhuo Zeng;Qiuliang Wang;Yong Chen;Kangshuai Wang;Benzhe Zhou;Xiaoyu Ji;Fangliang Dong;Shunzhong Chen;Yinming Dai;Zili Zhang;Lei Wang;Jianhua Liu;Lei Qi","doi":"10.1109/TASC.2025.3650502","DOIUrl":"https://doi.org/10.1109/TASC.2025.3650502","url":null,"abstract":"Equivalent contact resistivity is a key parameter that affects the dynamic process and overcurrent characteristic of the non-insulation (NI) high-temperature superconducting coil. Adding stainless steel material between turns of a parallel-wound NI coil results in the formation of various types of internal contact interfaces. Therefore, describing the shunt behavior of the coil, i.e., the parallel-wound metal-insulation (PWMI) coil, requires more than one equivalent contact resistivity, which makes it difficult to determine their specific values only through coil inductance and time constant. To handle this problem, we propose a method to acquire distinct equivalent contact resistivities of the PWMI coil. In this method, the equivalent contact resistivities are inverted based on the measured coil voltage or magnetic field. The bridge to connect the experimental data and equivalent contact resistivities is the streamlined field–circuit coupling model based on the <italic>T</i>–<italic>A</i> formulation, which can reflect the complex electromagnetic topology and the distribution of equivalent contact resistivities of the PWMI coil. After obtaining the measurement results, the least-squares method is used to optimize the equivalent contact resistivities until the simulation curve is sufficiently consistent with the experimental curve. In order to improve the efficiency of the optimization, we construct the lumped circuit model of the PWMI coil. Before the optimization process begins, the initial values of equivalent contact resistivities can be obtained based on this model, which can reduce the search scope of the optimization. The results of multiprocess testing indicate that using the equivalent contact resistivities obtained by the proposed method can effectively predict the transient behavior of the coil.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 2","pages":"1-12"},"PeriodicalIF":1.8,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146026575","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 : 2026-01-05DOI: 10.1109/TASC.2026.3650872
Rintaro Mori;Ryota Kobayashi;Itsuhiro Kakeya
In this article, we have developed a construction method of equivalent circuits for an intrinsic Josephson junction stack using the modularization feature in LTspice. This method improves the readability of circuit diagrams in circuit simulations of terahertz (THz)-radiating Josephson plasma emitters and enhances scalability, such as modifying the number of coherently oscillating junctions. These improvements enable easier simulation of complex models and parameter sweeps, contributing to device optimization for practical THz emitters.
{"title":"Enhancing Equivalent Circuit Simulation of Intrinsic Josephson Junction Stacks Using Modularization of LTspice Elements","authors":"Rintaro Mori;Ryota Kobayashi;Itsuhiro Kakeya","doi":"10.1109/TASC.2026.3650872","DOIUrl":"https://doi.org/10.1109/TASC.2026.3650872","url":null,"abstract":"In this article, we have developed a construction method of equivalent circuits for an intrinsic Josephson junction stack using the modularization feature in LTspice. This method improves the readability of circuit diagrams in circuit simulations of terahertz (THz)-radiating Josephson plasma emitters and enhances scalability, such as modifying the number of coherently oscillating junctions. These improvements enable easier simulation of complex models and parameter sweeps, contributing to device optimization for practical THz emitters.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 4","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146175917","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 : 2025-12-31DOI: 10.1109/TASC.2025.3649716
N. Müller;J. Bonilla-Neira;J. Geria;M. García Redondo;L. Ferreyro;M. Hampel;M. Wegner;A. Almela;S. Kempf
The search for primordial B-modes in the cosmic microwave background (CMB) requires highly sensitive and scalable detector systems. The magnetic microbolometer (MMB) is an emerging detector concept that exploits the magnetic properties of paramagnetic materials at sub-kelvin temperatures, offering bolometers with a high dynamic range and low intrinsic noise. In recent years, the microwave SQUID multiplexer ($mu$MUX) has become a key technology to efficiently read large low-temperature detector arrays, enabling the readout of hundreds to thousands of detectors over a single transmission line with low noise and minimal power dissipation while reducing the cryogenic setup complexity. In this work, we report the design, fabrication and characterization of a $mu$MUX optimized for MMB detectors and share our latest experimental results from a bolometer prototype. These findings provide valuable insight of the $mu$MUX in advancing next-generation CMB instrumentation and also demonstrate its suitability for novel detector technologies such as the MMB.
{"title":"Development of a Microwave SQUID Multiplexer for Magnetic Microbolometers","authors":"N. Müller;J. Bonilla-Neira;J. Geria;M. García Redondo;L. Ferreyro;M. Hampel;M. Wegner;A. Almela;S. Kempf","doi":"10.1109/TASC.2025.3649716","DOIUrl":"https://doi.org/10.1109/TASC.2025.3649716","url":null,"abstract":"The search for primordial B-modes in the cosmic microwave background (CMB) requires highly sensitive and scalable detector systems. The magnetic microbolometer (MMB) is an emerging detector concept that exploits the magnetic properties of paramagnetic materials at sub-kelvin temperatures, offering bolometers with a high dynamic range and low intrinsic noise. In recent years, the microwave SQUID multiplexer (<inline-formula><tex-math>$mu$</tex-math></inline-formula>MUX) has become a key technology to efficiently read large low-temperature detector arrays, enabling the readout of hundreds to thousands of detectors over a single transmission line with low noise and minimal power dissipation while reducing the cryogenic setup complexity. In this work, we report the design, fabrication and characterization of a <inline-formula><tex-math>$mu$</tex-math></inline-formula>MUX optimized for MMB detectors and share our latest experimental results from a bolometer prototype. These findings provide valuable insight of the <inline-formula><tex-math>$mu$</tex-math></inline-formula>MUX in advancing next-generation CMB instrumentation and also demonstrate its suitability for novel detector technologies such as the MMB.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 6","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2025-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146175901","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 : 2025-12-31DOI: 10.1109/TASC.2025.3649784
Yiming Ma;Yusuke Shimada;Hongye Gao;Yuta Hasegawa;Shinnosuke Tokuta;Akiyasu Yamamoto;Akinori Yamanaka;Satoshi Hata
For polycrystalline cobalt-doped BaFe2As2 (Ba122:Co) superconductors, controlling their microstructure, such as grain size, crystallographic texture, is crucial for achieving high critical current densities (Jc). A prevailing academic view holds that heat treatment is a key step in forming a desired crystallographic texture. This study performed in-situ heating and four-dimensional scanning transmission electron microscopy (4D-STEM) observation to characterize microstructural evolution in precursor Ba122:Co powders prepared by high-energy ball milling and subsequent spark plasma sintering. A formation path for the Ba122 phase was revealed: a crystallographic orientation relationship was recognized between fine Ba122 grains and adjacent larger FeAs grains in the precursor powders, which suggests epitaxial growth of the Ba122 phase from the FeAs phase. However, in the subsequent in-situ heating process, the microstructural changes in the thin foil specimens of the precursor powders exhibited a different trend from that of bulk specimens of the precursor powders: the fine Ba122 grains did not coarsen but exhibit grain refinement and amorphization. The observed results described above were discussed from the viewpoints of the microstructural control of polycrystalline Ba122:Co.
{"title":"Polycrystalline Phase Formation of Co-Doped BaFe2As2 Studied by In-Situ 4D-STEM","authors":"Yiming Ma;Yusuke Shimada;Hongye Gao;Yuta Hasegawa;Shinnosuke Tokuta;Akiyasu Yamamoto;Akinori Yamanaka;Satoshi Hata","doi":"10.1109/TASC.2025.3649784","DOIUrl":"https://doi.org/10.1109/TASC.2025.3649784","url":null,"abstract":"For polycrystalline cobalt-doped BaFe<sub>2</sub>As<sub>2</sub> (Ba122:Co) superconductors, controlling their microstructure, such as grain size, crystallographic texture, is crucial for achieving high critical current densities (<italic>J</i><sub>c</sub>). A prevailing academic view holds that heat treatment is a key step in forming a desired crystallographic texture. This study performed in-situ heating and four-dimensional scanning transmission electron microscopy (4D-STEM) observation to characterize microstructural evolution in precursor Ba122:Co powders prepared by high-energy ball milling and subsequent spark plasma sintering. A formation path for the Ba122 phase was revealed: a crystallographic orientation relationship was recognized between fine Ba122 grains and adjacent larger FeAs grains in the precursor powders, which suggests epitaxial growth of the Ba122 phase from the FeAs phase. However, in the subsequent in-situ heating process, the microstructural changes in the thin foil specimens of the precursor powders exhibited a different trend from that of bulk specimens of the precursor powders: the fine Ba122 grains did not coarsen but exhibit grain refinement and amorphization. The observed results described above were discussed from the viewpoints of the microstructural control of polycrystalline Ba122:Co.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2025-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146026519","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 : 2025-12-31DOI: 10.1109/TASC.2025.3649790
Richard Pascua;Michael de Leon;Sang Heon Lee;Hyung-Seop Shin
Multilayer REBCO-coated conductor (CC) tapes undergo various stresses and strains when utilized in superconducting devices such as high-field magnets and coils. The stresses encountered by REBCO tapes include radial transverse tensile stresses from Lorenz forces and thermal stresses arising from differences in the thermal expansion coefficients of the constituent layers during quenching. These stresses can cause delamination at multiple interfaces within the REBCO CC tape’s multilayer architecture, compromising its integrity and leading to catastrophic failure of the superconducting device. Meanwhile, the Cu stabilizer surrounding the CC tape plays a key role in preventing delamination failure by binding multiple constituent layers with different mechanical properties and maintaining structural stability against transverse external forces. However, the effect of slit edges created during CC tape manufacturing on delamination resistance under transverse loading remains unclear. To address this critical research gap, we conducted comprehensive delamination tests using the anvil method. We compared the effects of the slit edge geometry and the Cu layer at the edges on the mechanical delamination strength of REBCO CC tapes. By conducting a comprehensive analysis, we aimed to examine the roles of edge geometry and interfacial properties in the delamination behavior of REBCO CC tapes. This will offer valuable insights for optimizing the design and fabrication of these high-field coils, contributing to the development of more robust and reliable superconducting devices.
{"title":"Effects of Edge Geometry and Interface Characteristics on Delamination Strength of REBCO Tapes Under Transverse Tension Using Anvil Method","authors":"Richard Pascua;Michael de Leon;Sang Heon Lee;Hyung-Seop Shin","doi":"10.1109/TASC.2025.3649790","DOIUrl":"https://doi.org/10.1109/TASC.2025.3649790","url":null,"abstract":"Multilayer REBCO-coated conductor (CC) tapes undergo various stresses and strains when utilized in superconducting devices such as high-field magnets and coils. The stresses encountered by REBCO tapes include radial transverse tensile stresses from Lorenz forces and thermal stresses arising from differences in the thermal expansion coefficients of the constituent layers during quenching. These stresses can cause delamination at multiple interfaces within the REBCO CC tape’s multilayer architecture, compromising its integrity and leading to catastrophic failure of the superconducting device. Meanwhile, the Cu stabilizer surrounding the CC tape plays a key role in preventing delamination failure by binding multiple constituent layers with different mechanical properties and maintaining structural stability against transverse external forces. However, the effect of slit edges created during CC tape manufacturing on delamination resistance under transverse loading remains unclear. To address this critical research gap, we conducted comprehensive delamination tests using the anvil method. We compared the effects of the slit edge geometry and the Cu layer at the edges on the mechanical delamination strength of REBCO CC tapes. By conducting a comprehensive analysis, we aimed to examine the roles of edge geometry and interfacial properties in the delamination behavior of REBCO CC tapes. This will offer valuable insights for optimizing the design and fabrication of these high-field coils, contributing to the development of more robust and reliable superconducting devices.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2025-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145982242","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 : 2025-12-29DOI: 10.1109/TASC.2025.3644628
{"title":"IEEE Transactions on Applied Superconductivity Information for Authors","authors":"","doi":"10.1109/TASC.2025.3644628","DOIUrl":"https://doi.org/10.1109/TASC.2025.3644628","url":null,"abstract":"","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 1","pages":"C4-C4"},"PeriodicalIF":1.8,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11318111","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145879970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-26DOI: 10.1109/TASC.2025.3648679
Joshua D. Fuhrman;Fred M. Finkbeiner;Joseph S. Adams;Simon R. Bandler;Rachel B. Borrelli;James A. Chervenak;Tannaz Farrahi;Felipe A. Colazo Petit;Renata S. Cumbee;Samuel V. Hull;Richard L. Kelley;Caroline A. Kilbourne;Haruka Muramatsu;Frederick Scott Porter;Asha Rani;Kazuhiro Sakai;Stephen J. Smith;Ambarish C. Venkatasubraman;Nicholas A. Wakeham;Edward J. Wassell;Michael C. Witthoeft;Sang H. Yoon
The X-IFU instrument for ESA’s upcoming flagship mission Athena will use Mo/Au bilayer transition-edge sensors (TES) with Au/Bi X-ray absorbers to form a kilopixel microcalorimeter array. Such detectors require careful calibration to maintain their best possible performance, but such calibrations can change over long periods of time when exposed to certain environmental conditions. We have previously reported the effects of humidity and elevated temperature on prototype array characteristics. In that study, storage of a prototype array at 60 $^{circ }$C for ten days under vacuum produced an unexpected shift in the TES critical temperature T$_{c}$ (+13% to +19%) and normal resistance R$_{n}$ (+4%). In this work, we continue investigating shifts in array characteristics after long-duration temperature exposures so that safe storage and handling conditions for X-IFU flight arrays can be set. A prototype array exposed to 35 $^{circ }$C under vacuum for 26 days gradually increased in TES normal resistance. The energy scale of a second prototype array was measured before aging and then recovered to within 0.5 eV following a similar aging induced R$_{n}$ increase. Aging of the TES was studied directly by applying the same thermal conditions exclusively to Mo/Au bilayers on Si substrate. These measurements allow a better understanding of the cause of the observed shift by decoupling the TES bilayer from the remaining device structures, such as the SiNx membrane and the absorber. Four-point resistance measurements were used to readout the bilayer samples at 4.2 K. Bilayers aged in a vacuum generally saw no change or a slight increase in resistance, while bilayers aged in nitrogen gas decreased in resistance. Finally, we conclude with a comparative overview of all test results on prototype arrays and TES bilayers, elaborate on possible mechanisms for the observed shifts in characteristics, and make recommendations for maintaining the long-term stability of our devices.
{"title":"Accelerating Storage Lifetime Testing of Microcalorimeter Arrays for NewAthena X-IFU","authors":"Joshua D. Fuhrman;Fred M. Finkbeiner;Joseph S. Adams;Simon R. Bandler;Rachel B. Borrelli;James A. Chervenak;Tannaz Farrahi;Felipe A. Colazo Petit;Renata S. Cumbee;Samuel V. Hull;Richard L. Kelley;Caroline A. Kilbourne;Haruka Muramatsu;Frederick Scott Porter;Asha Rani;Kazuhiro Sakai;Stephen J. Smith;Ambarish C. Venkatasubraman;Nicholas A. Wakeham;Edward J. Wassell;Michael C. Witthoeft;Sang H. Yoon","doi":"10.1109/TASC.2025.3648679","DOIUrl":"https://doi.org/10.1109/TASC.2025.3648679","url":null,"abstract":"The X-IFU instrument for ESA’s upcoming flagship mission Athena will use Mo/Au bilayer transition-edge sensors (TES) with Au/Bi X-ray absorbers to form a kilopixel microcalorimeter array. Such detectors require careful calibration to maintain their best possible performance, but such calibrations can change over long periods of time when exposed to certain environmental conditions. We have previously reported the effects of humidity and elevated temperature on prototype array characteristics. In that study, storage of a prototype array at 60 <inline-formula><tex-math>$^{circ }$</tex-math></inline-formula>C for ten days under vacuum produced an unexpected shift in the TES critical temperature T<inline-formula><tex-math>$_{c}$</tex-math></inline-formula> (+13% to +19%) and normal resistance R<inline-formula><tex-math>$_{n}$</tex-math></inline-formula> (+4%). In this work, we continue investigating shifts in array characteristics after long-duration temperature exposures so that safe storage and handling conditions for X-IFU flight arrays can be set. A prototype array exposed to 35 <inline-formula><tex-math>$^{circ }$</tex-math></inline-formula>C under vacuum for 26 days gradually increased in TES normal resistance. The energy scale of a second prototype array was measured before aging and then recovered to within 0.5 eV following a similar aging induced R<inline-formula><tex-math>$_{n}$</tex-math></inline-formula> increase. Aging of the TES was studied directly by applying the same thermal conditions exclusively to Mo/Au bilayers on Si substrate. These measurements allow a better understanding of the cause of the observed shift by decoupling the TES bilayer from the remaining device structures, such as the SiNx membrane and the absorber. Four-point resistance measurements were used to readout the bilayer samples at 4.2 K. Bilayers aged in a vacuum generally saw no change or a slight increase in resistance, while bilayers aged in nitrogen gas decreased in resistance. Finally, we conclude with a comparative overview of all test results on prototype arrays and TES bilayers, elaborate on possible mechanisms for the observed shifts in characteristics, and make recommendations for maintaining the long-term stability of our devices.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 6","pages":"1-7"},"PeriodicalIF":1.8,"publicationDate":"2025-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146057653","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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