Pub Date : 2025-12-23DOI: 10.1109/TASC.2025.3646984
Nicolas Rotheudt;Jean-François Fagnard;Tomas Hlasek;Jan Plechacek;Philippe Vanderbemden
Combining high-temperature superconducting bulks and jointless closed-loop coated conductors recently demonstrated promising magnetic shielding/screening properties when they are zero-field cooled andsubjected to an inhomogeneous applied field. The present work focuses on studying how their screening properties evolve if several magnetic field excitation cycles are applied, as it is the case in practical applications. This study is carried out both experimentally and numerically. The main result is that more than 95% of the field attenuation (screening factor SF) obtained after the first ramp still remain after 300 cycles. This result is explained by using the numerically computed current density distribution in the bulk alone. The slight decrease in SF after several cycles is found to be smaller than the field attenuation arising from conventional current relaxation (or flux creep) if the magnetic field is kept constant after the first increasing ramp. These results demonstrate the potential of such superconducting screens for practical applications with a large number of excitation applied field cycles.
{"title":"Magnetic Screening Behavior of Hybrid High-Temperature Superconducting Screens Subjected to Successive Excitation Cycles: Experiments and Numerical Study","authors":"Nicolas Rotheudt;Jean-François Fagnard;Tomas Hlasek;Jan Plechacek;Philippe Vanderbemden","doi":"10.1109/TASC.2025.3646984","DOIUrl":"https://doi.org/10.1109/TASC.2025.3646984","url":null,"abstract":"Combining high-temperature superconducting bulks and jointless closed-loop coated conductors recently demonstrated promising magnetic shielding/screening properties when they are zero-field cooled andsubjected to an inhomogeneous applied field. The present work focuses on studying how their screening properties evolve if several magnetic field excitation cycles are applied, as it is the case in practical applications. This study is carried out both experimentally and numerically. The main result is that more than 95% of the field attenuation (screening factor SF) obtained after the first ramp still remain after 300 cycles. This result is explained by using the numerically computed current density distribution in the bulk alone. The slight decrease in SF after several cycles is found to be smaller than the field attenuation arising from conventional current relaxation (or flux creep) if the magnetic field is kept constant after the first increasing ramp. These results demonstrate the potential of such superconducting screens for practical applications with a large number of excitation applied field cycles.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-6"},"PeriodicalIF":1.8,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145982287","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}
Voltage taps remain the standard and reliable diagnostic tool for detecting quenches in superconducting magnets. However, they identify a quench only at the time of voltage rise and do not provide information on earlier physical precursors. In this work, we investigate whether acoustic emission data can reveal precursor activity that occurs before conventional voltage detection using machine learning techniques. We introduce an event selection method and a weakly supervised machine learning procedure to learn data-driven criteria for identifying potential acoustic precursors to quenches. Two Convolutional Neural Network (CNN) architectures are trained: one on acoustic sensor events from our selection procedure and one on the Fast Fourier Transforms (FFTs) of these events. Both networks are trained iteratively using confidence-weighted loss functions to associate certain subsets of training data with a precursor label. We evaluate the performance of these models by examining the time distribution of events classified as potential precursors relative to the quench onset. Results indicate that the proposed approach can possibly distinguish acoustic emission events occurring closer to the quench from earlier acoustic activity during ramping, suggesting the potential for flagging quench precursors in acoustic data.
{"title":"A Weakly Supervised Machine Learning Procedure for Acoustic Emission Quench Diagnostics","authors":"Maira Khan;Steven Krave;Vittorio Marinozzi;Jennifer Ngadiuba;Stoyan Stoynev;Nhan Tran","doi":"10.1109/TASC.2025.3647009","DOIUrl":"https://doi.org/10.1109/TASC.2025.3647009","url":null,"abstract":"Voltage taps remain the standard and reliable diagnostic tool for detecting quenches in superconducting magnets. However, they identify a quench only at the time of voltage rise and do not provide information on earlier physical precursors. In this work, we investigate whether acoustic emission data can reveal precursor activity that occurs before conventional voltage detection using machine learning techniques. We introduce an event selection method and a weakly supervised machine learning procedure to learn data-driven criteria for identifying potential acoustic precursors to quenches. Two Convolutional Neural Network (CNN) architectures are trained: one on acoustic sensor events from our selection procedure and one on the Fast Fourier Transforms (FFTs) of these events. Both networks are trained iteratively using confidence-weighted loss functions to associate certain subsets of training data with a precursor label. We evaluate the performance of these models by examining the time distribution of events classified as potential precursors relative to the quench onset. Results indicate that the proposed approach can possibly distinguish acoustic emission events occurring closer to the quench from earlier acoustic activity during ramping, suggesting the potential for flagging quench precursors in acoustic data.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 3","pages":"1-6"},"PeriodicalIF":1.8,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145982158","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}
Epitaxial iron chalcogenide (FeCh, Ch = Se, Te) film deposited by pulsed laser deposition (PLD) represents the gold standard to obtain high superconducting performances. (100) CaF2 single crystal represents the ideal substrate due to structural compatibility, low lattice mismatch and chemical compatibility with FeCh. Epitaxial thin FeCh films grown on CaF2 show optimal performances, with zero-resistance critical temperature Tc0 as high as 9.2 K and 17 K for FeSe and Fe(Se,Te), respectively. Higher Tc up to 20 K can be obtained using a seed layer in Fe(Se,Te).However, film buckling and delamination sometimes occur. Furthermore, the presence of submicrometric wrinkles arranged in graticule pattern was occasionally observed. In this contribution, we provide information on extended defect formation in epitaxial FeCh thin films deposited on (100) CaF2 single crystal by PLD, and their influence on the superconducting properties of such films.
脉冲激光沉积（PLD）外延硫系铁（FeCh, Ch = Se, Te）薄膜是获得高超导性能的金标准。（100） CaF2单晶与FeCh具有结构相容性、低晶格失配和化学相容性，是理想的衬底材料。在CaF2上生长的外延薄膜表现出最佳性能，FeSe和Fe（Se,Te）的零电阻临界温度Tc0分别高达9.2 K和17 K。在Fe（Se,Te）中使用种子层可以获得高达20 K的较高Tc。然而，有时会发生薄膜屈曲和分层。此外，偶尔观察到以网格模式排列的亚微米皱纹的存在。在这篇文章中，我们提供了PLD沉积在（100）CaF2单晶上的外延FeCh薄膜的扩展缺陷形成的信息，以及它们对这种薄膜超导性能的影响。
{"title":"Epitaxial Fe(Se,Te) Film Deposited on CaF2 Single Crystal Substrate: Defect Generation and Film Stability","authors":"Angelo Vannozzi;Antonella Mancini;Andrea Masi;Laura Piperno;Valentina Galluzzi;Alessandro Rufoloni;Giuseppe Celentano","doi":"10.1109/TASC.2025.3645747","DOIUrl":"https://doi.org/10.1109/TASC.2025.3645747","url":null,"abstract":"Epitaxial iron chalcogenide (FeCh, Ch = Se, Te) film deposited by pulsed laser deposition (PLD) represents the gold standard to obtain high superconducting performances. (100) CaF<sub>2</sub> single crystal represents the ideal substrate due to structural compatibility, low lattice mismatch and chemical compatibility with FeCh. Epitaxial thin FeCh films grown on CaF<sub>2</sub> show optimal performances, with zero-resistance critical temperature <italic>T</i><sub>c0</sub> as high as 9.2 K and 17 K for FeSe and Fe(Se,Te), respectively. Higher <italic>T</i><sub>c</sub> up to 20 K can be obtained using a seed layer in Fe(Se,Te).However, film buckling and delamination sometimes occur. Furthermore, the presence of submicrometric wrinkles arranged in graticule pattern was occasionally observed. In this contribution, we provide information on extended defect formation in epitaxial FeCh thin films deposited on (100) CaF<sub>2</sub> single crystal by PLD, and their influence on the superconducting properties of such films.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-4"},"PeriodicalIF":1.8,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886630","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 : 2025-12-22DOI: 10.1109/TASC.2025.3645709
X. Y. Tan;S. Y. Gao;X. S. Yang;H. Zhang;J. Jiang;J. M. Zhu
Stacked high-temperature superconducting (HTS) cables, with their high current-carrying capacity and high structural strength, show significant advantages in strong electric applications. However, in an alternating magnetic field environment, the conductors will generate AC losses, which can cause local overheating. Filamentary technology can effectively reduce the AC losses. This work investigates the magnetization and transport losses of stacked HTS cables based on multi-filamentary REBCO tapes. Results directly demonstrates the fact of the multi-filamentary structure in reducing magnetization loss. As the twist angle increased, magnetization losses first decreased and then stabilized. At low magnetic fields, the difference in magnetization loss between the original cable and the multi-filamentary cable is relatively small. Under higher magnetic fields, the magnetization loss of the original cable is significantly higher than that of the multi-filamentary cable. The transport losses of the multi-filamentary cable are always lower than those of the original cable. The optimization effect of filamentization on magnetization losses is significantly stronger than that on transport losses.
{"title":"AC Losses in Striated REBCO Stacked Tape Cables","authors":"X. Y. Tan;S. Y. Gao;X. S. Yang;H. Zhang;J. Jiang;J. M. Zhu","doi":"10.1109/TASC.2025.3645709","DOIUrl":"https://doi.org/10.1109/TASC.2025.3645709","url":null,"abstract":"Stacked high-temperature superconducting (HTS) cables, with their high current-carrying capacity and high structural strength, show significant advantages in strong electric applications. However, in an alternating magnetic field environment, the conductors will generate AC losses, which can cause local overheating. Filamentary technology can effectively reduce the AC losses. This work investigates the magnetization and transport losses of stacked HTS cables based on multi-filamentary REBCO tapes. Results directly demonstrates the fact of the multi-filamentary structure in reducing magnetization loss. As the twist angle increased, magnetization losses first decreased and then stabilized. At low magnetic fields, the difference in magnetization loss between the original cable and the multi-filamentary cable is relatively small. Under higher magnetic fields, the magnetization loss of the original cable is significantly higher than that of the multi-filamentary cable. The transport losses of the multi-filamentary cable are always lower than those of the original cable. The optimization effect of filamentization on magnetization losses is significantly stronger than that on transport losses.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886628","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 : 2025-12-19DOI: 10.1109/TASC.2025.3645158
R. Konishi;Y. Emori;R. Ozumi;H. Handa;H. Miyazaki;S. Miura;H. Sasa;M. Iwakuma
To reduce carbon dioxide emissions from aircraft, superconducting electric propulsion systems are attracting attention. For aircraft, high power density is particularly important, and increasing the power density requires higher rotational speed. Therefore, we are studying a saddle-shaped field coil made with REBa2Cu3O7-δ (REBCO) tape. This coil can be fixed directly to the shaft, which helps provide the mechanical strength needed for high-speed rotation. However, because of the shape characteristics of the REBCO tape, the coil ends tend to become long, increasing the axial length of the motor. In addition, excessive bending or twisting can damage the tape; thus, careful design is necessary. In this study, we developed a design method to shorten the saddle-shaped field coil and evaluated its electromagnetic performance. We introduced a generalized flatwise curvature to represent bending and twisting and set the allowable curvature of the REBCO tape to 0.1 mm-1 based on its mechanical limits. Using this condition, we designed two types of shortened coils. Model A arranges the coils based on the curvature of the innermost coil, while Model B equalizes the curvature of all coils to prevent interference at the coil ends. Three-dimensional finite-element analysis revealed that the axial gap flux density distribution of both models is almost the same. However, Model B has a slightly larger high-flux-density region because its straight part is longer, resulting in better output performance. The obtained torque also exhibits a strong proportional relationship with the axial integral of the gap flux density, confirming that the coil ends are important regions that contribute to motor output.
{"title":"Design of Shortened REBa2Cu3O7-δ Saddle-Shaped Field Coil Ends for Fully Superconducting Synchronous Motors Using Generalized Flatwise Curvature","authors":"R. Konishi;Y. Emori;R. Ozumi;H. Handa;H. Miyazaki;S. Miura;H. Sasa;M. Iwakuma","doi":"10.1109/TASC.2025.3645158","DOIUrl":"https://doi.org/10.1109/TASC.2025.3645158","url":null,"abstract":"To reduce carbon dioxide emissions from aircraft, superconducting electric propulsion systems are attracting attention. For aircraft, high power density is particularly important, and increasing the power density requires higher rotational speed. Therefore, we are studying a saddle-shaped field coil made with REBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> (REBCO) tape. This coil can be fixed directly to the shaft, which helps provide the mechanical strength needed for high-speed rotation. However, because of the shape characteristics of the REBCO tape, the coil ends tend to become long, increasing the axial length of the motor. In addition, excessive bending or twisting can damage the tape; thus, careful design is necessary. In this study, we developed a design method to shorten the saddle-shaped field coil and evaluated its electromagnetic performance. We introduced a generalized flatwise curvature to represent bending and twisting and set the allowable curvature of the REBCO tape to 0.1 mm<sup>-1</sup> based on its mechanical limits. Using this condition, we designed two types of shortened coils. Model A arranges the coils based on the curvature of the innermost coil, while Model B equalizes the curvature of all coils to prevent interference at the coil ends. Three-dimensional finite-element analysis revealed that the axial gap flux density distribution of both models is almost the same. However, Model B has a slightly larger high-flux-density region because its straight part is longer, resulting in better output performance. The obtained torque also exhibits a strong proportional relationship with the axial integral of the gap flux density, confirming that the coil ends are important regions that contribute to motor output.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-6"},"PeriodicalIF":1.8,"publicationDate":"2025-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145830802","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 : 2025-12-19DOI: 10.1109/TASC.2025.3645151
Keith Krause;Michael C. Hamilton;Mark Adams
Josephson parametric amplifiers (JPAs) have become an important component of superconducting applications. Simulating these circuits is vital for optimizing their performance, including their gain and stability. Previously, simulating JPAs has been inefficient due to the limits of using SPICE-based simulators that work in the time domain. JPAs are better suited to frequency domain simulations over a broad frequency range and parameter space. We present JPA simulations using the recently released flux-aware Josephson junction (JJ) and inductor models in Keysight Advanced Design Systems (ADS). We simulate two different flux-driven JPAs: one based on an RF SQUID, and another based on a DC SQUID. We efficiently run harmonic balance simulations over a wide range of circuit parameters. We compare the use of RF and DC SQUIDs in these JPAs by analyzing their simulation results. This work provides a foundation for future SQUID-based JPA simulations in Keysight ADS.
约瑟夫森参量放大器（JPAs）已成为超导应用的重要组成部分。模拟这些电路对于优化它们的性能至关重要，包括它们的增益和稳定性。以前，由于使用基于spice的在时域工作的模拟器的限制，模拟jpa的效率很低。jpa更适合于宽频率范围和参数空间的频域模拟。我们使用Keysight Advanced Design Systems （ADS）中最近发布的磁通感知Josephson结（JJ）和电感模型进行JPA模拟。我们模拟了两种不同的磁通驱动jpa：一种基于RF SQUID，另一种基于DC SQUID。我们在广泛的电路参数范围内有效地运行谐波平衡模拟。通过分析仿真结果，比较了RF和DC squid在这些jpa中的使用情况。这项工作为Keysight ADS中未来基于squid的JPA模拟提供了基础。
{"title":"Flux-Driven Josephson Parametric Amplifiers Based on an RF SQUID and DC SQUID in Keysight ADS","authors":"Keith Krause;Michael C. Hamilton;Mark Adams","doi":"10.1109/TASC.2025.3645151","DOIUrl":"https://doi.org/10.1109/TASC.2025.3645151","url":null,"abstract":"Josephson parametric amplifiers (JPAs) have become an important component of superconducting applications. Simulating these circuits is vital for optimizing their performance, including their gain and stability. Previously, simulating JPAs has been inefficient due to the limits of using SPICE-based simulators that work in the time domain. JPAs are better suited to frequency domain simulations over a broad frequency range and parameter space. We present JPA simulations using the recently released flux-aware Josephson junction (JJ) and inductor models in Keysight Advanced Design Systems (ADS). We simulate two different flux-driven JPAs: one based on an RF SQUID, and another based on a DC SQUID. We efficiently run harmonic balance simulations over a wide range of circuit parameters. We compare the use of RF and DC SQUIDs in these JPAs by analyzing their simulation results. This work provides a foundation for future SQUID-based JPA simulations in Keysight ADS.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-6"},"PeriodicalIF":1.8,"publicationDate":"2025-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145929399","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 : 2025-12-18DOI: 10.1109/TASC.2025.3645746
A. Angrisani Armenio;A. Masi;L. Piperno;G. Celentano;A. Mancini
Coated conductors (CCs) based on iron-based superconductors (IBS) represent a cost-effective alternative to high-temperature superconductors (HTS). Among them, the FeSe0.5Te0.5 (FST) compound is the simplest in the IBS family, demonstrating excellent properties as an epitaxial film. These characteristics make it highly suitable for low-temperature and high-field applications, providing advantages over low-temperature superconductors. Present studies have demonstrated the feasibility of a simple architecture that provides a single metallic buffer layer for the subsequent growth of the superconductor film. From the analysis of the critical current density (JC), these films exhibit excellent superconducting properties both in temperature and in an applied magnetic field, even compared to similar samples grown on single crystals like CaF2, with a value of around 2 MA/cm2 at 4.2 K in self-field, and greater than 0.1 MA/cm2 at 4.2 K up to 17.5 T. Moreover, the angular behavior of JC at different applied magnetic fields shows an almost isotropic behavior, thanks to a large peak when the field is applied perpendicular to the crystallographic ab-plane. This effective pinning landscape may be related to nanostructured grains with a high density of low-angle boundaries, as evidenced by microstructural analysis.
{"title":"Critical Current Properties of FST on Simple Coated Conductor Architecture","authors":"A. Angrisani Armenio;A. Masi;L. Piperno;G. Celentano;A. Mancini","doi":"10.1109/TASC.2025.3645746","DOIUrl":"https://doi.org/10.1109/TASC.2025.3645746","url":null,"abstract":"Coated conductors (CCs) based on iron-based superconductors (IBS) represent a cost-effective alternative to high-temperature superconductors (HTS). Among them, the FeSe<sub>0.5</sub>Te<sub>0.5</sub> (FST) compound is the simplest in the IBS family, demonstrating excellent properties as an epitaxial film. These characteristics make it highly suitable for low-temperature and high-field applications, providing advantages over low-temperature superconductors. Present studies have demonstrated the feasibility of a simple architecture that provides a single metallic buffer layer for the subsequent growth of the superconductor film. From the analysis of the critical current density (J<sub>C</sub>), these films exhibit excellent superconducting properties both in temperature and in an applied magnetic field, even compared to similar samples grown on single crystals like CaF<sub>2</sub>, with a value of around 2 MA/cm<sup>2</sup> at 4.2 K in self-field, and greater than 0.1 MA/cm<sup>2</sup> at 4.2 K up to 17.5 T. Moreover, the angular behavior of J<sub>C</sub> at different applied magnetic fields shows an almost isotropic behavior, thanks to a large peak when the field is applied perpendicular to the crystallographic ab-plane. This effective pinning landscape may be related to nanostructured grains with a high density of low-angle boundaries, as evidenced by microstructural analysis.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886623","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}
To optimize the superconducting properties of PbMo6S8 (PMS) bulks, we refined the precursor stoichiometry and applied a controlled heat-treatment method—slow ramping, multi-step holds, and a low-vacuum atmosphere—that ensures complete reaction and uniform phase formation in the Pb–Mo–S system. Microstructural analysis, phase-composition characterization, and superconducting performance evaluation were carried out. Results reveal that in this work PMS prepared from elemental Pb, Mo and S powders reaches a sharp superconducting transition at a superconducting transition temperature (Tc) about 14 K and the critical current density (Jc) was 4 × 104 A cm−2 at 4.2 K, self-field. The enhanced performance is attributed to a synergistic flux-pinning effect. The refined grain structure increases the grain-boundary density, while nanometer-scale lattice distortions and dislocations—whose characteristic size matches the superconducting coherence length ξ ≈ 2 nm—act as additional strong pinning centers. Consequently, point and surface pinning operate concurrently, markedly improving Jc under applied magnetic fields. These findings provide a practical route for fabricating high-performance PMS superconductors through elemental-powder processing.
为了优化PbMo6S8 （PMS）块体的超导性能，我们改进了前驱体化学计量学，并应用了一种受控热处理方法——慢速升温、多步保温和低真空气氛——以确保Pb-Mo-S体系中反应完全和相形成均匀。进行了显微组织分析、相组成表征和超导性能评价。结果表明，由Pb、Mo和S单质粉末制备的PMS在超导转变温度（Tc）约14 K时实现了急剧的超导转变，在4.2 K自场下，临界电流密度（Jc）为4 × 104 a cm−2。增强的性能归因于协同的通量钉钉效应。细化的晶粒结构增加了晶界密度，而纳米尺度的晶格畸变和位错（其特征尺寸与超导相干长度ξ≈2 nm相匹配）则是额外的强钉住中心。因此，点和面钉同时工作，显著提高了外加磁场下的Jc。这些发现为通过元素粉末加工制备高性能PMS超导体提供了一条实用的途径。
{"title":"Enhanced Superconducting Performance in PbMo6S8 Bulk Materials via a Novel Processing Technique","authors":"Botao Shao;Guobiao Kang;Jixing Liu;Shengnan Zhang;Zhenyu Chen;Lei Zhi;Qingyang Wang;Jianfeng Li;Pingxiang Zhang","doi":"10.1109/TASC.2025.3645723","DOIUrl":"https://doi.org/10.1109/TASC.2025.3645723","url":null,"abstract":"To optimize the superconducting properties of PbMo<sub>6</sub>S<sub>8</sub> (PMS) bulks, we refined the precursor stoichiometry and applied a controlled heat-treatment method—slow ramping, multi-step holds, and a low-vacuum atmosphere—that ensures complete reaction and uniform phase formation in the Pb–Mo–S system. Microstructural analysis, phase-composition characterization, and superconducting performance evaluation were carried out. Results reveal that in this work PMS prepared from elemental Pb, Mo and S powders reaches a sharp superconducting transition at a superconducting transition temperature (<italic>T<sub>c</sub></i>) about 14 K and the critical current density (<italic>J<sub>c</sub></i>) was 4 × 10<sup>4</sup> A cm<sup>−2</sup> at 4.2 K, self-field. The enhanced performance is attributed to a synergistic flux-pinning effect. The refined grain structure increases the grain-boundary density, while nanometer-scale lattice distortions and dislocations—whose characteristic size matches the superconducting coherence length ξ ≈ 2 nm—act as additional strong pinning centers. Consequently, point and surface pinning operate concurrently, markedly improving <italic>J<sub>c</sub></i> under applied magnetic fields. These findings provide a practical route for fabricating high-performance PMS superconductors through elemental-powder processing.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886664","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}
Magnets with noncircular aperture are desired for fixed-field accelerators to accommodate horizontal orbit offset between beams of different energy. For muon colliders, an elliptic bore allows for concentration of radiation shielding on the midplane and combined-function fields in the same aperture are required in the arc magnets. In this article, we present the design of an Nb-Ti combined-function canted–cosine–theta (CCT) magnet with an elliptic aperture. We first review the basic principles to construct the CCT coil path for dipole and quadrupole fields on an elliptic surface. We conducted an optimization study considering windability and field quality, resulting in a magnet with short-sample current of $text{12.1} ,mathrm{k}mathrm{A}$ at $text{4.2} ,mathrm{K}$, generating $text{4.38} ,text{T}$ dipole field and 31.6$text{T}$$mathrm{/}$$mathrm{m}$ quadrupole gradient. Finally, stress analysis with full 3-D models was carried out to ensure mechanical robustness.
{"title":"Design of an Elliptic-Aperture Combined-Function Superconducting Magnet","authors":"Yufan Yan;Lucas Brouwer;Diego Arbelaez;Jean-Francois Croteau;Paolo Ferracin;Jose Luis Rudeiros Fernandez;Ian Pong;Thomas Lipton;Soren Prestemon","doi":"10.1109/TASC.2025.3645595","DOIUrl":"https://doi.org/10.1109/TASC.2025.3645595","url":null,"abstract":"Magnets with noncircular aperture are desired for fixed-field accelerators to accommodate horizontal orbit offset between beams of different energy. For muon colliders, an elliptic bore allows for concentration of radiation shielding on the midplane and combined-function fields in the same aperture are required in the arc magnets. In this article, we present the design of an Nb-Ti combined-function canted–cosine–theta (CCT) magnet with an elliptic aperture. We first review the basic principles to construct the CCT coil path for dipole and quadrupole fields on an elliptic surface. We conducted an optimization study considering windability and field quality, resulting in a magnet with short-sample current of <inline-formula><tex-math>$text{12.1} ,mathrm{k}mathrm{A}$</tex-math></inline-formula> at <inline-formula><tex-math>$text{4.2} ,mathrm{K}$</tex-math></inline-formula>, generating <inline-formula><tex-math>$text{4.38} ,text{T}$</tex-math></inline-formula> dipole field and 31.6<inline-formula><tex-math>$text{T}$</tex-math></inline-formula><inline-formula><tex-math>$mathrm{/}$</tex-math></inline-formula><inline-formula><tex-math>$mathrm{m}$</tex-math></inline-formula> quadrupole gradient. Finally, stress analysis with full 3-D models was carried out to ensure mechanical robustness.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 2","pages":"1-9"},"PeriodicalIF":1.8,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145830962","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 : 2025-12-18DOI: 10.1109/TASC.2025.3645751
L. Piperno;A. Masi;A. Rufoloni;A. Vannozzi;A. Mancini;G. Celentano;N. Pompeo;E. Silva;G. Sotgiu
A possible strategy to maximize the efficiency of RF cavities inside haloscopes is to coat the inside of the cavity with a low-resistivity material. Currently employed for this purpose are superconductors such as Nb-Ti, Nb3Sn and ReBCO compounds. A possible alternative is the iron-based superconductor FeSe, competitive for its intrinsic physical properties and for its possibility of being electrodeposited as thick films on metallic electrodes of potentially any geometry, including curved surfaces such as those of the cavities. This chemical technique has been successfully employed in recent years for the deposition of FeSe films, but optimization of the process is still lacking in the literature, as well as studies related specifically to the coating of RF cavities. In this work, we show how the electrodeposition of FeSe can lead to thick superconducting films (approx. 1 µm) on metallic substrates. By tuning the production process, we demonstrate it is possible to reproducibly obtain samples with Tc(onset)∼8 K and zero resistance at temperatures above liquid He.
{"title":"Electrodeposition of Superconducting Iron Selenide Thick Films as a New Possible Approach to the Coating of RF Cavities","authors":"L. Piperno;A. Masi;A. Rufoloni;A. Vannozzi;A. Mancini;G. Celentano;N. Pompeo;E. Silva;G. Sotgiu","doi":"10.1109/TASC.2025.3645751","DOIUrl":"https://doi.org/10.1109/TASC.2025.3645751","url":null,"abstract":"A possible strategy to maximize the efficiency of RF cavities inside haloscopes is to coat the inside of the cavity with a low-resistivity material. Currently employed for this purpose are superconductors such as Nb-Ti, Nb<sub>3</sub>Sn and ReBCO compounds. A possible alternative is the iron-based superconductor FeSe, competitive for its intrinsic physical properties and for its possibility of being electrodeposited as thick films on metallic electrodes of potentially any geometry, including curved surfaces such as those of the cavities. This chemical technique has been successfully employed in recent years for the deposition of FeSe films, but optimization of the process is still lacking in the literature, as well as studies related specifically to the coating of RF cavities. In this work, we show how the electrodeposition of FeSe can lead to thick superconducting films (approx. 1 µm) on metallic substrates. By tuning the production process, we demonstrate it is possible to reproducibly obtain samples with <italic>T</i><sub>c</sub>(onset)∼8 K and zero resistance at temperatures above liquid He.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145929432","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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