IEEE Transactions on Applied Superconductivity最新文献

{"title":"Partial Homogenization Methods to Simulate HTS Tapes Using the H and T-A Formulations","authors":"Inês S. P. Peixoto;Dmitry Sotnikov;Luis F. D. Bucho;João F. P. Fernandes;Silvio Vaschetto;Paulo J. da Costa Branco;Douglas Araujo;Bernhard Auchmann","doi":"10.1109/TASC.2026.3660617","DOIUrl":"10.1109/TASC.2026.3660617","url":null,"abstract":"REBCO coated conductor tapes are a promising technology for developing high-field accelerator magnets since their increased current carrying capacity and operational temperature allows achieving higher-fields and current levels with higher thermal margin. Superconducting materials still present challenges associated with their non-negligible losses in transient conditions, hence, finite element analyses become essential to design feasible superconducting systems. The <italic>H</i> formulation is known in literature for its accuracy, while the <italic>T-A</i> formulation offers computational efficiency. Nonetheless, both methods remain computationally demanding, especially when the superconducting tapes are modelled considering the extreme aspect ratios of different materials in the layered tapes. Homogenized models have been proposed to reduce computational requirements, however, modelling all layers as a single domain can impose the current to flow through all conducting layers rather than only the REBCO layer, even when its resistivity is very low. This study presents a comparative analysis using the <italic>H</i> and the <italic>T-A</i> formulations for a partially homogenized model, where the superconducting layer is modelled independently from the remaining conducting layers, and a fully homogenized model. The models' accuracy for transport loss estimation in transient conditions is discussed and compared with experimental loss measurements for a REBCO tape powered with AC currents.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148488172","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}

{"title":"Long-Term Evaluation of Joint Resistivity in Lap Joints of REBCO Tapes With Indium Depending on Pre-Joint Process and Storage Temperature","authors":"Reo Tamura;Satoshi Ito;Ryoichiro Hayasaka;Nagato Yanagi;Hidetoshi Hashizume","doi":"10.1109/TASC.2026.3668736","DOIUrl":"10.1109/TASC.2026.3668736","url":null,"abstract":"Bridge-type mechanical lap joints with indium foil insertion have been developed for joint winding of high-temperature superconducting (HTS) helical coils in heliotron-type stellarator fusion reactors. While joints between copper-stabilized Rare-earth Barium Copper Oxide (REBCO) tapes have demonstrated consistently low resistance, their long-term stability remains insufficiently understood. In this study, we first quantified volumetric resistivity of CuIn₂ formed at the Cu/In interface using a mechanical lap joint of copper-stabilized REBCO tapes with indium insertion based on four-terminal resistance measurement and cross-sectional Scanning Electron Microscope and Energy Dispersive X-ray Spectroscopy (SEM-EDX) analysis. Subsequently, we evaluated the time-dependent evolution of joint resistivity under different pre-treatment conditions (with or without ethanol cleaning) and storage temperatures (300 K or 77 K). Based on these results, a model was developed to separate diffusion-driven and non-diffusional contributions to joint resistivity. The results revealed that storage at 300 K leads to a monotonic increase in joint resistivity, primarily due to CuIn₂ growth, while storage at 77 K suppresses such changes. Additionally, in samples not treated with ethanol cleaning, a significant increase in resistivity occurring with a delay at 300 K was observed, consistent with corrosion-related mechanisms.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148488282","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}

{"title":"Microstructure and Superconducting Properties of Yttrium Barium Copper Oxide Thin Film With Patterned Substrates for Ultra-Fine Multi-Filaments","authors":"Akiyoshi Matsumoto;Shuuichi Ooi;Satoshi Hata;Taiki Wada;Ryo Teranishi;Yuji Tsuchiya","doi":"10.1109/TASC.2026.3655686","DOIUrl":"10.1109/TASC.2026.3655686","url":null,"abstract":"Yttrium barium copper oxide (YBCO) superconductors are promising candidates for superconducting magnets operating at low temperatures and high magnetic fields, as well as for advanced electric power devices. Commercially available YBCO wires are manufactured in tape form, by depositing a thin YBCO layer atop multiple buffer layers on a metal substrate. This coated conductor structure closely resembles a single crystal, with well-aligned crystallographic axes, thereby exhibiting high critical current densities. However, challenges remain in reducing screening currents and AC losses for practical applications. In this study, we present a multifilamentary YBCO thin film design with patterned elevated stripes, fabricated using photolithography on substrates. Various stripe materials, including SiO₂, and Al₂O, were evaluated by depositing YBCO on the STO/stripe structures. Magnetooptical imaging demonstrated that non-superconducting stripes separate the superconducting regions, irrespective of the stripe material used. Transmission electron microscopy (TEM/STEM)-EDX analysis revealed that YBCO on STO/SiO₂ stripes formed crystals with varied orientations, whereas STO/Al₂O₃ stripes resulted in the formation of impurity phases. These findings indicate that substrate patterning with stripe structures is a viable approach for realizing multifilamentary coated conductors, potentially reducing AC losses and enhancing future superconductor applications.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-4"},"PeriodicalIF":1.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148489457","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}

{"title":"A Possible Approach to Improve Angular Dependent Critical Current Characteristics of REBCO Coated Conductors by Face-to-Face Double Stacked Architecture","authors":"Miyuki Nakamura;Takanobu Kiss;Zeyu Wu;Ivan Veshchunov;Kamil Etxagibel;Vladimir Vyatkin;Marat Gaifullin;Valery Petrykin;Sergey Lee","doi":"10.1109/TASC.2026.3653723","DOIUrl":"10.1109/TASC.2026.3653723","url":null,"abstract":"REBa₂Cu₃O_7-δ (REBCO, RE: rare earth element) coated conductors (CCs) have superior in-field performance compared to low-temperature superconductors and Bi-based superconductors, however, due to its crystal structure, REBCO CCs exhibit significant anisotropy, i.e., critical current density (<italic>J</i>_c) is generally high for <italic>B</i> // <italic>a-b</i> and low for <italic>B</i> // <italic>c</i>-axis. Isotropic angular dependence would be ideal for such applications as magnets and coils, because anisotropic angular dependence will hinder current carrying capability in the winding and also make it more difficult for quench protection. To realize an isotropic angular dependence, artificial pinning centers (APCs), such as BaMO₃ (M: Metal), have been introduced to enhance <italic>J</i>_c for <italic>B</i> // <italic>c</i>-axis. However, it is still challenging to enhance pinning over all angles. In this study, we investigated a possible way to improve the angular dependence of REBCO CCs by applying face-to-face double-stacked (FFDS) configuration. Our previous study showed that FFDS interface resistivity is around 50 nΩcm² at 77 K, enabling sufficient current sharing with small enough dissipation in cases of local <italic>J</i>_c degradation in one side of the REBCO CC. In addition, Based on this finding, we examined whether to compensate for the angular dependence of the REBCO CCs. We made a FFDS CC by combining two REBCO CCs with different angular dependences, i.e., YBa₂Cu₃O_7-δ (YBCO) CC with low <italic>J</i>_c for <italic>B</i> // <italic>c</i>-axis and EuBa₂Cu₃O_7-δ (EuBCO) with BaHfO₃ (BHO) doping CC which has high <italic>J</i>_c for <italic>B</i> // <italic>c</i>-axis. <italic>Current–voltage (I-V)</i> measurements at various angles confirmed that FFDS CCs facilitate current sharing under applied fields. As a result, we analyze the <italic>I</i>-<italic>V</i> characteristics by applying an equivalent circuit model and confirmed the more isotropic angle dependence of <italic>I</i>_c properties as designed. In conclusion, the FFDS configuration provides a practical means to current-carrying performance compared to the original CC strands and presents a practical method for tailoring REBCO CCs angular dependence with flexibility.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-4"},"PeriodicalIF":1.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148490317","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}

{"title":"Development of Ag-Added InSn Solders for ReBCO Joints","authors":"Nooshin Goodarzi;Kévin Berger;Alexander Molodyk;Mark Ainslie;Tayebeh Mousavi","doi":"10.1109/TASC.2025.3646983","DOIUrl":"10.1109/TASC.2025.3646983","url":null,"abstract":"This study explores ternary Ag-added InSn solders to develop low-resistance, reliable, and mechanically robust joints between YBCO tapes, an essential requirement for superconducting magnets, including the magnets in the fusion industry. To investigate the impact of Ag addition to the widely used SnIn solder, several solders were made by adding small amounts of Ag (1-5wt.% ) to the eutectic In-Sn solder. Lap joints were fabricated between YBCO tapes using these solders and were characterized for electrical resistivity, microstructure, and mechanical properties. According to the results, Ag addition changes the solder bulk structure with minimum impact on the interface and mainly dissolves in the In-rich phase of the solder. The joints made with Ag-added solders show significantly higher mechanical strength and ductility, with fracture shifting from the joint to the tape outside the joint region, and reasonably low electrical resistance. The optimized 5wt.% Ag addition to the binary In-Sn solder showed the best compromised joining performance as a result of a homogenous joint microstructure, offering a promising approach towards more reliable joints for superconducting magnet applications.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145982295","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}

{"title":"Simultaneous Multi-Scale Homogeneous H-Phi Thin-Shell Model for Efficient Simulations of Stacked HTS Coils","authors":"Louis Denis;Benoît Vanderheyden;Christophe Geuzaine","doi":"10.1109/TASC.2026.3652981","DOIUrl":"10.1109/TASC.2026.3652981","url":null,"abstract":"The simulation of large-scale high-temperature superconducting (HTS) magnets is a computational challenge due to the multiple spatial scales involved, from the magnet to the detailed turn-to-turn geometry. To reduce the computational cost associated with finite-element (FE) simulations of insulated HTS coils, the simultaneous multi-scale homogeneous (SMSH) method can be considered. It combines a macroscopic-scale homogenized magnet model with multiple single-tape models and solves both scales monolithically. In this work, the SMSH method is reformulated using the <inline-formula><tex-math>$h$</tex-math></inline-formula>-<inline-formula><tex-math>$phi$</tex-math></inline-formula> thin-shell (TS) approximation, where analyzed tapes are collapsed into thin surfaces, simplifying mesh generation. Moreover, the magnetic field is expressed as the gradient of the magnetic scalar potential outside the analyzed tapes. The discretized field is then described with nodal functions, further reducing the size of the FE problem compared to standard <inline-formula><tex-math>$h$</tex-math></inline-formula> formulations. The proposed <inline-formula><tex-math>$h$</tex-math></inline-formula>-<inline-formula><tex-math>$phi$</tex-math></inline-formula> SMSH-TS method is verified against state-of-the-art homogenization methods on a 2-D benchmark problem of stacks of HTS tapes. The results show good agreement in terms of AC losses, turn voltage and local current density, with a significant reduction in simulation time compared to reference models. All models are open-source.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-7"},"PeriodicalIF":1.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146082166","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}

{"title":"Measurements of Thermal Resistance Between Metallic Surfaces for High Current HTS Cable-in-Conduit Conductor","authors":"Simone Severo;Laura Savoldi;Klaus-Peter Weiss;Nadezda Bagrets","doi":"10.1109/TASC.2025.3640139","DOIUrl":"10.1109/TASC.2025.3640139","url":null,"abstract":"High temperature superconductors (HTS) are promising candidates for high current Cable-In-Conduit Conductors (CICCs) for large high-field magnets. In many cases, these CICCs are made from stacks of several HTS tapes. This work focuses on the thermal contact resistance in various metal-to-metal interfaces among tapes and between tapes and surrounding materials. Three main configurations were examined: soldered tapes, unsoldered tapes, and braided copper structures wrapped around the HTS tapes (BRAST). Samples were tested in a controlled cryogenic environment, from 6 K to 300 K, under applied forces ranging from 50 N to 200 N. The analysis reveals that thermal contact resistance plays a prominent role at low temperatures and can be reduced by increasing the applied force. For soldered tapes, an additional reduction in thermal contact resistance was observed after the removal of surface oxides. Unsoldered tapes, by contrast, showed higher sensitivity to contact pressure, pointing to the importance of precise mechanical alignment. These observations highlight the importance of interface quality, contact characteristics, and surface preparation in minimizing thermal contact resistance in HTS cables. By varying the temperature and applied force during measurements, it was possible to characterize the distinct contributions from each interface type, offering valuable insights for improving thermal performance in superconducting systems operating at cryogenic temperatures.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145929554","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}

{"title":"Electro-Mechanical Characteristics of REBCO Tapes Over a Wide Temperature Using Pulsed Current","authors":"S. Kume;Y. Tsuchiya;S. Awaji","doi":"10.1109/TASC.2026.3659448","DOIUrl":"10.1109/TASC.2026.3659448","url":null,"abstract":"The electro-mechanical properties of REBCO tapes with Cu stabilizing layer were evaluated over a wide temperature range from 30 to 77 K under self-field conditions using the pulsed current method. This approach enabled stable critical current measurements in the kiloampere range while effectively suppressing Joule heating, thereby allowing the simultaneous acquisition of the relationships among tensile strain, critical current, and stress. The results showed that the irreversible strain, <italic>ϵ</i>_irr, defined by a 2% degradation in the critical current, remained nearly constant at approximately 0.4% throughout the temperature range of 30–77 K, indicating negligible temperature dependence. Moreover, since <italic>ϵ</i>_irr was smaller than the yield strain, <italic>ϵ</i>_y, it was clarified that electrical degradation occurred prior to the onset of plastic deformation in the metallic substrate. The effective Young's modulus, <italic>E</i>_0.3%, determined from the slope in the initial elastic region (0–0.3%), increased with decreasing temperature, exhibiting a parabolic temperature dependence. These results indicate that while the elastic properties of REBCO tapes are sensitive to temperature, their electro-mechanical limit, represented by <italic>ϵ</i>_irr, is essentially temperature-independent. The findings suggest that the value of <italic>ϵ</i>_irr obtained at 77 K can be directly applied as a design parameter for high-field REBCO magnets operating at lower temperatures (30–50 K). This study contributes to improving the mechanical reliability and establishing precise design criteria for REBCO-based high-field superconducting magnets.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147362353","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}

{"title":"Inductive Excitation Tests of REBCO-Assembled Conductor Coil in Liquid Hydrogen by Using Alternating-Current Primary Coil","authors":"M. Ohya;K. Shimada;T. Obuchi;T. Gotomyo;S. Okabe;T. Suzuki;S. Imagawa;H. Kobayashi","doi":"10.1109/TASC.2026.3670772","DOIUrl":"10.1109/TASC.2026.3670772","url":null,"abstract":"This paper presents an AC inductive energization method for evaluating high-temperature superconducting (HTS) assembled conductors cooled by liquid hydrogen. A short-circuited secondary coil composed of REBCO wires was fabricated and tested under liquid-nitrogen and liquid-hydrogen environments. In liquid-nitrogen cooling, phase shifts and waveform distortions in the Rogowski-coil voltage were observed when the secondary current approached the conductor's critical current (<inline-formula><tex-math>${{{bm{I}}}_{bm{C}}}$</tex-math></inline-formula>), demonstrating that voltage signals can serve as reliable indicators of <inline-formula><tex-math>${{{bm{I}}}_{bm{C}}}$</tex-math></inline-formula>. Under liquid-hydrogen cooling, secondary currents up to 4985 A were achieved before the power supply shut down because of overvoltage protection. These results establish AC inductive energization as a safe, non-destructive diagnostic method for HTS conductors and highlight the potential of liquid hydrogen for next-generation large-scale superconducting devices.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147557522","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}

{"title":"AC Loss of Double-Pancake Coils Wound With Striated Copper-Coated REBCO Tape Using the Laser-Scribed Method","authors":"Yuuki Himeno;Takaemi Suenaga;Ryoma Oishi;Yuji Nishida;Shun Miura;Hiromasa Sasa;Koichi Yoshida;Hiroshi Miyazaki;Masataka Iwakuma;Teruo Izumi;Takato Machi;Hishiro T. Hirose;Miyuki Nakamura","doi":"10.1109/TASC.2026.3664847","DOIUrl":"10.1109/TASC.2026.3664847","url":null,"abstract":"Reducing AC losses in superconducting AC devices is crucial as it significantly contributes to decreasing the cryogenic load. One effective approach to mitigate the hysteresis loss of REBa₂Cu₃O₇−δ (REBCO) superconducting tapes is to subdivide the superconducting layer into multiple filaments and minimize the filament width. Our research group has successfully reduced the AC loss in short-length segmented tapes using laser scribing. In previous studies, striated conductors with only a silver stabilization layer were used, but there were concerns about current bypassing during quenching. In this study, we developed striated copper-coated REBCO tape using laser scribing. To suppress localized heating during quenching, copper-coated tapes were striated using laser ablation. However, exposure of the edge during laser ablation poses the risk of moisture corrosion. To avoid this, the entire tape was coated with electrodeposited polyimide to protect the exposed areas. Subsequently, the AC losses of the striated and non-striated tapes were evaluated. First, the AC losses of short samples were assessed using the saddle-shaped pickup coil method. Subsequently, a double-pancake coil was fabricated using these tapes, and its AC losses were evaluated in liquid nitrogen. These coils had an inner diameter of 40 mm, outer diameter of 59.04 mm, and consisted of a double-pancake structure with 80 turns per pancake.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-6"},"PeriodicalIF":1.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147796112","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}