Fermilab is upgrading its Booster synchrotron to increase ramp rate and intensity. This is part of the Proton Improvement Plan (PIP-II) that will allow the Main Injector to achieve proton beam power of 1.2 MW within the next few years. This upgrade includes running the 55-year-old Booster magnets at 20 Hz instead of the usual 15 Hz, and construction of some shorter and wider aperture versions of these combined-function gradient magnets. Magnetic measurements were performed to characterize the present 15 Hz AC performance, and then again with 20 Hz ramp cycle to ensure performance and compatibility in this new operating regime. A 3 m-long curved flat-coil was developed for these measurements using Printed Circuit Board (PCB) technology. The probe also has a separate 0.5 m-long body-field probe, allowing integral, body, and end fields to be measured across 100 mm of the magnet aperture. The sampling rate for these measurements during the AC cycle was 200 kHz, and field resolution was better than 0.01%. Details of the probe, measurements, and results are presented.
{"title":"Magnetic Measurements of Fermilab Rapid-Cycling Booster Gradient Magnets","authors":"J. DiMarco;D. Assell;T. Cummings;D. Eddy;D. Johnson;V. Kashikhin;M. Kifarkis;J. Kuharik;J. Larson;M. Mubarak;S. Poopathi;K. Triplett","doi":"10.1109/TASC.2025.3643818","DOIUrl":"https://doi.org/10.1109/TASC.2025.3643818","url":null,"abstract":"Fermilab is upgrading its Booster synchrotron to increase ramp rate and intensity. This is part of the Proton Improvement Plan (PIP-II) that will allow the Main Injector to achieve proton beam power of 1.2 MW within the next few years. This upgrade includes running the 55-year-old Booster magnets at 20 Hz instead of the usual 15 Hz, and construction of some shorter and wider aperture versions of these combined-function gradient magnets. Magnetic measurements were performed to characterize the present 15 Hz AC performance, and then again with 20 Hz ramp cycle to ensure performance and compatibility in this new operating regime. A 3 m-long curved flat-coil was developed for these measurements using Printed Circuit Board (PCB) technology. The probe also has a separate 0.5 m-long body-field probe, allowing integral, body, and end fields to be measured across 100 mm of the magnet aperture. The sampling rate for these measurements during the AC cycle was 200 kHz, and field resolution was better than 0.01%. Details of the probe, measurements, and results are presented.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 3","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145830818","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 : 2025-12-10DOI: 10.1109/TASC.2025.3642326
Wei Pi;Junhao Liang;Yan Li;Yixiang Wu;Heng Zhang;Yinshun Wang
As the development of superconducting materials reaches the bottleneck, it is worth exploring new method to obtain superconducting tapes with better performance through the composite method. In this article, BSCCO tape and REBCO tape are composited. The current distribution of the hybrid superconducting tape is investigated based on the percolation flow model, and the corresponding experiments are also carried out. The current transfer process of the hybrid superconducting tape is also simulated with the change of current and temperature. The results show that the hybrid superconducting tape has a wider temperature range and can still carry large current above the temperature of 100 K.
{"title":"Current Distribution in BSCCO/REBCO Hybrid Superconducting Tape Based on Percolation Flow Model","authors":"Wei Pi;Junhao Liang;Yan Li;Yixiang Wu;Heng Zhang;Yinshun Wang","doi":"10.1109/TASC.2025.3642326","DOIUrl":"https://doi.org/10.1109/TASC.2025.3642326","url":null,"abstract":"As the development of superconducting materials reaches the bottleneck, it is worth exploring new method to obtain superconducting tapes with better performance through the composite method. In this article, BSCCO tape and REBCO tape are composited. The current distribution of the hybrid superconducting tape is investigated based on the percolation flow model, and the corresponding experiments are also carried out. The current transfer process of the hybrid superconducting tape is also simulated with the change of current and temperature. The results show that the hybrid superconducting tape has a wider temperature range and can still carry large current above the temperature of 100 K.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 2","pages":"1-6"},"PeriodicalIF":1.8,"publicationDate":"2025-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145802377","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 : 2025-12-08DOI: 10.1109/TASC.2025.3641864
Sergey K. Tolpygo;Ravi Rastogi;David Kim;Terence J. Weir;Neel Parmar;Evan B. Golden
Increasing integration scale of superconductor electronics requires employing kinetic inductors and self-shunted Josephson junctions (JJs) for miniaturizing inductors and JJs. We have been developing a ten-superconductor-layer planarized fabrication process with NbN kinetic inductors and searching for suitable self-shunted JJs to potentially replace high Josephson critical current density, Jc, Nb/Al-AlOx/Nb junctions. We report on the fabrication and electrical properties of NbN/NbNx/NbN junctions produced by reactive sputtering in Ar+N2 mixture on 200-mm wafers at 200 °C and incorporated into a planarized process with two Nb ground planes and NbN wiring layer. Here, NbN is a stoichiometric nitride with superconducting critical temperature Tc = 15 K, and NbNx is a high resistivity nonsuperconducting nitride deposited using a higher nitrogen partial pressure than for the NbN electrodes. For comparison, we co-fabricated Nb/NbNx/Nb JJs using the same NbNx barriers deposited at 20 °C. We varied the NbNx barrier thickness from 5 to 20 nm, resulting in the range of Jc from about 1 mA/µm2 down to ∼10 µA/µm2, and extracted coherence length of 3 and 4 nm in NbNx deposited, respectively, at 20 and 200 °C. Both types of JJs are well described by the resistively and capacitively shunted junction model without any excess current. We found the Jc of NbN/NbNx/NbN JJs to be somewhat lower than that of Nb/NbNx/Nb JJs with the same barrier thickness, despite a much higher Tc and energy gap of NbN than of Nb electrodes. IcRn products up to ∼ 0.5 mV were obtained for JJs with Jc ∼ 0.6 mA/µm2. Jc(T) dependences have been measured.
{"title":"Fabrication and Properties of NbN/NbNx/NbN and Nb/NbNx/Nb Josephson Junctions","authors":"Sergey K. Tolpygo;Ravi Rastogi;David Kim;Terence J. Weir;Neel Parmar;Evan B. Golden","doi":"10.1109/TASC.2025.3641864","DOIUrl":"https://doi.org/10.1109/TASC.2025.3641864","url":null,"abstract":"Increasing integration scale of superconductor electronics requires employing kinetic inductors and self-shunted Josephson junctions (JJs) for miniaturizing inductors and JJs. We have been developing a ten-superconductor-layer planarized fabrication process with NbN kinetic inductors and searching for suitable self-shunted JJs to potentially replace high Josephson critical current density, <italic>J</i><sub>c</sub>, Nb/Al-AlO<italic><sub>x</sub></i>/Nb junctions. We report on the fabrication and electrical properties of NbN/NbN<italic><sub>x</sub></i>/NbN junctions produced by reactive sputtering in Ar+N<sub>2</sub> mixture on 200-mm wafers at 200 °C and incorporated into a planarized process with two Nb ground planes and NbN wiring layer. Here, NbN is a stoichiometric nitride with superconducting critical temperature <italic>T<sub>c</sub></i> = 15 K, and NbN<italic><sub>x</sub></i> is a high resistivity nonsuperconducting nitride deposited using a higher nitrogen partial pressure than for the NbN electrodes. For comparison, we co-fabricated Nb/NbN<italic><sub>x</sub></i>/Nb JJs using the same NbN<italic><sub>x</sub></i> barriers deposited at 20 °C. We varied the NbN<italic><sub>x</sub></i> barrier thickness from 5 to 20 nm, resulting in the range of <italic>J</i><sub>c</sub> from about 1 mA/µm<sup>2</sup> down to ∼10 µA/µm<sup>2</sup>, and extracted coherence length of 3 and 4 nm in NbN<italic><sub>x</sub></i> deposited, respectively, at 20 and 200 °C. Both types of JJs are well described by the resistively and capacitively shunted junction model without any excess current. We found the <italic>J</i><sub>c</sub> of NbN/NbN<italic><sub>x</sub></i>/NbN JJs to be somewhat lower than that of Nb/NbN<italic><sub>x</sub></i>/Nb JJs with the same barrier thickness, despite a much higher <italic>T</i><sub>c</sub> and energy gap of NbN than of Nb electrodes. <italic>I</i><sub>c</sub><italic>R</i><sub>n</sub> products up to ∼ 0.5 mV were obtained for JJs with <italic>J</i><sub>c</sub> ∼ 0.6 mA/µm<sup>2</sup>. <italic>J</i><sub>c</sub>(<italic>T</i>) dependences have been measured.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 4","pages":"1-6"},"PeriodicalIF":1.8,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146026626","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 : 2025-12-05DOI: 10.1109/TASC.2025.3639528
Jason Walter;Adam C. Weis;Kan-Ting Tsai;Meng-Ju Yu;Naveen Katam;Alex F. Kirichenko;Oleg A. Mukhanov;Shu-Jen Han;Igor V. Vernik
As quantum computing processors increase in size, there is growing interest in developing cryogenic electronics to overcome significant challenges to system scaling. Single flux-quantum (SFQ) circuits offer a promising alternative to remote, bulky, and power-hungry room temperature electronics. To meet the need for digital qubit control, readout, and co-processing, SFQ circuits must be adapted to operate at millikelvin temperatures near quantum processors. SEEQC's SFQuClass digital quantum management approach proximally places energy-efficient SFQ (ERSFQ) circuits and qubits in a multi-chip module. This enables extremely low power dissipation, compatible with a typical dilution cryostat's limited cooling power, while maintaining high processing speed and low error rates. We report on systematic testing from 4 K to 10 mK of a comprehensive set of ERSFQ cells, as well as more complex circuits such as programmable counters and demultiplexers used in digital qubit control. We compare the operating margins and error rates of these circuits and find that, at millikelvin, bias margins decrease and the center of the margins (i.e., the optimal bias current value) increases by ∼15%, compared to 4.2 K. The margins can be restored by thermal annealing by reducing Josephson junction (JJ) critical current Ic. To provide guidance for how circuit parameters vary from 4.2 K to millikelvin, relevant analog process control monitors (PCMs) were tested in the temperature range of interest. The measured JJ critical current (of the PCM JJ arrays) increases by ∼15% when decreasing temperature from 4.2 K to millikelvin, in good agreement with both theory and the empirically measured change in the center of bias margins for the tested digital circuits.
{"title":"Single Flux Quantum Circuit Operation at Millikelvin Temperatures","authors":"Jason Walter;Adam C. Weis;Kan-Ting Tsai;Meng-Ju Yu;Naveen Katam;Alex F. Kirichenko;Oleg A. Mukhanov;Shu-Jen Han;Igor V. Vernik","doi":"10.1109/TASC.2025.3639528","DOIUrl":"https://doi.org/10.1109/TASC.2025.3639528","url":null,"abstract":"As quantum computing processors increase in size, there is growing interest in developing cryogenic electronics to overcome significant challenges to system scaling. Single flux-quantum (SFQ) circuits offer a promising alternative to remote, bulky, and power-hungry room temperature electronics. To meet the need for digital qubit control, readout, and co-processing, SFQ circuits must be adapted to operate at millikelvin temperatures near quantum processors. SEEQC's SFQuClass digital quantum management approach proximally places energy-efficient SFQ (ERSFQ) circuits and qubits in a multi-chip module. This enables extremely low power dissipation, compatible with a typical dilution cryostat's limited cooling power, while maintaining high processing speed and low error rates. We report on systematic testing from 4 K to 10 mK of a comprehensive set of ERSFQ cells, as well as more complex circuits such as programmable counters and demultiplexers used in digital qubit control. We compare the operating margins and error rates of these circuits and find that, at millikelvin, bias margins decrease and the center of the margins (i.e., the optimal bias current value) increases by ∼15%, compared to 4.2 K. The margins can be restored by thermal annealing by reducing Josephson junction (JJ) critical current <italic>I<sub>c</sub></i>. To provide guidance for how circuit parameters vary from 4.2 K to millikelvin, relevant analog process control monitors (PCMs) were tested in the temperature range of interest. The measured JJ critical current (of the PCM JJ arrays) increases by ∼15% when decreasing temperature from 4.2 K to millikelvin, in good agreement with both theory and the empirically measured change in the center of bias margins for the tested digital circuits.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-6"},"PeriodicalIF":1.8,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145766207","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 : 2025-12-05DOI: 10.1109/TASC.2025.3639017
Heonhwan Kim;Sinhye Na;Yangjin Jung;Youngkyoung Kim;Seongtaek You;Sanghyeun Je
Large-scale scientific facilities such as fusion reactors and particle accelerators increasingly require high-performance Low-Temperature Superconducting (LTS) wires with enhanced thermo-magnetic stability. Reducing sub-element size has been shown to effectively suppress magnetization losses and improve low-field stability. Building on our earlier development of Distributed Barrier Strand (DBS) wires, which incorporate individual diffusion barriers to enhance thermo-magnetic stability, Kiswire Advanced Technology Co., Ltd. (KAT) refined the DBS architecture by further reducing the physical sub-element diameter. In this work, the diameter was reduced by 29% (Design 1) and 40% (Design 2), yielding hysteresis-loss reductions of 17% and 32%, respectively, while maintaining high critical current densities of 1,149 A/mm2 and 1,053 A/mm2 at 16 T. Additionally, the reduced-Dsub DBS wires exhibited high RRR values, further confirming the effectiveness of the refined design in maintaining consistent stability. These results demonstrate that sub-element size refinement enhances thermo-magnetic stability in DBS conductors, in agreement with trends observed in existing Nb3Sn studies, while preserving manufacturability and high-field transport performance. This study establishes reduced- Dsub DBS wires as promising candidates for next-generation high-field magnet applications.
{"title":"A Study on Various Wire Designs for Reducing the Sub-Element Diameter of High-Jc Nb3Sn Wires","authors":"Heonhwan Kim;Sinhye Na;Yangjin Jung;Youngkyoung Kim;Seongtaek You;Sanghyeun Je","doi":"10.1109/TASC.2025.3639017","DOIUrl":"https://doi.org/10.1109/TASC.2025.3639017","url":null,"abstract":"Large-scale scientific facilities such as fusion reactors and particle accelerators increasingly require high-performance Low-Temperature Superconducting (LTS) wires with enhanced thermo-magnetic stability. Reducing sub-element size has been shown to effectively suppress magnetization losses and improve low-field stability. Building on our earlier development of Distributed Barrier Strand (DBS) wires, which incorporate individual diffusion barriers to enhance thermo-magnetic stability, Kiswire Advanced Technology Co., Ltd. (KAT) refined the DBS architecture by further reducing the physical sub-element diameter. In this work, the diameter was reduced by 29% (Design 1) and 40% (Design 2), yielding hysteresis-loss reductions of 17% and 32%, respectively, while maintaining high critical current densities of 1,149 A/mm<sup>2</sup> and 1,053 A/mm<sup>2</sup> at 16 T. Additionally, the reduced-<italic>D</i><sub>sub</sub> DBS wires exhibited high <italic>RRR</i> values, further confirming the effectiveness of the refined design in maintaining consistent stability. These results demonstrate that sub-element size refinement enhances thermo-magnetic stability in DBS conductors, in agreement with trends observed in existing Nb<sub>3</sub>Sn studies, while preserving manufacturability and high-field transport performance. This study establishes reduced- <italic>D</i><sub>sub</sub> DBS wires as promising candidates for next-generation high-field magnet applications.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145830837","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}
The ITER superconducting magnet system comprises 18 Toroidal Field (TF) coils, one Central Solenoid (CS), 6 Poloidal Field (PF) coils, and 18 Correction Coils (CC). These superconducting coils are integrated using robust, flexible structures and over 4700 high-grade large studs ranging from M24 to M160. During assembly, these studs are preloaded from hundreds to thousands of kN with Hydraulic Tensioners or Multi-jack bolt Tensioners (MJT or Superbolts). Since preload losses are inevitable under current methods with hydraulic tensioners, and the maximum allowable loads are constrained by the material's yield strength as per ITER Magnet Structure Design Criteria, these constraints create a narrow operational window for successful assembly to the expected preload. Precise preload control is critical to ensuring proper integration of the superconducting magnets. Ultrasonic bolt load measurement emerges as a promising solution, especially in scenarios where one end of the stud is inaccessible after installation. Calibration tests at ITER are underway to validate the use of this method for preload measurement during machine assembly. This article presents calibration test results, including velocity, stress factor, load factor, preload loss, and field calibration measurements. It concludes with insights from the design and manufacturing of high-grade studs, highlighting their impact on achieving accurate preload control via ultrasonic inspection.
{"title":"Calibration Test for Preload Control With Ultrasonic Checking for Magnet Studs During ITER Machine Assembly","authors":"Shiqiang Han;Ignacio Aviles Santillana;Thierry Schild;Gonzalo Arnau Izquierdo;Shihang Wang;Gilles Rinaudo;Maciej Burkowski;Lionel Poncet;Fabrice Simon;Yury Ilin;Yasuyuki Miyoshi;Igor Rodin;Stefano Sgobba;Patrick Petit;Sebastien Koczorowski;Jens Reich","doi":"10.1109/TASC.2025.3634066","DOIUrl":"https://doi.org/10.1109/TASC.2025.3634066","url":null,"abstract":"The ITER superconducting magnet system comprises 18 Toroidal Field (TF) coils, one Central Solenoid (CS), 6 Poloidal Field (PF) coils, and 18 Correction Coils (CC). These superconducting coils are integrated using robust, flexible structures and over 4700 high-grade large studs ranging from M24 to M160. During assembly, these studs are preloaded from hundreds to thousands of kN with Hydraulic Tensioners or Multi-jack bolt Tensioners (MJT or Superbolts). Since preload losses are inevitable under current methods with hydraulic tensioners, and the maximum allowable loads are constrained by the material's yield strength as per ITER Magnet Structure Design Criteria, these constraints create a narrow operational window for successful assembly to the expected preload. Precise preload control is critical to ensuring proper integration of the superconducting magnets. Ultrasonic bolt load measurement emerges as a promising solution, especially in scenarios where one end of the stud is inaccessible after installation. Calibration tests at ITER are underway to validate the use of this method for preload measurement during machine assembly. This article presents calibration test results, including velocity, stress factor, load factor, preload loss, and field calibration measurements. It concludes with insights from the design and manufacturing of high-grade studs, highlighting their impact on achieving accurate preload control via ultrasonic inspection.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 3","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145778227","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}
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.
{"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":"https://doi.org/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":"2025-12-04","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}
Pub Date : 2025-12-04DOI: 10.1109/TASC.2025.3640122
Yi Ge;Hui Yu;Guanqiu Yuan;Bohan Tang;Bowen Xie;Shili Jiang;Donghui Jiang;Guangli Kuang
This work investigates a hybrid passive screen integrating superconductors and ferromagnets. The screening structure consists of multiple superconducting bulks, stacked closed-loop eye-shaped coated conductors, and a ferromagnetic (FM) sheet. The stacked coated conductors are concentrically arranged around the bulks, with the FM sheet positioned on the upper surface of the bulks. The screening effects are examined through experimental measurements and finite element calculations. We investigate superconducting screens of various structures, firstly, revealing that the combination of superconductors provides superior screening performance compared to using bulks alone. Furthermore, partial reversal of the tapes’ directions was applied to optimize geometrical asymmetry. The superconducting-FM hybrid screen was then tested, achieving a substantial reduction in residual magnetic flux density (up to 38%) in the gap region while simultaneously improving field uniformity. Importantly, the established numerical model enables further exploration and optimization of the screen, allowing for expanded screening volume and operation at higher magnetic field levels.
{"title":"Investigation of Magnetic Screening Performance Enhancement Using Various Superconductors and Ferromagnets","authors":"Yi Ge;Hui Yu;Guanqiu Yuan;Bohan Tang;Bowen Xie;Shili Jiang;Donghui Jiang;Guangli Kuang","doi":"10.1109/TASC.2025.3640122","DOIUrl":"https://doi.org/10.1109/TASC.2025.3640122","url":null,"abstract":"This work investigates a hybrid passive screen integrating superconductors and ferromagnets. The screening structure consists of multiple superconducting bulks, stacked closed-loop eye-shaped coated conductors, and a ferromagnetic (FM) sheet. The stacked coated conductors are concentrically arranged around the bulks, with the FM sheet positioned on the upper surface of the bulks. The screening effects are examined through experimental measurements and finite element calculations. We investigate superconducting screens of various structures, firstly, revealing that the combination of superconductors provides superior screening performance compared to using bulks alone. Furthermore, partial reversal of the tapes’ directions was applied to optimize geometrical asymmetry. The superconducting-FM hybrid screen was then tested, achieving a substantial reduction in residual magnetic flux density (up to 38%) in the gap region while simultaneously improving field uniformity. Importantly, the established numerical model enables further exploration and optimization of the screen, allowing for expanded screening volume and operation at higher magnetic field levels.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 1","pages":"1-11"},"PeriodicalIF":1.8,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145778474","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 : 2025-12-04DOI: 10.1109/TASC.2025.3640154
Ivan P. Nevirkovets
Self-shunted, high-jc Josephson junctions are required for the development of high-density integrated circuits of superconducting electronics. For this purpose, various electrode and barrier materials have been considered by researchers. Here, fabrication and electrical characterization of Nb/TaNx/Nb Josephson junctions is reported. At the thickness of TaNx layer of about 10 nm, the junctions are self-shunted and display the critical current density, jc, above 100 kA/cm2, and the effective critical voltage, V′c, of about 0.68 mV at 4.2 K. The devices with jc = 67 kA/cm2 and V′c = 0.96 mV are also fabricated. The effective critical voltage is defined as V′c = IcRq, where Ic is the Josephson critical current and Rq is the resistance of the quasiparticle branch of the current-voltage characteristic at the level of maximum Ic. In addition, Nb-based junctions with a composite TaNx/(Pd-Ni) barrier were fabricated and characterized. The thickness of TaNx was fixed while the thickness of Pd-Ni was varied. As a result, the characteristic voltage Vc = IcRN (where RN is the normal-state resistance of the junction) initially decreased, but then increased with the thickness of Pd-Ni, indicating the transition to the π state. For some value of the thickness of Pd-Ni, the diode effect was observed. It is suggested that the junctions are promising for applications in superconducting electronics including single-flux quantum digital and quantum computing circuits.
{"title":"Characteristics of Nb-Based Josephson Junctions With TaNx and TaNx/(Pd-Ni) Barriers","authors":"Ivan P. Nevirkovets","doi":"10.1109/TASC.2025.3640154","DOIUrl":"https://doi.org/10.1109/TASC.2025.3640154","url":null,"abstract":"Self-shunted, high-<italic>j</i><sub>c</sub> Josephson junctions are required for the development of high-density integrated circuits of superconducting electronics. For this purpose, various electrode and barrier materials have been considered by researchers. Here, fabrication and electrical characterization of Nb/TaN<italic><sub>x</sub></i>/Nb Josephson junctions is reported. At the thickness of TaN<italic><sub>x</sub></i> layer of about 10 nm, the junctions are self-shunted and display the critical current density, <italic>j</i><sub>c</sub>, above 100 kA/cm<sup>2</sup>, and the effective critical voltage, <italic>V′</i><sub>c</sub>, of about 0.68 mV at 4.2 K. The devices with <italic>j</i><sub>c</sub> = 67 kA/cm<sup>2</sup> and <italic>V′</i><sub>c</sub> = 0.96 mV are also fabricated. The effective critical voltage is defined as <italic>V′</i><sub>c</sub> = <italic>I</i><sub>c</sub><italic>R</i><sub>q</sub>, where <italic>I</i><sub>c</sub> is the Josephson critical current and <italic>R</i><sub>q</sub> is the resistance of the quasiparticle branch of the current-voltage characteristic at the level of maximum <italic>I</i><sub>c</sub>. In addition, Nb-based junctions with a composite TaN<italic><sub>x</sub></i>/(Pd-Ni) barrier were fabricated and characterized. The thickness of TaN<italic><sub>x</sub></i> was fixed while the thickness of Pd-Ni was varied. As a result, the characteristic voltage <italic>V</i><sub>c</sub> = <italic>I</i><sub>c</sub><italic>R</i><sub>N</sub> (where <italic>R</i><sub>N</sub> is the normal-state resistance of the junction) initially decreased, but then increased with the thickness of Pd-Ni, indicating the transition to the π state. For some value of the thickness of Pd-Ni, the diode effect was observed. It is suggested that the junctions are promising for applications in superconducting electronics including single-flux quantum digital and quantum computing circuits.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 5","pages":"1-4"},"PeriodicalIF":1.8,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145929563","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 : 2025-12-02DOI: 10.1109/TASC.2025.3639424
Yituo Zhao;Hai Wang;Shijian Wang;Jiajun Chen;Yifan Wu;Zhidan Zhang;Xiangyan Kong
Superconducting detectors, with their advantages of low noise and high energy resolution, have become key components for astronomical observation. Time-division multiplexing (TDM) scheme is a widely used technology for the readout of large sensor arrays, owing to its advantages in scalability, ease of integration, and low-noise performance. A primary limitation, however, is the degradation of the signal-to-noise ratio due to noise aliasing, which constrains the scaling of the multiplexing factor. To address this issue, we developed a front-end superconducting switch based on Josephson junction (JJ). Specifically, we fabricated Josephson junction switch (JJ-switch) cells where each junction is shunted by a 4-Ω resistor to ensure its nonhysteretic current-voltage characteristics. Three independent channels are designed on one switch chip, the inductance of Lin and superconducting quantum interference device (SQUID) are fixed values, but the resistance of Rin has three values: 0.1, 1, and 2.5 Ω. The output of each switch channel is magnetically coupled to a dedicated input SQUID via an independent input coil, with a coefficient of 4.68 μA/Φ0. Finally, the signal transmission ratio, noise, and system sensitivity of the switch were characterized at an operating temperature of 4.2 K. This work verifies the transmission characteristics of the JJ-switch, which will provide a new device foundation for the TDM readout of large-scale superconducting detector arrays.
{"title":"Study on the Signal Transmission of the RL-Branch in Josephson Junction Switch","authors":"Yituo Zhao;Hai Wang;Shijian Wang;Jiajun Chen;Yifan Wu;Zhidan Zhang;Xiangyan Kong","doi":"10.1109/TASC.2025.3639424","DOIUrl":"https://doi.org/10.1109/TASC.2025.3639424","url":null,"abstract":"Superconducting detectors, with their advantages of low noise and high energy resolution, have become key components for astronomical observation. Time-division multiplexing (TDM) scheme is a widely used technology for the readout of large sensor arrays, owing to its advantages in scalability, ease of integration, and low-noise performance. A primary limitation, however, is the degradation of the signal-to-noise ratio due to noise aliasing, which constrains the scaling of the multiplexing factor. To address this issue, we developed a front-end superconducting switch based on Josephson junction (JJ). Specifically, we fabricated Josephson junction switch (JJ-switch) cells where each junction is shunted by a 4-Ω resistor to ensure its nonhysteretic current-voltage characteristics. Three independent channels are designed on one switch chip, the inductance of <italic>L</i><sub>in</sub> and superconducting quantum interference device (SQUID) are fixed values, but the resistance of <italic>R</i><sub>in</sub> has three values: 0.1, 1, and 2.5 Ω. The output of each switch channel is magnetically coupled to a dedicated input SQUID via an independent input coil, with a coefficient of 4.68 μA/Φ<sub>0</sub>. Finally, the signal transmission ratio, noise, and system sensitivity of the switch were characterized at an operating temperature of 4.2 K. This work verifies the transmission characteristics of the JJ-switch, which will provide a new device foundation for the TDM readout of large-scale superconducting detector arrays.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 4","pages":"1-5"},"PeriodicalIF":1.8,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146082272","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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