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}
Pub Date : 2025-11-28DOI: 10.1109/TASC.2025.3638446
Jinzhao Zhao;Guangtong Ma;Cheng Luo;Zhenhua Su;Libin Cui;Menglong Guo;Jun Luo
Electrodynamic suspension (EDS) has a broad application prospect in high-speed magnetic levitation transportation due to its advantages, such as strong self-stabilization ability and simple control. However, in high-speed application scenarios, flat-plate permanent magnet electric suspension has a high magnetic drag force and requires a large amount of weight of the installed permanent magnets. To ameliorate these problems, this article addresses the plate-type superconducting EDS system with a higher lift-to-drag ratio. First, the structure and principles of the superconducting EDS system are presented. Second, a 3-D analytical model of the electromagnetic force considering the transverse end effect is established by the magnetic vector potential equation and the boundary conditions at the end of the conductor plate. Among them, the source magnetic field of the superconducting magnet array required by the boundary conditions is solved by the coil discretization idea. Then, the reliability of the proposed analytical model is verified by comparing the computational results of the analytical model with the finite element simulation results. Finally, based on the 3-D analytical model, the suspension stiffness characteristics of the superconducting EDS system and the influence of specific parameters on the system's suspension performance are analyzed.
{"title":"Three-Dimensional Analytical Modeling of Plate-Type Superconducting Electrodynamic Suspension for Electromagnetic Launch Application","authors":"Jinzhao Zhao;Guangtong Ma;Cheng Luo;Zhenhua Su;Libin Cui;Menglong Guo;Jun Luo","doi":"10.1109/TASC.2025.3638446","DOIUrl":"https://doi.org/10.1109/TASC.2025.3638446","url":null,"abstract":"Electrodynamic suspension (EDS) has a broad application prospect in high-speed magnetic levitation transportation due to its advantages, such as strong self-stabilization ability and simple control. However, in high-speed application scenarios, flat-plate permanent magnet electric suspension has a high magnetic drag force and requires a large amount of weight of the installed permanent magnets. To ameliorate these problems, this article addresses the plate-type superconducting EDS system with a higher lift-to-drag ratio. First, the structure and principles of the superconducting EDS system are presented. Second, a 3-D analytical model of the electromagnetic force considering the transverse end effect is established by the magnetic vector potential equation and the boundary conditions at the end of the conductor plate. Among them, the source magnetic field of the superconducting magnet array required by the boundary conditions is solved by the coil discretization idea. Then, the reliability of the proposed analytical model is verified by comparing the computational results of the analytical model with the finite element simulation results. Finally, based on the 3-D analytical model, the suspension stiffness characteristics of the superconducting EDS system and the influence of specific parameters on the system's suspension performance are analyzed.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 1","pages":"1-11"},"PeriodicalIF":1.8,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145729376","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 direct grid-connected high-temperature superconducting synchronous condenser (HTSSC) has high application potential in the new energy grid, based on its advantages of strong inertia support, high short-circuit capacity, high power density, and fast response speed. Therefore, this article explores the feasible technical solutions for direct grid-connected HTSSCs. By comparing the advantages and disadvantages of stators with different air-core armature structures in high-voltage applications, the stator with ring-type air-core armature is selected as the design basis. The insulation system and cooling system of the 35 kV high-voltage stator are comprehensively designed. The insulation reliability and anticorona ability of the high-voltage stator are verified through electric field simulation. At the same time, the cooling effect of the air-cooling system on the armature winding and the stator core is verified through temperature field simulation. The results show that the special insulation system of the stator with ring-type air-core armature can achieve an armature current density of 3.5 A/mm$^{2}$, which is higher than that of the traditional synchronous condenser of the same power level. Therefore, the stator with ring-type air-core armature has the potential for high-voltage applications and can support the direct grid-connected operation of the HTSSC.
{"title":"Design of High-Voltage Stator With Ring-Type Air-Core Armature for Direct Grid-Connected HTS Synchronous Condenser","authors":"Jiabo Shou;Chao Luo;Jien Ma;Pengcheng Huang;Yuang Zheng;Jie Chao;Youtong Fang","doi":"10.1109/TASC.2025.3638852","DOIUrl":"https://doi.org/10.1109/TASC.2025.3638852","url":null,"abstract":"The direct grid-connected high-temperature superconducting synchronous condenser (HTSSC) has high application potential in the new energy grid, based on its advantages of strong inertia support, high short-circuit capacity, high power density, and fast response speed. Therefore, this article explores the feasible technical solutions for direct grid-connected HTSSCs. By comparing the advantages and disadvantages of stators with different air-core armature structures in high-voltage applications, the stator with ring-type air-core armature is selected as the design basis. The insulation system and cooling system of the 35 kV high-voltage stator are comprehensively designed. The insulation reliability and anticorona ability of the high-voltage stator are verified through electric field simulation. At the same time, the cooling effect of the air-cooling system on the armature winding and the stator core is verified through temperature field simulation. The results show that the special insulation system of the stator with ring-type air-core armature can achieve an armature current density of 3.5 A/mm<inline-formula><tex-math>$^{2}$</tex-math></inline-formula>, which is higher than that of the traditional synchronous condenser of the same power level. Therefore, the stator with ring-type air-core armature has the potential for high-voltage applications and can support the direct grid-connected operation of the HTSSC.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 1","pages":"1-12"},"PeriodicalIF":1.8,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145729283","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 : 2025-11-28DOI: 10.1109/TASC.2025.3638705
Timur V. Filippov;Sukanya S. Meher;M. Eren Çelik;Dmitri E. Kirichenko;Anubhav Sahu;Aaron J. Barker;Stephen R. Whiteley
The balanced comparator (BC), a pair of Josephson junctions, is a key building block and decision-making element for the rapid single flux quantum (RSFQ) logic cells. The properties of the BC define the maximum clock frequency and bit error rate of RSFQ cells and circuits. Comparators are well characterized by two parameters, the gray zone (GZ) and the gray zone threshold (GZT). Both parameters depend on the dynamic properties of a pair of junctions forming the BC and its surrounding circuitry. In addition, the gray zone depends on the thermal noise in Josephson junctions. The GZ and GZT parameters can be easily measured for various BCs and be used for model-to-hardware correlations. This makes the BC a unique circuit to validate and calibrate any Josephson simulator by comparing measured and simulated characteristics, including both dynamic and noise properties. In this article, we used a set of BCs designed for the SFQ5ee fabrication process at MIT Lincoln Laboratory to validate and calibrate the Synopsys PrimeSim HSPICE simulator. We were able to match experimental and simulated results and reproduce in simulations the main features observed experimentally and predicted theoretically. A list of recommended design variations to validate a Josephson simulator is provided.
{"title":"The Balanced Comparator as a Benchmark Circuit to Validate Josephson Simulators","authors":"Timur V. Filippov;Sukanya S. Meher;M. Eren Çelik;Dmitri E. Kirichenko;Anubhav Sahu;Aaron J. Barker;Stephen R. Whiteley","doi":"10.1109/TASC.2025.3638705","DOIUrl":"https://doi.org/10.1109/TASC.2025.3638705","url":null,"abstract":"The balanced comparator (BC), a pair of Josephson junctions, is a key building block and decision-making element for the rapid single flux quantum (RSFQ) logic cells. The properties of the BC define the maximum clock frequency and bit error rate of RSFQ cells and circuits. Comparators are well characterized by two parameters, the gray zone (GZ) and the gray zone threshold (GZT). Both parameters depend on the dynamic properties of a pair of junctions forming the BC and its surrounding circuitry. In addition, the gray zone depends on the thermal noise in Josephson junctions. The GZ and GZT parameters can be easily measured for various BCs and be used for model-to-hardware correlations. This makes the BC a unique circuit to validate and calibrate any Josephson simulator by comparing measured and simulated characteristics, including both dynamic and noise properties. In this article, we used a set of BCs designed for the SFQ5ee fabrication process at MIT Lincoln Laboratory to validate and calibrate the Synopsys PrimeSim HSPICE simulator. We were able to match experimental and simulated results and reproduce in simulations the main features observed experimentally and predicted theoretically. A list of recommended design variations to validate a Josephson simulator is provided.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"36 4","pages":"1-6"},"PeriodicalIF":1.8,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146026559","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}
Rapid changes in gradient magnetic fields induce eddy currents, posing a considerable challenge to the accuracy and stability of magnetic resonance imaging (MRI) systems. Accurate measurement of eddy currents is crucial for the rapid and efficient design of eddy current compensation parameters. The “six-point sample method” provides a systematic way to measure and quantify gradient eddy currents while its coils have inherent limitations in channel isolation. The device proposed in this study leverages the shielding effect of coaxial cables to reduce mutual interference between coils. It utilizes coaxial cables to construct coil units and compares the channels crosstalk with traditional copper-strip coils. Following system calibration, eddy current compensation was implemented on the 1.5-T MRI scanner using the dedicated eddy current measurement device. Results revealed that −15 dB coupling was achieved at a distance of 72 mm for the coaxial-cable coils, which was more than half shorter than the 120 mm required for the copper-strip coils. In addition, the coaxial-cable coils exhibited better transmission characteristics. With a power crosstalk ratio above 30 dB between any two units, the channel isolation is remarkably higher than that of copper-strip coils, exceeding it by approximately 50%. The device was employed to measure the eddy currents and subsequently, based on the results, compensation parameters were rapidly iterated to achieve good eddy current correction.
梯度磁场的快速变化会产生涡流，这对磁共振成像系统的准确性和稳定性提出了相当大的挑战。准确的涡流测量对于快速有效地设计涡流补偿参数至关重要。“六点采样法”提供了一种系统的方法来测量和量化梯度涡流，但其线圈在通道隔离方面存在固有的局限性。本研究提出的装置利用同轴电缆的屏蔽效应来减少线圈之间的相互干扰。它利用同轴电缆构建线圈单元，并将通道串扰与传统的铜带线圈进行比较。系统校准后，使用专用涡流测量装置对1.5 t MRI扫描仪进行涡流补偿。结果表明，同轴电缆线圈在72 mm的距离上实现了−15 dB的耦合，比铜带线圈所需的120 mm缩短了一半以上。此外，同轴电缆线圈具有更好的传输特性。当任意两个单元之间的功率串扰比大于30 dB时，通道隔离度显著高于铜带线圈，高出约50%。利用该装置对涡流进行测量，并根据测量结果快速迭代补偿参数，获得良好的涡流校正效果。
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Pub Date : 2025-11-27DOI: 10.1109/TASC.2025.3633527
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