In the straight beam lines of the SuperKEKB Tsukuba area, 16 conventional sextupole magnets have been installed at intervals of 20–35 m. To achieve high luminosity, higher precision beam tuning with sextupole magnets is required. In KEK, a study on a superconducting sextupole magnet system involving three types of corrector magnets is ongoing. Considering the operating temperature of the system, an A15 compound superconductor, Nb3Al, is being studied for use as the cable material, and the development of the reaction and winding coil production with Nb3Al cable has been attempted. This study developed an Nb3Al ultra-fine strand superconducting cable with a strand of φ50 μm for the corrector magnets, and the critical currents of the cable were measured as functions of the bending radius and the temperature. This paper reports the temperature dependence of the critical currents of the bent Nb3Al cables after heat treatment.
{"title":"Study on the Supercondicting Performance of Ultra-fine Strand Nb3Al Cables","authors":"Ryuichi Ueki;Norihito Ohuchi;Akihiro Kikuchi;Masaru Yamamoto;Kazuyuki Aoki;Yasushi Arimoto","doi":"10.1109/TASC.2025.3532235","DOIUrl":"https://doi.org/10.1109/TASC.2025.3532235","url":null,"abstract":"In the straight beam lines of the SuperKEKB Tsukuba area, 16 conventional sextupole magnets have been installed at intervals of 20–35 m. To achieve high luminosity, higher precision beam tuning with sextupole magnets is required. In KEK, a study on a superconducting sextupole magnet system involving three types of corrector magnets is ongoing. Considering the operating temperature of the system, an A15 compound superconductor, Nb<sub>3</sub>Al, is being studied for use as the cable material, and the development of the reaction and winding coil production with Nb<sub>3</sub>Al cable has been attempted. This study developed an Nb<sub>3</sub>Al ultra-fine strand superconducting cable with a strand of φ50 μm for the corrector magnets, and the critical currents of the cable were measured as functions of the bending radius and the temperature. This paper reports the temperature dependence of the critical currents of the bent Nb<sub>3</sub>Al cables after heat treatment.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-5"},"PeriodicalIF":1.7,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10855675","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143471819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-27DOI: 10.1109/TASC.2025.3534167
Xin Liu;Yutong Fu;Weihang Peng;Yue Zhao;Yawei Wang
Parallel-wound No-insulation (PWNI) high-temperature superconducting (HTS) coil wound with parallel-stacked tapes is a prospective choice for fast ramping and high thermal stability magnet, which has been applied to the development of high-field toroidal field demo magnets by MIT/CFS and Tokamak Energy. Previous studies have analyzed the enhanced thermal stability of the PWNI HTS coil and its underlying mechanism, while they focus on a single initial hotspot position. This study is to illustrate quench behaviors of PWNI HTS coils under different initial quench positions, including different parallel-stacked tapes and different turns near terminal joints. A Multiphysics model combining the equivalent circuit network model of PWNI coils, FEM heat transfer module, and T-A model is used to calculate the electromagnetic and thermal properties. Results show that a counterclockwise coupling current is induced on turns without normal zone, regardless of the initial local quench positions, which is an inherent characteristic of PWNI HTS coils. This induced coupling current increases with the initial quench position moving outwards. Specifically, the maximum current in the coil with a heat disturbance near the outer terminal is approximately 1.2 times that near the inner terminal, enhancing the potential risk of overcurrent quench. Moreover, local hotspots initiating near the terminal joints (the high-risk area in magnets) result in a higher temperature rise, with a peak temperature reaching up to 1.3 times of that in PWNI coils with local hotspots initiating on middle turns.
{"title":"Influence of Quench Position on Quench Behaviors of Parallel-Wound No-Insulation HTS Coils","authors":"Xin Liu;Yutong Fu;Weihang Peng;Yue Zhao;Yawei Wang","doi":"10.1109/TASC.2025.3534167","DOIUrl":"https://doi.org/10.1109/TASC.2025.3534167","url":null,"abstract":"Parallel-wound No-insulation (PWNI) high-temperature superconducting (HTS) coil wound with parallel-stacked tapes is a prospective choice for fast ramping and high thermal stability magnet, which has been applied to the development of high-field toroidal field demo magnets by MIT/CFS and Tokamak Energy. Previous studies have analyzed the enhanced thermal stability of the PWNI HTS coil and its underlying mechanism, while they focus on a single initial hotspot position. This study is to illustrate quench behaviors of PWNI HTS coils under different initial quench positions, including different parallel-stacked tapes and different turns near terminal joints. A Multiphysics model combining the equivalent circuit network model of PWNI coils, FEM heat transfer module, and T-A model is used to calculate the electromagnetic and thermal properties. Results show that a counterclockwise coupling current is induced on turns without normal zone, regardless of the initial local quench positions, which is an inherent characteristic of PWNI HTS coils. This induced coupling current increases with the initial quench position moving outwards. Specifically, the maximum current in the coil with a heat disturbance near the outer terminal is approximately 1.2 times that near the inner terminal, enhancing the potential risk of overcurrent quench. Moreover, local hotspots initiating near the terminal joints (the high-risk area in magnets) result in a higher temperature rise, with a peak temperature reaching up to 1.3 times of that in PWNI coils with local hotspots initiating on middle turns.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-7"},"PeriodicalIF":1.7,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143379564","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 Cryogenic AntiCoincidence Detector (CryoAC) is a key element of the X-ray Integral Field Unit (X-IFU) on board the future ATHENA X-ray observatory. It is a TES-based detector designed to reduce the particle background of the instrument, thereby increasing its sensitivity. The detector design is driven by an end-to-end simulator which includes the electro-thermal modelling of the detector and the dynamics of its readout chain. Here, we present the measurements carried out on the last CryoAC single pixel prototype, namely DM127, in order to evaluate the critical thermal parameters of the detector and consequently to tune and validate the CryoAC end-to-end simulator.
{"title":"The TES-Based Cryogenic AntiCoincidence Detector of ATHENA X-IFU: Validation of the Thermal End-to-End Simulator Toward the Updated Demonstration Model (DM 1.1)","authors":"Matteo D'Andrea;Claudio Macculi;Simone Lotti;Luigi Piro;Andrea Argan;Gabriele Minervini;Guido Torrioli;Fabio Chiarello;Lorenzo Ferrari Barusso;Edvige Celasco;Flavio Gatti;Daniele Grosso;Manuela Rigano;Daniele Brienza;Elisabetta Cavazzuti;Angela Volpe","doi":"10.1109/TASC.2025.3534160","DOIUrl":"https://doi.org/10.1109/TASC.2025.3534160","url":null,"abstract":"The Cryogenic AntiCoincidence Detector (CryoAC) is a key element of the X-ray Integral Field Unit (X-IFU) on board the future ATHENA X-ray observatory. It is a TES-based detector designed to reduce the particle background of the instrument, thereby increasing its sensitivity. The detector design is driven by an end-to-end simulator which includes the electro-thermal modelling of the detector and the dynamics of its readout chain. Here, we present the measurements carried out on the last CryoAC single pixel prototype, namely DM127, in order to evaluate the critical thermal parameters of the detector and consequently to tune and validate the CryoAC end-to-end simulator.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-7"},"PeriodicalIF":1.7,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430594","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 : 2025-01-27DOI: 10.1109/TASC.2025.3534184
Sasan Razmkhah;Pascal Febvre;Massoud Pedram
We present a novel approach for tunable superconductor microwave transmission lines and resonators that can be integrated on-chip using standard Al or Nb-based fabrication processes. By leveraging the nonlinear inductance of a Josephson junction, the impedance and, consequently, the resonance frequency of the lines can be adjusted via a small DC signal. This signal is inductively coupled to a superconducting quantum interference device loop, with the circuit designed to remain open at microwave frequencies, effectively preventing energy leakage. The simplicity and tunability of this design make it adaptable to various applications. In this work, we demonstrate the multiplexing capability of such design for use in dynamic connections between control circuits and qubits, as well as dynamic routing in quantum circuits.
{"title":"qConnect: Increasing Qubit Connectivity in Quantum Computing Fabric Using Active Transmission Lines","authors":"Sasan Razmkhah;Pascal Febvre;Massoud Pedram","doi":"10.1109/TASC.2025.3534184","DOIUrl":"https://doi.org/10.1109/TASC.2025.3534184","url":null,"abstract":"We present a novel approach for tunable superconductor microwave transmission lines and resonators that can be integrated on-chip using standard Al or Nb-based fabrication processes. By leveraging the nonlinear inductance of a Josephson junction, the impedance and, consequently, the resonance frequency of the lines can be adjusted via a small DC signal. This signal is inductively coupled to a superconducting quantum interference device loop, with the circuit designed to remain open at microwave frequencies, effectively preventing energy leakage. The simplicity and tunability of this design make it adaptable to various applications. In this work, we demonstrate the multiplexing capability of such design for use in dynamic connections between control circuits and qubits, as well as dynamic routing in quantum circuits.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-4"},"PeriodicalIF":1.7,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143446212","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 : 2025-01-27DOI: 10.1109/TASC.2025.3534153
K. Sakai;J. S. Adams;S. R. Bandler;J. A. Chervenak;R. S. Cumbee;F. M. Finkbeiner;J. D. Fuhrman;S. V. Hull;R. L. Kelley;C. A. Kilbourne;H. Muramatsu;F. S. Porter;S. J. Smith;N. A. Wakeham;E. J. Wassell
We are developing a real-time X-ray pulse processor for the Line Emission Mapper (LEM) mission, a NASA X-ray probe concept for imaging and spectroscopy in the 0.2 to 2 keV range. The main detector is a hybrid Transition Edge Sensor (TES) array with a 33' outer array with “Hydra” multiplexing and a 7' × 7' inner subarray. The ∼4,000 TES sensors are read out using time-division multiplexing (TDM) technology. We are developing room-temperature digital readout electronics based on laboratory TDM electronics, where all X-ray pulses are processed in real-time to reduce the size of the data transmission. The process includes pulse triggering, grading, extraction, and optimal filtering performed in the FPGA of the TDM column electronics. In this paper we describe the real-time pulse processing firmware for a LEM flight-like prototype electronics and demonstrate count rate capability. We also demonstrate that it provides identical performance compared to conventional offline pulse-processing.
{"title":"Real-Time Pulse Processing on the Time-Division Multiplex Readout Electronics of the Transition Edge Sensor for the Line Emission Mapper (LEM)","authors":"K. Sakai;J. S. Adams;S. R. Bandler;J. A. Chervenak;R. S. Cumbee;F. M. Finkbeiner;J. D. Fuhrman;S. V. Hull;R. L. Kelley;C. A. Kilbourne;H. Muramatsu;F. S. Porter;S. J. Smith;N. A. Wakeham;E. J. Wassell","doi":"10.1109/TASC.2025.3534153","DOIUrl":"https://doi.org/10.1109/TASC.2025.3534153","url":null,"abstract":"We are developing a real-time X-ray pulse processor for the Line Emission Mapper (LEM) mission, a NASA X-ray probe concept for imaging and spectroscopy in the 0.2 to 2 keV range. The main detector is a hybrid Transition Edge Sensor (TES) array with a 33' outer array with “Hydra” multiplexing and a 7' × 7' inner subarray. The ∼4,000 TES sensors are read out using time-division multiplexing (TDM) technology. We are developing room-temperature digital readout electronics based on laboratory TDM electronics, where all X-ray pulses are processed in real-time to reduce the size of the data transmission. The process includes pulse triggering, grading, extraction, and optimal filtering performed in the FPGA of the TDM column electronics. In this paper we describe the real-time pulse processing firmware for a LEM flight-like prototype electronics and demonstrate count rate capability. We also demonstrate that it provides identical performance compared to conventional offline pulse-processing.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-5"},"PeriodicalIF":1.7,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430361","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 current study explores the effect of adding BaCeO3 nanoparticles to Y-Ba-Cu-O (YBCO) composites, synthesized by the infiltration and growth process (IGP). BaCeO3 nanoparticles synthesized using a wet-chemical method are added in two ways: directly to Y2BaCuO5 (Y-211) preform (set A) and indirectly through infiltrated liquid phase by adding to the YBa2Cu3O7-δ (Y-123) source pellet (set B). The sol-casting technique was used for the uniform distribution of nanoparticles in the precursor powders by polymerization. Further processing of the preform pellets of composites by IGP led to single-grain growth in the composites, except at the highest (1 wt.%) BaCeO3 content (x) in set A. It has been observed through detailed magnetization and microstructural studies that the addition of BaCeO3 nanoparticles enabled interesting effects on the flux pinning landscape within the material. A systematic reduction in Y-211 particle size in both cases (sets A and B) indicates that BaCeO3 nanoparticles react and refine the Y-211 phase significantly. Fishtail effect was observed at moderate concentrations and the optimum content of 0.5 wt.% BaCeO3 addition enabled to achieve best critical current density and pinning force density at two studied temperatures of 50 and 77 K. Performance observed at x = 1 wt.% BaCeO3 addition in set B is similar to that of 0.5 wt.% sample in set A. This shows that the properties are generally governed by the final BaCeO3 content present in the YBCO matrix. A study of flux pinning mechanisms suggests point pinning at low x, whereas δk pinning is operative at medium x, where the fishtail effect is observed. Higher concentrations (1 wt.%) limited the single-grain growth, leading to a very broad diamagnetic transition and deteriorated the superconducting properties within the samples.
{"title":"Flux Pinning by BaCeO3 Nanoparticles in Single-Grain YBCO Superconductors","authors":"Venkatesulu Reddy Boggala;Pawan Kumar Verma;Ramu Naidu Savu;Seshu Bai Vummethala;Devendra Kumar Namburi","doi":"10.1109/TASC.2025.3534256","DOIUrl":"https://doi.org/10.1109/TASC.2025.3534256","url":null,"abstract":"The current study explores the effect of adding BaCeO<sub>3</sub> nanoparticles to Y-Ba-Cu-O (YBCO) composites, synthesized by the infiltration and growth process (IGP). BaCeO<sub>3</sub> nanoparticles synthesized using a wet-chemical method are added in two ways: directly to Y<sub>2</sub>BaCuO<sub>5</sub> (Y-211) preform (set A) and indirectly through infiltrated liquid phase by adding to the YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-</sub><italic><sub>δ</sub></i> (Y-123) source pellet (set B). The sol-casting technique was used for the uniform distribution of nanoparticles in the precursor powders by polymerization. Further processing of the preform pellets of composites by IGP led to single-grain growth in the composites, except at the highest (1 wt.%) BaCeO<sub>3</sub> content (<italic>x</i>) in set A. It has been observed through detailed magnetization and microstructural studies that the addition of BaCeO<sub>3</sub> nanoparticles enabled interesting effects on the flux pinning landscape within the material. A systematic reduction in Y-211 particle size in both cases (sets A and B) indicates that BaCeO<sub>3</sub> nanoparticles react and refine the Y-211 phase significantly. Fishtail effect was observed at moderate concentrations and the optimum content of 0.5 wt.% BaCeO<sub>3</sub> addition enabled to achieve best critical current density and pinning force density at two studied temperatures of 50 and 77 K. Performance observed at <italic>x</i> = 1 wt.% BaCeO<sub>3</sub> addition in set B is similar to that of 0.5 wt.% sample in set A. This shows that the properties are generally governed by the final BaCeO<sub>3</sub> content present in the YBCO matrix. A study of flux pinning mechanisms suggests point pinning at low <italic>x</i>, whereas <italic>δk</i> pinning is operative at medium <italic>x</i>, where the fishtail effect is observed. Higher concentrations (1 wt.%) limited the single-grain growth, leading to a very broad diamagnetic transition and deteriorated the superconducting properties within the samples.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 3","pages":"1-14"},"PeriodicalIF":1.7,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143465882","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 : 2025-01-24DOI: 10.1109/TASC.2025.3533395
Bárbara Maria Oliveira Santos;Natália Godinho dos Santos;Gabriel dos Santos;Rubens de Andrade
The J-A formulation has been investigated as an easy and fast way to model superconducting systems in finite-element software. It is based on the common A-formulation, but two equations are applied. One to compute the magnetic field, which is the A-formulation equation, and one to compute the current density directly. By doing this, it is possible to use resistivity instead of conductivity to represent the superconductor, thereby eliminating a circular variable problem. This formulation has been investigated in both 2D and 3D, for thin-film approximations and homogenization methods, and the method to couple it with electric circuits has been recently proposed. This work explores it further by using the J-A formulation with circuit coupling and electro-thermal model to compute the thermal behavior of superconducting systems. It is applied to the pulsed-magnetization of HTS jointless loops, a system which has been investigated experimentally in previous works. The system is composed of a transformer with a common copper primary coil and the HTS jointless loop as secondary coil. The HTS loop placed in a nitrogen bath, modeled by the electro-thermal analogy method. An electric circuit is used to model the current continuity of the HTS loop. The J-A formulation computes the current density and the magnetic field. The pulses are investigated with a fixed pulse length and several pulse magnitudes, each in a different simulation. The induced persistent current is compared for all magnitudes, as well as the temperature rise for all layers of the HTS tape.
{"title":"Simulation of Pulsed-Magnetization of HTS Jointless Loops With J-A Formulation With Circuit Coupling and Thermal Modeling","authors":"Bárbara Maria Oliveira Santos;Natália Godinho dos Santos;Gabriel dos Santos;Rubens de Andrade","doi":"10.1109/TASC.2025.3533395","DOIUrl":"https://doi.org/10.1109/TASC.2025.3533395","url":null,"abstract":"The J-A formulation has been investigated as an easy and fast way to model superconducting systems in finite-element software. It is based on the common A-formulation, but two equations are applied. One to compute the magnetic field, which is the A-formulation equation, and one to compute the current density directly. By doing this, it is possible to use resistivity instead of conductivity to represent the superconductor, thereby eliminating a circular variable problem. This formulation has been investigated in both 2D and 3D, for thin-film approximations and homogenization methods, and the method to couple it with electric circuits has been recently proposed. This work explores it further by using the J-A formulation with circuit coupling and electro-thermal model to compute the thermal behavior of superconducting systems. It is applied to the pulsed-magnetization of HTS jointless loops, a system which has been investigated experimentally in previous works. The system is composed of a transformer with a common copper primary coil and the HTS jointless loop as secondary coil. The HTS loop placed in a nitrogen bath, modeled by the electro-thermal analogy method. An electric circuit is used to model the current continuity of the HTS loop. The J-A formulation computes the current density and the magnetic field. The pulses are investigated with a fixed pulse length and several pulse magnitudes, each in a different simulation. The induced persistent current is compared for all magnitudes, as well as the temperature rise for all layers of the HTS tape.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-4"},"PeriodicalIF":1.7,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430549","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 : 2025-01-24DOI: 10.1109/TASC.2025.3533468
Felix T. Jaeckel;Conjeepuram V. Ambarish;Ayshea Banes;Haiyue Duane;Natalie Lesnjak;Miriam M. Marino;Dan McCammon;Sophia Nowak;Avirup Roy;Sixing Xu;Jiacheng Yan;Joseph S. Adams;Simon R. Bandler;James Chervenak;Renata S. Cumbee;Fred M. Finkbeiner;Joshua Fuhrman;Samuel V. Hull;Richard Kelley;Caroline A. Kilbourne;Frederick Porter;Kazuhiro Sakai;Stephen J. Smith;Nicholas A. Wakeham;Edward J. Wassell
It has long been recognized that weak-link effects play an important role in transition edge sensors (Sadleir et al., 2010 and Sadleir et al., 2011), especially when the intrinsic transition temperature of the leads is much higher than that of the device itself. The weak-link physics has also been identified as an important complication if the TES is read-out under MHz-range AC bias for multiplexing purposes (Gottardi et al., 2014). More recently, it has been proposed that the commonly observed “excess” Johnson noise could also be explained as a white Johnson noise component that is mixed down into the signal band from higher frequencies via Josephson oscillations on a non-linear I-V relation (Gottardi et al., 2021 and Wessels et al., 2021). In recent experiments with small scale Mo/Au (50 $mu$m length, 15 $mu$m wide) TES devices with Nb leads (fabricated at GSFC) with a small DC bias applied, we have been able to directly observe Josephson oscillations over a kHz to MHz frequency range. The spectrum of the oscillations is well described by a simple damped oscillator model, with its center frequency scaling in direct proportion to the voltage across the TES. The second harmonic is also observed at small bias. If nothing else, we show that the Josephson oscillations provide a straightforward way to determine the value of the shunt-resistor with accuracy of $mathbf {10^{-4}}$ or better, as well as the offset voltage of the bias circuit. This is complementary to our previous work demonstrating that Shapiro steps in the IV curve induced by AC magnetic fields can be used for shunt resistor calibration (Zhou et al., 2018). Further work will be needed to determine if this effect can be observed in larger TES or those with relatively low-$mathbf {T_{c}}$ contacts, where Shapiro steps are too weak to observe. It remains to be seen whether additional insights on the mixed-down Johnson noise can be obtained from a physics-based model of the weak-link.
{"title":"Direct Observation of Josephson Oscillations in DC-Biased Transition-Edge Sensors","authors":"Felix T. Jaeckel;Conjeepuram V. Ambarish;Ayshea Banes;Haiyue Duane;Natalie Lesnjak;Miriam M. Marino;Dan McCammon;Sophia Nowak;Avirup Roy;Sixing Xu;Jiacheng Yan;Joseph S. Adams;Simon R. Bandler;James Chervenak;Renata S. Cumbee;Fred M. Finkbeiner;Joshua Fuhrman;Samuel V. Hull;Richard Kelley;Caroline A. Kilbourne;Frederick Porter;Kazuhiro Sakai;Stephen J. Smith;Nicholas A. Wakeham;Edward J. Wassell","doi":"10.1109/TASC.2025.3533468","DOIUrl":"https://doi.org/10.1109/TASC.2025.3533468","url":null,"abstract":"It has long been recognized that weak-link effects play an important role in transition edge sensors (Sadleir et al., 2010 and Sadleir et al., 2011), especially when the intrinsic transition temperature of the leads is much higher than that of the device itself. The weak-link physics has also been identified as an important complication if the TES is read-out under MHz-range AC bias for multiplexing purposes (Gottardi et al., 2014). More recently, it has been proposed that the commonly observed “excess” Johnson noise could also be explained as a white Johnson noise component that is mixed down into the signal band from higher frequencies via Josephson oscillations on a non-linear I-V relation (Gottardi et al., 2021 and Wessels et al., 2021). In recent experiments with small scale Mo/Au (50 <inline-formula><tex-math>$mu$</tex-math></inline-formula>m length, 15 <inline-formula><tex-math>$mu$</tex-math></inline-formula>m wide) TES devices with Nb leads (fabricated at GSFC) with a small DC bias applied, we have been able to directly observe Josephson oscillations over a kHz to MHz frequency range. The spectrum of the oscillations is well described by a simple damped oscillator model, with its center frequency scaling in direct proportion to the voltage across the TES. The second harmonic is also observed at small bias. If nothing else, we show that the Josephson oscillations provide a straightforward way to determine the value of the shunt-resistor with accuracy of <inline-formula><tex-math>$mathbf {10^{-4}}$</tex-math></inline-formula> or better, as well as the offset voltage of the bias circuit. This is complementary to our previous work demonstrating that Shapiro steps in the IV curve induced by AC magnetic fields can be used for shunt resistor calibration (Zhou et al., 2018). Further work will be needed to determine if this effect can be observed in larger TES or those with relatively low-<inline-formula><tex-math>$mathbf {T_{c}}$</tex-math></inline-formula> contacts, where Shapiro steps are too weak to observe. It remains to be seen whether additional insights on the mixed-down Johnson noise can be obtained from a physics-based model of the weak-link.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-6"},"PeriodicalIF":1.7,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422754","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}
This study investigates the potential for joint damage in REBCO MRI magnets due to mechanical vibration induced by gradient coil operation. A 6 T REBCO MRI magnet, developed as part of the Korea Medical Device Development Fund (KMDF) project, was analyzed to assess its susceptibility to gradient coil-induced vibrations. The eigenfrequency range of the magnet was identified to be within 1,787–2,000 Hz, which overlaps with the operational frequency range of the gradient coil (1–2,000 Hz). Simulations using a simplified two single pancake (SP) coil model revealed that peak stress levels at the joints could reach up to 700 MPa during resonance, approaching the tensile limit of REBCO tapes. The study suggests operating the gradient coil at frequencies at least 500 Hz away from the identified resonance range to prevent potential joint damage. Additionally, the use of wider joints between SP coils is recommended to concentrate resonance frequencies, making it easier to avoid dangerous operating conditions.
{"title":"Potential Joint Damage in a REBCO MRI Magnet Due to the Gradient Coil-Induced Vibration","authors":"Wonju Jung;Kibum Choi;Hyunsoo Park;Geonyoung Kim;Jeonghwan Park;Dongwoo Lee;Jung Tae Lee;Seungyong Hahn","doi":"10.1109/TASC.2025.3527940","DOIUrl":"https://doi.org/10.1109/TASC.2025.3527940","url":null,"abstract":"This study investigates the potential for joint damage in REBCO MRI magnets due to mechanical vibration induced by gradient coil operation. A 6 T REBCO MRI magnet, developed as part of the Korea Medical Device Development Fund (KMDF) project, was analyzed to assess its susceptibility to gradient coil-induced vibrations. The eigenfrequency range of the magnet was identified to be within 1,787–2,000 Hz, which overlaps with the operational frequency range of the gradient coil (1–2,000 Hz). Simulations using a simplified two single pancake (SP) coil model revealed that peak stress levels at the joints could reach up to 700 MPa during resonance, approaching the tensile limit of REBCO tapes. The study suggests operating the gradient coil at frequencies at least 500 Hz away from the identified resonance range to prevent potential joint damage. Additionally, the use of wider joints between SP coils is recommended to concentrate resonance frequencies, making it easier to avoid dangerous operating conditions.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-5"},"PeriodicalIF":1.7,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143403943","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 : 2025-01-24DOI: 10.1109/TASC.2025.3533460
Nadina Gheorghiu;Charles R. Ebbing;Timothy J. Haugan
We have previously found magnetism and superconductivity in hydrogenated graphite [Gheorghiu, et al. (2020)]. Herein, the two phenomena are observed in hydrogenated graphite foils. As the strength of the magnetic field is increased, the temperature-dependent magnetization shows several transitions between different states: from Néel paramagnetic, to antiferromagnetic, to ferromagnetic superconductor, to high-temperature superconductor with the critical temperature for the dominant phase Tc ∼ 50–60 K. The latter might be an orbital paramagnetic glass ordering of π Josephson-coupled SC domains akin to a macroscopic quantization of the system. The magnetization loops show the kink feature characteristic to granular SC. The ferromagnetism is observed up to room temperature. Thus, we observe both magnetism and superconductivity in hydrogenated graphite foils.
{"title":"Magnetism and Superconductivity in Hydrogenated Graphite Foils","authors":"Nadina Gheorghiu;Charles R. Ebbing;Timothy J. Haugan","doi":"10.1109/TASC.2025.3533460","DOIUrl":"https://doi.org/10.1109/TASC.2025.3533460","url":null,"abstract":"We have previously found magnetism and superconductivity in hydrogenated graphite [Gheorghiu, et al. (2020)]. Herein, the two phenomena are observed in hydrogenated graphite foils. As the strength of the magnetic field is increased, the temperature-dependent magnetization shows several transitions between different states: from Néel paramagnetic, to antiferromagnetic, to ferromagnetic superconductor, to high-temperature superconductor with the critical temperature for the dominant phase <italic>T<sub>c</sub></i> ∼ 50–60 K. The latter might be an orbital paramagnetic glass ordering of π Josephson-coupled SC domains akin to a macroscopic quantization of the system. The magnetization loops show the kink feature characteristic to granular SC. The ferromagnetism is observed up to room temperature. Thus, we observe both magnetism and superconductivity in hydrogenated graphite foils.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-5"},"PeriodicalIF":1.7,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422867","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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