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}
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}
Pub Date : 2025-01-24DOI: 10.1109/TASC.2025.3530325
Gaël Berthet;Wonju Jung;Hyunsoo Park;Seungyong Hahn;Sangjin Lee
HTS tapes are central to many future technologies and, as such, are the subject of significant research aimed to improve their properties. The production of long and high-quality $mathrm{(RE)Ba}_{2}text{Cu}_{3}mathrm{O}_{7-delta }$ (REBCO) tapes being a challenging task, spools commercially available tend to be relatively short. Therefore, joints are critical points during applications, prompting extensive efforts to develop joints with low resistivity and good mechanical properties. Consequently, this study focuses on the recently developed copper diffusion bonding (diff. bond.) method. Using three different spools, the properties of the copper diff. bond. joints are compared to the solder joints. The results indicate that copper diff. bond. joints generally have lower surface resistivity compared to their soldered counterparts. Additionally, the results also showed a slightly better repeatability in joints resistance compared to the solder joints. On the other hand, one spool gave contradictory results having lower joint resistance and better repeatability for the soldering method which could not be explained.
{"title":"Comparison of the Electrical Properties of Copper Diffusion-Bonded Joints and Solder Joints for $mathrm{(RE)Ba}_{2}text{Cu}_{3}mathrm{O}_{7-delta }$ Tapes","authors":"Gaël Berthet;Wonju Jung;Hyunsoo Park;Seungyong Hahn;Sangjin Lee","doi":"10.1109/TASC.2025.3530325","DOIUrl":"https://doi.org/10.1109/TASC.2025.3530325","url":null,"abstract":"HTS tapes are central to many future technologies and, as such, are the subject of significant research aimed to improve their properties. The production of long and high-quality <inline-formula><tex-math>$mathrm{(RE)Ba}_{2}text{Cu}_{3}mathrm{O}_{7-delta }$</tex-math></inline-formula> (REBCO) tapes being a challenging task, spools commercially available tend to be relatively short. Therefore, joints are critical points during applications, prompting extensive efforts to develop joints with low resistivity and good mechanical properties. Consequently, this study focuses on the recently developed copper diffusion bonding (diff. bond.) method. Using three different spools, the properties of the copper diff. bond. joints are compared to the solder joints. The results indicate that copper diff. bond. joints generally have lower surface resistivity compared to their soldered counterparts. Additionally, the results also showed a slightly better repeatability in joints resistance compared to the solder joints. On the other hand, one spool gave contradictory results having lower joint resistance and better repeatability for the soldering method which could not be explained.","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":"143403814","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.2025.3533473
Y. G. Shi;Q. Guo;H. C. Kou;C. G. Wang;J. Y. Chen;J. P Li;G. Y. Han;Z. Li;B. Wu;J. F. Li;X. H. Liu;Y. Feng;P. X. Zhang
Doping with Ti is crucial for enhancing the upper critical field of Nb3Sn strand produced by internal tin process. This study investigates the effects of different Ti doping methods and concentrations on the low-temperature performance of Nb3Sn strand. We compare two methods: one replaces Nb cores with NbTi cores, while the other integrates Ti into Sn ingots to form SnTi alloys, with adjustable Ti content. Four Nb3Sn strand with varying Ti concentrations were produced using these methods. Microstructural and performance tests show that Ti doping refines Nb3Sn grains. Jc increases with Ti content from 0% to 2%, but decreases beyond 2% due to grain growth from excessive Ti. Additionally, the larger Ti6Sn5 phase in the SnTi alloy results in more breakage during processing. Thus, using SnCu alloy as the Sn source and NbTi rods for Ti doping is a more feasible approach for the production of Nb3Sn strands.
{"title":"Effect of Titanium Content and Doping Method on Phase Formation and Properties of Nb3Sn Strand","authors":"Y. G. Shi;Q. Guo;H. C. Kou;C. G. Wang;J. Y. Chen;J. P Li;G. Y. Han;Z. Li;B. Wu;J. F. Li;X. H. Liu;Y. Feng;P. X. Zhang","doi":"10.1109/TASC.2025.3533473","DOIUrl":"https://doi.org/10.1109/TASC.2025.3533473","url":null,"abstract":"Doping with Ti is crucial for enhancing the upper critical field of Nb<sub>3</sub>Sn strand produced by internal tin process. This study investigates the effects of different Ti doping methods and concentrations on the low-temperature performance of Nb<sub>3</sub>Sn strand. We compare two methods: one replaces Nb cores with NbTi cores, while the other integrates Ti into Sn ingots to form SnTi alloys, with adjustable Ti content. Four Nb<sub>3</sub>Sn strand with varying Ti concentrations were produced using these methods. Microstructural and performance tests show that Ti doping refines Nb<sub>3</sub>Sn grains. <italic>J</i><sub>c</sub> increases with Ti content from 0% to 2%, but decreases beyond 2% due to grain growth from excessive Ti. Additionally, the larger Ti<sub>6</sub>Sn<sub>5</sub> phase in the SnTi alloy results in more breakage during processing. Thus, using SnCu alloy as the Sn source and NbTi rods for Ti doping is a more feasible approach for the production of Nb<sub>3</sub>Sn strands.","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":"143403944","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}
In coils composed of stacked no-insulation (NI) high temperature superconductor (HTS) tapes, the current flow patterns can significantly differ from transposed counterparts due to larger self/mutual inductances and contact resistances. In this study, three two-tape co-wound HTS coils are wound with different insulation methods, fully insulated, NI, and partially insulated. The charging test is performed and the experimental results are analyzed by observing the voltage ratio of two tapes. The voltage ratios show deviations from the theoretical inductive voltage ratios implying uneven current distribution between the tapes. A numerical analysis is carried out with a simulation model that couples the distributed circuit model with the finite element method model to understand these phenomena. Using the model, sensitivity analysis is adopted to explain quantitatively the contributions of each circuit parameter to non-uniform current distribution. Pinpointing the precise current distribution between tapes is challenging, yet experimental and numerical analysis results show certain tendencies influenced by inductive and resistive properties.
{"title":"Experimental and Numerical Analysis on Non-Uniform Current Distribution in Two-Tape Co-Wound HTS Coil","authors":"Jung Tae Lee;Jaemin Kim;Hyunsoo Park;Jonghoon Yoon;JuKyung Cha;Jaheum Koo;Wonju Jung;Geonyoung Kim;Chaemin Im;Yufan Yan;Sangjun Oh;Seungyong Hahn","doi":"10.1109/TASC.2025.3532929","DOIUrl":"https://doi.org/10.1109/TASC.2025.3532929","url":null,"abstract":"In coils composed of stacked no-insulation (NI) high temperature superconductor (HTS) tapes, the current flow patterns can significantly differ from transposed counterparts due to larger self/mutual inductances and contact resistances. In this study, three two-tape co-wound HTS coils are wound with different insulation methods, fully insulated, NI, and partially insulated. The charging test is performed and the experimental results are analyzed by observing the voltage ratio of two tapes. The voltage ratios show deviations from the theoretical inductive voltage ratios implying uneven current distribution between the tapes. A numerical analysis is carried out with a simulation model that couples the distributed circuit model with the finite element method model to understand these phenomena. Using the model, sensitivity analysis is adopted to explain quantitatively the contributions of each circuit parameter to non-uniform current distribution. Pinpointing the precise current distribution between tapes is challenging, yet experimental and numerical analysis results show certain tendencies influenced by inductive and resistive properties.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-5"},"PeriodicalIF":1.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143360956","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 : 2025-01-23DOI: 10.1109/TASC.2025.3533394
Takanobu Mato;So Noguchi
This paper proposes a simple analytical expression to estimate the temperature of no-insulation (NI) high-temperature superconducting (HTS) coils when a local normal zone appears. The combination of the NI winding technology and HTS, especially rare-earth barium copper oxide (REBCO), enables high-field generation with high thermal stability. Since the advent of the NI winding technology, a few simulation techniques have been improved: the finite element method (FEM) and the partial element equivalent circuit (PEEC) are well-established as of today. The PEEC method can simulate the coil behaviors relatively fast compared with the FEM simulation due to the number of elements. However, the computation time is still long, particularly when a normal-state transition is simulated coupled with thermal analysis due to the extreme non-linearity of the superconductors. Therefore, we have previously proposed a simple and versatile analytical expression to estimate NI HTS coil temperatures in the cases of ramping down with an arbitrary speed and sudden discharging. Compared with PEEC simulations, the analytical formulae were validated in both cases under the assumption that the NI HTS coil is perfectly superconducting. In this paper, taking further realistic considerations into account, an NI HTS coil with a few normal-state turns is modeled, and its temperature is also formulated. The calculation results are validated with the PEEC model, and the accuracy and usable range of the proposed method is also discussed.
{"title":"A Simple Method to Estimate Coil Temperature With Local Normal-State Region","authors":"Takanobu Mato;So Noguchi","doi":"10.1109/TASC.2025.3533394","DOIUrl":"https://doi.org/10.1109/TASC.2025.3533394","url":null,"abstract":"This paper proposes a simple analytical expression to estimate the temperature of no-insulation (NI) high-temperature superconducting (HTS) coils when a local normal zone appears. The combination of the NI winding technology and HTS, especially rare-earth barium copper oxide (REBCO), enables high-field generation with high thermal stability. Since the advent of the NI winding technology, a few simulation techniques have been improved: the finite element method (FEM) and the partial element equivalent circuit (PEEC) are well-established as of today. The PEEC method can simulate the coil behaviors relatively fast compared with the FEM simulation due to the number of elements. However, the computation time is still long, particularly when a normal-state transition is simulated coupled with thermal analysis due to the extreme non-linearity of the superconductors. Therefore, we have previously proposed a simple and versatile analytical expression to estimate NI HTS coil temperatures in the cases of ramping down with an arbitrary speed and sudden discharging. Compared with PEEC simulations, the analytical formulae were validated in both cases under the assumption that the NI HTS coil is perfectly superconducting. In this paper, taking further realistic considerations into account, an NI HTS coil with a few normal-state turns is modeled, and its temperature is also formulated. The calculation results are validated with the PEEC model, and the accuracy and usable range of the proposed method is also discussed.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-5"},"PeriodicalIF":1.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143360929","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 : 2025-01-23DOI: 10.1109/TASC.2025.3532906
D. Araujo;B. Auchmann;A. Brem;T. Michlmayr;A. Haziot;E. Ravaioli
Stress-management of Nb3Sn coils offers a promising approach for high-field magnets by reducing conductor stress. The combination of stress-management and the common-coils magnet type simplifies manufacturing processes, such as utilizing the coil former in reaction and impregnation tooling. The common-coils architecture provides an attractive solution for 2-in-1 dipole magnets, with its racetrack geometry facilitating manufacturing and potentially allowing the react-and-wind (R&W) technique for cost-effective large-scale production. A key contribution of this work is overcoming the need for pole coils to achieve field quality by introducing an asymmetric design using only common-coils. The PSI 2-in-1 dipole magnet, featuring eight stress-managed Nb3Sn layers, employs bladder-and-keys technology for pre-loading at room temperature, eliminating the need for an aluminum shell or pads. The magnet includes two cable grades spliced in the low-field region, along with other features discussed in this paper. This work presents the conceptual design, including 3D magnetic design, mechanical analysis, and protection results.
{"title":"Electromechanical Design of Nb3Sn Stress Managed Asymmetric Common-Coils","authors":"D. Araujo;B. Auchmann;A. Brem;T. Michlmayr;A. Haziot;E. Ravaioli","doi":"10.1109/TASC.2025.3532906","DOIUrl":"https://doi.org/10.1109/TASC.2025.3532906","url":null,"abstract":"Stress-management of Nb<sub>3</sub>Sn coils offers a promising approach for high-field magnets by reducing conductor stress. The combination of stress-management and the common-coils magnet type simplifies manufacturing processes, such as utilizing the coil former in reaction and impregnation tooling. The common-coils architecture provides an attractive solution for 2-in-1 dipole magnets, with its racetrack geometry facilitating manufacturing and potentially allowing the react-and-wind (R&W) technique for cost-effective large-scale production. A key contribution of this work is overcoming the need for pole coils to achieve field quality by introducing an asymmetric design using only common-coils. The PSI 2-in-1 dipole magnet, featuring eight stress-managed Nb<sub>3</sub>Sn layers, employs bladder-and-keys technology for pre-loading at room temperature, eliminating the need for an aluminum shell or pads. The magnet includes two cable grades spliced in the low-field region, along with other features discussed in this paper. This work presents the conceptual design, including 3D magnetic design, mechanical analysis, and protection results.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-5"},"PeriodicalIF":1.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422822","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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