Pub Date : 2024-12-16DOI: 10.1109/TASC.2024.3512521
Haolan Chen;Mingyang Wang;Tiantian Cai;Zhuyong Li;Zhijian Jin
The stack structure of REBCO tapes is an effective way to increase the current carrying capacity. However, under the influence of anisotropy and high aspect ratio, REBCO tape has a low utilization rate in the stack structure. The purpose of this paper is to optimize the stack structure to improve the utilization rate of REBCO tapes. In order to calculate the critical current in the electric network model of stacked structure, the J model is introduced first. Then, based on the electric network model, the influence of different stack structures (including normal REBCO tape and defective REBCO tape) on the critical current is analyzed. The optimized structure can carry more currents, which is conducive to the development of REBCO tape applications.
{"title":"Critical Current Optimization for Stacks of REBCO Tapes With Defects","authors":"Haolan Chen;Mingyang Wang;Tiantian Cai;Zhuyong Li;Zhijian Jin","doi":"10.1109/TASC.2024.3512521","DOIUrl":"https://doi.org/10.1109/TASC.2024.3512521","url":null,"abstract":"The stack structure of REBCO tapes is an effective way to increase the current carrying capacity. However, under the influence of anisotropy and high aspect ratio, REBCO tape has a low utilization rate in the stack structure. The purpose of this paper is to optimize the stack structure to improve the utilization rate of REBCO tapes. In order to calculate the critical current in the electric network model of stacked structure, the \u0000<italic>J</i>\u0000 model is introduced first. Then, based on the electric network model, the influence of different stack structures (including normal REBCO tape and defective REBCO tape) on the critical current is analyzed. The optimized structure can carry more currents, which is conducive to the development of REBCO tape applications.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-5"},"PeriodicalIF":1.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142918305","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 : 2024-12-16DOI: 10.1109/TASC.2024.3519083
Jianyi Jiang;Jozef Kvitkovic;Caitlynn Linville;Jamia Brown;Jakeyvan Jones;Daniel S. Davis;Youngjae Kim;Fumitake Kametani;Ulf P. Trociewitz;Eric E. Hellstrom;David C. Larbalestier;Jean-Francois Croteau;Christopher Escobar;Tengming Shen
Bi-2212 Rutherford cables have been fabricated into flat racetrack coils and canted-cosine-theta dipole magnets. The performance gap between the magnets made with Rutherford cables and the “short-sample-limit” is about 30%. To better understand the influence of Rutherford cable processing on the strand performance, we studied three Bi-2212 wires with filament architectures of 37 × 18 and 55 × 18 and diameters of 0.8 and 1.0 mm. To simulate the deformation caused by cabling process, the three wires were rolled with thickness reductions ranging from 10% to 30%. The aspect ratios of rolled strands are between 1.29 and 2.05. The low aspect-ratio wire is also an interesting form for fabricating solenoid coils with higher packing density. The round and rolled strands were heat-treated under 50 bar and with maximum heat treatment temperatures of 885.5 °C and 890.5 °C. The rolling deformation reduced filament size uniformity, resulting in filament merging in fully heat-treated wires. It was found that rolling reduction reduced wire critical current density ( JE ) by 16 to 18%, but the JE decrease saturated at 15 to 20% of the thickness reduction. It is believed that the reduced JE results from the filament merging caused by rolling and non-uniform shrinking during overpressure heat treatment.
{"title":"Effects of Rolling Reduction on Critical Current Density and Microstructure of Bi-2212 Wires","authors":"Jianyi Jiang;Jozef Kvitkovic;Caitlynn Linville;Jamia Brown;Jakeyvan Jones;Daniel S. Davis;Youngjae Kim;Fumitake Kametani;Ulf P. Trociewitz;Eric E. Hellstrom;David C. Larbalestier;Jean-Francois Croteau;Christopher Escobar;Tengming Shen","doi":"10.1109/TASC.2024.3519083","DOIUrl":"https://doi.org/10.1109/TASC.2024.3519083","url":null,"abstract":"Bi-2212 Rutherford cables have been fabricated into flat racetrack coils and canted-cosine-theta dipole magnets. The performance gap between the magnets made with Rutherford cables and the “short-sample-limit” is about 30%. To better understand the influence of Rutherford cable processing on the strand performance, we studied three Bi-2212 wires with filament architectures of 37 × 18 and 55 × 18 and diameters of 0.8 and 1.0 mm. To simulate the deformation caused by cabling process, the three wires were rolled with thickness reductions ranging from 10% to 30%. The aspect ratios of rolled strands are between 1.29 and 2.05. The low aspect-ratio wire is also an interesting form for fabricating solenoid coils with higher packing density. The round and rolled strands were heat-treated under 50 bar and with maximum heat treatment temperatures of 885.5 °C and 890.5 °C. The rolling deformation reduced filament size uniformity, resulting in filament merging in fully heat-treated wires. It was found that rolling reduction reduced wire critical current density (\u0000<italic>J<sub>E</sub></i>\u0000) by 16 to 18%, but the \u0000<italic>J<sub>E</sub></i>\u0000 decrease saturated at 15 to 20% of the thickness reduction. It is believed that the reduced \u0000<italic>J<sub>E</sub></i>\u0000 results from the filament merging caused by rolling and non-uniform shrinking during overpressure heat treatment.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-5"},"PeriodicalIF":1.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142890374","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 : 2024-12-16DOI: 10.1109/TASC.2024.3519081
Dabin Wei;Zhuangwei Chen;Xuechun Wang;Difan Zhou;Kai Zhang;Haixiao Deng
The bulk high-temperature superconducting undulator can produce an on-axis magnetic field of up to 2.1 T for a period as short as 10 mm, outperforming current permanent magnet and low-temperature superconducting undulators. This paper presents a comprehensive analysis of the electromagnetic-mechanical coupling in RE-Ba-Cu-O (REBCO) bulk superconductors within the HTS undulator during the assembly, cool down and field-cooled magnetization processes. It is calculated that the compressive stress exerted by the copper disk upon cooling to 77 K significantly exceeds the pre-stress from the shrink-fit assembly. This indicates that the interference amount between the REBCO bulk and the copper disk can be minimized, allowing for a small degree of interference amount to facilitate shrink-fit assembly while ensuring effective thermal contact for enhanced heat conduction efficiency. It is observed that the maximum first principal stress in the REBCO bulk superconductor after field-cooled magnetization from 7 T is reduced to below 50 MPa when accounting for the pre-stress induced by the copper disk. To validate these computational findings, we developed a strain measurement system to assess the mechanical stress in the REBCO bulk superconductor after cooling to 77 K. The experimental results demonstrated good agreement with the simulation results.
{"title":"Mechanical Stress Analysis of RE-Ba-Cu-O Bulk Superconductors for the HTS Undulator During Assembly, Cool down and Field-Cooled Magnetization","authors":"Dabin Wei;Zhuangwei Chen;Xuechun Wang;Difan Zhou;Kai Zhang;Haixiao Deng","doi":"10.1109/TASC.2024.3519081","DOIUrl":"https://doi.org/10.1109/TASC.2024.3519081","url":null,"abstract":"The bulk high-temperature superconducting undulator can produce an on-axis magnetic field of up to 2.1 T for a period as short as 10 mm, outperforming current permanent magnet and low-temperature superconducting undulators. This paper presents a comprehensive analysis of the electromagnetic-mechanical coupling in RE-Ba-Cu-O (REBCO) bulk superconductors within the HTS undulator during the assembly, cool down and field-cooled magnetization processes. It is calculated that the compressive stress exerted by the copper disk upon cooling to 77 K significantly exceeds the pre-stress from the shrink-fit assembly. This indicates that the interference amount between the REBCO bulk and the copper disk can be minimized, allowing for a small degree of interference amount to facilitate shrink-fit assembly while ensuring effective thermal contact for enhanced heat conduction efficiency. It is observed that the maximum first principal stress in the REBCO bulk superconductor after field-cooled magnetization from 7 T is reduced to below 50 MPa when accounting for the pre-stress induced by the copper disk. To validate these computational findings, we developed a strain measurement system to assess the mechanical stress in the REBCO bulk superconductor after cooling to 77 K. The experimental results demonstrated good agreement with the simulation results.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-5"},"PeriodicalIF":1.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905780","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 : 2024-12-16DOI: 10.1109/TASC.2024.3519419
Calvin C. T. Chow;Min Zhang;K. T. Chau
Cryogenic electrical machines can have high power densities because conductors can carry large current densities at low temperatures. This article compares four types of conductors: copper Litz wire, aluminum Litz wire, MgB $_{2}$ multifilamentary wire, and REBCO tape, and one set of material parameters are used for each conductor for case studies in this article. Based on analytical loss formulas from the literature, the conductors' loss at different engineering current densities, temperatures, and external magnetic fields are compared. The effect of striating REBCO tapes is also investigated. On an individual conductor level, under simultaneous transport ac with external ac field of amplitude 0.4 T, both at 150 Hz, we find that when MgB $_{2}$ and REBCO carry ac close to their critical current densities, their losses are lower than the losses of the Litz wires at the same current densities. Further, we consider 3 MW, 4500 rev/min, 150 Hz machines with magnetic loading of 0.4 T when the armature is made of the different conductors. As the current density in armature conductors increases, the machine volume decreases. At 77.5 K, machines with copper and aluminum Litz wires have lower losses than machines with REBCO for the same machine volumes. At 20 K, for small machine volumes, machines with aluminum Litz wire armatures have the lowest losses.
{"title":"Analytical AC Loss Comparison Between REBCO, MgB$_{2}$, Copper, and Aluminum Litz Wires for Cryogenic Electrical Machines","authors":"Calvin C. T. Chow;Min Zhang;K. T. Chau","doi":"10.1109/TASC.2024.3519419","DOIUrl":"https://doi.org/10.1109/TASC.2024.3519419","url":null,"abstract":"Cryogenic electrical machines can have high power densities because conductors can carry large current densities at low temperatures. This article compares four types of conductors: copper Litz wire, aluminum Litz wire, MgB\u0000<inline-formula><tex-math>$_{2}$</tex-math></inline-formula>\u0000 multifilamentary wire, and REBCO tape, and one set of material parameters are used for each conductor for case studies in this article. Based on analytical loss formulas from the literature, the conductors' loss at different engineering current densities, temperatures, and external magnetic fields are compared. The effect of striating REBCO tapes is also investigated. On an individual conductor level, under simultaneous transport ac with external ac field of amplitude 0.4 T, both at 150 Hz, we find that when MgB\u0000<inline-formula><tex-math>$_{2}$</tex-math></inline-formula>\u0000 and REBCO carry ac close to their critical current densities, their losses are lower than the losses of the Litz wires at the same current densities. Further, we consider 3 MW, 4500 rev/min, 150 Hz machines with magnetic loading of 0.4 T when the armature is made of the different conductors. As the current density in armature conductors increases, the machine volume decreases. At 77.5 K, machines with copper and aluminum Litz wires have lower losses than machines with REBCO for the same machine volumes. At 20 K, for small machine volumes, machines with aluminum Litz wire armatures have the lowest losses.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 2","pages":"1-16"},"PeriodicalIF":1.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142937835","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 : 2024-12-16DOI: 10.1109/TASC.2024.3518461
Anthony I. Huber;Jason Austermann;James A. Beall;James Burgoyne;Scott Chapman;Douglas Henke;Johannes Hubmayr;Jeffrey Van Lanen;Adrian Sinclair;Anna K. Vaskuri;Michael R. Vissers;Jordan Wheeler
The Prime-Cam instrument is a first generation instrument under development for the 6-m Fred Young Submillimeter Telescope (FYST), which will be sited on Cerro Chajnantor in the Chilean Atacama Desert at an elevation of 5600 m. Among the instrument modules planned for the Prime-Cam instrument, the 850 GHz module is the highest frequency and of particular importance to the astronomical community due to the absence of near-future proposals for instruments at similar wavelengths and at equivalent sites. Success of the 850 GHz module hinges on the development of state-of-the-art detector arrays. The 850 GHz module will consist of approximately 45,000 titanium-nitride, polarization-sensitive, lumped-element kinetic inductance detectors, meaning the module will field more microwave kinetic inductance detectors than any other millimeter-wave receiver to date. The detectors are being designed to be read out using a multi-octave readout architecture, allowing for approximately double the multiplexing of other CCAT modules. We present the parameter space explored in the development of these detectors, including testing a means of shorting inductors to modify the resonance with minimal changes to the absorber architecture and testing different volumes of the inductor. Results and optical characterization of the prototype pixels for the 850 GHz instrument module are presented. The 850 GHz module is expected to be observing in 2026.
{"title":"High-Density Photon-Noise-Limited Multi-Octave Submillimeter Kinetic Inductance Detectors for the Prime-Cam 850 GHz Module","authors":"Anthony I. Huber;Jason Austermann;James A. Beall;James Burgoyne;Scott Chapman;Douglas Henke;Johannes Hubmayr;Jeffrey Van Lanen;Adrian Sinclair;Anna K. Vaskuri;Michael R. Vissers;Jordan Wheeler","doi":"10.1109/TASC.2024.3518461","DOIUrl":"https://doi.org/10.1109/TASC.2024.3518461","url":null,"abstract":"The Prime-Cam instrument is a first generation instrument under development for the 6-m Fred Young Submillimeter Telescope (FYST), which will be sited on Cerro Chajnantor in the Chilean Atacama Desert at an elevation of 5600 m. Among the instrument modules planned for the Prime-Cam instrument, the 850 GHz module is the highest frequency and of particular importance to the astronomical community due to the absence of near-future proposals for instruments at similar wavelengths and at equivalent sites. Success of the 850 GHz module hinges on the development of state-of-the-art detector arrays. The 850 GHz module will consist of approximately 45,000 titanium-nitride, polarization-sensitive, lumped-element kinetic inductance detectors, meaning the module will field more microwave kinetic inductance detectors than any other millimeter-wave receiver to date. The detectors are being designed to be read out using a multi-octave readout architecture, allowing for approximately double the multiplexing of other CCAT modules. We present the parameter space explored in the development of these detectors, including testing a means of shorting inductors to modify the resonance with minimal changes to the absorber architecture and testing different volumes of the inductor. Results and optical characterization of the prototype pixels for the 850 GHz instrument module are presented. The 850 GHz module is expected to be observing in 2026.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-7"},"PeriodicalIF":1.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912483","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}
It is known that high-temperature superconducting (HTS) magnets can operate in higher temperature margin compared with conventional low-temperature superconductors, and the characteristics of AC loss and screening current are very important for the optimal design of HTS magnets. In this article, two methods for evaluating the critical current of HTS magnet at different temperatures are compared. The effects of operating temperature and applied external magnetic field on the AC loss and screening current of the HTS magnet stacked by annular plates are discussed and analyzed. The results show that when the amplitude of the ac magnetic field is lower than that of the fully penetrating magnetic field, the magnetization loss decreases with the decrease of the operating temperature. The hysteresis loop area of the HTS magnet stacked by Rare-Earth-BaCu oxides annular plates increases at higher temperature under the same magnetic field.
{"title":"AC Loss and Screening Current Calculation of HTS Magnet Stacked by Annular Plates With Different Temperatures","authors":"Qi Li;Yingmin Cui;Yinshun Wang;Ziyu Pi;Xinkai Zhu;Gang Lyu","doi":"10.1109/TASC.2024.3518565","DOIUrl":"https://doi.org/10.1109/TASC.2024.3518565","url":null,"abstract":"It is known that high-temperature superconducting (HTS) magnets can operate in higher temperature margin compared with conventional low-temperature superconductors, and the characteristics of AC loss and screening current are very important for the optimal design of HTS magnets. In this article, two methods for evaluating the critical current of HTS magnet at different temperatures are compared. The effects of operating temperature and applied external magnetic field on the AC loss and screening current of the HTS magnet stacked by annular plates are discussed and analyzed. The results show that when the amplitude of the ac magnetic field is lower than that of the fully penetrating magnetic field, the magnetization loss decreases with the decrease of the operating temperature. The hysteresis loop area of the HTS magnet stacked by Rare-Earth-BaCu oxides annular plates increases at higher temperature under the same magnetic field.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 2","pages":"1-10"},"PeriodicalIF":1.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142890155","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 : 2024-12-16DOI: 10.1109/TASC.2024.3517564
Alicia Middleton;Steve K. Choi;Samantha Walker;Jason Austermann;James R. Burgoyne;Victoria Butler;Scott C. Chapman;Abigail T. Crites;Cody J. Duell;Rodrigo G. Freundt;Anthony I. Huber;Zachary B. Huber;Johannes Hubmayr;Ben Keller;Lawrence T. Lin;Michael D. Niemack;Darshan Patel;Adrian K. Sinclair;Ema Smith;Anna Vaskuri;Eve M. Vavagiakis;Michael Vissers;Yuhan Wang;Jordan Wheeler
Prime-Cam, one of the primary instruments for the Fred Young Submillimeter Telescope (FYST) developed by the CCAT Collaboration, will house up to seven instrument modules, with the first operating at 280 GHz. Each module will include three arrays of superconducting microwave kinetic inductance detectors (KIDs). The first KID array fabricated for the 280 GHz module uses titanium-nitride (TiN) as the superconducting material and has 3,456 individual detectors, while the other two arrays use aluminum. This paper presents the design and laboratory characterization of the 280 GHz TiN array, which is cooled below its critical temperature to $sim$ 0.1K and read out over six RF feedlines. LED mapping, a technique for matching the measured resonant frequency of a detector to its physical position, was performed on the array so that the results can be used to lithographically trim the KID capacitors and increase the yield of the array by reducing frequency collisions. We present the methods and results of LED mapping the 280 GHz TiN KID array before deployment on FYST.
{"title":"CCAT: LED Mapping and Characterization of the 280 GHz TiN KID Array","authors":"Alicia Middleton;Steve K. Choi;Samantha Walker;Jason Austermann;James R. Burgoyne;Victoria Butler;Scott C. Chapman;Abigail T. Crites;Cody J. Duell;Rodrigo G. Freundt;Anthony I. Huber;Zachary B. Huber;Johannes Hubmayr;Ben Keller;Lawrence T. Lin;Michael D. Niemack;Darshan Patel;Adrian K. Sinclair;Ema Smith;Anna Vaskuri;Eve M. Vavagiakis;Michael Vissers;Yuhan Wang;Jordan Wheeler","doi":"10.1109/TASC.2024.3517564","DOIUrl":"https://doi.org/10.1109/TASC.2024.3517564","url":null,"abstract":"Prime-Cam, one of the primary instruments for the Fred Young Submillimeter Telescope (FYST) developed by the CCAT Collaboration, will house up to seven instrument modules, with the first operating at 280 GHz. Each module will include three arrays of superconducting microwave kinetic inductance detectors (KIDs). The first KID array fabricated for the 280 GHz module uses titanium-nitride (TiN) as the superconducting material and has 3,456 individual detectors, while the other two arrays use aluminum. This paper presents the design and laboratory characterization of the 280 GHz TiN array, which is cooled below its critical temperature to \u0000<inline-formula><tex-math>$sim$</tex-math></inline-formula>\u0000 0.1K and read out over six RF feedlines. LED mapping, a technique for matching the measured resonant frequency of a detector to its physical position, was performed on the array so that the results can be used to lithographically trim the KID capacitors and increase the yield of the array by reducing frequency collisions. We present the methods and results of LED mapping the 280 GHz TiN KID array before deployment on FYST.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-4"},"PeriodicalIF":1.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905690","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 : 2024-12-16DOI: 10.1109/TASC.2024.3518463
Hiroaki Kumakura
Densification of MgB $_{text{2}}$ core in an in situ PIT MgB $_{text{2}}$ wire is one of the key factors to increase J c values. Hot pressing, cold pressing before a heat treatment and hot isostatic pressing (HIP) are effective in densifying the core and thus, increasing J c values. Mechanical alloying or mechanical milling of Mg+B precursor powder by a high-energy ball milling is also effective in increasing the core density and J c values. Upper critical field H c2 is another important parameter. Carbon doping to MgB $_{text{2}}$ not only increases H c2 but also decreases the anisotropy in H c2 , both of which are effective in enhancing J c of MgB $_{text{2}}$ wires in magnetic fields. The doping of some kinds of hydrocarbon or carbohydrate to a Mg+B precursor powder and the use of carbon-coated B powder as a starting material is effective for in situ PIT MgB $_{text{2}}$ wires. Internal Mg diffusion (IMD) method much increases the MgB $_{text{2}}$ filling density and J c higher than 10 5 A/cm 2 is obtained at 20 K and 4 T by using carbon-doped B powder. Solenoid coils were fabricated with IMD wires and coil tests were carried out. Concerning to AC loss of MgB $_{text{2}}$ wires, cabling of small diameter mono-core MgB $_{text{2}}$ wires is one of the effective methods to reduce both hysteresis loss and coupling loss. Superconducting joints of unreacted C-doped multi-filamentary wire showed joint resistance of 10 −14 Ω at 20 K. But joint I c was only 1/4 of wire I c . A joint of reacted mono-core wire was reported to have resistance of 10 −14 Ω at 20 K, 1 T. Excellent joint I c of 78% of wire I c were obtained.
{"title":"Resent Progress on MgB2 Wires","authors":"Hiroaki Kumakura","doi":"10.1109/TASC.2024.3518463","DOIUrl":"https://doi.org/10.1109/TASC.2024.3518463","url":null,"abstract":"Densification of MgB\u0000<inline-formula><tex-math>$_{text{2}}$</tex-math></inline-formula>\u0000 core in an in situ PIT MgB\u0000<inline-formula><tex-math>$_{text{2}}$</tex-math></inline-formula>\u0000 wire is one of the key factors to increase \u0000<italic>J</i>\u0000<sub>c</sub>\u0000 values. Hot pressing, cold pressing before a heat treatment and hot isostatic pressing (HIP) are effective in densifying the core and thus, increasing \u0000<italic>J</i>\u0000<sub>c</sub>\u0000 values. Mechanical alloying or mechanical milling of Mg+B precursor powder by a high-energy ball milling is also effective in increasing the core density and \u0000<italic>J</i>\u0000<sub>c</sub>\u0000 values. Upper critical field \u0000<italic>H</i>\u0000<sub>c2</sub>\u0000 is another important parameter. Carbon doping to MgB\u0000<inline-formula><tex-math>$_{text{2}}$</tex-math></inline-formula>\u0000 not only increases \u0000<italic>H</i>\u0000<sub>c2</sub>\u0000 but also decreases the anisotropy in \u0000<italic>H</i>\u0000<sub>c2</sub>\u0000, both of which are effective in enhancing \u0000<italic>J</i>\u0000<sub>c</sub>\u0000 of MgB\u0000<inline-formula><tex-math>$_{text{2}}$</tex-math></inline-formula>\u0000 wires in magnetic fields. The doping of some kinds of hydrocarbon or carbohydrate to a Mg+B precursor powder and the use of carbon-coated B powder as a starting material is effective for in situ PIT MgB\u0000<inline-formula><tex-math>$_{text{2}}$</tex-math></inline-formula>\u0000 wires. Internal Mg diffusion (IMD) method much increases the MgB\u0000<inline-formula><tex-math>$_{text{2}}$</tex-math></inline-formula>\u0000 filling density and \u0000<italic>J</i>\u0000<sub>c</sub>\u0000 higher than 10\u0000<sup>5</sup>\u0000 A/cm\u0000<sup>2</sup>\u0000 is obtained at 20 K and 4 T by using carbon-doped B powder. Solenoid coils were fabricated with IMD wires and coil tests were carried out. Concerning to AC loss of MgB\u0000<inline-formula><tex-math>$_{text{2}}$</tex-math></inline-formula>\u0000 wires, cabling of small diameter mono-core MgB\u0000<inline-formula><tex-math>$_{text{2}}$</tex-math></inline-formula>\u0000 wires is one of the effective methods to reduce both hysteresis loss and coupling loss. Superconducting joints of unreacted C-doped multi-filamentary wire showed joint resistance of 10\u0000<sup>−14</sup>\u0000 Ω at 20 K. But joint \u0000<italic>I</i>\u0000<sub>c</sub>\u0000 was only 1/4 of wire \u0000<italic>I</i>\u0000<sub>c</sub>\u0000. A joint of reacted mono-core wire was reported to have resistance of 10\u0000<sup>−14</sup>\u0000 Ω at 20 K, 1 T. Excellent joint \u0000<italic>I</i>\u0000<sub>c</sub>\u0000 of 78% of wire \u0000<italic>I</i>\u0000<sub>c</sub>\u0000 were obtained.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-7"},"PeriodicalIF":1.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142938213","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 : 2024-12-16DOI: 10.1109/TASC.2024.3517565
Thomas A. Baker;Daniel T. Becker;Joseph W. Fowler;Mark W. Keller;Daniel S. Swetz;Joel N. Ullom
Arrays of microcalorimeters based on transition-edge sensors (TESs) are being actively deployed to laboratories all over the world. A TES microcalorimeter array produces very large quantities of data and users of these devices have varying levels of experience, so it is important to provide robust software for data acquisition and analysis that can function with minimal user supervision. This software should be capable of addressing common phenomena that can adversely affect spectrum quality. Gain jumping is one such phenomenon that is characterized by abrupt changes in the gain of a device. Left unaddressed, gain jumps can degrade spectra by introducing false peaks. We are not aware of any previously published methods for resetting gain jumps during data acquisition or existing algorithms for correcting data that is degraded by gain jumps. We have developed automated methods for detecting and correcting gain jumps in gamma-ray TES microcalorimeters. We present a procedure for resetting gain jumps during a live data acquisition that involves briefly driving the TES into its normal state using the bias current. We also describe an algorithm for locating gain jumps and identifying unique gain states within existing microcalorimeter data. Finally, we provide a possible approach for correcting gain jumps after they have been identified.
{"title":"Detecting and Correcting Gain Jumps in TES Microcalorimeters","authors":"Thomas A. Baker;Daniel T. Becker;Joseph W. Fowler;Mark W. Keller;Daniel S. Swetz;Joel N. Ullom","doi":"10.1109/TASC.2024.3517565","DOIUrl":"https://doi.org/10.1109/TASC.2024.3517565","url":null,"abstract":"Arrays of microcalorimeters based on transition-edge sensors (TESs) are being actively deployed to laboratories all over the world. A TES microcalorimeter array produces very large quantities of data and users of these devices have varying levels of experience, so it is important to provide robust software for data acquisition and analysis that can function with minimal user supervision. This software should be capable of addressing common phenomena that can adversely affect spectrum quality. Gain jumping is one such phenomenon that is characterized by abrupt changes in the gain of a device. Left unaddressed, gain jumps can degrade spectra by introducing false peaks. We are not aware of any previously published methods for resetting gain jumps during data acquisition or existing algorithms for correcting data that is degraded by gain jumps. We have developed automated methods for detecting and correcting gain jumps in gamma-ray TES microcalorimeters. We present a procedure for resetting gain jumps during a live data acquisition that involves briefly driving the TES into its normal state using the bias current. We also describe an algorithm for locating gain jumps and identifying unique gain states within existing microcalorimeter data. Finally, we provide a possible approach for correcting gain jumps after they have been identified.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-5"},"PeriodicalIF":1.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905689","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 : 2024-12-16DOI: 10.1109/TASC.2024.3519074
Fumitake Kametani;Shah Alam Limon;Keyou Mao;Eric Hellstrom;Chiara Tarantini
It is still largely elusive whether K-doped BaFe 2 As 2 (K-Ba122) is granular due to the intrinsic blocking effects at the grain boundaries (GBs). We investigated the remnant magnetization characteristics of a K-Ba122 polycrystalline bulk. Remnant magnetization is effective to evaluate the contribution of magnetization from multi-scale current loops particularly if electromagnetic granularity is present due to weakly coupled GBs. The derivative of remnant magnetization of the K-Ba122 sample showed only a single peak, which was markedly dependent on the specimen size and shifted toward lower field as the specimen size decreases, strongly indicating that the current loop is intergrain. However, the high angle annular dark field scanning transmission electron microscope (HAADF-STEM) analysis revealed that this sample still has nano-cracks at GBs, degrading the continuous network of strong intergrain connectivity. Such extrinsically degraded network of intergrain connectivity can also be seen as a size-dependence of remnant magnetization Jc , which indicated the presence of strongly localized regions with much higher Jc than the bulk Jc . Our study suggested that the extrinsic GB nano-cracks are still the major cause of connectivity degradation, and the intrinsic current suppression might not be practically detectable at clean, fully connected GBs.
{"title":"Remnant Magnetization Behavior of a K-Doped Ba122 Polycrystalline Bulk","authors":"Fumitake Kametani;Shah Alam Limon;Keyou Mao;Eric Hellstrom;Chiara Tarantini","doi":"10.1109/TASC.2024.3519074","DOIUrl":"https://doi.org/10.1109/TASC.2024.3519074","url":null,"abstract":"It is still largely elusive whether K-doped BaFe\u0000<sub>2</sub>\u0000As\u0000<sub>2</sub>\u0000 (K-Ba122) is granular due to the intrinsic blocking effects at the grain boundaries (GBs). We investigated the remnant magnetization characteristics of a K-Ba122 polycrystalline bulk. Remnant magnetization is effective to evaluate the contribution of magnetization from multi-scale current loops particularly if electromagnetic granularity is present due to weakly coupled GBs. The derivative of remnant magnetization of the K-Ba122 sample showed only a single peak, which was markedly dependent on the specimen size and shifted toward lower field as the specimen size decreases, strongly indicating that the current loop is intergrain. However, the high angle annular dark field scanning transmission electron microscope (HAADF-STEM) analysis revealed that this sample still has nano-cracks at GBs, degrading the continuous network of strong intergrain connectivity. Such extrinsically degraded network of intergrain connectivity can also be seen as a size-dependence of remnant magnetization \u0000<italic>J<sub>c</sub></i>\u0000, which indicated the presence of strongly localized regions with much higher \u0000<italic>J<sub>c</sub></i>\u0000 than the bulk \u0000<italic>J<sub>c</sub></i>\u0000. Our study suggested that the extrinsic GB nano-cracks are still the major cause of connectivity degradation, and the intrinsic current suppression might not be practically detectable at clean, fully connected GBs.","PeriodicalId":13104,"journal":{"name":"IEEE Transactions on Applied Superconductivity","volume":"35 5","pages":"1-5"},"PeriodicalIF":1.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905781","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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