Pub Date : 2024-09-17DOI: 10.1088/1361-6668/ad7646
Wenchao Li, Caida Fu, Chen Guo, He Huang, Chao Yao, Xianping Zhang and Yanwei Ma
Iron-based superconductors with ultra-high upper critical fields and low anisotropy have attracted much attention for superconducting mechanisms and high-field applications. In practical applications, improving the mechanical strength and heat treatment temperature of superconducting tapes is of great significance for the improvement of transport current as well as stability. In this paper, (Ba, K)Fe2As2(Ba-122) superconducting tapes with Cu/Nb/Ag composite sheaths were successfully fabricated using a pre-composite process, which provides a feasible method for the fabrication of high-strength superconducting wires and tapes. It is shown that Cu/Nb/Ag composite sheathed tapes can be sintered at 880 °C, and tapes sintered at 880 °C have the highest transport properties as well as excellent superconductivity of the superconducting cores, as demonstrated by a series of characterizations. In addition, other superconducting properties of the tapes sintered at 880 °C, including grain orientation, flux pinning, upper critical field and irreversible field, were also studied. It was found that none of the three sheaths fractured after sintering and the superconducting core had a high c-axis texture and densities. The high mechanical strength of the Cu/Nb/Ag composite sheathed tape was also demonstrated by comparative tensile experiments. The results indicate that the low-cost Ba-122 tapes with Cu/Nb/Ag composite sheaths hold great promise for future practical applications.
{"title":"Enhanced mechanical strength and texture of (Ba,K)Fe2As2 Cu/Ag composite sheathed tapes with Nb barrier layer","authors":"Wenchao Li, Caida Fu, Chen Guo, He Huang, Chao Yao, Xianping Zhang and Yanwei Ma","doi":"10.1088/1361-6668/ad7646","DOIUrl":"https://doi.org/10.1088/1361-6668/ad7646","url":null,"abstract":"Iron-based superconductors with ultra-high upper critical fields and low anisotropy have attracted much attention for superconducting mechanisms and high-field applications. In practical applications, improving the mechanical strength and heat treatment temperature of superconducting tapes is of great significance for the improvement of transport current as well as stability. In this paper, (Ba, K)Fe2As2(Ba-122) superconducting tapes with Cu/Nb/Ag composite sheaths were successfully fabricated using a pre-composite process, which provides a feasible method for the fabrication of high-strength superconducting wires and tapes. It is shown that Cu/Nb/Ag composite sheathed tapes can be sintered at 880 °C, and tapes sintered at 880 °C have the highest transport properties as well as excellent superconductivity of the superconducting cores, as demonstrated by a series of characterizations. In addition, other superconducting properties of the tapes sintered at 880 °C, including grain orientation, flux pinning, upper critical field and irreversible field, were also studied. It was found that none of the three sheaths fractured after sintering and the superconducting core had a high c-axis texture and densities. The high mechanical strength of the Cu/Nb/Ag composite sheathed tape was also demonstrated by comparative tensile experiments. The results indicate that the low-cost Ba-122 tapes with Cu/Nb/Ag composite sheaths hold great promise for future practical applications.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"187 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142255961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6668/ad74a1
Elmira Baeva, Anna Kolbatova, Nadezhda Titova, Soham Saha, Alexandra Boltasseva, Simeon Bogdanov, Vladimir M Shalaev, Alexander Semenov, Gregory N Goltsman and Vadim Khrapai
We investigate the effect of various fluctuation mechanisms on the DC resistance in superconducting (SC) devices based on epitaxial titanium nitride (TiN) films. The samples we studied show a relatively steep resistive transition (RT), with a transition width , depending on the film thickness (20 nm, 9 nm, and 5 nm) and device dimensions. This value is significantly broader than expected due to conventional SC fluctuations ( ). The shape and width of the RT can be perfectly described by the well-known effective medium theory, which allows us to understand the origin of the inhomogeneity in the SC properties of TiN films. We propose that this inhomogeneity can have both dynamic and static origins. The dynamic mechanism is associated with spontaneous fluctuations in electron temperature (T-fluctuations), while the static mechanism is due to a random spatial distribution of surface magnetic disorder (MD). Our analysis has revealed clear correlations between the transition width and material parameters as well as device size for both proposed mechanisms. While T-fluctuations may contribute significantly to the observed transition width, our findings suggest that the dominant contribution comes from the MD mechanism. Our results provide new insights into the microscopic origin of broadening of the SC transition and inhomogeneity in thin SC films.
{"title":"Natural width of the superconducting transition in epitaxial TiN films","authors":"Elmira Baeva, Anna Kolbatova, Nadezhda Titova, Soham Saha, Alexandra Boltasseva, Simeon Bogdanov, Vladimir M Shalaev, Alexander Semenov, Gregory N Goltsman and Vadim Khrapai","doi":"10.1088/1361-6668/ad74a1","DOIUrl":"https://doi.org/10.1088/1361-6668/ad74a1","url":null,"abstract":"We investigate the effect of various fluctuation mechanisms on the DC resistance in superconducting (SC) devices based on epitaxial titanium nitride (TiN) films. The samples we studied show a relatively steep resistive transition (RT), with a transition width , depending on the film thickness (20 nm, 9 nm, and 5 nm) and device dimensions. This value is significantly broader than expected due to conventional SC fluctuations ( ). The shape and width of the RT can be perfectly described by the well-known effective medium theory, which allows us to understand the origin of the inhomogeneity in the SC properties of TiN films. We propose that this inhomogeneity can have both dynamic and static origins. The dynamic mechanism is associated with spontaneous fluctuations in electron temperature (T-fluctuations), while the static mechanism is due to a random spatial distribution of surface magnetic disorder (MD). Our analysis has revealed clear correlations between the transition width and material parameters as well as device size for both proposed mechanisms. While T-fluctuations may contribute significantly to the observed transition width, our findings suggest that the dominant contribution comes from the MD mechanism. Our results provide new insights into the microscopic origin of broadening of the SC transition and inhomogeneity in thin SC films.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6668/ad7641
Yuwei Zhou, Ge Ye, Shuaishuai Luo, Yu Song, Xin Lu and Huiqiu Yuan
The vanadium-based kagome metals AV3Sb5 (A = K, Rb, and Cs) host a superconducting ground state that coexists with an unconventional charge density wave (CDW). The CDW state exhibits experimental signatures of chirality, electronic nematicity, and time-reversal-symmetry-breaking, raising the questions whether the superconductivity (SC) in AV3Sb5 may also be unconventional, how SC interplays with CDW, and how the two orders evolve upon tuning. This article reviews studies of the superconducting pairing symmetry, and the tuning of SC and CDW in the AV3Sb5 compounds. Various experimental techniques consistently find that CsV3Sb5 exhibits nodeless SC, which remains robust regardless whether the CDW is present. Under hydrostatic pressure, SC in AV3Sb5 becomes enhanced as the CDW is gradually suppressed, revealing a competition between the two orders. In CsV3Sb5, a new CDW state emerges under pressure that competes more strongly with SC relative to the CDW at ambient pressure, and results in two superconducting domes that coexist with CDW. After the CDW in AV3Sb5 is fully suppressed with hydrostatic pressure, a further increase in pressure leads to a nonmonotonic evolution of the superconducting transition temperature driven by lattice modulations. Thickness is shown to be a powerful tuning parameter in AV3Sb5 thin flakes, revealing the evolution of CDW and SC upon dimensional reduction, and can be combined with hydrostatic pressure to shed light on the interplay between SC and CDW. Based on results reviewed in this article, we discuss outstanding issues to be addressed in the AV3Sb5 systems.
{"title":"Kagome materials AV3Sb5 (A = K,Rb,Cs): pairing symmetry and pressure-tuning studies","authors":"Yuwei Zhou, Ge Ye, Shuaishuai Luo, Yu Song, Xin Lu and Huiqiu Yuan","doi":"10.1088/1361-6668/ad7641","DOIUrl":"https://doi.org/10.1088/1361-6668/ad7641","url":null,"abstract":"The vanadium-based kagome metals AV3Sb5 (A = K, Rb, and Cs) host a superconducting ground state that coexists with an unconventional charge density wave (CDW). The CDW state exhibits experimental signatures of chirality, electronic nematicity, and time-reversal-symmetry-breaking, raising the questions whether the superconductivity (SC) in AV3Sb5 may also be unconventional, how SC interplays with CDW, and how the two orders evolve upon tuning. This article reviews studies of the superconducting pairing symmetry, and the tuning of SC and CDW in the AV3Sb5 compounds. Various experimental techniques consistently find that CsV3Sb5 exhibits nodeless SC, which remains robust regardless whether the CDW is present. Under hydrostatic pressure, SC in AV3Sb5 becomes enhanced as the CDW is gradually suppressed, revealing a competition between the two orders. In CsV3Sb5, a new CDW state emerges under pressure that competes more strongly with SC relative to the CDW at ambient pressure, and results in two superconducting domes that coexist with CDW. After the CDW in AV3Sb5 is fully suppressed with hydrostatic pressure, a further increase in pressure leads to a nonmonotonic evolution of the superconducting transition temperature driven by lattice modulations. Thickness is shown to be a powerful tuning parameter in AV3Sb5 thin flakes, revealing the evolution of CDW and SC upon dimensional reduction, and can be combined with hydrostatic pressure to shed light on the interplay between SC and CDW. Based on results reviewed in this article, we discuss outstanding issues to be addressed in the AV3Sb5 systems.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1088/1361-6668/ad74ea
Qing-Yu Wang and Cun Xue
Hybrid multi-superconducting structures exist in a variety of superconducting devices, such as superconductor–insulator–superconductor multilayer structure in superconducting radio-frequency cavities, bilayer structures in superconducting electronic devices, and superconducting wires. Investigating the vortex dynamics at microscopic scale is crucial for applications of hybrid superconducting structures.The time-dependent Ginzburg–Landau (TDGL) theory is a powerful tool for describing the vortex dynamics in superconductors through the order parameter and vector potential A. However, the difference in order parameter , coherence length , and GL parameters among the components of hybrid systems will bring significant challenges to numerical simulation of TDGL equations. Meanwhile, the energy dissipation associated with vortex motion necessitates considering the thermal effects on vortex dynamics. In this paper, we introduce an efficient, stable, and parallel implicit finite-difference algorithm, implemented on GPU, for coupling the TDGL and thermal diffusion equations for hybrid structures. Linearization of nonlinear source terms is applied to TDGL-II to enhance the stability of algorithm. The iterative Jacobi method is applied to the generalized TDGL-I. Alternating direction implicit methods combined with tridiagonal matrix method or CTDMA are used to solve TDGL-II and heat diffusion equations with different boundary conditions. This algorithm enables us to explore the vortex dynamics with associated thermal effects of mesoscopic large hybrid multi-superconducting structures within reasonable amounts of computational time. Our approach aids in revealing and understanding the underlying physical mechanisms behind the collective response of vortices, and contributes to the mastery, adjustment, and optimization of superconductivities in hybrid structures.
{"title":"Stable implicit numerical algorithm of time-dependent Ginzburg–Landau theory coupled with thermal effect for vortex behaviors in hybrid superconductor systems","authors":"Qing-Yu Wang and Cun Xue","doi":"10.1088/1361-6668/ad74ea","DOIUrl":"https://doi.org/10.1088/1361-6668/ad74ea","url":null,"abstract":"Hybrid multi-superconducting structures exist in a variety of superconducting devices, such as superconductor–insulator–superconductor multilayer structure in superconducting radio-frequency cavities, bilayer structures in superconducting electronic devices, and superconducting wires. Investigating the vortex dynamics at microscopic scale is crucial for applications of hybrid superconducting structures.The time-dependent Ginzburg–Landau (TDGL) theory is a powerful tool for describing the vortex dynamics in superconductors through the order parameter and vector potential A. However, the difference in order parameter , coherence length , and GL parameters among the components of hybrid systems will bring significant challenges to numerical simulation of TDGL equations. Meanwhile, the energy dissipation associated with vortex motion necessitates considering the thermal effects on vortex dynamics. In this paper, we introduce an efficient, stable, and parallel implicit finite-difference algorithm, implemented on GPU, for coupling the TDGL and thermal diffusion equations for hybrid structures. Linearization of nonlinear source terms is applied to TDGL-II to enhance the stability of algorithm. The iterative Jacobi method is applied to the generalized TDGL-I. Alternating direction implicit methods combined with tridiagonal matrix method or CTDMA are used to solve TDGL-II and heat diffusion equations with different boundary conditions. This algorithm enables us to explore the vortex dynamics with associated thermal effects of mesoscopic large hybrid multi-superconducting structures within reasonable amounts of computational time. Our approach aids in revealing and understanding the underlying physical mechanisms behind the collective response of vortices, and contributes to the mastery, adjustment, and optimization of superconductivities in hybrid structures.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1088/1361-6668/ad7642
Yixin Liu, Yuchuan Liu, Zulei Xu, Aobo Yu, Xiaoni Wang, Wei Peng, Yu Wu, Gang Mu and Zhi-Rong Lin
The interplay between substrates and superconducting thin films has attracted increasing attention. Here, we report an in-depth investigation on superconducting properties of the epitaxial TiN thin films grown on three different substrates by dc reactive magnetron sputtering. The TiN films grown on (0001) sapphire exhibit (111) crystal orientation, while that grown on (100) Si and MgO substrates exhibit (100) orientation. Moreover, the samples grown on Si reveal a relatively lower level of disorder, accompanied by the higher critical transition temperature Tc and smaller magnitude of upper critical field slope near Tc. Remarkably, we uncovered a rather high value of superconducting gap (with = 3.05) in TiN film on Si indicating a very strong coupling superconductivity, in sharp contrast to the case using sapphires and MgO as the substrate which reveals a weak-coupling feature. The comprehensive analysis considering the scenarios of the three substrate shows that the grain size of the thin films may be an important factor influencing the superconductivity.
衬底与超导薄膜之间的相互作用已引起越来越多的关注。在此，我们报告了通过直流反应磁控溅射技术在三种不同衬底上生长的外延 TiN 薄膜超导特性的深入研究。生长在（0001）蓝宝石上的 TiN 薄膜呈现出（111）晶体取向，而生长在（100）硅和氧化镁基底上的 TiN 薄膜呈现出（100）取向。此外，在硅上生长的样品显示出相对较低的无序水平，同时临界转变温度 Tc 较高，Tc 附近的上临界场斜率较小。值得注意的是，我们在硅基 TiN 薄膜中发现了相当高的超导间隙值（with = 3.05），这表明其具有非常强的耦合超导性，这与使用蓝宝石和氧化镁作为衬底的情况形成鲜明对比，后者显示出弱耦合特征。对三种衬底情况的综合分析表明，薄膜的晶粒尺寸可能是影响超导性的一个重要因素。
{"title":"From weak to strong-coupling superconductivity tuned by substrate in TiN films","authors":"Yixin Liu, Yuchuan Liu, Zulei Xu, Aobo Yu, Xiaoni Wang, Wei Peng, Yu Wu, Gang Mu and Zhi-Rong Lin","doi":"10.1088/1361-6668/ad7642","DOIUrl":"https://doi.org/10.1088/1361-6668/ad7642","url":null,"abstract":"The interplay between substrates and superconducting thin films has attracted increasing attention. Here, we report an in-depth investigation on superconducting properties of the epitaxial TiN thin films grown on three different substrates by dc reactive magnetron sputtering. The TiN films grown on (0001) sapphire exhibit (111) crystal orientation, while that grown on (100) Si and MgO substrates exhibit (100) orientation. Moreover, the samples grown on Si reveal a relatively lower level of disorder, accompanied by the higher critical transition temperature Tc and smaller magnitude of upper critical field slope near Tc. Remarkably, we uncovered a rather high value of superconducting gap (with = 3.05) in TiN film on Si indicating a very strong coupling superconductivity, in sharp contrast to the case using sapphires and MgO as the substrate which reveals a weak-coupling feature. The comprehensive analysis considering the scenarios of the three substrate shows that the grain size of the thin films may be an important factor influencing the superconductivity.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1088/1361-6668/ad7645
Mingming Yu, Shichun Huang, Yong Zhao, Xiangcheng Gu, Long Peng, Jiwei Lai, Tongtong Zhu, Yihan Wang, Andong Wu, Teng Tan, Yuan He, Hongwen Cao, Yunpeng Cao and Kun Zhang
Medium-temperature baking (Mid-T baking) is an innovative method employed to enhance the unloaded quality factor Q0 of superconducting radio-frequency niobium (SRF Nb) cavities at cryogenic temperatures. This study presents an interstitial oxygen diffusion model based on the decomposition of the natural oxide to clarify the improved performance of the Nb cavities after undergoing Mid-T baking. Additionally, the correlation between the interstitial oxygen within the RF penetration depth and the surface resistance of the Nb cavities has been explored. The parameter for the oxide decomposition was determined using in-situ x-ray photoelectron spectroscopy (XPS), where the thickness of the oxide/carbide layer was calculated from the peak fitting of Nb 3d spectra and the attenuation law of the photoelectron beam. The interstitial oxygen diffusion model, validated by the semi-quantitative distribution along the depth determined by time-of-flight secondary ion mass spectrometry, quantifies the oxygen atomic concentration within the RF penetration depth in Mid-T baked Nb material. In the baking temperature range of 300 °C–400 °C, the calculated oxygen concentration from the interstitial oxygen diffusion model demonstrates a more pronounced dependence on the baking temperature than the baking time. This suggests that more precise control of the interstitial oxygen concentration can be achieved by adjusting the baking temperature. Furthermore, it has been observed that maintaining a uniform and moderate oxygen concentration throughout the depth is essential for optimal Bardeen–Cooper–Schrieffer resistance. This study paves the way for more efficient processing optimization and enhancing understanding of the mechanism behind RF loss in Nb cavities.
中温烘烤（Mid-T baking）是一种创新方法，用于在低温条件下提高超导射频铌（SRF Nb）空穴的空载品质因数 Q0。本研究提出了一种基于天然氧化物分解的间隙氧扩散模型，以阐明经过 Mid-T 烘烤后铌空穴性能的提高。此外，还探讨了射频穿透深度内的间隙氧与铌空穴表面电阻之间的相关性。氧化物分解的参数是通过原位 X 射线光电子能谱（XPS）确定的，其中氧化物/碳化物层的厚度是根据 Nb 3d 光谱的峰拟合和光电子束的衰减规律计算得出的。通过飞行时间二次离子质谱测定的沿深度的半定量分布验证了间隙氧扩散模型，该模型量化了 Mid-T 烘焙铌材料射频穿透深度内的氧原子浓度。在 300 °C-400 °C 的焙烧温度范围内，根据间隙氧扩散模型计算出的氧浓度对焙烧温度的依赖性比对焙烧时间的依赖性更明显。这表明，通过调整烘烤温度可以更精确地控制间隙氧浓度。此外，研究还发现，在整个深度保持均匀适度的氧气浓度对于获得最佳的巴丁-库珀-施里弗抗性至关重要。这项研究为更有效地优化加工和加深了解铌腔射频损耗背后的机理铺平了道路。
{"title":"Study on the interstitial oxygen diffusion to understand the reduction of cryogenic RF loss for the superconducting radio-frequency niobium cavities","authors":"Mingming Yu, Shichun Huang, Yong Zhao, Xiangcheng Gu, Long Peng, Jiwei Lai, Tongtong Zhu, Yihan Wang, Andong Wu, Teng Tan, Yuan He, Hongwen Cao, Yunpeng Cao and Kun Zhang","doi":"10.1088/1361-6668/ad7645","DOIUrl":"https://doi.org/10.1088/1361-6668/ad7645","url":null,"abstract":"Medium-temperature baking (Mid-T baking) is an innovative method employed to enhance the unloaded quality factor Q0 of superconducting radio-frequency niobium (SRF Nb) cavities at cryogenic temperatures. This study presents an interstitial oxygen diffusion model based on the decomposition of the natural oxide to clarify the improved performance of the Nb cavities after undergoing Mid-T baking. Additionally, the correlation between the interstitial oxygen within the RF penetration depth and the surface resistance of the Nb cavities has been explored. The parameter for the oxide decomposition was determined using in-situ x-ray photoelectron spectroscopy (XPS), where the thickness of the oxide/carbide layer was calculated from the peak fitting of Nb 3d spectra and the attenuation law of the photoelectron beam. The interstitial oxygen diffusion model, validated by the semi-quantitative distribution along the depth determined by time-of-flight secondary ion mass spectrometry, quantifies the oxygen atomic concentration within the RF penetration depth in Mid-T baked Nb material. In the baking temperature range of 300 °C–400 °C, the calculated oxygen concentration from the interstitial oxygen diffusion model demonstrates a more pronounced dependence on the baking temperature than the baking time. This suggests that more precise control of the interstitial oxygen concentration can be achieved by adjusting the baking temperature. Furthermore, it has been observed that maintaining a uniform and moderate oxygen concentration throughout the depth is essential for optimal Bardeen–Cooper–Schrieffer resistance. This study paves the way for more efficient processing optimization and enhancing understanding of the mechanism behind RF loss in Nb cavities.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-06DOI: 10.1088/1361-6668/ad70de
P Kováč, D Berek, J Kováč, M Búran, M Hain, T Melišek, I Hušek
The Rutherford cable here was made of 12 single-core MgB2in-situ wires with an NbTi resistive barrier and a CuNi outer sheath. The uniformity of the wires and cables was analyzed using x-ray microtomography. The critical currents of the wire and cable samples were measured at 4.2 K in the outer fields from 4.0 to 8.0 T, and at 15 K–25 K in fields from 1.0 to 5.5 T. Magnetization AC losses were measured at temperatures of 20 K–40 K, external fields of 0.001–0.1 T and frequencies of 72 and 144 Hz. The obtained results show high engineering current density and reduced losses in the MgB2 cable, which can be especially interesting for windings of superconducting motors or generators.
这里的卢瑟福电缆由 12 根单芯 MB2 原位导线、铌钛电阻屏障和铜镍外护套组成。使用 X 射线显微层析成像分析了导线和电缆的均匀性。在温度为 20 K-40 K、外磁场为 0.001-0.1 T 和频率为 72 和 144 Hz 的条件下，测量了导线和电缆样品的临界电流。结果表明，MgB2 电缆的工程电流密度高，损耗小，特别适用于超导电机或发电机的绕组。
{"title":"A Rutherford MgB2 cable with resistive NbTi barriers and a CuNi30 sheath","authors":"P Kováč, D Berek, J Kováč, M Búran, M Hain, T Melišek, I Hušek","doi":"10.1088/1361-6668/ad70de","DOIUrl":"https://doi.org/10.1088/1361-6668/ad70de","url":null,"abstract":"The Rutherford cable here was made of 12 single-core MgB<sub>2</sub> <italic toggle=\"yes\">in-situ</italic> wires with an NbTi resistive barrier and a CuNi outer sheath. The uniformity of the wires and cables was analyzed using x-ray microtomography. The critical currents of the wire and cable samples were measured at 4.2 K in the outer fields from 4.0 to 8.0 T, and at 15 K–25 K in fields from 1.0 to 5.5 T. Magnetization AC losses were measured at temperatures of 20 K–40 K, external fields of 0.001–0.1 T and frequencies of 72 and 144 Hz. The obtained results show high engineering current density and reduced losses in the MgB<sub>2</sub> cable, which can be especially interesting for windings of superconducting motors or generators.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-05DOI: 10.1088/1361-6668/ad74a2
Chao Li, Gengyao Li, Ying Xin, Bin Li
High-temperature superconducting (HTS) magnets are promising in high field applications. However, due to inevitable joint resistance and flux creep, HTS magnets still face challenges in maintaining field stability in their closed-loop operation. HTS flux pumps can charge closed HTS magnets wirelessly, thus allowing lower cryogenic loading and more flexible arrangements in HTS magnet systems. In this work, a full-bridge flux pump using two AC field-controlled switches is proposed, which can charge HTS magnets during whole cycles. Therefore, the charging speed of the proposed full-bridge flux pump is at least one time larger than half-bridge flux pumps. A numerical model and an experimental prototype are developed to verify the working principle of the proposed full-bridge flux pump. Simulation and experimental tests are carried out to investigate the working characteristics of the proposed flux pump. The proposed flux pump has huge potential in the application scenarios where high charging speed is required.
{"title":"A full-bridge flux pump using two switches: numerical model and experimental prototype","authors":"Chao Li, Gengyao Li, Ying Xin, Bin Li","doi":"10.1088/1361-6668/ad74a2","DOIUrl":"https://doi.org/10.1088/1361-6668/ad74a2","url":null,"abstract":"High-temperature superconducting (HTS) magnets are promising in high field applications. However, due to inevitable joint resistance and flux creep, HTS magnets still face challenges in maintaining field stability in their closed-loop operation. HTS flux pumps can charge closed HTS magnets wirelessly, thus allowing lower cryogenic loading and more flexible arrangements in HTS magnet systems. In this work, a full-bridge flux pump using two AC field-controlled switches is proposed, which can charge HTS magnets during whole cycles. Therefore, the charging speed of the proposed full-bridge flux pump is at least one time larger than half-bridge flux pumps. A numerical model and an experimental prototype are developed to verify the working principle of the proposed full-bridge flux pump. Simulation and experimental tests are carried out to investigate the working characteristics of the proposed flux pump. The proposed flux pump has huge potential in the application scenarios where high charging speed is required.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-05DOI: 10.1088/1361-6668/ad74a0
Ruolin Wang, Haiwen Liu, Jiaxin Kuang, Hongliang Tian, Sidong Wang
The design of tunable dual-narrowband high-temperature superconducting (HTS) filter based on coding superconducting metamaterials aided by grey wolf algorithm (GWA) is proposed in this paper. By virtue of the characteristics of right/left-handed bands and scale of deep sub-wavelength, the tunable metamaterials unit loaded with varactor is designed, with coupling types of coding pairs further studied. A tunable sixth-order HTS filter circuit is then constructed, whose layout is effectively optimized by newly developed GWA method. Simulated frequency responses demonstrate that the center frequencies of dual-band respectively locate at 170.1–177.2 MHz (Band I) and 185.2–194.1 MHz (Band II), with 3 dB fractional bandwidth of 0.65%–0.61% and 0.62%–0.57%. The deeply miniaturized circuit size is 0.037 × 0.046 λ2g, and the close-to-band rejection level reaches 80 dB. Experimental results of fabricated prototype measured at 70 K validate the feasibility of described design method for high order tunable HTS filter.
{"title":"A tunable dual-narrowband HTS filter using coding superconducting metamaterials aided by grey wolf algorithm","authors":"Ruolin Wang, Haiwen Liu, Jiaxin Kuang, Hongliang Tian, Sidong Wang","doi":"10.1088/1361-6668/ad74a0","DOIUrl":"https://doi.org/10.1088/1361-6668/ad74a0","url":null,"abstract":"The design of tunable dual-narrowband high-temperature superconducting (HTS) filter based on coding superconducting metamaterials aided by grey wolf algorithm (GWA) is proposed in this paper. By virtue of the characteristics of right/left-handed bands and scale of deep sub-wavelength, the tunable metamaterials unit loaded with varactor is designed, with coupling types of coding pairs further studied. A tunable sixth-order HTS filter circuit is then constructed, whose layout is effectively optimized by newly developed GWA method. Simulated frequency responses demonstrate that the center frequencies of dual-band respectively locate at 170.1–177.2 MHz (Band I) and 185.2–194.1 MHz (Band II), with 3 dB fractional bandwidth of 0.65%–0.61% and 0.62%–0.57%. The deeply miniaturized circuit size is 0.037 × 0.046 λ2g, and the close-to-band rejection level reaches 80 dB. Experimental results of fabricated prototype measured at 70 K validate the feasibility of described design method for high order tunable HTS filter.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-04DOI: 10.1088/1361-6668/ad7174
Pierre Bernstein, Yiteng Xing, Jacques Noudem, Antonio Morandi, Pier Luigi Ribani, Giacomo Russo, Sebastien Lemonnier, Fabian Delorme
We report the levitation and guidance forces of two set-ups including a 120 mm diameter MgB2 disc cooled down to 20 K. The first one included the disc and a 30 mm thick and 100 mm diameter NdFeB magnet and is labelled as PM100 set-up. The second one called PM70 set-up included a 70 mm diameter and 35 mm thick magnet. All the measurements were carried out after cooling down the superconductor with a 30 mm separation between the magnet and the superconductor. Some remarkable results were obtained. It was reported by Xing et al (2024 Supercond. Sci. Technol.37 02LT01) that the levitation force measured with the PM100 set-up has reached the strong value of 678 N at 5 mm separation between the magnet and the superconductor. In this new report, in addition to a comparison of the levitation forces measured on both set-ups, we report guidance force measurements. We show that this force decreases for the PM100 set-up as the magnet-superconductor distance decreases, while the guidance force of the PM70 set-up increases, as was reported for set-ups including Halbach guideways sections. Reproducing the measured levitation forces with analytical models, we show, on the one hand, that the large levitation forces measured with the PM100 set-up are due to the non-homogeneity of the magnetic field above the PM100 magnet. On the other hand, we explain the behaviour of the PM70 set-up guidance force by the low modulation of the magnetic moment of the superconductor resulting from the magnet motion.
{"title":"Investigations of the behaviour of superconducting magnetic levitating set-ups including a large MgB2 disc and a smaller NdFeB magnet","authors":"Pierre Bernstein, Yiteng Xing, Jacques Noudem, Antonio Morandi, Pier Luigi Ribani, Giacomo Russo, Sebastien Lemonnier, Fabian Delorme","doi":"10.1088/1361-6668/ad7174","DOIUrl":"https://doi.org/10.1088/1361-6668/ad7174","url":null,"abstract":"We report the levitation and guidance forces of two set-ups including a 120 mm diameter MgB<sub>2</sub> disc cooled down to 20 K. The first one included the disc and a 30 mm thick and 100 mm diameter NdFeB magnet and is labelled as PM100 set-up. The second one called PM70 set-up included a 70 mm diameter and 35 mm thick magnet. All the measurements were carried out after cooling down the superconductor with a 30 mm separation between the magnet and the superconductor. Some remarkable results were obtained. It was reported by Xing <italic toggle=\"yes\">et al</italic> (2024 <italic toggle=\"yes\">Supercond. Sci. Technol.</italic> <bold>37</bold> 02LT01) that the levitation force measured with the PM100 set-up has reached the strong value of 678 N at 5 mm separation between the magnet and the superconductor. In this new report, in addition to a comparison of the levitation forces measured on both set-ups, we report guidance force measurements. We show that this force decreases for the PM100 set-up as the magnet-superconductor distance decreases, while the guidance force of the PM70 set-up increases, as was reported for set-ups including Halbach guideways sections. Reproducing the measured levitation forces with analytical models, we show, on the one hand, that the large levitation forces measured with the PM100 set-up are due to the non-homogeneity of the magnetic field above the PM100 magnet. On the other hand, we explain the behaviour of the PM70 set-up guidance force by the low modulation of the magnetic moment of the superconductor resulting from the magnet motion.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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