Pub Date : 2024-08-09DOI: 10.1088/1361-6668/ad6d9b
Xinyuan Liu, Xianping Zhang, C. Dong, Minghui Tang, C. Yao, Wenchao Li, Dongliang Wang, Yanwei Ma
122-type iron-based superconductors have attracted significant attention owing to their potential for high-field applications. Therefore, the study of the reaction mechanism is indispensable. In this work, the phase formation process and reaction kinetics of the Ba-K-Fe-As system were investigated in comparison with the Fe-As and Ba-Fe-As systems. Our findings suggest two main stages of the phase formation process: formation of the iron arsenide phase and its transformation to the 122-phase. It shows that FeAs forms slowly below 300°C in the Ba-K-Fe-As system, and the formation significantly accelerates at ~400°C. KFe2As2 starts to generate at ~640°C and gradually transforms into Ba0.6K0.4Fe2As2. Furthermore, using the Flynn-Wall-Ozawa method and the Kissinger method, the kinetic parameters of the exothermic peak at ~400-580°C for these three systems were obtained, including the most probable mechanism function f(α), apparent activation energy E, and apparent pre-exponential factor A. Our results suggest that all three systems exhibit complex reactions characterized by f(α) = (1-α)n (1 < n < 2). The presence of the kinetic compensation effect in the three systems was discovered, implying similarities in their respective reaction mechanisms. Additionally, influence mechanism of K doping on the apparent activation energy and reaction rate was analyzed.
{"title":"Phase formation and kinetic analysis of (Ba, K)Fe2As2 superconductor","authors":"Xinyuan Liu, Xianping Zhang, C. Dong, Minghui Tang, C. Yao, Wenchao Li, Dongliang Wang, Yanwei Ma","doi":"10.1088/1361-6668/ad6d9b","DOIUrl":"https://doi.org/10.1088/1361-6668/ad6d9b","url":null,"abstract":"\u0000 122-type iron-based superconductors have attracted significant attention owing to their potential for high-field applications. Therefore, the study of the reaction mechanism is indispensable. In this work, the phase formation process and reaction kinetics of the Ba-K-Fe-As system were investigated in comparison with the Fe-As and Ba-Fe-As systems. Our findings suggest two main stages of the phase formation process: formation of the iron arsenide phase and its transformation to the 122-phase. It shows that FeAs forms slowly below 300°C in the Ba-K-Fe-As system, and the formation significantly accelerates at ~400°C. KFe2As2 starts to generate at ~640°C and gradually transforms into Ba0.6K0.4Fe2As2. Furthermore, using the Flynn-Wall-Ozawa method and the Kissinger method, the kinetic parameters of the exothermic peak at ~400-580°C for these three systems were obtained, including the most probable mechanism function f(α), apparent activation energy E, and apparent pre-exponential factor A. Our results suggest that all three systems exhibit complex reactions characterized by f(α) = (1-α)n (1 < n < 2). The presence of the kinetic compensation effect in the three systems was discovered, implying similarities in their respective reaction mechanisms. Additionally, influence mechanism of K doping on the apparent activation energy and reaction rate was analyzed.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141921664","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 : 2024-08-09DOI: 10.1088/1361-6668/ad6d9d
T. Espenhahn, R. Hühne
Superconducting magnetic bearings usually combine a setup of permanent magnets and superconducting bulks. The bearing size is typically scaled up to increase the levitation force as the force density is limited in such setups due to the magnetic flux density and its spatial gradient. As alternative, the permanent magnets might be replaced by a superconducting coil. To test this, jointless coils were prepared by a wind and flip technology using coated conductors of different tape manufacturers. The realized pancake coils were studied at liquid nitrogen temperature. Numerical simulations yielded a magnetic field of up to 0.5 T at 77 K for coils with a inner diameter of 20 mm. The prepared coils were charged with a superconducting dynamo, in which two magnet configurations were tested. A clear dependence on the magnet size and frequency was found for the charging characteristics. A magnetic field of about 0.3 T at 77 K was imprinted in one of the coils. However, a degradation of the coils was found over time indicated by some delamination at the cutted edges, which reduced the maximum achievable magnetic field after a few weeks. Nevertheless, a fully superconducting bearing was realized with by combining the jointless coil with an additional YBCO bulk. After charging the coil with the dynamo, a levitation force of up to 10 N at 77 K was measured under zero-field cooling conditions. The generated levitation force decayed only slightly after charging indicating low losses in the coil.
超导磁悬浮轴承通常由永磁体和超导块体组合而成。由于磁通密度及其空间梯度会限制磁力密度，轴承的尺寸通常会按比例放大，以增加悬浮力。作为替代方案，可以用超导线圈代替永久磁铁。为了验证这一点，我们使用不同磁带制造商生产的涂层导体，通过卷绕和翻转技术制备了无接头线圈。我们在液氮温度下对已实现的薄饼线圈进行了研究。数值模拟得出，内径为 20 毫米的线圈在 77 K 时的磁场可达 0.5 T。用超导发电机为制备好的线圈充电，测试了两种磁铁配置。发现充电特性与磁铁尺寸和频率有明显的关系。其中一个线圈在 77 K 时产生了约 0.3 T 的磁场。然而，随着时间的推移，线圈出现了退化，切割边缘出现了一些分层，几周后，可达到的最大磁场也随之降低。尽管如此，通过将无接头线圈与额外的 YBCO 块体相结合，还是实现了全超导轴承。用发电机对线圈充电后，在零磁场冷却条件下，在 77 K 时测量到了高达 10 N 的悬浮力。产生的悬浮力在充电后仅有轻微衰减，这表明线圈中的损耗很小。
{"title":"A fully superconducting magnetic bearing with a jointless coil excited by a superconducting dynamo","authors":"T. Espenhahn, R. Hühne","doi":"10.1088/1361-6668/ad6d9d","DOIUrl":"https://doi.org/10.1088/1361-6668/ad6d9d","url":null,"abstract":"\u0000 Superconducting magnetic bearings usually combine a setup of permanent magnets and superconducting bulks. The bearing size is typically scaled up to increase the levitation force as the force density is limited in such setups due to the magnetic flux density and its spatial gradient. As alternative, the permanent magnets might be replaced by a superconducting coil. To test this, jointless coils were prepared by a wind and flip technology using coated conductors of different tape manufacturers. The realized pancake coils were studied at liquid nitrogen temperature. Numerical simulations yielded a magnetic field of up to 0.5 T at 77 K for coils with a inner diameter of 20 mm. The prepared coils were charged with a superconducting dynamo, in which two magnet configurations were tested. A clear dependence on the magnet size and frequency was found for the charging characteristics. A magnetic field of about 0.3 T at 77 K was imprinted in one of the coils. However, a degradation of the coils was found over time indicated by some delamination at the cutted edges, which reduced the maximum achievable magnetic field after a few weeks. Nevertheless, a fully superconducting bearing was realized with by combining the jointless coil with an additional YBCO bulk. After charging the coil with the dynamo, a levitation force of up to 10 N at 77 K was measured under zero-field cooling conditions. The generated levitation force decayed only slightly after charging indicating low losses in the coil.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141925048","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 : 2024-08-09DOI: 10.1088/1361-6668/ad6d9a
Alexia Mullings, P. Mensah, P. Cheetham, A. K. Das, Nagaraju Guvvala, Chul H. Kim, Sastry D Pamidi
Design innovations to manage the electric field enhancements and successful use of cryogenic epoxy EP37 as electrical insulation for high temperature superconducting (HTS) cables for electric aircraft applications are reported. Detailed finite element analysis (FEA) of the electric field distribution shows that the highest electric field is at the interface of the ground and electrical insulation layers. The FEA led to the design, fabrication, and experimental characterization of four model cables with stress cones and a direct bond of the ground and insulation layers. Enhanced partial discharge inception voltage (PDIV) was achieved in the model cables by minimizing the electric field enhancements at the ground layer interface. Using a helium gas mixture with 4 mol% H2, with higher intrinsic dielectric strength than pure helium, further enhanced the PDIV. The results warrant further studies on long HTS cables with EP37 as electrical insulation with a direct bond between the insulation and ground layers.
{"title":"Performance enhancements of HTS power cables by minimizing the electric field enhancements for electric transport applications","authors":"Alexia Mullings, P. Mensah, P. Cheetham, A. K. Das, Nagaraju Guvvala, Chul H. Kim, Sastry D Pamidi","doi":"10.1088/1361-6668/ad6d9a","DOIUrl":"https://doi.org/10.1088/1361-6668/ad6d9a","url":null,"abstract":"\u0000 Design innovations to manage the electric field enhancements and successful use of cryogenic epoxy EP37 as electrical insulation for high temperature superconducting (HTS) cables for electric aircraft applications are reported. Detailed finite element analysis (FEA) of the electric field distribution shows that the highest electric field is at the interface of the ground and electrical insulation layers. The FEA led to the design, fabrication, and experimental characterization of four model cables with stress cones and a direct bond of the ground and insulation layers. Enhanced partial discharge inception voltage (PDIV) was achieved in the model cables by minimizing the electric field enhancements at the ground layer interface. Using a helium gas mixture with 4 mol% H2, with higher intrinsic dielectric strength than pure helium, further enhanced the PDIV. The results warrant further studies on long HTS cables with EP37 as electrical insulation with a direct bond between the insulation and ground layers.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141922573","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 : 2024-08-09DOI: 10.1088/1361-6668/ad6d9c
Donghui Liu, Wanbo Wei, Yunkai Tang, Dongke Li
In recent years, there has been growing concern about the mechanical deformation induced by the screening currents in high-field high-temperature superconducting (HTS) magnets. Screening-current-induced mechanical damage and critical current degradation have emerged as significant issues in the design and operation of HTS magnets. Currently, it is a challenging topic to consider both the nonlinear E-J power-law relationship of the REBa2Cu3O7-x (REBCO) coated conductors (CCs) and the nonlinear interface-damaged constitutive relationship in the numerical simulation. This paper presents an electro-mechanical model combining T-A formulation with the cohesive zone model (CZM) for an epoxy-impregnated REBCO insert coil, taking into account the mechanical damage dependence of the critical current of REBCO CCs. The model is validated with experimental data. Additionally, numerical results indicate that delamination and current-carrying degradation in the coil are caused by the large electromagnetic force generated by the screening current during the high-field magnetization process. The effects of screening currents on the electromagnetic and mechanical properties of the coils exhibit a significant difference between scenarios with and without consideration of the damage-dependent critical current of REBCO CCs. The underlying mechanisms leading to edge and internal damage of the REBCO CC in the coil are clarified by different failure modes. Simulations neglecting the degradation of the critical current can overestimate the stress, strain, and damage zone growth of the coil, while underestimating the current-carrying deterioration in the high field. Furthermore, a detailed analysis is conducted on the screening-current-induced mechanical damage and critical current degradation under different background fields. Finally, the influences of the structural parameters, bobbin, overband and geometric position on the delamination damage and current-carrying degradation of the coil are further investigated. This work could provide theoretical references for the design and analysis of high-field HTS insert magnets.
近年来，人们越来越关注高场高温超导（HTS）磁体中屏蔽电流引起的机械变形。屏蔽电流引起的机械损伤和临界电流衰减已成为 HTS 磁体设计和运行中的重要问题。目前，在数值模拟中既要考虑 REBa2Cu3O7-x (REBCO) 涂层导体 (CC) 的非线性 E-J 幂律关系，又要考虑非线性界面损伤构成关系，是一个具有挑战性的课题。本文针对环氧树脂浸渍的 REBCO 插入线圈提出了一个结合 T-A 公式和内聚区模型 (CZM) 的电动力学模型，并考虑了 REBCO CC 临界电流的机械损伤依赖性。该模型通过实验数据进行了验证。此外，数值结果表明，线圈中的分层和载流性能下降是由高场磁化过程中屏蔽电流产生的巨大电磁力造成的。屏蔽电流对线圈电磁和机械性能的影响在考虑和不考虑 REBCO CC 损伤临界电流的情况下有显著差异。不同的失效模式阐明了导致线圈中 REBCO CC 边缘和内部损坏的基本机制。忽略临界电流衰减的模拟可能会高估线圈的应力、应变和损伤区的增长，同时低估高磁场中的载流衰减。此外，还详细分析了不同背景场下屏蔽电流引起的机械损伤和临界电流衰减。最后，进一步研究了结构参数、线盘、过带和几何位置对线圈分层损伤和载流劣化的影响。这项工作可为高场 HTS 插入磁体的设计和分析提供理论参考。
{"title":"Screening-current-induced mechanical damage and critical current degradation in epoxy-impregnated REBCO insert coils","authors":"Donghui Liu, Wanbo Wei, Yunkai Tang, Dongke Li","doi":"10.1088/1361-6668/ad6d9c","DOIUrl":"https://doi.org/10.1088/1361-6668/ad6d9c","url":null,"abstract":"\u0000 In recent years, there has been growing concern about the mechanical deformation induced by the screening currents in high-field high-temperature superconducting (HTS) magnets. Screening-current-induced mechanical damage and critical current degradation have emerged as significant issues in the design and operation of HTS magnets. Currently, it is a challenging topic to consider both the nonlinear E-J power-law relationship of the REBa2Cu3O7-x (REBCO) coated conductors (CCs) and the nonlinear interface-damaged constitutive relationship in the numerical simulation. This paper presents an electro-mechanical model combining T-A formulation with the cohesive zone model (CZM) for an epoxy-impregnated REBCO insert coil, taking into account the mechanical damage dependence of the critical current of REBCO CCs. The model is validated with experimental data. Additionally, numerical results indicate that delamination and current-carrying degradation in the coil are caused by the large electromagnetic force generated by the screening current during the high-field magnetization process. The effects of screening currents on the electromagnetic and mechanical properties of the coils exhibit a significant difference between scenarios with and without consideration of the damage-dependent critical current of REBCO CCs. The underlying mechanisms leading to edge and internal damage of the REBCO CC in the coil are clarified by different failure modes. Simulations neglecting the degradation of the critical current can overestimate the stress, strain, and damage zone growth of the coil, while underestimating the current-carrying deterioration in the high field. Furthermore, a detailed analysis is conducted on the screening-current-induced mechanical damage and critical current degradation under different background fields. Finally, the influences of the structural parameters, bobbin, overband and geometric position on the delamination damage and current-carrying degradation of the coil are further investigated. This work could provide theoretical references for the design and analysis of high-field HTS insert magnets.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141921207","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 : 2024-08-07DOI: 10.1088/1361-6668/ad68d1
M Houbart, J-F Fagnard, P Harmeling, J Dular, A R Dennis, D K Namburi, J H Durrell, C Geuzaine, B Vanderheyden and P Vanderbemden
The ability of bulk high-temperature superconductors to trap magnetic flux densities up to one order of magnitude larger than the saturation magnetization of conventional ferromagnetic materials offers the prospect of generating large magnetic flux density gradients. Combining multiple superconductors, akin to assembling a Halbach array of permanent magnets, may increase the generated gradient even further. The associated challenge is that superconductors are prone to demagnetization when exposed to field components perpendicular to their main magnetization direction. In the present work, we investigate the magnetic flux density gradient achieved with a pair of cubic, bulk, large-grain melt-textured superconductors in the presence of a background DC magnetic field at 77 K. We investigate the increase of the performance when decreasing the temperature down to 59 K. The studied configuration consists in two facing cubic YBa2Cu3O superconductors of 6 mm side with anti-parallel magnetization directions. It is obtained after the simultaneous magnetization of the samples followed by a rotation of 180∘ of the top superconductor. Although the background field reduces the trapped field ability of individual samples, it is shown that this phenomenon is significantly mitigated at 65 K and at 59 K compared to 77 K. The results reveal that a sample-to-sample distance ( mm) of the order of their size is sufficient to avoid any mutual demagnetization effect during the rotational motion. Furthermore, it is shown that decreasing the temperature is not only beneficial in increasing the field and field gradient achieved but also in extending the range of background fields in which the superconductor can be rotated without demagnetization. This superconducting assembly yields a magnetic flux density gradient exceeding that of an isolated superconductor and has the potential to surpass the capabilities of permanent magnets.
块状高温超导体捕获磁通密度的能力比传统铁磁材料的饱和磁化大一个数量级，这为产生大磁通密度梯度提供了前景。将多个超导体组合在一起，类似于组装一个由永磁体组成的哈尔巴赫阵列，可以进一步增加所产生的梯度。与此相关的挑战是，当超导体暴露在与其主磁化方向垂直的磁场成分中时，很容易发生退磁。在本研究中，我们研究了一对立方体、块状、大晶粒熔融质地超导体在 77 K 背景直流磁场下实现的磁通密度梯度。样品同时磁化后，顶部超导体旋转 180∘。虽然背景磁场降低了单个样品的磁场捕获能力，但与 77 K 相比，这种现象在 65 K 和 59 K 时得到了显著缓解。结果表明，样品与样品之间的距离（毫米）与其大小相当，足以避免旋转运动过程中的任何相互退磁效应。此外，研究还表明，降低温度不仅有利于增加所实现的磁场和磁场梯度，还有利于扩大背景磁场的范围，在此范围内，超导体可以旋转而不会退磁。这种超导组件产生的磁通密度梯度超过了孤立超导体的磁通密度梯度，并有可能超越永久磁铁的能力。
{"title":"Enhancing the magnetic field gradient between two superconductors with rotational motion under a background DC field","authors":"M Houbart, J-F Fagnard, P Harmeling, J Dular, A R Dennis, D K Namburi, J H Durrell, C Geuzaine, B Vanderheyden and P Vanderbemden","doi":"10.1088/1361-6668/ad68d1","DOIUrl":"https://doi.org/10.1088/1361-6668/ad68d1","url":null,"abstract":"The ability of bulk high-temperature superconductors to trap magnetic flux densities up to one order of magnitude larger than the saturation magnetization of conventional ferromagnetic materials offers the prospect of generating large magnetic flux density gradients. Combining multiple superconductors, akin to assembling a Halbach array of permanent magnets, may increase the generated gradient even further. The associated challenge is that superconductors are prone to demagnetization when exposed to field components perpendicular to their main magnetization direction. In the present work, we investigate the magnetic flux density gradient achieved with a pair of cubic, bulk, large-grain melt-textured superconductors in the presence of a background DC magnetic field at 77 K. We investigate the increase of the performance when decreasing the temperature down to 59 K. The studied configuration consists in two facing cubic YBa2Cu3O superconductors of 6 mm side with anti-parallel magnetization directions. It is obtained after the simultaneous magnetization of the samples followed by a rotation of 180∘ of the top superconductor. Although the background field reduces the trapped field ability of individual samples, it is shown that this phenomenon is significantly mitigated at 65 K and at 59 K compared to 77 K. The results reveal that a sample-to-sample distance ( mm) of the order of their size is sufficient to avoid any mutual demagnetization effect during the rotational motion. Furthermore, it is shown that decreasing the temperature is not only beneficial in increasing the field and field gradient achieved but also in extending the range of background fields in which the superconductor can be rotated without demagnetization. This superconducting assembly yields a magnetic flux density gradient exceeding that of an isolated superconductor and has the potential to surpass the capabilities of permanent magnets.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940707","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 : 2024-08-06DOI: 10.1088/1361-6668/ad68ab
Minghu Shen, Li Lei, Jian Ju, Hua Zong, Gaoyang Zhao and Pengrong Ren
In this work, a (Bi, Pb)2Sr2Ca2Cu3O10+δ ((Bi, Pb)-2223) solution with good film-forming capability and chemical stability was synthesized through using metal acetates as raw materials, acrylic acid as an additive, and anhydrous methanol as a solvent to adjust the sol formula. Subsequently, (Bi, Pb)-2223 thin films were fabricated on LaAlO3 (LAO) single-crystal substrates via dip-coating technology at different heat treatment temperatures, and the structures and properties of (Bi, Pb)-2223 films were characterized. It was found that when the sol stoichiometric ratio of Bi: Pb: Sr: Ca: Cu was controlled at 1.9: 0.35: 2: 2: 3 and the gel film was heat-treated at 860 °C and dwelled for 120 min in an mixed atmosphere of N2: O2 = 96: 4, the prepared thin film with a pure (Bi, Pb)-2223 superconducting phase exhibited excellent biaxial texture, a dense surface structure, and had a Tc of 106 K and a ΔTc of 6 K. The microstructure analysis revealed a layered epitaxial growth of the film along the LAO substrate with a regular arrangement of atoms and a consistent interlayer spacing.
{"title":"Preparation of high purity phase (Bi, Pb)-2223 superconducting films by sol–gel method","authors":"Minghu Shen, Li Lei, Jian Ju, Hua Zong, Gaoyang Zhao and Pengrong Ren","doi":"10.1088/1361-6668/ad68ab","DOIUrl":"https://doi.org/10.1088/1361-6668/ad68ab","url":null,"abstract":"In this work, a (Bi, Pb)2Sr2Ca2Cu3O10+δ ((Bi, Pb)-2223) solution with good film-forming capability and chemical stability was synthesized through using metal acetates as raw materials, acrylic acid as an additive, and anhydrous methanol as a solvent to adjust the sol formula. Subsequently, (Bi, Pb)-2223 thin films were fabricated on LaAlO3 (LAO) single-crystal substrates via dip-coating technology at different heat treatment temperatures, and the structures and properties of (Bi, Pb)-2223 films were characterized. It was found that when the sol stoichiometric ratio of Bi: Pb: Sr: Ca: Cu was controlled at 1.9: 0.35: 2: 2: 3 and the gel film was heat-treated at 860 °C and dwelled for 120 min in an mixed atmosphere of N2: O2 = 96: 4, the prepared thin film with a pure (Bi, Pb)-2223 superconducting phase exhibited excellent biaxial texture, a dense surface structure, and had a Tc of 106 K and a ΔTc of 6 K. The microstructure analysis revealed a layered epitaxial growth of the film along the LAO substrate with a regular arrangement of atoms and a consistent interlayer spacing.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940708","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 : 2024-08-06DOI: 10.1088/1361-6668/ad68ac
S Burioli, G Iannone, G De Marzi, D D’Agostino, G Avallone, A Gagno, M Bracco, A Leveratto, A Traverso, D Pedrini, R Valente, M Prioli, P Piccardo, A Malagoli, S Farinon and R Musenich
In the framework of studies on high-field magnets for future accelerators, a specific project called ASTRACT focuses on the effect of transverse strain on the critical current of Nb3Sn wires. The first phase of the project addresses the effects of strain imposed on Nb3Sn wires before heat treatment and the development of a procedure to directly compare critical current measurements with values extracted from magnetization cycles. A Nb3Sn RRP-Ti wire was deformed to different values of transverse strain (10%, 15%, 20%, and 25%), and long samples were collected for transport measurements at 4.2 K, in a background field ranging from 10 to 14 T. Short samples were used for magnetization measurements (VSM technique). Additionally, SEM images of the cross-section were collected at different longitudinal positions along the wire for each strain value. This paper proposes a method based on SEM image analysis and magnetization measurements analysis to study the effect of bundle deformation on transport properties. The procedure requires morphological information provided by SEM images after appropriate numerical processing. Verification through statistical comparison between the Ic transport and VSM data is also conducted. Direct critical current measurements showed no degradation due to deformation up to 25%. The method introduced, independent of transport data, can reach the same conclusions by considering the real shape of the bundles.
在未来加速器高磁场磁体研究框架内，一个名为 ASTRACT 的具体项目侧重于横向应变对 Nb3Sn 线临界电流的影响。该项目的第一阶段研究了热处理前施加在铌3硒导线上的应变的影响，并开发了一种程序，可将临界电流测量值与从磁化周期中提取的值直接进行比较。将 Nb3Sn RRP-Ti 金属丝变形到不同的横向应变值（10%、15%、20% 和 25%），并在 4.2 K 和 10 到 14 T 的背景场中采集长样品进行传输测量。此外，针对每个应变值，还在金属丝的不同纵向位置收集了横截面的 SEM 图像。本文提出了一种基于 SEM 图像分析和磁化测量分析的方法，用于研究线束变形对传输特性的影响。该方法需要 SEM 图像提供的形态信息，并经过适当的数值处理。此外，还通过 Ic 传输和 VSM 数据之间的统计比较进行了验证。直接临界电流测量结果表明，变形不超过 25% 不会导致电流下降。所引入的方法独立于传输数据，可通过考虑线束的实际形状得出相同的结论。
{"title":"A novel numerical approach for analyzing experimental data on critical current degradation in Nb3Sn wires caused by transverse deformations preceding heat treatment","authors":"S Burioli, G Iannone, G De Marzi, D D’Agostino, G Avallone, A Gagno, M Bracco, A Leveratto, A Traverso, D Pedrini, R Valente, M Prioli, P Piccardo, A Malagoli, S Farinon and R Musenich","doi":"10.1088/1361-6668/ad68ac","DOIUrl":"https://doi.org/10.1088/1361-6668/ad68ac","url":null,"abstract":"In the framework of studies on high-field magnets for future accelerators, a specific project called ASTRACT focuses on the effect of transverse strain on the critical current of Nb3Sn wires. The first phase of the project addresses the effects of strain imposed on Nb3Sn wires before heat treatment and the development of a procedure to directly compare critical current measurements with values extracted from magnetization cycles. A Nb3Sn RRP-Ti wire was deformed to different values of transverse strain (10%, 15%, 20%, and 25%), and long samples were collected for transport measurements at 4.2 K, in a background field ranging from 10 to 14 T. Short samples were used for magnetization measurements (VSM technique). Additionally, SEM images of the cross-section were collected at different longitudinal positions along the wire for each strain value. This paper proposes a method based on SEM image analysis and magnetization measurements analysis to study the effect of bundle deformation on transport properties. The procedure requires morphological information provided by SEM images after appropriate numerical processing. Verification through statistical comparison between the Ic transport and VSM data is also conducted. Direct critical current measurements showed no degradation due to deformation up to 25%. The method introduced, independent of transport data, can reach the same conclusions by considering the real shape of the bundles.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940710","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 : 2024-08-05DOI: 10.1088/1361-6668/ad680d
Amlan Datta, Kamal R Joshi, Giulia Berti, Sunil Ghimire, Aidan Goerdt, Makariy A Tanatar, Deborah L Schlagel, Matthew F Besser, Dapeng Jing, Matthew J Kramer, Maria Iavarone and Ruslan Prozorov
The effect of annealing on the superconducting properties of niobium single crystals was studied using optical, magnetic, and scanning tunneling microscopy (STM) methods. Pieces of the same crystal boule were studied before and after the annealing at 800 , 1400 , and near the melting point of niobium (2477 ). The initial samples had a high hydrogen content and low-temperature imaging revealed large hydrides (hundreds of micrometers) appearing below 190 K. The formation of these large precipitates is already completely suppressed by annealing at 800 . However, the overall superconducting properties of the annealed samples did not improve and, in fact, worsened. In particular, the superconducting transition temperature decreased, the upper critical field increased, and the pinning strength increased. In the STM study, the sample was annealed initially at 400 , measured, annealed at 1700 , and measured again. The STM revealed a ‘dirty’ superconducting gap with a significant spatial variation in tunneling conductance after annealing at 400 . The clean gap was recovered after annealing at 1700 . This is likely due to oxygen redistribution near the surface, which is always covered by oxide layers in as-grown crystals. Our results indicate that vacuum annealing at least up to 1400 , while removing a large percentage of hydrogen, introduces additional nanosized defects, likely hydride precipitates, that act as efficient pair-breaking and pinning centers. The dimensionless scattering rate is estimated to have increased from to about after annealing at 1400 . These results on single crystals differ drastically from those obtained in polycrystalline bulk niobium (i.e. cut from superconducting radio-frequency cavities), where annealing is known to have a significant positive effect that is attributed to the improvement of the crystalline structure masking the more subtle influence of the hydrides.
{"title":"The nontrivial effects of annealing on superconducting properties of Nb single crystals","authors":"Amlan Datta, Kamal R Joshi, Giulia Berti, Sunil Ghimire, Aidan Goerdt, Makariy A Tanatar, Deborah L Schlagel, Matthew F Besser, Dapeng Jing, Matthew J Kramer, Maria Iavarone and Ruslan Prozorov","doi":"10.1088/1361-6668/ad680d","DOIUrl":"https://doi.org/10.1088/1361-6668/ad680d","url":null,"abstract":"The effect of annealing on the superconducting properties of niobium single crystals was studied using optical, magnetic, and scanning tunneling microscopy (STM) methods. Pieces of the same crystal boule were studied before and after the annealing at 800 , 1400 , and near the melting point of niobium (2477 ). The initial samples had a high hydrogen content and low-temperature imaging revealed large hydrides (hundreds of micrometers) appearing below 190 K. The formation of these large precipitates is already completely suppressed by annealing at 800 . However, the overall superconducting properties of the annealed samples did not improve and, in fact, worsened. In particular, the superconducting transition temperature decreased, the upper critical field increased, and the pinning strength increased. In the STM study, the sample was annealed initially at 400 , measured, annealed at 1700 , and measured again. The STM revealed a ‘dirty’ superconducting gap with a significant spatial variation in tunneling conductance after annealing at 400 . The clean gap was recovered after annealing at 1700 . This is likely due to oxygen redistribution near the surface, which is always covered by oxide layers in as-grown crystals. Our results indicate that vacuum annealing at least up to 1400 , while removing a large percentage of hydrogen, introduces additional nanosized defects, likely hydride precipitates, that act as efficient pair-breaking and pinning centers. The dimensionless scattering rate is estimated to have increased from to about after annealing at 1400 . These results on single crystals differ drastically from those obtained in polycrystalline bulk niobium (i.e. cut from superconducting radio-frequency cavities), where annealing is known to have a significant positive effect that is attributed to the improvement of the crystalline structure masking the more subtle influence of the hydrides.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940709","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 : 2024-08-05DOI: 10.1088/1361-6668/ad68d5
Yicong Huang, Yao Wu, Haohui Zhang, Han Zhou, Wenzhi Zhang, Enhua Chen, Wenqian Liu, Chaoyun Zhang, Shangqing Li, Xiaoliang Wang, Daqian Liu, Xiuyan Peng and Jianxin Lin
We report on the fabrication, structural, and electrical transport characterizations of superconducting nanowire arrays based on nano-laser direct writing (NLDW). The thermal excitation-induced micro/nano fabrication based on the interactions between NLDW and superconducting Nb films was experimentally analyzed and simulated. Experimentally, the arrays of superconducting nanowires have an area of 190 × 190 with a critical transition temperature Tc of 7.8 K and a critical current density Jc of 20.8 MA cm−2 at 4.0 K. The width and arrangement of the nanowires are precisely controlled, exhibiting a minimal loss of 0.6 K in Tc and excellent Jc after LDW. The width of superconducting nanowires could be further optimized by adjusting parameters such as laser power, irradiation gap, and delay of points. Compared with electron beam lithography and focused ion beam, to some extent, the nanowires fabrication process based on NLDW provides a more efficient and cost-effective path for fabricating large-area superconducting circuits and devices.
我们报告了基于纳米激光直写（NLDW）的超导纳米线阵列的制造、结构和电传输特性。实验分析和模拟了基于 NLDW 和超导铌薄膜之间相互作用的热激发微/纳米制造。实验结果表明，超导纳米线阵列的面积为 190 × 190，临界转变温度 Tc 为 7.8 K，4.0 K 时的临界电流密度 Jc 为 20.8 MA cm-2。通过调整激光功率、照射间隙和点延迟等参数，可以进一步优化超导纳米线的宽度。与电子束光刻和聚焦离子束相比，基于 NLDW 的纳米线制造工艺在一定程度上为制造大面积超导电路和器件提供了一条更高效、更经济的途径。
{"title":"Large-area superconducting nanowire arrays fabricated by nano laser direct writing","authors":"Yicong Huang, Yao Wu, Haohui Zhang, Han Zhou, Wenzhi Zhang, Enhua Chen, Wenqian Liu, Chaoyun Zhang, Shangqing Li, Xiaoliang Wang, Daqian Liu, Xiuyan Peng and Jianxin Lin","doi":"10.1088/1361-6668/ad68d5","DOIUrl":"https://doi.org/10.1088/1361-6668/ad68d5","url":null,"abstract":"We report on the fabrication, structural, and electrical transport characterizations of superconducting nanowire arrays based on nano-laser direct writing (NLDW). The thermal excitation-induced micro/nano fabrication based on the interactions between NLDW and superconducting Nb films was experimentally analyzed and simulated. Experimentally, the arrays of superconducting nanowires have an area of 190 × 190 with a critical transition temperature Tc of 7.8 K and a critical current density Jc of 20.8 MA cm−2 at 4.0 K. The width and arrangement of the nanowires are precisely controlled, exhibiting a minimal loss of 0.6 K in Tc and excellent Jc after LDW. The width of superconducting nanowires could be further optimized by adjusting parameters such as laser power, irradiation gap, and delay of points. Compared with electron beam lithography and focused ion beam, to some extent, the nanowires fabrication process based on NLDW provides a more efficient and cost-effective path for fabricating large-area superconducting circuits and devices.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940713","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 : 2024-07-29DOI: 10.1088/1361-6668/ad650d
Julien Dular, Fredrik Magnus, Erik Schnaubelt, Arjan Verweij, Mariusz Wozniak
In this paper, we propose the Coupled Axial and Transverse currents (I) (CATI) method, as an efficient and accurate finite element approach for modelling the electric and magnetic behavior of periodic composite superconducting conductors. The method consists of a pair of two-dimensional models coupled via circuit equations to account for the conductor geometrical periodicity. This allows to capture three-dimensional effects with two-dimensional models and leads to a significant reduction in computational time compared to conventional three-dimensional models. After presenting the method in detail, we verify it by comparison with reference finite element models, focussing on its application to twisted multifilamentary superconducting strands. In particular, we show that the CATI method captures the transition from uncoupled to coupled filaments, with accurate calculation of the interfilament coupling time constant. We then illustrate the capabilities of the method by generating detailed loss maps and magnetization curves of given strand types for a range of external transverse magnetic field excitations, with and without transport current.
{"title":"Coupled axial and transverse currents method for finite element modelling of periodic superconductors","authors":"Julien Dular, Fredrik Magnus, Erik Schnaubelt, Arjan Verweij, Mariusz Wozniak","doi":"10.1088/1361-6668/ad650d","DOIUrl":"https://doi.org/10.1088/1361-6668/ad650d","url":null,"abstract":"In this paper, we propose the Coupled Axial and Transverse currents (I) (CATI) method, as an efficient and accurate finite element approach for modelling the electric and magnetic behavior of periodic composite superconducting conductors. The method consists of a pair of two-dimensional models coupled via circuit equations to account for the conductor geometrical periodicity. This allows to capture three-dimensional effects with two-dimensional models and leads to a significant reduction in computational time compared to conventional three-dimensional models. After presenting the method in detail, we verify it by comparison with reference finite element models, focussing on its application to twisted multifilamentary superconducting strands. In particular, we show that the CATI method captures the transition from uncoupled to coupled filaments, with accurate calculation of the interfilament coupling time constant. We then illustrate the capabilities of the method by generating detailed loss maps and magnetization curves of given strand types for a range of external transverse magnetic field excitations, with and without transport current.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141865757","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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