Superconductor Science and Technology最新文献

{"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":"90 22","pages":""},"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}

{"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":"18 23","pages":""},"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}

{"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":"67 23","pages":""},"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}

{"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":"15 4","pages":""},"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}

{"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":"11 1","pages":""},"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}

{"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":"23 1","pages":""},"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}

{"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":"99 1","pages":""},"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}

{"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":"57 1","pages":""},"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}

{"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":"134 1","pages":""},"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}

{"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":"67 1","pages":""},"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}