Superconductor Science and Technology最新文献

{"title":"Modeling of contact resistivity and simplification of 3D homogenization strategy for the H formulation","authors":"Sijian Wang, H. Yong, Youhe Zhou","doi":"10.1088/1361-6668/ad541f","DOIUrl":"https://doi.org/10.1088/1361-6668/ad541f","url":null,"abstract":"\u0000 The finite element method (FEM) provides a powerful support for the calculations of superconducting electromagnetic responses. It enables the analysis of large-scale high-temperature superconducting (HTS) systems by the popular H formulation. Nonetheless, modeling of contact resistivity in three-dimensional (3D) FEM is still a matter of interest. The difficulty stems from the large aspect ratio of the contact layer in numerical modeling. Nowadays, an available solution is to model the contact layer with zero thickness but requires the discontinuity conditions of the magnetic field. In this paper, the energy variational method is utilized to incorporate the contribution of contact resistivity into the H formulation. From the perspective of energy transfer, the contact resistivity is related to the energy dissipation of the radial current flowing through the contact interface. In terms of applications, this method can be employed to calculate the charging delay of no-insulation (NI) coils and the current sharing behaviors of CORC cables. One advantage of this model is that the magnetic field is continuous and hence can be easily implemented in FEM. Additionally, it requires fewer degrees of freedom and hence presents advantages in computational efficiency. Moreover, this method can be employed to simplify the 3D H homogeneous model for insulated coils. The above discussions demonstrate that the proposed model is a promising tool for the modeling of contact resistivity.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"3 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141266199","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":"Winding angle optimization and testing of small-scale, non-planar, high-temperature superconducting stellarator coils","authors":"P. Huslage, David Kulla, J. Lobsien, Tristan Schuler, Eve V Stenson","doi":"10.1088/1361-6668/ad5382","DOIUrl":"https://doi.org/10.1088/1361-6668/ad5382","url":null,"abstract":"\u0000 We designed and constructed two non-planar coils with high-temperature superconductors (HTS) based on shapes from the Wendelstein 7-X stellarator. Tape track orientation of the HTS was optimized to reduce the coil size as much as possible while staying within the strain limits of the Gadolinium Barium Copper Oxide (GdBCO) superconductor. This resulted in average coil radii of 0.23 m and 0.48 m at strain limits of up 0.45 % to for the coil shapes that were chosen. The coils were produced by winding the GdBCO tapes onto 3D-printed plastic frames. We confirmed the integrity of the superconducting layer after winding by spatially resolved measurement of the critical current and by energizing the coils in liquid nitrogen. Coil 1 showed a resistance of 1.75 µΩ and did not have any critical current degradation, while coil 5 had a resistance of 195 µΩ and showed only one dropout, attributable to a handling error. We measured the magnetic field of the coil with a 3-axis Hall probe system and found good agreement with predictions. This work demonstrates the manufacturing of small-scale, non-planar magnetic coils from commercially available HTS.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"44 40","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141270200","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":"Enhancement of electron-phonon coupling due to increased magnetism and applied hydrostatic pressure in FeSe","authors":"Xiaofang Ouyang, Zeyi Song, Yuzhong Zhang","doi":"10.1088/1361-6668/ad5383","DOIUrl":"https://doi.org/10.1088/1361-6668/ad5383","url":null,"abstract":"\u0000 Inspired by the parabolic trend of the superconducting transition temperature(Tc) of bulk FeSe under hydrostatic pressure, we investigated the effect of magnetism and hydrostatic pressure on the electron-phonon coupling (EPC) in FeSe using density-functional perturbation theory. We found that both magnetism and hydrostatic pressure enhanced EPC. The enhancement of the EPC is mainly attributed to phonon softening and deformation potential induced by magnetism, rather than Fermi surface nesting. Furthermore, we investigated the effect of spin fluctuations on superconductivity by applying the random phase approximation method (RPA). A possible application of our results to the phase diagram of FeSe under hydrostatic pressure was discussed, and we demonstrated that when EPC and spin fluctuations are both considered, a parabolic superconducting Tc may be obtained, providing a plausible explanation for the phase of FeSe under hydrostatic pressure.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"19 18","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141270912","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":"Superconductivity in breathing kagome-structured C14 Laves phase XOs2(X = Zr, Hf)","authors":"P K Meena, M Mandal, P Manna, S Srivastava, S Sharma, P Mishra and R P Singh","doi":"10.1088/1361-6668/ad4a32","DOIUrl":"https://doi.org/10.1088/1361-6668/ad4a32","url":null,"abstract":"Recently, the emergence of superconductivity in kagome metals has generated significant interest due to its interaction with flat bands and topological electronic states, which exhibit a range of unusual quantum characteristics. This study thoroughly investigates largely unexplored breathing kagome structure C14 Laves phase compounds XOs2 (X = Zr, Hf) by XRD, electrical transport, magnetization, and specific heat measurements. Our analyses confirm the presence of the MgZn2-type structure in ZrOs2 and HfOs2 compounds, exhibiting type-II superconductivity with critical temperature ( ) values of 2.90(3) K and 2.69(6) K, respectively. Furthermore, specific heat measurements and electron–phonon coupling constants for both compounds indicate weakly coupled fully gapped superconductivity.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141168818","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":"Low field anomaly in the critical current of Ba1‑xKxFe2As2 tapes","authors":"N. Strickland, Shen V Chong, Chiheng Dong, Xianping Zhang, Yanwei Ma, Zhenan Jiang","doi":"10.1088/1361-6668/ad4f5d","DOIUrl":"https://doi.org/10.1088/1361-6668/ad4f5d","url":null,"abstract":"\u0000 Ba1-xKxFe2As2 superconductors have strong potential for magnet applications through their very high upper critical field, relatively high superconducting transition temperature and manufacturability through the powder-in-tube (PIT) route. However, the critical current density in PIT tapes is still low compared to the incumbent technologies, so a greater understanding of the limiting factors is required. We have measured in-field critical currents (Ic) of stainless steel and silver double-sheathed monofilament Ba0.6K0.4Fe2As2 superconductor tapes at elevated temperatures from 15 K to 35 K. At 20 K the critical current density is up to 140 kA/cm2 in low (optimal) field and 22 kA/cm2 in 8 T. In the low-field region we observe an anomalous and sharp suppression of Ic centred at zero field. This feature is non-hysteretic for lower temperatures and perpendicular field, but becomes hysteretic for higher temperatures in perpendicular field and all temperatures in parallel field. The low-field suppression is reflected also in the n-values which can otherwise be very high, in excess of 100, in optimal field. Magnetic-field hysteresis of Ic is generally attributed to flux exclusion / flux trapping in granular superconductors and this is likely to be the case also in the present conductors. The low-field Ic anomaly also likely has its origin in the planar granularity, while magnetic phases in grains or grain boundaries may also play a role.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"34 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141109346","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":"Current sharing in double-sided REBCO tapes","authors":"Shengchen Xue, Yi Li, Lingfeng Zhu, Bhabesh Sarangi, Jithin sai sandra, Jian Rong, Nghia Mai, Siwei Chen, Atik Chavda, Umesh Sambangi, Jithin Peram, Prakash Parthiban, V. Selvamanickam","doi":"10.1088/1361-6668/ad4e76","DOIUrl":"https://doi.org/10.1088/1361-6668/ad4e76","url":null,"abstract":"\u0000 Current sharing between RE-Ba-Cu-O (REBCO, RE=rare earth) tapes within a high-temperature superconducting (HTS) coil or cable is important to avoid damage from uncontrolled quench of superconducting devices operating at high currents. Current sharing between REBCO tapes is found to be limited by contact resistivity between the adjacent tapes, which is about 20x higher in the REBCO-facing-substrate (face-to-back) configuration that is commonly used in devices compared to a REBCO-facing-REBCO (face-to-face) configuration. Double-sided REBCO tapes always offer face-to-face contacts between adjacent tapes, and this benefit for excellent current sharing has been validated in experiments wherein an artificial defect is introduced in one tape in a 2-ply tape stack. Additionally, current sharing between the two REBCO layers within one double-sided REBCO tape has also been investigated. Slotting of the double-sided tapes, wherein slots through the insulating buffer stack are filled with a conductive material, has been found to significantly enhance the current sharing from one REBCO layer to the opposite layer.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"16 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141114567","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":"Estimation of magnetic levitation and lateral forces in MgB2 superconducting bulks with various dimensional sizes using artificial intelligence techniques","authors":"Shahin Alipour Bonab, Yiteng Xing, Giacomo Russo, Massimo Fabbri, A. Morandi, Pierre Bernstein, Jacques G Noudem, M. Yazdani-Asrami","doi":"10.1088/1361-6668/ad4e77","DOIUrl":"https://doi.org/10.1088/1361-6668/ad4e77","url":null,"abstract":"\u0000 The advent of superconducting bulks, because of their compactness and performance, offers new perspectives and opportunities in many applications and sectors, such as magnetic field shielding, motors/generators, NMR/MRI, magnetic bearings, flywheel energy storage, Maglev trains, among others. The investigation and characterization of bulks typically relies on time-consuming and expensive experimental campaigns; hence the development of effective surrogate models would considerably speed up the research progress around them. In this study, we have first produced an experimental dataset with the levitation and lateral forces between different MgB2 bulks and one permanent magnet under different operating conditions. Next, we have exploited the dataset to develop surrogate models based on Artificial Intelligence (AI) techniques, namely Extremely Gradient Boosting (XGBoost), Support Vector Machine Regressor (SVR), and Kernel Ridge Regression (KRR). After the tuning of the hyperparameters of the AI models, the results demonstrated that SVR is the superior technique and can predict levitation and lateral forces with a worst-case accuracy scenario 99.86% in terms of goodness of fit to experimental data. Moreover, the response time of these models for prediction of new datapoints is ultra-fast.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"129 19","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141115094","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 route to fabricate low resistance joints between Eu–Ba–Cu–O bulk, single grain superconductors","authors":"J V J Congreve, Y Shi, N C Tutt, R W Taylor, C Bumby, A R Dennis, H Druiff, D Weerakonda Arachchilage, J H Durrell and D A Cardwell","doi":"10.1088/1361-6668/ad44ea","DOIUrl":"https://doi.org/10.1088/1361-6668/ad44ea","url":null,"abstract":"The fabrication of large (RE)–Ba–Cu–O single grains [(RE)BCO], where RE = Y, Gd, Eu or Sm, with the complex geometries required for many practical applications is currently limited by the time intensive, complex nature of the grain growth process. In addition, the shapes achievable using established melt processing techniques, such as top seeded melt growth, are constrained significantly by the limited number of post-processing techniques readily available. Machining of these materials is also difficult given their ceramic-like mechanical properties, which makes them both brittle and hard. A potential alternative to the slow and inflexible melt growth processes is to join many small, single grains to form one large composite grain, connected by electrically and mechanically high-performance joints. A reliable joining technique would also greatly reduce the need for post-growth machining processes. In this work we extend our previous investigation of the use of single grain YBCO-Ag as an intermediate joining material to achieve effective and reliable superconducting joints between EuBCO-Ag bulk, single grain superconductors. The technique reported in the earlier studies requires limited specialist equipment and does not require tight process parameter control, since there is no need to re-grow the joining material at the intergrain interface. This technique is of particular interest given that the difference between the peritectic temperatures of the bulk superconductor and the intermediate joining material is large. We report the properties of seven joints engineered at different joining temperatures. The trapped field properties of the resulting joined samples were measured and the microstructure at the position of the joint examined. We demonstrate that this simple and the rapid joining technique makes it possible to manufacture composite grains in an industrially important (RE)BCO bulk superconductor with comparable superconducting properties to those of a single grain of similar dimensions.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"140 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141149008","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":"23 Tesla high temperature superconducting pocket magnet","authors":"Chukun Gao, Pin-Hui Chen, Nicholas Alaniva, Snædís Björgvinsdóttir, Ioannis Pagonakis, Alexander Däpp, Michael Urban, Ronny Gunzenhauser and Alexander Barnes","doi":"10.1088/1361-6668/ad44df","DOIUrl":"https://doi.org/10.1088/1361-6668/ad44df","url":null,"abstract":"We present a compact 23 T no-insulation (NI) magnet that was wound with 60 m of 10 mm wide high temperature superconducting (HTS) tape. The magnet consists of only one pocket-sized double pancake (DP) coil with an inner diameter of ∼6 mm, a height of 20 mm, and an outer diameter of 41.6 mm. Another NI coil of similar size but with a larger inner diameter of 8 mm reached a slightly lower magnetic field of 21 T. We also present a smaller coil which was wound with only 20 m of HTS tape and still achieved a magnetic field of 16 T. During the experiments in liquid helium, each coil was charged to a current between 690 A and 850 A, corresponding to a high current density of 1500–1900 A mm−2. The small bore size and high current density contributed to the high fields generated by these coils. We present the fabrication details, helium tests and repeatability analysis of these ‘pocket’ magnets.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"162 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141149010","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":"Crossover from Cooper-pair hopping to single-electron hopping in Pb x (TiO2) 1−x granular films","authors":"Zhi-Hao He, Zi-Yan Han, Kuang-Hong Gao, Zi-Wu Wang and Zhi-Qing Li","doi":"10.1088/1361-6668/ad4a35","DOIUrl":"https://doi.org/10.1088/1361-6668/ad4a35","url":null,"abstract":"The electrical transport properties of Pbx(TiO2) (x being the Pb volume fraction and ranging from ∼0.45 to ∼0.72) granular films are investigated experimentally. The charging energy of the Pb granules is reduced to less than the superconducting gap of Pb granules for the low temperature insulating films by using high-k dielectric TiO2 as the insulating matrix. For the insulating films in the vicinity of the superconductor-insulator transition, Cooper-pair hopping governs the low-temperature hopping transport. For these films, the low-temperature magnetoresistance is positive at low field and the resistivity vs temperature for Cooper-pair hopping obeys an Efros–Shklovsii-type variable-range-hopping law. A crossover from Cooper-pair-dominated hopping to single-electron-dominated hopping is observed with decreasing x. The emergence of single-electron-dominated hopping in the more insulating films is due to the causation that the intergrain Josephson coupling becomes too weak for Cooper pairs to hop between adjacent Pb granules.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141149027","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}