Superconductor Science and Technology最新文献

{"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}

{"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}

{"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}

{"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 MgB₂ <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 MgB₂ 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}

{"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}

{"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}

{"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 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 <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}

{"title":"Molybdenum low-resistance thin-film resistors for cryogenic devices","authors":"Yu P Korneeva, M A Dryazgov, N V Porokhov, N N Osipov, M I Krasilnikov, A A Korneev, M A Tarkhov","doi":"10.1088/1361-6668/ad6adb","DOIUrl":"https://doi.org/10.1088/1361-6668/ad6adb","url":null,"abstract":"We present a study of thin-film Mo resistors for NbN electronics operating at cryogenic temperatures. The key step is the 0.5–1.5 keV ion cleaning–activation of NbN before Mo deposition, which allows us to obtain a high-quality Mo/NbN interface. This, together with an additional Al bandage layer in the area of the contact pads, allows us to reduce the contact resistance below 1 Ω. The quality of the interfaces is confirmed by transmission electron microscopy and x-ray reflectometry.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"58 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208381","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":"Responsibility of small defects for the low radiation tolerance of coated conductors","authors":"Raphael Unterrainer, Davide Gambino, Florian Semper, Alexander Bodenseher, Daniele Torsello, Francesco Laviano, David X Fischer, Michael Eisterer","doi":"10.1088/1361-6668/ad70db","DOIUrl":"https://doi.org/10.1088/1361-6668/ad70db","url":null,"abstract":"Rare-earth-barium-copper-oxide based coated conductors exhibit a relatively low radiation robustness compared to e.g. Nb₃Sn due to the <italic toggle=\"yes\">d</italic>-wave symmetry of the order parameter, rendering impurity scattering pair breaking. The type and size of the introduced defects influence the degrading effects on the superconducting properties; thus the disorder cannot be quantified by the number of displaced atoms alone. In order to develop degradation mitigation strategies for radiation intense environments, it is relevant to distinguish between detrimental and beneficial defect structures. Gadolinium-barium-copper-oxide based samples irradiated with the full TRIGA Mark II fission reactor spectrum accumulate a high density of point-like defects and small clusters due to <italic toggle=\"yes\">n</italic> - <italic toggle=\"yes\">γ</italic> capture reactions of gadolinium. This leads to a 14–15 times stronger degradation of the critical temperature compared to samples shielded from slow neutrons. At the same time both irradiation techniques lead to the same degradation behavior of the critical current density as function of the transition temperature <inline-formula>\u0000<tex-math><?CDATA $J_{mathrm{c}} (T_{mathrm{c}})$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>J</mml:mi><mml:mrow><mml:mrow><mml:mi mathvariant=\"normal\">c</mml:mi></mml:mrow></mml:mrow></mml:msub><mml:mo stretchy=\"false\">(</mml:mo><mml:msub><mml:mi>T</mml:mi><mml:mrow><mml:mrow><mml:mi mathvariant=\"normal\">c</mml:mi></mml:mrow></mml:mrow></mml:msub><mml:mo stretchy=\"false\">)</mml:mo></mml:mrow></mml:math><inline-graphic xlink:href=\"sustad70dbieqn1.gif\"></inline-graphic></inline-formula>. Furthermore, annealing the degraded samples displayed the same <inline-formula>\u0000<tex-math><?CDATA $T_{mathrm{c}}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mrow><mml:mrow><mml:mi mathvariant=\"normal\">c</mml:mi></mml:mrow></mml:mrow></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"sustad70dbieqn2.gif\"></inline-graphic></inline-formula> recovery rates, indicating the universality of the defects responsible for the degradation. Since the primary knock on atom of the <italic toggle=\"yes\">n</italic> - <italic toggle=\"yes\">γ</italic> reaction as well as the recoil energy is known, we used molecular dynamics simulations to calculate which defects are formed in the neutron capture process and density functional theory to assess their influence on the local density of states. The defects found in the simulation were mainly single defects as well as clusters consisting of Oxygen Frenkel pairs, however, more complex defects such as Gd<inline-formula>\u0000<tex-math><?CDATA $ ^{mathrm{Cu}}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msup><mml:mrow></mml:mrow><mml:mrow><mml:mi>C</mml:mi><mml:mi>u</mml:mi></mml:mrow></mml:msup></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"sustad70dbieqn3.gif\"></inline-grap","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208397","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":"Electromagnetic and thermal performance study on a canted stack of REBCO tapes","authors":"Mingyang Wang, Xuan’ang Meng, Xueliang Wang, Haosheng Ye, Xuan Zhou, Jie Sheng, Zhuyong Li, Zhijian Jin","doi":"10.1088/1361-6668/ad6e25","DOIUrl":"https://doi.org/10.1088/1361-6668/ad6e25","url":null,"abstract":"Due to the critical current limitation of a single rare-earth barium copper oxide (REBCO) tape, stacking methods are generally employed to increase the current carrying capacity in practical high-temperature superconducting (HTS) applications. However, the overall critical current is strongly dependent on the self-magnetic field, which is influenced by the geometrical arrangement of conductors in the stack. Due to their brittle ceramic properties, REBCO tapes are conventionally bent along the thickness side of the tape. However, the difference in bending radii of the outer and inner tape surfaces in the stack may lead to fracture deformation, thereby limiting the stacking number of REBCO tapes. To balance the stacking number with the bending issue, a canted stack is proposed as a variant of the normal stack for REBCO tapes. As a potential HTS intermediate component, it is imperative to conduct a comprehensive study on the electromagnetic and thermal performance of the canted stack. The unique geometrical arrangement of the canted stack introduces new factors that affect the critical current and transport AC loss. This paper concludes with the special influencing factors of canted stacks, including canted angle, stacking number, tape width, and spatial structure. The metal interleaving method is introduced for spatial distribution changing and thermal stability. Furthermore, orthogonal analysis is performed to elucidate the comprehensive correlation among these multiple factors. This study provides insights into the overall critical current and transport AC loss for different combinations of canted stack and establishes a predicting function for critical current to support the structural design of canted stacks. Based on the specific case study, the improved capability of the canted stack is confirmed by both experiments and simulations.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208398","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}