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Effect of edge cracks on critical current degradation in rebco tapes under tensile stress

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Superconductivity 2022年第1期1卷 52-62页

作者： Zhirong Yang Yi Li Peng Song Mingzhi Guan Feng Feng Timing Qu State Key Laboratory of Tribology Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China Department of Mechanical Engineering Advanced Manufacturing InstituteTexas Center for SuperconductivityUniversity of HoustonHoustonTX 77024USA Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China Lab of Intelligent Manufacturing and Precision Machining Tsinghua Shenzhen International Graduate SchoolTsinghua UniversityShenzhen 518055China

The slitting process for manufacturing REBa2Cu3O7δ(rebco,RE=Rare earth)tapes of required width significantly improves the production efficiency and reduces production costs.However,edge cracks induced by the slitting process of wide rebco tapes may cause premature degradation under high tensile stress in highfield magnets.Therefore,it is necessary to evaluate the effect of edge cracks of rebco tapes on the critical current(Ic)degradation.Firstly,Ic degradation under artificial cracks was measured to validate the applicability of linear elastic fracture mechanics for the rebco layer.The maximum circumferential stress criterion was used to derive the mixed-mode stress intensity factor of multiple oblique edge cracks.A semi-analytical model considering edge crack properties such as angleβ,spacing d,and length a,was built to evaluate the critical load and critical crack.We found that when the stress intensity factor at the crack tip is below KIC?2:3 MPa ffiffiffiffim p,edge cracks did not propagate.We examined commercial rebco tapes manufactured by two different processes,concluding that edge cracks in these tapes will not cause premature degradation.

关键词： rebco Degradation Stress intensity factor Multiple oblique edge cracks Fracture toughness

Interaction of Two Parallel Cracks in rebco Bulk Superconductors under Applied Magnetic Field

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Chinese Physics Letters 2016年第7期33卷 147-151页

作者：张朝霞薛峰苟晓凡 Faculty of Civil Engineering & Mechanics Jiangsu University College of Mechanics and Materials Hohai University

Interactions of two collinear and parallel a/b-plane cracks in rebco （where RE is a rare-earth element and usually Y is adopted） bulk superconductors under the Lorentz force resulted from the applied magnetic field are studied. By using the derived boundary integral equation for the crack problem of a cylindrical bulk superconductor under the applied magnetic field, we comprehensively investigate the stress intensity factor （SIF） of modes I and II at the crack tips of the two collinear and parallel cracks with their sizes, relative positions and the applied magnetic field. The calculated results show that in most cases, the SIF of mode I is found to be about tens of times of the one of mode II, and all the SIFs are always proportional to increase in the applied magnetic field, and the cracks near the center are more dangerous due to the larger Lorentz force.

关键词： of on is mode rebco for in

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rebco电缆接头端子制备工艺研究

低温与超导 2023年第8期51卷 1-4,11页

作者：赵川漪金环周超秦经刚肖冠宇刘海红中国科学院合肥物质科学研究院合肥230031 中国科学技术大学合肥230026

焊料填充法是制备rebco导体接头的常用方法。由于rebco带材对温度敏感,所以在制备接头过程中应严格控制焊料温度及操作时间。实验采用熔点为145℃的锡铅焊料(Pb_(32)Sn_(50)Sb_(0.1))制备rebco电缆接头,电缆接头部位的加热温度控制在18... 详细信息

焊料填充法是制备rebco导体接头的常用方法。由于rebco带材对温度敏感,所以在制备接头过程中应严格控制焊料温度及操作时间。实验采用熔点为145℃的锡铅焊料(Pb_(32)Sn_(50)Sb_(0.1))制备rebco电缆接头,电缆接头部位的加热温度控制在180℃左右。为评估该制备工艺下电缆接头的性能情况,在77 K、自场及4.2 K、10 T背场条件下测试了由该电缆绕制成的内插线圈的接头电阻。结果表明,在rebco电缆接头端子制备过程中未发生损伤且性能良好,证实了设计的电缆接头端子制备工艺可靠性高。

关键词： rebco CICC导体超导接头制备技术低温测试

聚变堆用堆叠型rebco超导股线的交流损耗特性研究

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低温与超导 2023年第11期51卷 29-36页

作者：周小盟赖小强左佳欣朱运鹏侯炳林李鹏远核工业西南物理研究院成都610041

制备了一种面向聚变堆磁体用的堆叠型rebco超导股线,采用电测法,用锁相放大器及数字采集卡对液氮环境下该种超导股线的传输损耗进行了测量。基于H公式对股线传输损耗进行了有限元模拟,并与实验值、理论值进行了对比,工频下不同加载电流... 详细信息

制备了一种面向聚变堆磁体用的堆叠型rebco超导股线,采用电测法,用锁相放大器及数字采集卡对液氮环境下该种超导股线的传输损耗进行了测量。基于H公式对股线传输损耗进行了有限元模拟,并与实验值、理论值进行了对比,工频下不同加载电流幅值下实验值与仿真值的平均差异为16.2%,验证了实验结果,为进一步研究更复杂情况下堆叠型rebco超导股线的交流损耗提供了参考。

关键词： rebco 堆叠型超导股线交流损耗 H公式

Optimizing coil configurations for AC loss reduction in rebco HTS fast-ramping magnets at cryogenic temperatures

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Superconductivity 2022年第3期3卷 133-142页

作者： Zhenan Jiang Honghai Song Wenjuan Song Rodney A.Badcock Robinson Research Institute Victoria University of WellingtonWellingtonNew Zealand Department of Physics and Astronomy State University of New York at Stony BrookNew YorkUSA James Watts School of Engineering University of GlasgowGlasgowUK

AC loss is one of the critical issues for designing rebco fast‐ramping magnets operating at cryogenic temperatures.There are many ways to reduce AC loss for coil windings.However,it is not clear which method is the most effective way to minimize AC loss in the coil windings for a given Ampere‐turns.In this work,we numerically studied coil configurations of several small superconducting magnets constructed from 12 mm SuperPower rebco coated conductors,for fast‐ramping application with the same Ampere‐turns to identify the lowest AC loss among them.The HTS magnets have a total turn number of 50 and inner diameter of 30 cm,carrying AC current operating in the temperature range of 20–40 K at 25 Hz.We incorporated several existing loss reduction strategies including spacing between the turns for single pancake coils,grading Ic values for the solenoid configuration,and applying flux diverters to shape the magnetic field around the coil windings.The simulation was implemented using a homogenized H‐formulation.Across all studied loss reduction methods,the use of flux diverters has the largest impact in AC loss reduction.The AC loss values in the solenoid winding comprising a stack of five single pancake coils with 0.1 mm turn‐to‐turn gap with the flux diverters agree well with those in the single pancake coil for 2 mm turn‐to‐turn gap with the flux diverters.Solenoid type coil configurations with flux diverters generate much smaller AC loss than the single pancake type with flux diverters when they generate the same center magnetic field.

关键词： Fast ramping magnet AC loss reduction H‐formulation rebco Flux diverters

Development of a Roebel structure transposed cable with in-plane bending of rebco tapes

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Superconductivity 2022年第3期3卷 73-82页

作者： Juan Wang Rui Kang Xin Chen Chao Yang Yingzhe Wang Chengtao Wang Qingjin Xu Accelerator Division Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China

A compact High Temperature Superconductor(HTS)cable that can carry large current is crucial for developing high field superconducting accelerator magnets.Herein,we are reporting a high current and low AC loss rebco cable that adopts the Roebel structure,but it is implemented by in‐plane bending stacked rebco tapes directly to realize the transposition,instead of by punching rebco tapes to the desired shape.The cable maximizes the utilization of the original rebco tapes,so that the material cost is significantly reduced comparing with the present“Roebel”rebco cable.Recently,a prototype cable has been successfully fabricated.The critical current of each rebco tape after cabling shows no degradation,and the cable’s measured critical current is 1939.8 A at 77 K and self‐field,which is very close to the predicted critical current by simulation.Calculations also show that the AC loss of the cable is lower compared with that of a simple rebco stack with the same cross‐section and current‐carrying capacity.In this paper,we first introduce the fabrication process of the cable.What follows is the measurement of the in‐plane bending performance of rebco tapes.Then,we present the design and fabrication of the prototype cable together with current‐carrying performance tests.Finally,the AC loss calculation and analysis of the cable are reported.

关键词： Transposed cable HTS rebco In‐plane bending High field magnet

Performance of highly flexible sub-cable for rebco Cable-In-Conduit conductor at 5.8 T applied field

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Superconductivity 2022年第3期3卷 127-132页

作者： Guanyu Xiao Huan Jin Chao Zhou Hongjun Ma Donghu Wang Fang Liu Huajun Liu Arend Nijhuis Arnaud Devred Institute of Plasma Physics Chinese Academy of SciencesPO Box 1126HefeiAnhui 230031China University of Science and Technology of China No.96JinZhai Road Baohe DistrictHefeiAnhui 230026China University of Twente Faculty of Science and Technology7522 NB EnschedeThe Netherlands European Organization for Nuclear Research(CERN) CH-1211 GenevaSwitzerland

Due to the high current capability and excellent flexibility,High Flexible rebco Cables(HFRC)have emerged as an important candidate for composite high‐temperature superconducting conductors.The rebco six around one Cable‐In‐Conduit Conductor(CICC)concept has been designed for application in the Central Solenoid(CS)coil of the China Fusion Engineering Test Reactor.In the application of fusion devices,the performance of CICC under electromagnetic(EM)loading and thermal stress is very important for reliable and economic operation.Therefore,a 1.22 m long sub‐cable with HFRC design for CICC was manufactured and tested at 4.2 K in a background magnetic field up to 5.8 T.The aim is to investigate the stability of the current‐carrying properties of the HFRC cable under electromagnetic and thermal cyclic loading.The test results show that the critical current(I_(c))of the HFRC cable reached 17.3 kA in a background magnetic field of 5.8 T at 4.2 K.Furthermore,no performance degradation was observed after 24 cycles of 80 kN/m peak load with a background field of 5.8 T and 8 warm‐up‐cool‐down cycles between 77 K and room temperature.The test results provide a good basis for the development of full‐size conductors in future magnet applications.

关键词： rebco HFRC cable CICC Electromagnetic cycling Performance degradation

Engineering-based design and fabrication procedure for mid-temperature rebco magnets accommodating the strong Ic anisotropy

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Superconductivity 2022年第1期1卷 34-44页

作者： Zili Zhang Benzhe Zhou Jianhua Liu Lei Wang Qiuliang Wang Institute of Electrical Engineering Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

An engineering-feasible design and fabrication procedure for REB2aCu3O7-x(rebco)magnets based on the strong Ic angle dependence at moderate temperatures(40–77 K)was developed.In this procedure,the Ic value of every rebco coil of the magnet is calculated from the Ic(B,θ)data of rebco tape at operating temperature with different applied fields,which is called the“full field-angle dependent Ic method.”This approach has significantly higher accuracy than the conventional method,which only focuses on the Ic value at the coil with the highest perpendicular field component.Additionally,the fitted lift factor at 45 K with different applied fields was closely related to the minimum Ic value at 77 K and 0.5 T.The engineering-feasible design and fabrication procedure for the rebco magnet was developed on the basis of the Ic values calculated via the“full field-angle dependent Ic method”and lifting-factor fitted method,and it had a design error ofrebco coils and will improve the applicability of rebco magnets in this temperature range.

关键词： rebco Current margin Angle dependence Artificial pinning center

rebco高温超导长带临界电流连续化测量及其均匀性表征

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中阿科技论坛（中英文） 2023年第7期 117-121页

作者：张永军李敏娟蔡传兵上海上创超导科技有限公司上海201401 上海大学物理系上海200444 上海市高温超导重点实验室上海200444

由于具有高临界转变温度(Tc)、高临界电流密度(Jc)和高上临界磁场(Bc2)等优点,第二代高温超导体(rebco,RE=稀土元素)得到广泛应用,临界电流(Ic)及其沿长度方向均匀性和n-值是重要的关键参数。文章综述了高温超导长带临界电流及其沿长度... 详细信息

由于具有高临界转变温度(Tc)、高临界电流密度(Jc)和高上临界磁场(Bc2)等优点,第二代高温超导体(rebco,RE=稀土元素)得到广泛应用,临界电流(Ic)及其沿长度方向均匀性和n-值是重要的关键参数。文章综述了高温超导长带临界电流及其沿长度方向均匀性以及n-值的测量方法,综合比较了各种测量方法的优缺点,并讨论了各种方法的适用范围、测量条件以及测试数据等,旨在为高温超导长带测量方案提供依据,为后续测量标准的制定提供参考。

关键词： rebco 高温超导长带临界电流测量方法 n-值