The development of high temperature superconducting(HTS)tapes has recently made great progress,and Bi-based tapes(1 G) and YBCO coated conductor(2 G)are commercially fabricated with practical length.Application of HTS...The development of high temperature superconducting(HTS)tapes has recently made great progress,and Bi-based tapes(1 G) and YBCO coated conductor(2 G)are commercially fabricated with practical length.Application of HTS in electric power apparatuses made important achievement,various superconducting devices were demonstrated in grid,laying solid foundation for their commercialization.However,since their intrinsic microscopic defects such as weak-link,granularity,small second phase likely exist,critical current and index n value of the HTS tapes in practical length are impossible homogeneous,which have significant influences on safety,stability and efficiency of the HTS apparatuses.Therefore,critical current and index n value are two important parameters describing inhomogeneity of HTS tapes,thus two important indices for evaluating quality of practical long HTS tapes.This paper focuses on main progresses in inhomogeneity of critical current and index n value measurements on HTS tapes using contact-free methods.The statistical analytical methods evaluating the inhomogeneity of critical current and index n value are suggested.They can provide essential references for design and operation of HTS apparatuses.展开更多
High Temperature Superconductor(HTS)materials can operate at higher magnetic fields up to 20 T with high critical current and higher operating temperature,compared to low temperature superconductors(LTS).A Highly Flex...High Temperature Superconductor(HTS)materials can operate at higher magnetic fields up to 20 T with high critical current and higher operating temperature,compared to low temperature superconductors(LTS).A Highly Flexible REBCO Cable(HFRC)is introduced at the Institute of Plasma Physics,Chinese Academy of Sciences(ASIPP);a cabling method that is suitable for REBCO HTS tape having anisotropic material properties in its thin REBCO layer.This type of HTS superconducting cable shows high potential for applications in nuclear fusion.The alternating currents and magnetic fields in tokamak type of fusion magnets,cause AC power losses in such cables,which can provoke instability of the conductor by induced currents and increase the temperature.As a first step in characterizing the electromagnetic(EM)performance of an HFRC cable,the AC loss and contact resistance of the HFRC prototype cable were measured at the University of Twente.The measurements were done in liquid helium(4.2 K)with AC magnetic fields,applied perpendicular to the cable's long axis.The AC loss was measured simultaneously by a calibrated gas flow calorimeter utilizing the helium boil-off method,and by the magnetization method using pick-up coils.For the applied test conditions,no coupling loss could be distinguished as a part of the overall AC loss.It is suggested that this might be explained by the shielding of the conductor interior from the applied magnetic field by the outer tape layer due to the high critical current density of the REBCO tape,leading to a high penetration field.展开更多
基金supported by the Specialized Research Fund for the Doc-toral Program of Higher Education(Grant No.D00033)the Foundation of North China Electric Power University(Grant No.KH0194)
文摘The development of high temperature superconducting(HTS)tapes has recently made great progress,and Bi-based tapes(1 G) and YBCO coated conductor(2 G)are commercially fabricated with practical length.Application of HTS in electric power apparatuses made important achievement,various superconducting devices were demonstrated in grid,laying solid foundation for their commercialization.However,since their intrinsic microscopic defects such as weak-link,granularity,small second phase likely exist,critical current and index n value of the HTS tapes in practical length are impossible homogeneous,which have significant influences on safety,stability and efficiency of the HTS apparatuses.Therefore,critical current and index n value are two important parameters describing inhomogeneity of HTS tapes,thus two important indices for evaluating quality of practical long HTS tapes.This paper focuses on main progresses in inhomogeneity of critical current and index n value measurements on HTS tapes using contact-free methods.The statistical analytical methods evaluating the inhomogeneity of critical current and index n value are suggested.They can provide essential references for design and operation of HTS apparatuses.
基金supported by the Strategic Priority Research Program of Chinese Academy of Science under Grant No.XDB25000000Comprehensive Research Facility for Fusion Technology Program of China under Contract No.2018-000052-73-01-001228+2 种基金the National Nature Science Foundation of China(No.52077212)the Youth Innovation Promotion Association,Chinese Academy of ScienceChina Scholarship Council.
文摘High Temperature Superconductor(HTS)materials can operate at higher magnetic fields up to 20 T with high critical current and higher operating temperature,compared to low temperature superconductors(LTS).A Highly Flexible REBCO Cable(HFRC)is introduced at the Institute of Plasma Physics,Chinese Academy of Sciences(ASIPP);a cabling method that is suitable for REBCO HTS tape having anisotropic material properties in its thin REBCO layer.This type of HTS superconducting cable shows high potential for applications in nuclear fusion.The alternating currents and magnetic fields in tokamak type of fusion magnets,cause AC power losses in such cables,which can provoke instability of the conductor by induced currents and increase the temperature.As a first step in characterizing the electromagnetic(EM)performance of an HFRC cable,the AC loss and contact resistance of the HFRC prototype cable were measured at the University of Twente.The measurements were done in liquid helium(4.2 K)with AC magnetic fields,applied perpendicular to the cable's long axis.The AC loss was measured simultaneously by a calibrated gas flow calorimeter utilizing the helium boil-off method,and by the magnetization method using pick-up coils.For the applied test conditions,no coupling loss could be distinguished as a part of the overall AC loss.It is suggested that this might be explained by the shielding of the conductor interior from the applied magnetic field by the outer tape layer due to the high critical current density of the REBCO tape,leading to a high penetration field.
