Experimental Study Of Electromagnetic Field Inverse Problem Of A HTS Tape With Defects Based On Micromagnetic Measurement

Because of the excellent electromagnetic properties,high temperature superconducting（HTS）materials have been widely concerned in the fields of high energy physics,high magnetic field and other modern high-tech and technological fields and gradually entered commercial application.But as a result of high temperature superconducting materials in heat treatment processing cooling cable and coil winding and operation process inevitably affected by mechanical force and high voltage magnetic effect,excessive deformation or force caused by the action of superconducting materials macroscopic defects such as cracks on internal flake off which cause the degradation of superconductivity of high temperature superconducting tape in the engineering application.This kind of phenomenon severely restricts the engineering application of high temperature superconducting tape.Because high temperature superconducting tape is composed of multiphase multicomponent materials preparation of multi-layer composite structure,all kinds of defects in the process of preparation or use of the damage can cause its mechanical or electromagnetic failure.It has become one of the key issues in the interdisciplinary and applied fields of high temperature superconductivity to explore the influence of defects on superconductivity of high temperature superconducting tape.Focusing on the influence of structural defects of REBCO HTS tape on the distribution characteristics of superconducting electromagnetic fields,a systematic experimental study on the distribution characteristics of electromagnetic fields and current density of REBCO coated HTS tape with defects（linear and circular）was carried out by using the research method of micromagnetic measurement experimental characterization and electromagnetic inversion methods.Firstly,the non-contact micromagnetic full-field detection platform of superconducting tape based on Hall probe scanning was build based on the third generation test system of force-electric coupling of superconducting material in low temperature environment and the synchronous full-field test and signal acquisition of current-carrying superconducting tape surface magnetic field were realized.The verification of the magnetic field on the surface of permanent magnet at room temperature and current distribution characteristics of ideal superconducting tape for current carrying was carried out and the results show that both the magnetic field checking method and the current density inversion method based on Fourier space BiotSavart law deconvolution operation proposed in this study have good reliability which lays a foundation for the subsequent research on the electromagnetic characteristics of non-ideal superconducting tape with defects.Secondly,the line defect area with different length（1mm,2mm and 3mm）at the edge of current carrying REBCO HTS tape was experimentally studied,and the influence of line crack defect on magnetic field distribution was obtained;based on the inversion method,the distribution of superconducting current density under different linear defects is analyzed.The results show that the magnetic field distribution and current density distribution in the tape area of the line defect show strong singularity.The extreme value of magnetic field magnetic induction intensity on the surface of the tape corresponds to the tip of the defect,which has a significant influence on the electromagnetic field distribution near the defect.And the longer the line defect,the greater the influence.Finally,an experimental study was carried out on the defects of current-carrying REBCO HTS tape with circular holes and semi-circular holes at the edges.The magnetic field distribution characteristics near the surface of the tape with defect was obtained through full-field scanning,and the current density distribution inside the superconducting tape with different defect shapes was obtained based on current density inversion.The results show that the magnetic field and current density distributions in the edge region of the superconducting tape with circular hole defects and boundary semi-circular defects show strong singularity under the condition of constant current.The extreme value of magnetic field induction intensity of superconducting tape with semicircle defect appears at semicircle boundary,which is similar to the result of linear defect...