Minimization of self-field effects in a YBa 2Cu 3O 7−δ superconducting annular conductor

Abstract

Measurements have been made on the transport critical-current density, J c, of a YBa 2Cu 3O 7−δ superconducting annulus as a function of internal magnetic field. A coaxial, current-return line was used to minimize the internal magnetic self-field generated by the transport current for an annular sample with an outer diameter of 0.98 cm and an inner diameter of 0.44 cm. Calculations of the area-averaged internal field as a function of fraction return current were performed and compared to measurements of sample voltage drop in the transition regime as a function of return current. Excellent agreement was obtained between experiment and calculation showing a minimum magnetic field effect for 40% coaxial return current. External magnetic fields were also used to investigate possible dependence of magnetic field orientation on transport current. Measurements of the sample magnetization were correlated with the magnetic field dependence of the transport measurements.