High Tc superconductor voltage-current simulator and the pulse method of measuring critical current

Abstract

A passive voltage-current ( V-I) simulator has been developed and tested using conventional direct current (d.c.) and pulse current methods. The simulator was designed to generate the extremely non-linear V-I characteristic of a superconductor and has a similar power-law behaviour. It is intended to be used to test various components of the measurement system such as instrumentation, measurement method and data analysis software, to determine the transport critical current, I c, or critical current density, J c, of a superconductor. This simulator does not emulate all the subtle effects of flux flow in a superconductor. However, it approximates a superconductor's major static and dynamic electrical characteristics. The simulator is therefore a necessary but incomplete test of a measurement system. Critical currents obtained on the simulator using the pulse and d.c. methods are compared and show close agreement. Also, preliminary comparisons of methods using bulk and thin film YBCO samples are given.