Development of critical current measurement standards

This paper deals with the development of criteria for critical current measurements. The two tasks investigated were: (1) the determination of critical current of short samples as a function of transition criterion, and (2) analysis of current transfer from sample holder to sample. Critical currents were measured using the equivalent resistivity criterion with sensitivities ranging from 10 -7 Ω-cm to 10 -12 Ω-cm and using the electric field criterion with sensitivities of 1 mV/cm to 100 nV/cm. Current transfer measurements were performed on monolithic conductors with critical currents greater than 1,000 amps. The results of the program are that no single measurement standard and no single test holder are suitable for all types of critical current measurements, and that sample holders must be designed with sufficiently large copper current contacts in order to minimize current transfer effects.