STANDARD REFERENCE DEVICES FOR HIGH-TEMPERATURE SUPERCONDUCTOR CRITICAL-CURRENT MEASUREMENTS

Obtaining repeatable critical current measurements for a high temperat ure superconductor (HTS) is a challenging task, since HTSs are highly susceptible to degradation due to mechanical stress, moisture, thermal cycling and aging. This paper discusses the development of a high tem perature superconducting standard reference device (SRD) to address th ese measurement concerns and gives preliminary data on its characteris tics. An SRD is an HTS specimen that has had its critical current I(c) non-destructively evaluated. Because HTSs are sensitive to mechanical alterations, minor changes in sample preparation or mounting procedur e could yield large changes in the measured critical current. Prelimin ary data on SRDs made using Bi-based oxide tapes (2212) with an Ag sub strate are presented. Differences between two consecutive measurements of I(c) can typically change by 40%; these deviations have been reduc ed to almost-equal-to 4%.