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

Obtaining repeatable critical current measurements for a high temperature 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 temperature superconducting standard reference device (SRD) to address these measurement concerns and gives preliminary data on its characteristics. 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 procedure could yield large changes in the measured critical current. Preliminary data on SRDs made using Bi-based oxide tapes (2212) with an Ag substrate are presented. Differences between two consecutive measurements of I(c) can typically change by 40%; these deviations have been reduced to almost-equal-to 4%.