USA INTERLABORATORY COMPARISON OF SUPERCONDUCTOR SIMULATOR CRITICAL-CURRENT MEASUREMENTS

An interlaboratory comparison of critical current (I-c) measurements w as conducted on the superconductor simulator, which is an electronic c ircuit that emulates the extremely nonlinear voltage-current character istic of a superconductor. These simulators are high precision instrum ents, and are useful for establishing the integrity of part of a super conductor measurement system. This study includes measurements from pa rticipating US laboratories, with NIST as the central, organizing labo ratory. This effort was designed to determine the sources of uncertain ty in I-c measurements due to uncertainties in the measurement apparat us, technique, or the analysis system. The participating laboratories measured the superconductor simulator with a variety of methods includ ing de and pulse. This comparison indicated the presence of systematic biases and higher variability at low voltages in the I-c determinatio ns of the measurement systems. All critical current measurements at a criterion of 10 mu V on the I-c simulator were within 2% of the NIST v alue for nominal critical currents of 2 and 50 A. These results could significantly benefit superconductor measurement applications that req uire high-precision quality assurance.