Study on Reproducibility of Transport Critical Current for HTSC
Standardization of the measurement procedure for transport critical current, which is the most important superconducting property of conductors, is expected in the fields of conductor fabrication for practical applications and magnet design. In VAMAS (the Versailles Project on Advanced Materials and Standards), in order to establish a standard procedure, much effort has been expended on this issue and studies on various aspects in I,-transport measurement have been performed. In this paper, we report the results on thermal cycle testing to verify the reproducibility of Is-transport measurement for Bi-system oxide/Ag composite conductors as a preliminary test for a round robin test (RRT). Two Bi-2223/Ag multifilamentary tapes, and a Bi-2212/Ag round shape wire are examined for htransport reproducibility with repeating measurement procedure including cooling from room temperature, Is-transport measurement at 77 K in zero magnetic field only for Bi-2223/Ag samples, It-transport measurement at 4.2 K in magnetic fields from 0 to 5 T, and heating to room temperature sequences. Two kinds of sample with low Ictransport show good reproducibility up to 10 times of the thermal cycle. The other kind of sample with high Is-transport show gradual degradation with repeating the measurement or steep degradation after several times of the thermal cycle. In RRT, variation less than 5% of Ic-transport is achieved except for some samples which show severe degradation.
KeywordsThermal Cycle Severe Degradation Composite Conductor Zero Magnetic Field Round Robin Test
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