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Abstract

Direct current tests performed in the past on the conductor samples of the toroidal field (TF) ITER coils revealed degradation of current sharing temperature, T-cs. The degradation progresses with repetitive electromagnetic loading, and also with thermal cycles between 4.5 K and room temperature. This feature was observed on short samples in SULTAN test facility (EPFL-SPC, Switzerland) as well as in TF Insert Coil tests in CSMC test facility (Naka, Japan). We present three independent observations suggesting that initiation of sample quench followed by a fast current discharge, which normally complements every I-c and T-cs test in both SULTAN and CSMC, enhances the T-cs degradation rate. The exact mechanism of this contribution to the degradation remains unidentified.

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