A STUDY ON CORRELATION BETWEEN Jc(4.2 K) AND CURRENT SHARING TEMPERATURE Tcs OF Nb3Sn STRANDS AND SHORT SAMPLE OF CONDUCTOR FOR TOROIDAL FIELD COILS OF ITER MAGNET SYSTEM

One of the main requirements for ITER Nb3Sn Toroidal Field (TF) conductor is a temperature margin of 0.7 K under 11.8 T peak field, 68 kA operating current, and operating temperature of 5 K, i.e. current sharing temperature Tcs = 5.7 K, while the performance of Nb3Sn strands used for the fabrication of the conductor is evaluated by critical current density Jc(4.2 K, 12 T). This work represents an analysis of experimentally revealed correlation between Jc(4.2 K, 12 T) and Tcs of several Nb3Sn strands and short sample of the TF conductor RFTF2 tested in SULTAN facility (SULTAN sample). The performance of the strands used for SULTAN sample fabrication is investigated in details. The paper includes the analysis of voltage‐current and voltage‐temperature characteristics. An assessment of strain influence on the performance and transition parameters (n and T0) of the strands is also presented. The results obtained for strands are compared with the test results of SULTAN sample RFTF2.