First results of a parametric study on coupling loss in subsize NET/ITER Nb/sub 3/Sn cabled specimen

The cable in conduit conductor for the ITER coils is required to function under pulse conditions and fields up to 13 T. A parametric study, restricted to a limited variation of the reference cable lay out, is necessary to identify the quantitative impact of manufacturing parameters on the coupling loss and to find out more precisely the value of the coupling loss time constant to be used in the AC loss computation. Here we present the first results of the AC coupling loss measurements on jacketed sub size conductors with variations in type of cabling, cabling stage, twist pitch and void fraction. The AC loss is determined mainly by the calorimetric way but partly also using a magnetometer. A sinusoidal AC field amplitude of 15-400 mT, superposed on a DC background field of B/sub dc/=0, 1 or 1.5 T, is applied to determine the coupling loss time constants for different specimens. The results up to now show large coupling current time constants especially for braided cables, for which n./spl tau/ can reach more than 1000 ms. For twisted cables with 81 strands n./spl tau/ values up to 300 ms are attained.<>