FIRST RESULTS OF A PARAMETRIC STUDY ON COUPLING LOSS IN SUBSIZE NET ITER NB3SN 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 calorimetric way but partly also using a magnetometer. A sinusoidal ac field amplitude of 15-400 mT, superposed on a de background field of B-dc=0, 1 or 1.5 T, is applied to determine the coupling loss time constants for different specimen. The results up to now show large coupling current time constants especially for braided cables, for which n.tau can reach more than 1000 ms. For twisted cables with 81 strands n.tau values up to 300 ms are attained.