Testing of a low-resistance joint of CICC for Indian tokamak SST-1

In the frame of CICC testing for sc coils of Indian tokamak SST-1 the soldered joint design was developed and tested up to 50 kA in a loop comprising the secondary winding of a sc transformer. The CICC (14.8/spl times/14.8 mm/sup 2/) was manufactured by Hitachi. It consists of 135 (3/spl times/3/spl times/3/spl times/5) Nb-Ti strands each 0.86 mm dia. In the current range from 10 kA to 45 kA the joint resistance remained almost constant (from 3.6 n/spl Omega/ to 4.0 n/spl Omega/) in the bias field of about 2 T. The temperature dependence of CICC quench current during its charging was measured and showed an excellent (98%) coincidence with critical current values of a single strand. The measured temperature increase of CICC was used to evaluate its self-field AC losses at different charging rates (1.3-1.8 kA/s) and then to estimate the transverse resistivity of the cable. Its low value (approximately 8/spl middot/10/sup -10/ /spl Omega//spl middot/m) most likely reflects the fact that the clean surfaces of the strands in the cable are too tightly pressed. This can negatively influence the CICC stability towards pulse electromagnetic disturbances.