Effect of thermal cycles on critical current and AC loss for superconducting coils having positive or negative thermal expansion bobbin

The effect of thermal cycles between room and liquid-nitrogen temperatures on the critical current ([I.sub.c]) and AC loss of two superconducting coils is examined. The results have shown that a moderate expansion in the size of the bobbin has decreased the AC loss and that excessive expansion has reduced the [I.sub.c] and has increased the AC loss.