PERFORMANCE OF PANCAKE COILS OF PARALLEL CO-WOUND AG BSCCO TAPE CONDUCTORS IN STATIC AND RAMPED MAGNETIC-FIELDS/

Critical Currents are reported for several Ag/BSCCO single-pancake coi ls in static magnetic fields ranging from 0 to 5 T and temperatures Fr om 4.2 K to 105 K, The sample coils were co-wound of one to six tape c onductors in parallel. Since the closed loops formed In such an arrang ement could lead to eddy current heating or instability in changing fi elds,,one of the coils was also tested in helium gas, in fields ramped at rates of up to 1.5 T/s, For these quasi-adiabatic tests, at each t emperature the transport current was set just below the critical value for a preset static field of 3.3 or 4.9 T. The field was then rapidly ramped down to zero, held for 20 sec, and then ramped back up to the original value. The maximum observed temperature transient of about 1. 7 K occurred at 9 K, for a field change of 4.75 T. The temperature tra nsients became negligible when the sample was immersed In liquid heliu m. Above 30 K, the transients 1 K. These results give confidence co-wo und HTSC coils are stable In a rapidly-ramped magnetic field, without undue eddy current heating.