Persistent Mode Operation of Bi₂Sr₂CaCu₂Ox/Ag Stacked Double Pancake Coils with Superconducting Joints

A persistent current mode magnet was successfully fabricated using Bi 2 Sr 2 CaCu 2 O x /Ag tapes. The magnet system consisted of four Bi 2 Sr 2 CaCu 2 O x /Ag double pancake coils as a magnet and a noninductively wound Bi 2 Sr 2 CaCu 2 O x /Ag–Au single pancake coil as a persistent current switch. The pancakes were stacked and jointed using a butt-jointing method to form a superconducting closed loop. Persistent current mode operation of the magnet was initiated in liquid helium, trapping a magnetic field of 1 T which corresponds to a loop current of 134 A. The voltage-current ( V–I ) characteristic of the closed loop was estimated from the decay of the trapped field. An index number in the V–I curve, n , above 30 and a loop resistance of 2×10 -10 Ω were observed for the loop current above 30 A after 116 hours.