Critical currents of silverhyphen;sheathed bismuthhyphen;based tapes at 20 K: Small coils and field orientation anisotropy in external fields up to 20 T

摘要

Critical currents, including field orientation anisotropy, of silverhyphen;sheathed bismuthhyphen;based superconducting tapes, for both small coils and short samples, have been measured at 20 K (liquid hydrogen) in external fields up to 20 T. The performance of two small coils is consistent with the critical current data of short samples. One coil, at 20 K and in a field of 20 T, for example, produced a self field of 0.35 T (Ic=136 A;Jc=1.7times;104A/cm2). Shorthyphen;sample critical current data indicate that field orientation anisotropy is more pronounced at 20 K than at 4.2 K. At 20 K and 20 T, e.g.,Jc(Hpar;), critical current density in the parallel field orientation, is 5.23times;104A/cm2, whileJc(Hperp;), critical current density in the perpendicular field orientation, is 1.75times;104A/cm2, an anisotropy factor,Jc(Hperp;)/Jc(Hpar;), of 0.34. In the field range 2ndash;15 T, the anisotropy factor at 20 K ranges 0.51ndash;0.55. thinsp;