Characteristics of High Temperature Operation in a Conduction Cooled (Nb,Ti)₃Sn Superconducting Magnet

Abstract

Intense investigations aiming at application workable at liquid nitrogen temperature have been performed, since the discovery of high temperature superconductors with the critical temperature T_c in excess of 77.3 K. Realization of practical superconductors at high temperature like 77.3 K is expected to significantly promote industrial development. The most important superconducting properties for application are the large critical current I_c and the high critical current density J_c. Especially, the large transport current in fields is a key parameter for power application. However, there exist many crucial issues in the J_c properties of high-T_c oxide superconductors. The flux creep behavior¹ is one of the difficult problems to be solved out for application at 77.3 K. Although the flux creep has been already understood through the model proposed by Anderson and Kim² in conventional low-T_c superconductors, it did not practically influence the usage at liquid helium temperature of 4.2 K for low-T_c superconductors, because of the negligibly small effect at 4.2 K. On the contrary, the extremely large flux creep phenomenon is observed at high temperature like 77.3 K in high-T_c superconductors. Therefore, the satisfactory solution of the flux creep is inevitable to realize a superconducting magnet employing high-T_c superconducting wires, which will be operated at 77.3 K, for instance.