Ramp-rate limitation experiments using a hybrid superconducting cable

Abstract

Ramp-rate limitation experiments were done in a new facility at the MIT (Massachusetts Institute of Technology) Plasma Fusion Center. The features of this new facility include (1) a superconducting pulse coil that can superimpose high ramp-down rates, up to 25 T s(-1), (2 T in 80 ms) at a background field up to 5 T, (2) new power supplies that can supply high rates of dl/dt and dB/dt to the sample under test and (3) a forced-flow supercritical helium system for cooling CICCs (Cable-in-Conduit Conductors). This paper discusses the results of the ramp-rate limitation experiments on a 27-strand hybrid Nb3Sn cable. The cable was tested under field ramps of up to 2.5 T s(-1) with various operating currents. It did not quench with dB/dt, field and average strand currents that were simultaneously above the operating range of TPX-PF (Tokamak Physics Experiment Poloidal Field) coils. Further ramp-rate limitation experiments revealed that the tested 27-strand hybrid cable has very high transient stability at ramped fields, extending out to average strand currents that are nearly triple the TPX-PF operating current. (C) 1996 Elsevier Science Limited