Experimental investigation to overcome the ramp-rate limitation of CICC superconducting magnets

RRL (ramp-rate limitation) is a phenomenon in which a magnet quenches before it reaches its apparent critical current. This paper is an experimental investigation not about the detailed influence of various parameters on the ramp-rate limitation, but about the general methodology to overcome it. A CICC (cable-in-conduit conductor) superconducting magnet has been made of three-strand NbTi triplet. The magnet produced a maximum 3.6 T/s ramp-rate at the inner most region. The temperature of the supercritical helium coolant was deliberately raised to investigate RRL-related quench. The main purpose of the experiment was to study RRL phenomena at the first and consecutive ramp-ups. If quench is avoided during the first ramp-up, the consecutive ramp-ups of the magnet have much higher resistance against the RRL. This paper describes several experimental observations of several interesting hysteretic characteristics of RRL