Experimental investigation on normal zone propagation in a close-packed superconducting solenoid

Results from quench dynamic process experiments are presented and discussed for a 30-cm bore, 5-T, close-packed superconducting solenoid using different magnet currents. From the experimental records of the potentials at several points within the winding, a clear picture of normal-zone propagation in the magnet has been obtained. Due to the simultaneous propagation in many layers and the many turns within the winding, normal-zone propagation in a magnet is much more complicated than in the superconductor. The velocity of the normal-zone propagation varies sharply with time; the maximum velocity being as much as two-orders-of-magnitude higher than the initial one. It is noted that the existing theory of normal-zone propagation in superconductor can provide the correct prediction only for the initial propagation velocity. Discussion related to the magnet self-protection performance is also presented.