NORMAL ZONE PROPAGATION IN ADIABATIC SUPERCONDUCTING MAGNETS OVER THE TEMPERATURE-RANGE 4.2-80-K

A theoretical analysis of operating temperature dependent normal zone propagation (NZP) has been performed in an adiabatic superconducting magnet over the temperature range 4.2-80 K. Because of the inverse dependence of NZP velocity on winding heat capacity, which increases sharply with temperature, above ≈ 20 K the normal zone hardly grows beyond its initial size and the hot spot temperature reaches well above 300 K. A computer simulation of NZP was applied to a small, two-coil solenoid system that was assumed to operate at any temperature between 4.2 and 80 K. The results corroborate the conclusion of the analysis: that the solenoid system is self-protecting for operating temperatures up to ≈ 20 K. This 'operational critical temperature' up to which an adiabatic magnet is self-protecting depends also on matrix current density and magnet size. © 1990.