Voltage Characteristics of Diodes Used for Passive Quench Protection of Low-Current Magnets

Cold diodes and resistors in parallel with the coils are keys components in the passive quench protection system of low-current (high inductance) superconducting magnets. The diodes prevent current from flowing in the circuits that are in parallel with sections of the superconducting coil when the magnet is being charged or discharged. The use of diodes and resistors in parallel with the superconducting coil sections reduce the peak voltages to ground and, in some cases, the hot-spot temperature in the magnet during a quench. This paper presents measurements of the onset (low current) forward voltage of several power diodes as a function of temperature and magnetic field.