Quench detector for large pulsed coils and quench analysis for the LASL/Westinghouse 20 MJ coil

A unique detection scheme has been devised for possible use in the test of the 20 MJ Induction Heating Coil. This scheme allows the sensing of plus or minus voltages less than 320 millivolts resistive in magnitude in coils which will have inductive voltage components as high as ±2.5 kVolts. The network which achieves this sensitivity is stable to less than 12.8 ppm. The method adopted involves the bucking out of the inductive voltage with two secondary co-wound flux sensing coils tapped at locations adjacent to voltage taps in the main superconducting coil. The detection scheme is recommended especially if large ripple or control voltages exist subsequent to the coil pulse. The most severe credible event which might quench the coil and/or damage the winding is exposure of the operating coil to gaseous cooling through lack of proper liquid level control. The detection scheme described will protect the coil against this and other abnormal conditions that could conceivably damage the coil.