Ground-plane insulation failure in the first TPC superconducting coil

On August 27, 1980, an insulation failure occurred during the testing of the TPC (Time Projection Chamber) thin superconducting solenoid. The accident caused shorts between the ultra pure aluminum (UPA) secondary circuit and the superconducting coil. There were also shorts between thee UPA circuit and ground. The results of an analysis of experimental data taken at 5 millisecond intervals by a data logger and a PDP-11 computer are presented. The results of X-ray and ultrasonic tests and the results of the coil autopsy are discussed. From the evidence, a most probable cause for the failure is given.