Localization of electrical insulation failures in superconducting collaredcoils by analysis of the distortion of a pulsed magnetic field

The localization of possible electrical faults in superconducting accelerat or magnets may, in most cases, be a complex, expensive and time-consuming p rocess. In particular, inter-turn short circuits and failures of the ground insulation are well detectable when the magnet is collared, but often disa ppear after disassembly for repair due to the release of the pre-stress in the coils. The fault localization method presented in this paper is based on the measu rement and analysis of the magnetic field generated inside the magnet apert ure by a high voltage pulse. The presence of the fault modifies the distrib ution of the current in the coils and produces a distortion of the magnetic field, The described method aims at locating both the longitudinal and azi muthal position of the fault-affected area, The test method, the transient case FEM models and the implemented experimental set-up are presented and d iscussed for the LHC dipole models.