Pulse Height Analysis of the Spike Signals on the Balance Voltage Observed in the LHD Helical Coils

摘要

Spike signals have been observed on the balance voltage of the superconducting helical coils of the Large Helical Device (LHD) during excitation tests. Pulse height analysis (PHA) was applied to the spike signals and the results show that the spike counts obey clear exponential distribution functions. The total intensity of spike signals reveals drastic decrease from the second run up to the same excitation point, which indicates a clear sign of training effect. Dependence of the measured count rate of spike signals on the coil current as well as excitation history seems very similar to that obtained by acoustic emission (AE) measurements for other coils.