Current Signals and X- Ray Spectra Analysis for a Vacuum High Voltage Holding Experiment

The High Voltage Padova Test Facility is an experimental device realized to investigate the high voltage insulation in vacuum in support of the negative neutral beam injector prototype for ITER, MITICA. Moreover, the experiment aims to give a contribution on the understanding of the voltage holding in vacuum, as a physical phenomenon. Two stainless steel electrodes, with few cm of gap in a high vacuum chamber, achieve a saturation breakdown value (up to 400 kV) after about ten hours. A highly time resolved X-ray diagnostic has been recently installed in the device, measuring the X events (single events are detected) produced during the high voltage conditioning: high energy fluxes are observed in correspondence to the current peaks collected by the electrodes. This contribution presents a characterization of the current and X-ray emission events in terms of frequency, amplitude and their occurrence with respect to the voltage between the electrodes.