Characterization of arcs in frequency domain

Arc detection systems are developed for ICRH on ITER to prevent arcs from damaging the RF components. One of the detectors, the Sub-Harmonic Arc Detector (SHAD) is based on the detection of the frequencies emitted in the MHz range by arcs [RI]. To ensure the high level of reliability required for this safety system, it is necessary to demonstrate that these frequencies present a signal with a Signal to Noise Ratio high enough to be detected under the wide range of operational conditions (frequency, power, configuration) and for the different types of arcs that can appear in the feeding lines and on the antennas (vacuum arc, glow discharge, multipactor-induced discharge). For each type of are, we analyze the evolution of the frequency spectrum relative to the evolution of other electrical parameters (reflected power, voltage).