Characterization of arcs in ICRF transmission lines

Too high voltages can cause arcs to develop within coaxial transmission lines of ICRF antennas. To avoid damage, arcing must be detected and the RF power switched off. To ensure a high level of safety, the specifications of the detectors have to be based on a fine characterization of arcs. A test bench comprising a coaxial resonator and a fast acquisition system makes it possible to analyze the effects of breakdowns on power, voltage, pressure and DC current in the electrodes. For different types of breakdowns (multipactor, vacuum arc and gas discharge) and different configurations (presence or not of magnetic field, level of injected power), we investigate the processes involved in the specific development of an arc inside a RF coaxial line. The resulting classification of phenomena and the impact on the operational system requirements are discussed.