Some considerations to the ITER snubbers

Efficiency high current accelerators are generally implemented in Tokamak fusion facility for heating and current driver purpose, where high voltage vacuum equipment is used. Due to that vacuum breakdown frequently occurs, snubber is often used as functional passive protection device to be inserted between the ion source and its acceleration power supply for arc quenching purpose where stray capacitance between its floating HV pole and ground plays the key role in designing the system. Due to the transformer effects of the core snubber, reactive voltage could be instantly generated by inserting time varying impedance in the main circuit to balance the suddenly disappeared resistance of the ion source, which limits the HV fault current. The stray capacitance is mainly due to the HV transmission lines. Based on the stray capacitance, time-varying resistor method and flux matching method are respectively developed for designing the snubbers. The two methods are integrated together from the basic transformer theory. By historically reviewing the requirements of ITER snubbers with experiments, it was found that varying impedance method may give more robust design.