On the Design of ITER Snubbers

High current accelerators are required being 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 lifetime extension with arc quenching 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. Based on the stray capacitance, timevarying resistor method and flux matching method are respectively developed for designing the snubbers. The two methods are integrated together by the transformer theory in the paper. By historically reviewing the requirements of ITER 1 MV snubbers with the test verified new theory, it was found that varying impedance method with new core material could give more compact and reliable design for ITER-1 MV snubbers.