Varistor development for in-vessel magnetic field coils in nuclear fusion devices

So called “varistors”, based on doped ceramic materials (Clarke, 1999; Gupta, 1990; Garcia, 2022; Modine, 1988) could provide interesting functionality for future nuclear fusion scientific experiments and power plants. They are of special interest for passive in-vessel coils but also for protection of active in-vessel coil feedthroughs. Due to the special high vacuum, high radiation environment, commercially available components are not sufficient for the required parameters. The IPP1 decided to start a technology development project in cooperation with the IKTS2 to improve parameter space and to demonstrate feasibility of the concepts described in this paper. Also very first results of already developed low-voltage, high current-density varistors are given.