A plasma initiator using a multi-winding transformer for large tokamak devices and the application to the poloidal field coil power supply system

This paper describes a multi-winding transformer as a plasma initiator in tokamak devices and the application to the design of poloidal field coil power supply system. The scale of tokamak device has been considerably increased based on some experimentally obtained scalings of a energy confinement, because the plasma performance has been improved with the current and size parameters. Since large tokamaks require the hybrid functional poloidal field coil system, the each coil power supplies must prepare the high voltage generation circuit for the plasma breakdown, and it causes increase in the number of current interrupters, disconnectors and the resisters. Therefore, the plasma position and shape control tend to be difficult especially in the start-up phase of the discharge. The plasma initiator proposed in this paper makes the plasma initiation circuit to be simple by unification of the high voltage generation circuit. It has similar ampere-turn and permeance distribution with the tokamak device and produces the magnetic field necessary for plasma breakdown. An application to FER tokamak proposed by JAERI is also presented.