Methods for Producing the Plasma Initiation Pulse in Ohmic Heating Circuits in Tokamak Power Reactors: Resistive Dissipation, Transient Inductive Storage, and Transient Capacitive Storage

The plasma initiation phase occurring at the beginning of the operating cycle of a tokamak has the role of transforming a weakly ionized high resistance gas into a low resistance plasma type discharge. A plasma initiation pulse achieves this transformation transmitting a high energy at high voltage (150-400 MJ at 60-80 kV for the EPR design) for tens of milliseconds duration. A recent study 1 showed that for EPR design using the resistive dissipation method, the pulse producing module represents by far the most costly part of the ohmic heating system. This paper compares the resistive dissipation method with transient storage methods: inductive and capacitive. While the capacitive method is relatively well known through its variant, the >Inall circuit,> the inductive transient storage method to produce the plasma initiation pulse is less well known. It consists of two closely coupled coils, one connected with a system of differentially compounded slow discharge homopolar machines. The magnetic energy is suddenly taken from the ohmic heating circuit and temporarily stored in the mutual inductance of the two coils – thus producing the pulse.