TSC Simulation of Transient CHI in New Electrode Configuration on QUEST

Abstract

In QUEST, transient Coaxial Helicity Injection (CHI) has now been implemented using a new electrode configuration in which the CHI insulator is not part of the vacuum boundary. In this paper, for the first time, suitable conditions for generation of the CHI-produced toroidal current in the QUEST vessel configuration were investigated using the Tokamak Simulation Code (TSC). The simulation results show that the configuration in which the biased electrode is located farther away from the injector flux coil requires higher currents in the injector coil to generate the required injector flux. Additionally, energizing a lower inboard poloidal field coil and possibly lowering the electrode plate closer to the injector flux coil may be necessary to improve injector flux shaping to permit a configuration that is more favorable for inducing flux closure.