Design and Simulation of an Interdigital Travelling Wave Antenna for Fast Wave Current Drive in SST-1 Tokamak

Abstract

In reactor-grade plasma, where density and temperature are very high, Fast Wave Current Drive (FWCD) technique can be used to launch fast waves inside the plasma to sustain the current for a longer duration. A Interdigital type travelling wave antenna is proposed alternative structure to the combline antenna to launch these fast waves for SST-1 tokamak at an operating frequency of 500 MHz and parallel refractive index of ~ 4.0. Multiphysics analysis is carried out to evaluate the RF and thermal performance of an antenna structure using COMSOL Multiphysics software. The simulation studies have shown that the thermal performance of the interdigital antenna is better than that of combline antenna for high input power. Simulation results show that the antenna exhibits band-pass characteristics with a return loss of less than 30 dB and insertion loss of ~ 0.23 dB. The simulation studies have been carried out with a vacuum and seawater loading in front of the antenna. Steady-state thermal analysis has shown that an appropriate cooling mechanism should be provided to facilitate carrying heat away from the structure if the antenna is operated with high input power for longer durations.