The Impact of the Resonator Shape of a Combline Travelling Wave Antenna on its RF and Thermal Performance

A combline type travelling wave antenna is traditionally used to launch fast waves in the tokamaks for enhancing the current drive. This paper presents a study on the difference in the peak RF electric fields and rise in temperature in a combline antenna for three different current strap shapes, viz., rectangular bars, filleted bars and cylindrical bars. Since the RF input to such a combline antenna is several hundreds of kWs of continuous wave (CW) power, such a study is essential to determine the appropriate resonator shape from the perspective of electrical breakdown and thermal management. In order to determine the optimum configuration of the current straps for an input power of 500 kW at 500 MHz, a multiphysics simulations which includes thermal and electromagnetic analysis is carried out using COMSOL.