Design of a slotted waveguide antenna to launch lower hybrid fast wave in the KSTAR Tokamak

Abstract

Lower hybrid fast wave (LHFW) has been proposed for heating and current drive in high density plasmas to overcome the density limit of conventional slow wave current drive (LHCD). The feasibility of the LHFW was tested through coupling experiments in the Versatile Experiment Spherical Torus (VEST) device. We design a 2.45 GHz waveguide antenna for the further investigation of the LHFW in the KSTAR tokamak. RF modelling of a slotted waveguide antenna is conducted in a vacuum and plasma medium using COMSOL in order to launch 2.45 GHz fast waves with n∥0 ∼ 2.87. A slotted waveguide antenna for the LHFW is designed according to simulation results which show field patterns for fast wave polarization, a n∥ spectrum and coupling efficiency between the antenna and plasmas.