ECE from MAST — Gaussian beams and antenna aiming problem

Abstract

The effect of the direction of the detected beam on the intensity of electron cyclotron emission (ECE) is studied. It is found that the combined effects of the strong dependence of the conversion efficiency of O mode at the plasma resonance on the direction of the incident wave and the partial screening of the beam waist by the vessel wall of the spherical tokamak MAST, can be responsible for the weakening of ECE for some frequencies.PACS : 52.35.Hr