Lower hybrid wave coupling in the Wega Tokamak

Abstract

The experimental data of the HF coupling measurements of the 4 waveguide grill of the Wega Tokamak have been compared with a linear coupling theory using a step density model. In order to minimize specific boundary effects which are not taken into account in the theory, the authors made use of data obtained when only the central waveguides are fed. The plasma density and its gradient at the mouth of the grill are estimated from probe measurements made with plasma conditions similar to those of the experimental coupling data. The qualitative agreement is always very good and a quantitative agreement is obtained in a relatively high density regime. The validity of the step density model is supported by the density dependence of the phases of the reflected signals.