Plasmadiagnostics by the excitation of eigenmodes of the magnetosonic wave in toroidal geometry

Abstract

The propagation of a magnetosonic wave with finite wavelength parallel to the magnetic field in a toroidal plasma is investigated. Measurements at a small pulsed experiment with a Tokamak like configuration and typical plasma parameters n_e=2*10¹⁴ cm^-3, T_e=10 eV are reported. The wave is coupled to the plasma by an antenna structure consisting of 4 single turn coils symmetrically located around the torus. Comparison of the experimental results with a simplified MHD-theory leads to the conclusion, that this antenna excites a hydromagnetic wave with a comparatively simple mode structure which allows to deduce information on plasma density and effective collision frequency from external measurements of the wave field.