Alfven wave coupling experiments of the TCA Tokamak

Abstract

Low power RF absorption experiments have been carried out on the TCA Tokamak using a complete toroidal antenna structure with ranges of frequency and wavelength such that the shear Alfven wave can be excited. The general features of the Alfven absorption are in agreement with predictions. Excitation of narrow resonance structures with Delta omega / omega <5% has been observed for the first time. These resonances are attributed to low n-number kink modes close to the threshold of the Alfven continuum at the plasma centre. They are observed for mode helicity of the same sign as that of the magnetic field.