Ion temperature and beam-driven plasma waves from collective scattering of gyrotron radiation in W7-AS

Collective scattering of gyrotron radiation and its potential for plasma diagnostics was investigated using the W7-AS stellarator. The ion temperature was determined from thermal spectra in neutral-beam-heated plasmas. The excitation of a narrow band plasma wave by a non-thermal ion component was observed and the wave characteristics were investigated experimentally. The results constitute an important step toward alpha -particle diagnostic via scattering of powerful microwave radiation.