Absorption of cyclotron waves at down-shifted frequencies by an energetic electron tail in the plt tokamak

Electron cyclotron wave absorption by moderately relativistic electrons in the low-density regime of the PLT tokamak is investigated. Appreciable wave damping is found for vertical propagation at frequencies of 50, 60, and 70 GHz when the spatially constant cyclotron frequency is 89 GHz. The perpendicular temperature Tj_(vu) of the fast tail is estimated from emission of radiation in the same direction. The results obtained are in satisfactory agreement with the theory of wave emission and absorption.