Studies of electron cyclotron emission from high density discharges in the ASDEX Tokamak

Abstract

Electron cyclotron emission measurements from high-density discharges (electron density n_e>or approximately=8*10¹⁹ m^-3) in the ASDEX Tokamak are analysed. The diagnostic is found to be resilient to the effects of plasma refraction. In particular, reliable electron temperatures may be derived from the second cyclotron harmonic in the plasma until electron densities within 4% of the critical density for the existence of the right-hand, or upper, cut-off are encountered. Comparisons of experimental observations with predictions of a newly developed two-dimensional emission code incorporating refraction yield very good agreement between the two.