Electron cyclotron emission from Tokamak plasmas - Experiment and computation

Measurements of electron cyclotron emission from TFR and Alcator Tokamak plasmas operating over a wide range of plasma conditions are presented and compared. For each device at low densities the emission is substantially, and similarly, non-thermal while at high densities it is close to thermal. Measurements made in an observation direction not previously employed (tangential) of electron cyclotron emission from a DITE Tokamak plasma are also presented. The spectrum consists essentially of symmetric lines at nf(ce0), suggesting that reflections of the radiation inside the torus totally destroy the anisotropy of the emission. The near-thermal emission spectra measured on TFR are compared with predictions of a code which takes into account, in a realistic fashion, the inhomogeneity of the plasma and reflections of the radiation inside the torus. Good agreement is found. From the emission measured radially in an optically thick line under high density conditions, an electron temperature profile is derived. The profile is compared with that measured by Thomson scattering, and good agreement is found.