Initial Electron Bernstein Wave Emission Measurements on the TJ-II Stellarator

Thermal electron emission at 28 GHz has been measured on the TJ-II stellarator. The emission from neutral beam-heated overdense plasmas, where the plasma density is greater than the ordinary-mode (O-mode) cutoff density, is consistent with electron thermal emission from mode-converted electron Bernstein waves (EBWs) via the Bernstein wave to extraordinary mode to ordinary mode scenario (B-X-O). Emission from underdense plasmas without neutral beam injection is consistent with the measurement of oblique electron cyclotron emission. Electron Bernstein wave emission measurements are being made to determine the optimum launch angle for planned EBW heating experiments and also to provide an indication of electron temperature evolution in overdense plasmas on TJ-II.