Fusion Science and Technology / Volume 55 / Number 1 / January 2009 / Pages 64-75
Technical Paper / Electron Cyclotron Emission and Electron Cyclotron Resonance Heating
A systematic disagreement between the electron temperature measured by electron cyclotron emission (ECE) (TECE) and laser Thomson scattering (TTS), which increases with TECE, is observed in JET and TFTR plasmas, such that TECE ~ 1.2 TTS when TECE ~ 10 keV. The disagreement is consistent with a non-Maxwellian distortion in the bulk electron momentum distribution. ITER is projected to operate with Te(0) ~ 20 to 40 keV so the disagreement between TECE and TTS could be >50%, with significant physics implications. The GENRAY ray-tracing code predicts that a two-view ECE system, with perpendicular and moderately oblique viewing antennas, would be sufficient to reconstruct a two-temperature bulk distribution. If the electron momentum distribution remains Maxwellian, the moderately oblique view could still be used to measure the electron temperature profile Te(R). A viewing dump will not be required for the oblique view, and plasma refraction will be minimal. The oblique view has a similar radial resolution to the perpendicular view, but with some reduction in radial coverage. Oblique viewing angles of up to 20 deg can be implemented without a major revision to the front end of the existing ITER ECE diagnostic design.