Abstract

Measurements of electron cyclotron emission (ECE) from the high field side of the TCV tokamak have been made on plasmas heated by second and third harmonic X-mode electron cyclotron heating (ECH) and electron cyclotron current drive (ECCD). Suprathermal ECE, up to a factor of six in excess of thermal emission, is detected in the presence of second harmonic X-mode (X2) ECCD and of third harmonic X-mode (X3) ECH. The measured ECE spectra are modelled using a bi-Maxwellian describing the bulk and the suprathermal electron populations. Suprathermal temperatures between 10 and 50 keV and densities in the range 1 x 10(17)-6 x 10(18) m(-3) are obtained, and correspond to 3-15 bulk temperatures and 1-20% bulk densities. Good agreement between ECE suprathermal temperatures and energetic photon temperatures, measured by a hard x-ray camera, is found. For optically thin X3 low field side injection in the presence of X2 CO-ECCD, the suprathermal population partly explains the discrepancy between global and first pass absorption measurements.

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