Radiation transport modeling for the interpretation of electron cyclotron emission at ASDEX Upgrade

The electron cyclotron emission (ECE) diagnostic is a well established and robust instrument for the localized measurement of the electron temperature Te. Because of the relativistic massincrease and the Doppler-shift, identifying the measured radiation temperature (Trad) with Te at the cold resonance position is not always appropriate. This applies for example to measurements with low optical depth, weak absorption near the cold resonance position, or oblique viewing angles. In such cases an electron cyclotron radiation transport forward model (ECFM) is required for the interpretation of the measurements. At ASDEX Upgrade an ECFM is employed in the routine analysis of the profile radiometer measurements.
 
In this talk the radiation transport model will be introduced and several applications of the model will be demonstrated: (i) Inferring Te from Trad measurements with weak absorption near the cold resonance in the presence of large Te gradients (plasma edge and core). (ii) Cross calibration of ECE diagnostics. (iii) Determination of the measurement position of oblique ECE diagnostics. (iv) Validation of Fokker-Planck calculated distribution functions via the comparison of synthetic ECE spectra with experimental observations.