Bayesian inference of the electron cyclotron emission diagnostic at Wendelstein 7-X

Wendelstein 7-X (W7-X) is an optimized stellarator that uses a 32 channel heterodyne electron cyclotron emission radiometer (ECE) as a standard diagnostic to measure the electron temperature profile with high temporal resolution. In order to obtain a systematic calibration procedure with rigorous uncertainty estimates, modelling within the Bayesian Minerva framework has been used to infer the absolute effective sensitivities and beam widths from a periodic switching between a (hot) source at room temperature and a (cold) source at liquid nitrogen temperature. As the ECE measures the radiation temperature and not directly the local electron temperature, a Gaussian process based profile inversion has been done to extract the electron temperature profile. For this purpose, the radiation transport code TRAVIS has been implemented in Minerva, allowing complex models of multiple diagnostics to include ECE data.