Electron temperature profile from optically grey X3-mode of electron cyclotron emission at Wendelstein 7-X using Bayesian analysis

The third harmonic extraordinary (X3) mode of electron cyclotron emission is investigated, aiming at its diagnostic capability towards the measurement of electron temperature, T ( e ), of plasmas with higher densities exceeding the second harmonic extraordinary (X2) mode cutoff. A Bayesian data-analysis approach is adopted through the forward modeling of the X3 emission observations to extract the underlying T ( e ) profile. Bayesian analysis shows that the high field side of the X3 emission spectrum is sufficient to provide the T ( e ) profile. Additionally, for plasma control purposes, a correction factor is provided to track continuous core T ( e ) from the measured radiation temperature of the optically grey X3 emission.