Determination of position on the measurement of electron temperature radial profile from electron cyclotron emission. Scaling of the apparent radial shift

Effect of relativistic frequency down-shift and optical thickness on the determination of the electron temperature profile from electron cyclotron emission in tokamak plasmas have been studied. Inclusion of relativistic and optical thickness effects results in a radial shift of the obtained electron temperature profile. In order to evaluate the shift for any tokamak, a scaling of the shift (Δr) is obtained: Δr(m)=0.0009 R(m) Te(keV) (1+50/(4τ)) for 170 > τ > 5, where R is major radius, Te is electron temperature, τ is the optical depth. Comparison between the scaling and the computational shifts for various devices are made, the good agreement between them is obtained within 2% of minor radius. Thus the scaling can be applied to any tokamak devices. (author)