Relativistic Broadening Effect on Application of Electron Cyclotron Emission Measurements to High Temperature Tenuous Tokamak Plasma

The effects of relativistic frequency broadening on the ECE measurements for a high temperature tenuous tokamak plasma are studied. Calculations of the radiation transfer are carried out assuming a spherically-symmetric relativistic Maxwellian distribution function for electrons. From the relativistic point of view, observation of the fundamental ordinary mode ECE along a major radius from the low field side is best for the measurement of the electron temperature profile. It is impossible to obtain the electron temperature profile using measurements from the high field side without information on the optical thickness along the propagation path.