A new diagnostic of the electron temperature in tokamaks, based on microwave transmission, is discussed. The method consists of measuring the optical depth of waves propagating along vertical chords, at frequencies close to the electron cyclotron frequency or its first few harmonics. By sweeping frequencies, the full absorption spectrum can be measured. It is shown that the width of the absorption line is proportional to the maximum electron temperature along the probing chord, which allows the measurement of the full temperature profile if several chords are available. The method has been implemented and tested on Tore Supra by using the ordinary mode on a single vertical chord, approximately crossing the magnetic axis, which yields the central temperature. The measurements are shown to be in good agreement with both Thomson scattering and electron cyclotron emission temperature measurements, in both the ohmic and the additionally heated regimes
Electron cyclotron wave propagation and absorption in the Compact Ignition Tokamak