ELECTRON-TEMPERATURE DIAGNOSTIC IN TOKAMAK PLASMAS BY MICROWAVE TRANSMISSION

A new diagnostic of the electron temperature in tokamaks. based on mic rowave transmission, is discussed. The method consists of measuring th e optical depth of waves propagating along vertical chords, at frequen cies close to the electron cyclotron frequency or its first few harmon ics. By sweeping frequencies, the full absorption spectrum can be meas ured. It is shown that the width of the absorption line is proportiona l to the maximum electron temperature along the probing chord, which a llows the measurement of the full temperature profile if several chord s are available. The method has been implemented and tested on Tore Su pra by using the ordinary mode on a single vertical chord, approximate ly crossing the magnetic axis, which yields the central temperature. T he measurements are shown to be in good agreement with both Thomson sc attering and electron cyclotron emission temperature measurements, in both the ohmic and the additionally heated regimes.