Correlation radiometry of electron cyclotron radiation in TEXT‐U (invited)

Very low level plasma density and temperature fluctuations can be responsible for anomalous transport in thermonuclear magnetic traps. Measuring these fluctuations by detecting plasma electron cyclotron emission (ECE) might indicate where, in ω−k space, the most dangerous instabilities are located. The most attractive feature of ECE is the good localization of the source, unique to this range of frequencies among plasma radiation. However, to maintain spatial resolution, only a small number of radiation modes should be detected. The consequent poor statistics of the ECE measurement allows one to measure only the average value for the temperature fluctuation amplitude via correlation analysis of two ECE signals with suitable correlation properties. Initial measurements of this kind have been performed successfully. But, results have only been partially conclusive as to the relevance of electrostatic turbulence to heat transport, due to still too limited poloidal spatial resolution and the inability to correlate the measured signals with corresponding potential fluctuations. Suggestions of how to extend the present results to correct for these drawbacks are discussed.