Density Profile and Fluctuation Measurements with Microwave Reflectometry on Gamma 10

The microwave reflectometry using FM and ultrashort-pulse radar techniques have been applied to GAMMA 10 in order to diagnose plasma density profile and fluctuations. The reliability of profile measurement using the FM reflectometer is investigated for various sweep times and local path length. It is demonstrated that the reconstructed density profiles seem to be improved when the sweep time is faster than 50–100 μs. The several reconstruction algorithms are introduced to analyze the fast time-varying data, such as, the maximum-entropy method and wavelet analysis as well as zero-cross fringe counting and digital complex demodulation method.

The reflectometers are applied to the measurement of density/magnetic fluctuations. The space-and time-resolving spectra of rf waves as well as low-frequency waves are obtained. The density and magnetic-field fluctuations are evaluated from both the reflectometer and cross-polarization scattering diagnostic method.