Q-Band X-Mode Reflectometry and Density Profile Reconstruction

By installing an X-mode polarized Q-band (32–56 GHz) reflectometry at the low field side on EAST, the zero density cutoff layer was determined and the edge density profile was measured in normally operating plasmas. A Monte Carlo procedure has been developed to analyze the density profiles by considering the error of time delay measured by reflectometry. By combining this Q-band and previously developed V- and W-band reflectometries, the density profiles from edge to core can be measured in most EAST experiments. The line integrated densities deduced from density profiles measured by reflectometry are consistent with those directly measured by a horizontal interferometer. The density pedestal measured by reflectometry shows a clear crash during an ELM (edge localized mode) event, after which the pedestal gradually increases and recovers in 10 ms and then remains little changed up to the next ELM.