Development of the quasi-optical combiner systems for density profile reflectometers on the EAST tokamak

The reflectometry diagnostics on experimental advanced superconducting tokamak (EAST) are composed of Q-band (32-56 GHz), V-band (48-76 GHz) and W-band (72-110 GHz) microwave reflectometers with X-mode polarization. The three reflectometers with separate frequency bands were launched independently in previous experiments and now are combined together by applying advanced microwave technology. A quasi-optical (QO) combiner/de-combiner by using frequency selective surfaces (FSSs) has been built to combine the three bands so that these waves (32-110 GHz) can be transmitted to the antenna by using one single oversized waveguide. Two double-ridged horns are used for launcher and receiver. The received waves are decoupled by using a QO de-combiner, the same with the combiner. The designed parameters and laboratory test results of the upgraded system have been presented. The density pedestal evolution during the edge localized modes (ELMs) in EAST plasma have been presented as an example for the application of the updated reflectometers.