Development of Microwave Imaging Reflectometry for KSTAR

A microwave imaging reflectometry (MIR) system for KSTAR is being developed to measure 2-D (poloidal $\times$ radial) image of the electron density fluctuations for turbulence based transport study. Prior to the full system, two-frequency prototype system will be tested for the 2012 KSTAR campaign. The system is capable to measure poloidal wave numbers from 0.5 to 2 cm$^{-1}$ with a 16 channel array of detectors that can image $\sim 13$ cm length of the poloidal plane. Due to the standing wave problem of lens based system (sharing optics with 2nd ECEI system), a new system based on reflective optics is being designed. The RF electronics, capable of simultaneous measurement of the reflected beams from two cut-off layers, has been developed and the laboratory test results with a corrugated reflecting target will be presented.