Development and validation of a multichannel edge density profile reflectometer embedded in ion cyclotron resonance heating (ICRH) antennas on EAST

A novel multichannel X-mode reflectometer has been developed for density measurements near the ion cyclotron resonance heating antennas on the Experimental Advanced Superconducting Tokamak. This system enables direct measurement of the edge density profile in the immediate vicinity of the antennas. Key challenges associated with long fundamental rectangular waveguides—significant attenuation and dispersion—are addressed through a combination of watt-level amplifiers and a digital mixing method calibrated via a closed-loop waveguide test. Furthermore, a dedicated peak-seeking algorithm is implemented to robustly determine the zero-density starting position (Rstart) under conditions of harmonic interference. Finally, a corrected reconstruction formula accounting for the dual-horn geometry confirms its negligible influence (≲0.5mm) on profile accuracy.