Development of a single-channel X-mode polarized W-band Plasma Waves Reflectometer (PWR) on Experimental Advanced Superconducting Tokamak (EAST)

Abstract A single-channel W-band Plasma Waves Reflectometer (PWR) with X-mode polarization has been designed and deployed on the Experimental Advanced Superconducting Tokamak (EAST) to detect high-frequency density fluctuations induced by plasma waves. The system employs a dual-channel Fractional-N frequency synthesizer (Channels A and B) as its signal source, which operates within a fundamental frequency range of 13–17.5 GHz. The synthesized signal is subsequently upconverted to the W-band (78–105 GHz) using a six-fold frequency multiplier. The output frequency and power of each channel can be independently configured via software control, and bench tests confirm stable output power performance for both channels. Channel A serves as the detection path, transmitting signals into the plasma. The reflected signal is then coupled with the signal from Channel B and fed into the data acquisition system. During the 2025 EAST experiments, the system successfully detected Edge Coherent Modes (ECMs) by configuring its probing frequency within the pedestal gradient region. ECMs are a class of phenomena often observed by the Poloidal Correlation Reflectometer (PCR) following the L-H transition, and this detection result verifies the PWR's reliable performance. Furthermore, during discharges with Ion Cyclotron Range of Frequencies (ICRF) heating, the system detected ICRF-induced density fluctuations in the plasma. These results demonstrate the feasibility of the PWR and its excellent measurement capabilities. In the future, the system will continue to be used for detecting plasma wave-induced density fluctuations and supporting related physics research on the EAST tokamak.