Multi-channel poloidal correlation reflectometry on experimental advanced superconducting tokamak.

Area of Science:

• Plasma physics
• Fusion energy research
• Diagnostic techniques

Background:

• Accurate measurement of plasma density fluctuations is crucial for understanding plasma confinement and stability in fusion devices.
• Previous diagnostic methods had limitations in spatial resolution and temporal coverage for detailed fluctuation analysis.

Purpose of the Study:

• To develop and implement a novel multi-channel poloidal correlation reflectometry system.
• To enhance the capability for spatially resolved measurements of plasma density fluctuations.
• To investigate plasma dynamics within the pedestal region of the Experimental Advanced Superconducting Tokamak.

Main Methods:

• Utilized eight dielectric resonator oscillators (12.5-18 GHz) as sources, up-converted to V band.
• Employed a single launch antenna and two poloidally separated receive antennas.
• Implemented I/Q demodulators and a filter bank for signal processing after down-conversion.

Main Results:

• The system successfully measured density fluctuations at 8 radial × 2 poloidal spatial points.
• A coherent mode exhibiting an increasing velocity from 50 kHz to 100 kHz was detected.
• The observed mode was localized within the steep gradient region of the plasma pedestal.

Conclusions:

• The developed multi-channel poloidal correlation reflectometry is an effective diagnostic for studying plasma fluctuations.
• The system's capability to resolve spatial and temporal characteristics provides valuable insights into pedestal dynamics.
• Further research can utilize this system to explore turbulence and transport mechanisms in fusion plasmas.