Design of a Doppler reflectometer for KSTAR.

Area of Science:

• Plasma physics
• Fusion energy research
• Diagnostic instrumentation

Background:

• Accurate measurement of plasma properties is crucial for understanding and controlling fusion devices.
• Poloidal propagation velocity is a key parameter influencing plasma confinement and stability in tokamaks.
• Existing diagnostic methods may have limitations in spatial or temporal resolution for certain plasma regimes.

Purpose of the Study:

• To design and develop a Doppler reflectometer system for measuring poloidal propagation velocity.
• To implement the system on the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak.
• To validate the performance of the new diagnostic during the 2014 KSTAR experimental campaign.

Main Methods:

• Utilized a V-band (50-75 GHz) operating frequency range.
• Employed a monostatic antenna configuration with extraordinary mode (X-mode) propagation.
• Implemented single sideband modulation with a 50 MHz intermediate frequency for heterodyne detection using a 200 MHz I/Q phase detector.
• Incorporated a corrugated conical horn antenna for Gaussian beam propagation approximation.
• Installed oversized rectangular waveguides within the tokamak vacuum vessel.

Main Results:

• The Doppler reflectometer system has been successfully designed and assembled.
• Key components including the antenna and waveguides are integrated into the KSTAR tokamak environment.
• The system is prepared for its first commissioning tests during the upcoming experimental campaign.

Conclusions:

• The developed Doppler reflectometer is a promising new diagnostic for KSTAR.
• It is expected to provide valuable data on poloidal plasma flow.
• Successful commissioning will enhance the understanding of plasma dynamics in KSTAR.