Electron cyclotron-electron Bernstein wave emission diagnostics for the COMPASS tokamak

Area of Science:

• Plasma Physics
• Fusion Energy
• Microwave Engineering

Background:

• The COMPASS tokamak in Prague is a new facility for fusion energy research.
• Accurate plasma diagnostics are crucial for understanding and controlling fusion processes.
• Electron cyclotron emission (ECE) and electron Bernstein waves (EBW) are important plasma phenomena.

Purpose of the Study:

• To design, construct, and calibrate a new 16-channel radiometer system for the COMPASS tokamak.
• To investigate the emission characteristics of electron cyclotron waves and electron Bernstein waves.
• To assess the impact of tokamak structures on antenna radiation patterns.

Main Methods:

• A 16-channel radiometer operating in three frequency bands was developed.
• An end-to-end calibration method incorporating a noise generator and PIN-switch was implemented.
• Antenna radiation characteristics (2D electric field) were measured in free space and within the tokamak chamber.

Main Results:

• The radiometer system is capable of detecting normal electron cyclotron emission (O1 or X2) or oblique electron Bernstein wave emission.
• Calibration procedures confirmed the system's accuracy, including steady recalibration capabilities.
• Measurements revealed structural degradation effects on the Gaussian beam shape within the tokamak chamber.
• Initial plasma radiation temperature measurements from low-field circular plasmas were successfully obtained.

Conclusions:

• The new radiometer system is a valuable diagnostic tool for the COMPASS tokamak.
• The calibration and measurement methods provide reliable data for plasma research.
• Understanding antenna-structure interactions is important for optimizing diagnostic performance in fusion devices.