Electron cyclotron beam measurement system in the Large Helical Device

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Applied Electromagnetics

Background:

• Accurate measurement of electron cyclotron (EC) heating power is crucial for understanding plasma behavior in fusion devices.
• Investigating the interaction physics between EC beams and plasma requires direct diagnostic capabilities.

Purpose of the Study:

• To develop and validate a direct measurement system for EC beams transmitted through plasma.
• To evaluate the EC heating power and analyze the physics of EC beam-plasma interactions within the Large Helical Device (LHD).

Main Methods:

• A novel system was designed using an isotropic graphite target plate and an infrared (IR) camera.
• The target plate is positioned to intercept the EC beam after it passes through the plasma column.
• The IR camera measures the temperature increase on the target plate, correlating it to the transmitted EC beam power.

Main Results:

• The system successfully measured the profile of the transmitted EC beam.
• The system demonstrated the capability to evaluate beam refraction effects within the plasma.
• The developed system is applicable in high magnetic fields (up to 2.75 T) and plasma densities (up to 0.8 × 10^19 m^-3).

Conclusions:

• The direct measurement system provides a reliable method for evaluating EC heating power and beam characteristics in fusion plasmas.
• This diagnostic tool enhances the understanding of EC beam-plasma interactions and wave propagation physics.
• The system's applicability to high magnetic field and density conditions makes it valuable for future fusion research.