Modulated submillimeter laser interferometer system for plasma density measurements

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Interferometry

Background:

• High-density tokamaks require precise electron density measurements for plasma control.
• Existing diagnostic methods may lack the resolution or sensitivity for these demanding environments.

Purpose of the Study:

• To develop and present a high-resolution submillimeter interferometer system.
• To enable accurate electron density measurements within the 10^14 to 2 x 10^15 cm^-3 range.

Main Methods:

• Utilizes phase modulation via difference frequency mixing of two cavity-tuned laser oscillators.
• Employs optically pumped CH3OH lasers operating at 118.8-micrometers with a novel output coupling design.
• Detects beat signals using a newly developed Ge:Li photoconductor for phase shift measurement.

Main Results:

• Achieved high resolution for electron density measurements in high-density tokamaks.
• Demonstrated a novel output coupling design for CH3OH lasers, ensuring good mode quality and low beam divergence.
• Developed a sensitive phase measurement technique unaffected by amplitude or frequency fluctuations.

Conclusions:

• The developed interferometer system is suitable for electron density diagnostics in high-density tokamaks.
• The novel laser and detector technologies contribute to improved plasma measurement capabilities.
• This system advances the tools available for fusion energy research and plasma physics studies.