Optical fiber interferometer application for high electron density measurements on compact torus plasmas.

Area of Science:

• Plasma Physics
• Optical Interferometry
• Fusion Energy Research

Background:

• Accurate measurement of electron density in compact torus (CT) plasmas is crucial for fusion energy research.
• Existing diagnostic methods may lack the required time or phase resolution for dynamic plasma phenomena.
• Optical interferometry offers a non-invasive approach for plasma characterization.

Purpose of the Study:

• To develop and optimize an optical fiber Mach-Zehnder interferometer for high-resolution electron density measurements in CT plasmas.
• To investigate and minimize phase noise for enhanced measurement accuracy.
• To validate the interferometer's performance through bench tests and initial plasma experiments.

Main Methods:

• Utilized a Mach-Zehnder interferometer operating at a 1.55 µm wavelength.
• Implemented an optical fiber configuration for enhanced spatial flexibility and signal transmission.
• Investigated and optimized interferometer phase noise characteristics.
• Calibrated the system using a piezoelectric ceramic actuator.
• Performed measurements on compact torus (CT) plasmas at two spatial locations.

Main Results:

• Achieved high time resolution of 0.1 µs and high phase resolution of 6.4 × 10^-4 rad.
• Demonstrated reliable electron density measurements at two distinct spatial points within the CT plasma.
• Successfully determined plasma bulk velocity using the time-of-flight method.
• Optimized phase noise significantly improved density measurement accuracy.

Conclusions:

• The developed optical fiber Mach-Zehnder interferometer is a reliable tool for high-resolution electron density measurements in CT plasmas.
• The system's performance allows for detailed plasma diagnostics and characterization.
• This technology has potential applications in fusion energy research and other plasma-based scientific endeavors.