Bench test of phase measurement on dispersion interferometer for EAST

Area of Science:

• Plasma physics
• Optical diagnostics
• Fusion energy research

Background:

• Traditional interferometers face challenges in electronic density measurement for fusion devices due to mechanical vibrations and fringe jumps.
• Dispersion interferometry (DI) using long-wavelength infrared light offers a solution by inherently canceling vibrations and inhibiting fringe jumps.

Purpose of the Study:

• To evaluate the performance of a dispersion interferometer (DI) for electronic density measurement.
• To validate the DI's phase measurement capabilities using a bench test setup with a wedge instead of plasma.

Main Methods:

• Bench testing of a dispersion interferometer (DI) using a wedge to simulate plasma.
• Phase measurement analysis and comparison with theoretical calculations.
• Background noise and baseline drift assessment without active vibration isolation.

Main Results:

• The DI demonstrated good agreement between measured and theoretical phase shifts during bench tests.
• Excellent baseline stability was observed, with drift below 2 × 10^17 m^-2 in 3 seconds and 5 × 10^17 m^-2 in 400 seconds.
• The DI performed well even without a dedicated vibration isolation system.

Conclusions:

• The dispersion interferometer (DI) is a viable tool for accurate electronic density measurements in fusion devices.
• The DI's ability to mitigate vibration and fringe jump issues makes it suitable for challenging environments like tokamaks.
• Further plasma data acquisition on the EAST tokamak is anticipated to confirm these findings in operational conditions.