Design of a real-time frequency stabilization system for dual laser-based interferometer on EAST.

Area of Science:

• Plasma physics
• Fusion energy research
• Optical diagnostics

Background:

• Intermediate frequency (IF) instability in the far-infrared polarimeter/interferometer (POINT) diagnostic on the Experimental Advanced Superconducting Tokamak (EAST) can compromise electron density measurements.
• Sudden and large IF shifts lead to diagnostic instability and potential errors.

Purpose of the Study:

• To develop and validate a comprehensive solution for stabilizing IF fluctuations in the POINT system.
• To ensure the accuracy and stability of electron density measurements during EAST experiments.

Main Methods:

• Analog IF signals are digitized using an analog-to-digital converter.
• A ZYNQ processor-based digital signal system processes the digitized signal.
• Fast Fourier Transform (FFT) determines the IF value by finding the maximum amplitude.
• A fuzzy control algorithm on the ZYNQ processor adjusts laser cavity length via piezoelectric ceramics for frequency stabilization.

Main Results:

• The system achieves IF stabilization within 850 ± 100 kHz.
• The control speed is 0.5 seconds per adjustment.
• The method demonstrates robustness against frequency variations up to 270 kHz.
• Effective management of sudden frequency shifts was confirmed.

Conclusions:

• The developed digital control system provides an efficient and rapid solution for IF stabilization.
• This stabilization is critical for maintaining the precision and reliability of the POINT system in EAST.
• The method ensures the accuracy of electron density measurements in tokamak fusion devices.