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

Y Wang; Y Yao; H Q Liu; Y Zhang; J M Zhang; Y X Jie; Z Y Zou

doi:10.1063/5.0187901

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

Rev Sci Instrum. 2024 Jul 1;95(7):073003. doi: 10.1063/5.0187901.

Authors

Y Wang¹, Y Yao², H Q Liu^{2

3}, Y Zhang², J M Zhang^{1

2

4}, Y X Jie², Z Y Zou³

Affiliations

¹ University of Science and Technology of China, Hefei 230026, People's Republic of China.
² Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, People's Republic of China.
³ Institute of Energy, Hefei Comprehensive National Science Center, Hefei 230031, People's Republic of China.
⁴ Institutes of Physical Science and Information Technology, Anhui University, Hefei, Anhui 230601, People's Republic of China.

PMID: 39037295
DOI: 10.1063/5.0187901

Abstract

This study addresses the challenge of intermediate frequency (IF) instability in the far-infrared polarimeter/interferometer (POINT) of the Experimental Advanced Superconducting Tokamak (EAST) to ensure the accuracy and stability of electron density measurements. Sudden and extensive IF shifts of the lasers can cause instability and even measurement errors of the diagnostic system. This paper introduces a comprehensive solution for stabilizing IF fluctuations. First, analog IF is converted into digital form using an analog-to-digital converter, and the digitalized signal is processed by a digital signal system based on a ZYNQ processor. The exact value of the IF is obtained by acquiring the point of maximum amplitude through the fast Fourier transform method, while the ZYNQ processor loaded with a fuzzy control algorithm will precisely adjust the laser cavity length via piezoelectric ceramics, achieving frequency stabilization within a target range. Comparative analyses confirm the method's efficacy in managing sudden frequency shifts, maintaining stability within 850 ± 100 kHz (a central frequency of 850 kHz, fluctuating within a range of ±100 kHz), with a control speed of 0.5 s per action and robust against variations up to 270 kHz. This efficient and rapid control mechanism fulfills the critical need for IF stabilization, ensuring the stability and precision of the POINT system in the EAST discharge experiments.