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As the light source of the interferometer, the HCN laser’s frequency stability is particularly important. This paper analyzes the significance of a frequency stabilization system and the principle of intermediate frequencies signal generation. We design a system which employs a two-cavity HCN laser to obtain a stable intermediate frequency (IF) output. The system is based on ARM embedded system with the principle of intermediate frequency acquisition. PID is the core algorithm of the system.

In the experimental advanced superconducting tokamak, density pump-out phenomena were observed by using a multi-channel polarimeter-interferometer system under different heating schemes of ion cyclotron resonant heating, electron cyclotron resonance heating, and neutral beam injection. The density pump-out was also induced with application of resonant magnetic perturbation, accompanied with a degradation of particle confinement. For the comparison analysis in all heating schemes, the typical plasma parameters are plasma current 400 kA, toroidal field 2 T, and line average density 2 × 1019 m−3. The experimental results show that the degree of pump-out is concerned with electron density and heating power. Low density deuterium low confinement (L-mode) plasmas (