Long-time measurements of line-integrated plasma electron density using a two-color homodyne optical fiber interferometer

作者：Tao Lan, Sen Zhang, Weixing Ding, G. Zhuang, Zhengwei Wu, Wenzhe Mao, Chen CHEN, Shijie Lan, Hangqi Xu, Tijian Deng, Junfeng Zhu, Jiaren Wu, Yiming Zu, Defeng Kong, Shoubiao Zhang, Yuan Yao, Peng Yuan, Zian Wei, Haiyang Zhou, Hai Wang, Xiaohui Wen, Jie Wu, Chu Zhou, A. D. Liu, Jinlin Xie, Hong Li, C. Xiao, Wandong Liu · 发表于：Review of Scientific Instruments · 年份：2021 · DOI：10.1063/5.0055570 · 被引用次数：5 · 研究领域：Magnetic confinement fusion research、Plasma Diagnostics and Applications、Laser-Plasma Interactions and Diagnostics

A two-color homodyne Mach–Zehnder (M–Z) optical fiber interferometer with wavelengths of 1.55 and 1.31 µm was developed for long-time measurement of line-integrated plasma electron density. A novel phase difference demodulation algorithm based on a single 3 × 3 optical coupler was implemented in a two-color optical fiber interferometer scheme for the first time. Our laboratory tests showed that this new optical fiber interferometer could determine the phase shift due to the low-frequency ambient vibration and could maintain high phase resolution measurement. The resolution of the new interferometer was less than 0.04 rad in 1000 s, corresponding to a line-averaged electron density of less than 1.0 × 1019 m−2. Actual plasma discharge experiments performed on KTX-CTI, which is a new compact torus injector (CTI) constructed at the Keda Torus eXperiment (KTX), showed that this interferometer has excellent several-second stability.