Electron density measurement by the three boundary channels of HCOOH laser interferometer on the HL-3 tokamak

作者：Mou, Junren^*; Li, Yonggao; Li, Yuan; Wang, Zaihong; Ding, Baogang; Wang, Haoxi; Yi, Jiang; Shi, Zhongbing

来源：PLASMA SCIENCE & TECHNOLOGY, 2024, 26(3): 034013.

DOI：10.1088/2058-6272/ad127a

• electron density
• interferometer
• HL-3

Far-infrared (FIR) interferometer is widely used to measure the electron density in the magnetically confined fusion plasma devices. A new FIR laser interferometer with a total of 13 channels (8 horizontal channels and 5 oblique channels) is under development on the HL-3 tokamak by using the formic-acid laser (HCOOH, f = 694 GHz). In order to investigate the boundary electron density activity during the divertor discharge, three horizontal interferometry channels located at Z = -97, -76, 76.5 cm have been successfully developed on HL-3 in 2023, and put into operation in recent experimental campaign, with a time resolution of < 1.0 mu s and line-integrated electron density resolution of similar to 7.0 <bold>x</bold> 10(16) m(-2). This paper mainly focuses on the optical design of the three-channel interferometry system, as well as optical elements and recent experimental result on HL-3.