The development of charge exchange recombination spectroscopy on the HL-3 tokamak

A 64-channel toroidal charge exchange recombination spectroscopy system has been developed on the HL-3 tokamak (R = 1.78 m，a = 0.65 m). It measures ion temperature and rotation velocity by monitoring the doppler broadening and doppler shift of the carbon line emission (C VI, n = 8–7, 529.06 nm). The time resolution of the system is up to 2.5 ms, and it normally operates at a time interval of 20 ms, which depends on the signal intensity. The spatial resolution is 1–2 cm covering R = 1.56 m to R = 2.40 m. The system consists of a shutter structure, an optical acquisition system, a fiber optic bundle, two sets of hyperspectral resolution spectrometers, and a data acquisition system. To address the issue of optical signal loss caused by the limited size of the reflecting mirror in the vacuum, a sunken glass viewing window and a lens with a front-placed entrance pupil is designed. It enables the optical signal, from the boundary to the core, to fully enter the lens via the reflecting mirror. Recently, the toroidal CXRS system routinely runs on the HL-3 tokamak, and the profiles and time evolutions of ion temperature and rotation velocity are uploaded quasi-real-time. The experimental data are shown for the cases of HL-3 plasma with edge transport barrier or with high ion temperature of 10 keV.