Design and calibration experiment of a two-photon absorption laser induced fluorescence diagnostic system for the Huanliu-3 tokamak

A two-photon absorption laser induced fluorescence (TALIF) diagnostic system is designed for measuring the density of deuterium atoms in the scrape-off layer (SOL) region of the Huanliu-3 (HL-3) tokamak. The system employs laser pulses at 10 Hz with an energy of 10 mJ per pulse (pulse width <8 ns) at 205 nm. To enhance the fluorescence intensity, a semi-confocal lens was designed to achieve a relatively large solid angle for fluorescence collection. A calibration experiment was conducted, establishing the relationship between fluorescence intensity and atomic deuterium (D) density using krypton (Kr) atoms as a reference. Experimental verification of the whole TALIF system has been successfully performed in a plasma environment. The feasibility of the TALIF for the measurements of the neutral particles is discussed, and an experimental result in the HL-3 tokamak edge plasma region is shown in this paper.