TALIF measurements of atomic deuterium in toroidal divertor simulator NAGDIS-T

The behavior of neutral deuterium (D) atoms is important for understanding the physics in the divertor region of nuclear fusion reactors. It is necessary to introduce an active measurement when considering the application to detached plasmas, where recombination processes dominate the processes determining the population distribution. In this work, we have developed a two-photon absorption laser-induced fluorescence (TALIF) system in the toroidal divertor simulator NAGDIS-T to measure D atomic density. The absolute D atomic density was obtained by calibrating the signal with the krypton TALIF signal. The gas pressure and power dependence of the D atomic density is shown. The D atomic density was in the range of 1.6 × 10¹⁸–1.4 × 10¹⁹ m⁻³, and the temperature was estimated to be $<$0.4 $\mathrm{eV}$. The behavior of the D atoms is discussed in terms of the production process.