Detection of water molecules in inert gas based plasma by the ratios of atomic spectral lines

A new approach is considered to detect the water leaks in inert plasma-forming gas present in the reactor chamber. It is made up of the intensity ratio of D α and H α spectral lines in combination with O, Ar and Xe lines intensity. The concentrations of H2O, O, H and D particles have been measured with high sensitivity. At the D2 admixture pressure = 0.025 mbar, we used the acquisition time of 10 s to measure the rate of water molecules injected from the outside, Γ0 = 1.4 10−9 mbar m3 s−1, and the incoming water molecules to plasma, Γ = 5 10−11 mbar m3 s−1. The scaling proves that at small D2 admixtures (10−4 mbar), the leaks with the rates Γ0 ≈ 6 10−12 mbar m3 s−1 and Γ ≈ 2 10−13 mbar m3 s−1 can be detected and measured. The difference between Γ0 and Γ values is due to the high degree of H2O dissociation, which can be up to 97–98%.