Electric fields and concentrations of charged and neutral hydrogen isotopic particles in the plasma of low pressure DC discharge

This paper presents the results of experimental and theoretical studies of the electric discharge characteristics and the concentration dependences of water isotopomers (H2O, HDO, and D2O) in a glow discharge in mixtures of helium with water vapor and molecular deuterium depending on the initial concentrations of H2O and D2. Measurements of the H2O and HDO concentrations were carried out by absorption diode laser spectroscopy in parallel with measurements of the axial electric field. The calculations were performed using a homogeneous kinetic model including balance equations for neutral and charged particles, which are solved together with the Boltzmann equation for the electron energy distribution function in the two-term approximation and the equation for the external electric circuit. A comparison was made of the experimental and calculated values of the concentrations of H2O and HDO, the stationary values of the electric field strength, and the discharge current. All abovementioned experimental parameters showed satisfactory agreement with the calculations. It was found that in self-consistent calculations, as well as in the experiment, the ratio of the concentrations of H2O and HDO was the same for different proportions of the initial concentrations of H2O and D2, and this ratio remained the same during the discharge action.