Numerical Simulation Study on the Influence of N₂ Concentration in Carrier Gas on Ionization Efficiency of Dielectric Barrier Discharge

As the rising demand for risk factor detection via mass spectrometry technology in the field of public safety and food safety, dielectric barrier discharge ion(DBDI) source has been rapidly developed. The concentration of the working gas in DBDI plays an important role in the signal/noise ratio of mass spectrometry detection by affecting ionization efficiency. In this study, a plasma fluid model of dielectric barrier discharge ionization containing 7 reactive ions under the action of He-N₂ mixed carrier gas was established, and the two-dimensional plasma fluid model was used to explore the influence of N₂ concentration on the ionization ability of the ion source. The results showed that the introduction of different amounts of N₂ into the He carrier gas could change the species number density of the plasma jet protonated water cluster reaction, and thus improve the ionization efficiency. In particular, it was found that the maximal number density of effective species could be achieved when the mole fraction of N₂ in carrier gas was 1.5%. In addition, the influence of design parameters, such as the diameter and the relative permittivity, on the number density of species was also considered in case studies and discussions. The results showed that the number density of species would gradually decrease with the increase of the tube diameter and the relative permittivity. The detailed parametric analyses of the N₂ mole fraction of carrier gas, the tube diameter and relative permittivity of the dielectric barrier will facilitate the ionization source structure,and finally improve the sensitivity and the stability of mass spectrometry detection.