Experimental analysis on effects of hydrogen addition on argon plasma jet at low vacuum

The effects of the addition of hydrogen on the properties of an argon plasma jet generated using a microwave plasma source under low-pressure conditions were experimentally investigated. Hydrogen was introduced at concentrations of 0.1%–1%, and the resulting changes in plasma jet characteristics were analyzed using optical emission spectroscopy (OES) and Langmuir probe (LP) measurements. The plasma jet length decreased significantly, and a reduction of over 60% occurred at a hydrogen concentration of 0.4% compared to that in pure argon plasma. The OES results indicated a reduction in Ar I intensities and a nonlinear trend in Hα and Hβ emission intensities. Based on LP measurements, decreases of 54% and 37% were observed in the electron temperature and plasma density, respectively, with 0.6% hydrogen addition. These effects are attributed to recombination reactions and interactions between argon and hydrogen species, which consume free electrons and metastable argon states.