Characterization of a plasma generated by a multisource vacuum arc with zirconium cathodes in a reactive gas atmosphere

The optical emission spectroscopy was applied in the study of the cathodic arc plasma produced by a multi-source arc device with zirconium cathodes. The experiments were carried out in the absence of the background gas and with nitrogen or a mixture of nitrogen and acetylene. An interelectrode region of the discharges were investigated. Significant changes in emission intensities of Zr I, Zr II, N2 and N2+ spectra were observed when N2 pressure increased from 0.2 to 2 Pa. For the plasma generated in the N2 and C2H2 mixture, a proportional increase in the emission intensities of all plasma species, with the exception of atomic zirconium and CN radical, vs. arc current was observed. These pressure and current dependencies suggest the electron impact excitation of plasma species from their ground levels and deexcitation by radiative decay. The excitation temperatures derived from Zr I and Zr II spectra were found to be 2300–3500 K and 4000–5600 K, respectively, while the ionization temperatures were between 3500 and 5300 K.