Comparison of excitation mechanisms in the analytical regions of a high-power two-jet plasma

• Excitation mechanisms were investigated in the analytical regions of a high-power TJP.
• Boltzmann population of excited levels of Fe atoms and ions takes place in all regions of the plasma flow.
• The considerable difference in Fe atomic and ionic excitation temperatures occurs.
• Penning ionization by metastable argon results in disturbance of LTE in the plasma.
• The region before the jet confluence is more non-equilibrium than after that.

Excitation mechanisms in the analytical regions of a high-power two-jet plasma were investigated. A new plasmatron recently developed was applied in this work. The Boltzmann population of excited levels of Fe atoms and ions was observed in both analytical regions, before and after the jet confluence, as well as in the jet confluence, which proves excitation of atoms and ions by electron impact. The disturbance of local thermodynamic equilibrium in all regions of the plasma flow was deduced on the basis of considerable difference in Fe atomic and ionic excitation temperatures. Such a difference is most likely to be caused by contribution of metastable argon to atom ionization. The region before the jet confluence has the greatest difference in Fe atomic and ionic excitation temperatures and is more non-equilibrium than the region after the confluence due to comparatively low electron and high metastable argon concentrations. Low electron concentration in this region provides lower background emission than in the region after the jet confluence, which leads to better detection limits for the majority of elements.