Optical characterization of atmospheric torch operating modes

Characterization of a low frequency (50–150 kHz) atmospheric pressure air plasma torch reveals two distinct regions of operation. The first is a primary non-transferred arc protrusion that is blown out of the nozzle; the second is downstream from this protrusion and characterized by a lower intensity after-glow exhaust plume. These unique regions maintain significantly different plasma parameters that drastically influence plasma materials interactions; specifically, energy deposition and plasma induced reactive chemistry vary significantly between these two regions. Comparison of these modes of operation will be based on optical emission and absorption spectroscopic diagnostics of the N2+ B-X system, OH A-X band, NO-γ, and O 5So -5P 777 nm transitions. A parametric study of optical measurements versus frequency, power, and air flow are conducted in an effort to better understand how these regions couple together and influence material processing conditions.