Electron energetics in a helium pulsed nanosecond discharge

Abstract

Summary form only given. Pulsed, nanosecond discharges (PNDs) are notable for their large volumes and nonthermal nature. The large volume is attractive for material processing and the nonthermal electron can be used to drive reactions with minimal gas or substrate heating. However, the stochasticity of such plasmas presents a challenge for simulations, while the short time scales and large fields limit experimental diagnostics. This has led to a degree of uncertainty in the electron energetics of PNDs, particularly when nonlocal electron effects become important. This uncertainty also inhibits the predictive capabilities for PNDs. This work examines the population kinetics of a helium PND, and uses them to infer conclusions about the electron energetics. Specifically, the absolute triplet metastable densities are measured with laser-absorption spectroscopy. These densities are used in combination with a global model of a helium plasma to predict plasma emissions. These emissions are compared with the measured plasma emissions. As this method assumes electron locality, the degree of agreement between the two should reflect the accuracy of this assumption. The results are discussed in the context of the electron energetics, and compared to preliminary results of PIC-MCC simulations.