Electrical and Computer Engineering ETDs

Publication Date

Summer 7-28-2026

Abstract

Gas discharge simulations are performed with particular focus on photoionization process in a positive streamer discharge. The effects of this process are investigated by isolating the change in photoionization mean free path (MFP) and keeping the additional processes constant. Furthermore, comparison are made between various effects of simulation parameters, such as initial conditions, geometry extent, simula- tion particle count etc. All of these simulations are performed using a modern Direct Simulation Monte Carlo Particle-in-Cell (DSMC-PIC) code developed by Sandia Na- tional Laboratories. Large scale simulations including 1 cm and 5 cm electrode gaps are performed under standard atmospheric condition air. Effects of photoionization on these discharges are investigated by changing the proportion of nitrogen and oxygen in the air mixture. It was shown that the changing photoionization MFP give significantly different results. Under normal conditions in standard air the discharge behaves like a streamer. With decrease in oxygen concentration a diffuse plasma is created that has stark differences than those of standard air streamer. As the oxygen concentration is reduced even further (in parts-per-million range) a discharge starts to behave like a streamer again. These effects are simulated with two types of initial conditions and are used to compare how the discharge behavior changes with a different initial plasma seeding. Simulated photon output of the discharges is provided to aid in future experimen- tal work. A simulated photon output could be used as a surrogate for a discharge photograph. This type of simulated output could be used to directly compare dis- charge photographs obtained during the experiment to those done in simulation. This type of simulation output can be finely tuned to match the optical performance to that of a real optical system that is used in experiment.

Keywords

plasma, streamer, discharge, photoionization

Project Sponsors

Sandia National Laboratories

Document Type

Thesis

Language

English

Degree Name

Electrical Engineering

Level of Degree

Doctoral

Department Name

Electrical and Computer Engineering

First Committee Member (Chair)

Jane Lehr

Second Committee Member

Mark Gilmore

Third Committee Member

Andrew Fierro

Fourth Committee Member

Christopher Moore

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