Date of Award

Spring 5-1-2020

Degree Type

Thesis

Degree Name

MS Physics

Department

Physics

Advisor

Jose Lopez, Ph.D.

Committee Member

Wei-Dong Zhu, Ph.D.

Committee Member

Alper Sahiner, Ph.D.

Keywords

plasma, helium-air, cold, appj

Abstract

Plasma is one of the most complicated, yet promising fields in physics due to its high efficiency and multitude of crucial applications such as biological sterilization, polymer modification, surface treatments, etching, agriculture, and facilitation of selective catalytic processes to name a few. With these advantages, mysteries still remain. With this in mind, in order to accurately gauge the total influence of the plasma applied in various processes, understanding what is being produced and how the production occurs is vital. To understand this, optical emission spectroscopy was used to gauge how the species generated are influenced by operation parameters such as voltage, frequency, flow rate, and distance along the effluent. It was found that increasing voltage increased the intensity of all species generated. The emission of OH (308 nm), He (706nm) and atomic O (777nm) were found to decrease as it got further away from the exit, while the emission of N2 (337nm), N2+ (391nm), and N2 (631nm) increased due to the increased air interaction. With an increase in flow rate, all species benefitted except N2 (337nm) and N2 (631nm) which peaked around 5 L/min due to increasing ionization of N2+ (391nm) at higher flow rates. Analysis of generation mechanisms show the significance of the Penning effect between metastable He and air molecules on specie production while electron impact mechanisms are heavily dependent on power coupling of the system. Reaction rates and loss mechanisms explain the temporal evolution of the plasma jet and its effect on specie production. Gas temperature was found to deviate slightly regardless of operational parameters.

Download

Share

COinS