Date of Award

Summer 2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical and Computer Engineering

Committee Director

Mounir Laroussi

Committee Member

Shirshak K. Dhali

Committee Member

Frederic D. McKenzie

Call Number for Print

Special Collections LD4331.E55 A428 2012

Abstract

Non-thermal plasma (NTP) jets driven by short DC pulses have attracted the attention of researchers within the past decade due to their promising bio-medical applications in the fields of wound healing, cancer treatment and sterilization. The ability to operate at atmospheric pressure, room temperature and simple device configuration has greatly contributed to their appeal and adoption in the plasma science community. However, the mechanisms that sustain the plasma generation and propagation in ambient air are currently a topic of debate. For instance, what appears as a continuous stream of a plasma plume extending outwards from a plasma device into the air for several centimeters actually consists of discrete ionization waves called "Plasma bullets" that travel at supersonic speeds without an externally applied electric field. Recently, this intriguing phenomenon has been in the spotlight and studied for experimental evidences in order to support the theoretical explanations. This thesis work aims to contribute to the knowledge base of plasma jet propagation mechanisms by providing the needed experimental evidence into the photoinozation theory. In order to accomplish this goal, a glass vacuum chamber is used to contain a plasma jet generated by a device called tube reactor. By means of changing the pressure as well as the gas contents inside this chamber, we study the dynamics of the plasma jet. The plasma jet's electrical, propagation, and optical emission properties are characterized to better understand the relationships between the background gas composition and the ability to sustain a plasma jet at various pressures. The results indicate that the non-thermal plasma generated by a tube reactor can be operated in one of two distinct modes depending on the background pressure: "Jet mode" and "Diffuse mode." Both of these modes exhibit unique plasma characteristics which are studied by means of high speed imaging using an ICCD camera, and emission spectroscopy using a high resolution spectrometer. Through these characterizations it is reported that the results support the photoionization theory for plasma bullet propagation as plasma bullets only propagate along the working gas channel. In the absence of a gas channel, the plasma loses its jet form and transitions into the diffuse mode to fill the entire volume of the chamber with non-thermal plasma. Furthermore, the findings regarding the relationship between background gas composition and plasma jet formation suggest that in order to sustain a plasma jet, there needs to be a physical boundary layer around the working gas channel.

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DOI

10.25777/sn21-rq62

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