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<b style="font-family: "Times New Roman", serif; font-size: 12pt; color: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; background-color: ;">NAME:</b><span style="font-family: "Times New Roman", serif; font-size: 12pt;"> Tam
Nguyen</span><br>
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<b><span style="color:#201F1E">ADVISORS: </span></b><span style="color:#201F1E">Dr. Vincent M. Donnelly and Dr. Demetre J. Economou</span><span style="color:#201F1E"> </span><span style="color:#660033"></span></p>
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<b><span style="color:#201F1E">DATE:</span></b><span style="color:#201F1E"> </span>Thursday, May 14, 2020<span style="color:#660033"></span></p>
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<b><span style="color:#201F1E">TIME</span></b><span style="color:#201F1E">: </span>
9:00 AM<span style="color:#660033"></span></p>
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<b><span style="color:#201F1E">LOCATION:</span></b><span style="color:#201F1E"> Zoom </span><span style="color:#660033"></span></p>
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<b><span style="font-size:14.0pt; color:#201F1E">TITLE:</span><span style="color:#201F1E"> </span><span style="color:#660033"></span></b></p>
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<b>INVESTIGATION OF ATMOSPHERIC PRESSURE PLASMA JET PROPERTIES AND OPERATIONS IN AMBIENT AIR</b><span style="color:#660033"></span></p>
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<b><span style="font-size:14.0pt; color:#201F1E">ABSTRACT:</span></b><b><span style="font-size:14.0pt; color:#660033"></span></b></p>
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<b><span style="font-size:14.0pt; color:#201F1E"> </span></b><b><span style="font-size:14.0pt; color:#660033"></span></b></p>
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Plasma is gas ionized by energizing electrons through electric fields, leading to various collisional reactions that result in a number of reactive species useful in many applications. A main characteristic of plasmas is the creation of luminous excited species
that relieve their energy through emissions. The capturing of these emissions: optical emission spectroscopy (OES) is a major method for plasma diagnostic. Atmospheric pressure plasma jet (APPJ) is a type of plasma that is distinctive for the creation of a
small plasma jet extending from the plasma reactor (often a quartz tube equipped with electrodes), making the APPJ a prime candidate for plasma medicine applications. This study aims to investigate the fundamental properties of APPJs that are relevant to applications
through the use of OES. Firstly, the excitation mechanisms of plasma species in a He APPJ was revealed through spatially and temporally resolved OES, showing the major role of He metastables in excitations of various air species. Secondly, the gas temperature
and electron density of Ar/He APPJs were derived by fitting the emission line shapes of N<sub>2</sub> and H, respectively. The gas temperature increases (400 K – 600 K for Ar, 650 K – 750 K for He) with increasing applied power (9 W – 18 W for Ar, 19 W – 24
W for He). Electron density of Ar plasma increases (2.5x10<sup>13</sup> cm<sup>-3</sup> to 5x10<sup>13</sup> cm<sup>-3</sup>) with a grounded copper sheet behind a quartz substrate. Finally, diffusion of air species into a He plasma jet was measured through
self-actinometry and controlled by addition of a shielding gas curtain separating the plasma gas from ambient air. Self-actinometry involves adding trace gases (Ar, N<sub>2</sub>, and O<sub>2</sub>) into the plasma feed gas and observing changes in Ar, N<sub>2</sub>,
O<sub>2</sub>, and He emission intensity in order to correlate emission intensity and mole fractions. Air mole fraction in the plasma center increases along the jet axis from none at 1 mm, to 10<sup>-3</sup> at 3 mm and 10<sup>-2</sup> at 5 mm axial distance
from the nozzle. Addition of N<sub>2</sub> shielding gas reduces air diffusion by 2 to 3 times.<span style="color:#660033"></span></p>
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