Date of Award

3-2021

Document Type

Thesis

Degree Name

Master of Science in Applied Physics

Department

Department of Engineering Physics

First Advisor

Anil Patnaik, PhD

Abstract

Understanding plasma plumes and the distribution of plasma species microseconds after their formation has a variety of applications in fields such as hypersonics, explosion and combustion dynamics, and nuclear fireball chemistry. In this work, Laser Induced Breakdown Spectroscopy (LIBS) using double pulses of 532 nm light were used to analyze samples of cerium in atmospheres of air, vacuum, and argon. Cerium was used in this experiment to serve as a plutonium surrogate. CeO2 powder was pressed with CaO at 90-10 ratio to produce calcium doped pellets for use as sputtering targets. Inclusion of calcium impurities allowed the identification of how calcium species locate relative to cerium species in the plume. In addition, schlieren imaging at 40 kHz was used to attempt to capture the shockwave and to relate the plume development to the spatial location of the chemical species from the spectra. Tests were primarily conducted at 10 torr and over a time period 0 ns to 5000 ns after the second laser pulse. 1D spatial information was captured along the vertical center of the plasma plume over an 8.43 mm field of view. Temperature was estimated to be on the order of 3500K. Electron density was found to be on the order of 3×1016 cm-3. The species spatial distributions were found to show fractionation of the species. Establishing that Ce-II, Ca-I, and Ca-II tend to collocate in a plasma plume with Ce-I being located separately until recombination. This study will aid the understanding of physio-chemical processes involved fireball evolution.

AFIT Designator

AFIT-ENP-MS-21-M-132

DTIC Accession Number

AD1145738

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