Date of Award

Spring 2021

Project Type

Dissertation

Program or Major

Physics

Degree Name

Doctor of Philosophy

First Advisor

Peter F Bloser

Second Advisor

James Ryan

Third Advisor

Mark McConnell

Abstract

The primary goal of my research was to measure the cosmic diffuse gamma-ray (CDG) background in the energy range of 0.4 - 2.5 MeV using the balloon flight data from the Advanced Scintillator Compton Telescope (ASCOT). ASCOT is a medium-energy gamma-ray Compton telescope that uses commercially available high performance scintillators—Cerium Bromide (CeBr3) and p-terphenyl—along with silicon photomultipliers (SiPMs) for light readout. It was built to address the lack of data in the gamma-ray energy range of 0.4 - 20 MeV. ASCOT was successfully launched on 2018 July 5 from the NASA Columbia Scientific Balloon Facility in Palestine, TX. We performed gamma-ray measurements from an altitude of 120,000 ft for five hours. This thesis describes in detail the design and calibration of the payload along with the analysis of the data. The growth curves obtained using the flight data for 5 to 100 g-cm–2 of residual atmosphere were used in conjunction with the Monte Carlo simulations of the instrument response to obtain a CDG flux value of (1.28 +/- 0.37)x10^-5 photons-cm–2-s–1-keV–1 for 0.4–0.7 MeV energy range. Our 3σ upper limit for CDG flux is 1.8 x 10^-5 photons-cm–2-s–1-keV–1 for 0.7–1.5 MeV and 2x10^-6 photons-cm–2-s–1-keV–1 for 1.5–2.5 MeV. These results agree well with earlier measurements

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