Date of Award

9-12-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Engineering Physics

First Advisor

John W. McClory, PhD

Abstract

Cs2LiYCl6:Ce3+ (CLYC) has the desirable property of being sensitive to both gamma rays and neutrons while producing waveforms suitable for pulse shape discrimination (PSD) to determine which radiation was detected. This dissertation examines the behavior of CLYC to support its further development for mobile and portable applications. First, the feasibility of performing PSD with CLYC and an inexpensive data acquisition system was examined. This system was able to clearly distinguish both events with a figure of merit of 1.42. Next, the performance of a SiPM was compared to a traditional PMT. Analysis showed that the SiPM degraded the energy resolution by an average of 34.0±0.7% (at 662 keV). Measurements were also taken using a CLYC crystal with two optical windows which was rotated to determine the direction of a neutron source with an accuracy of ±10°. An analysis of the ability of clustering algorithms to discriminate between gamma ray and neutron interactions was also performed. A methodology was developed and applied to separate these two interactions and provide the ability to isolate the 35Cl(n,p)35S interaction with thermal neutrons, which occurs close to the gamma ray region and is difficult to separate visually. Finally, the effect of temperature on a 7Li (99%) enriched CLYC crystal (important when the 35Cl(n,p)35S interaction is more desirable than 6Li(n,t)α interaction) was examined. Measurements agreed with previous results from 6Li (95%) enriched CLYC, but also indicated that identifying the cluster corresponding to thermal neutrons interacting with 35Cl was temperature dependent.

AFIT Designator

AFIT-ENP-DS-19-S-028

DTIC Accession Number

DTIC Pending

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