Doctoral Dissertations

Date of Award

5-2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Nuclear Engineering

Major Professor

Eric D. Lukosi

Committee Members

Jason P. Hayward, Jamie B. Coble, Stefan M. Spanier

Abstract

This research focuses on the evaluation of lithium indium diselenide (LISe) semiconductors in double-sided strip detector (DSSDs) designs as an example for the potential to achieve unparalleled neutron detection efficiency, spatial resolution, and timing resolution detection. LISe semiconductors offer high neutron detection efficiency due to the ~25% atomic ratio of Lithium-6, maximizing its efficiency of ~75% with 1 mm thickness at 2.8 angstroms. Furthermore, the 4.78 MeV 𝑄-value enables high intrinsic gamma discrimination in a pixelated design (electron range). These characteristics make LISe an alternative option for neutron radiography, energy-resolved imaging, and other neutron interrogation techniques. This dissertation summarizes my current efforts to enhance LISe-based neutron imaging systems to achieve an end goal of sub-5 μm spatial resolution and sub-1 μs timing resolution. My research focuses on using MATLAB and Silvaco to simulate the expected response of a LISe DSSD. These various datasets are then trained to Machine Learning models in order to predict the neutron interaction location based upon the induced signal across multiple strip electrodes. In addition, various DSSD designs were simulated to determine the strip electrode width/pitch that optimizes the tradeoff between signal integrity and reconstruction of the neutron absorption location. The addition of electronic and statistical noise to the signal as well as varying the charge collection efficiency was also explored. The improvement upon current neutron imaging systems has the opportunity to open new avenues of research that are not possible today.

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