Graduation Semester and Year
Spring 2026
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Physics and Applied Physics
Department
Physics
First Advisor
Jonathan Asaadi
Second Advisor
Ben Jones
Third Advisor
Andrew Brandt
Fourth Advisor
Muhammad Huda
Fifth Advisor
Michael Febbraro
Abstract
Physics offers a way to connect deeply with the mysteries that surround us. Advances in detector physics, particularly in neutrino experiments and rare-event searches, have expanded our ability to probe phenomena that challenge how we describe the universe. Each discovery brings us closer to understanding the unknown, returning us to a sense of wonder that motivates exploration. My work on detector technology was inspired by a concept paper from Professor David Nygren, in which he noted the speculative possibility of integrating photon detection into a charge readout for pixelated liquid argon time projection chambers (LArTPCs) using the photoconductor amorphous selenium (a-Se). This idea served as a practical starting point for addressing the challenge of incorporating photon detection directly on the anode plane, a requirement that arises naturally in pixelated systems where the charge readout is optically opaque to scintillation light. This dissertation builds on that foundation through a set of experimental studies that develop and characterize a-Se photodetectors for liquid-noble detectors. Chapter 1 establishes the scientific and technical context for this work, beginning with an overview of neutrino physics and the role of precision detection, followed by a discussion of LArTPCs and the emergence of pixelated, multimodal charge-and-light readout systems. Chapter 2 introduces a-Se as a photodetector, reviewing its material properties, historical use in radiation detection, and the considerations required to adapt a-Se for operation in liquid-noble environments. The remaining chapters consist of a sequence of publications that form the core experimental contributions. Chapter 3 presents a proof-of-principle study demonstrating stable low-field operation of windowless a-Se photodetectors using a lateral electrode geometry that permits direct optical absorption without a transmissive contact. The measurements demonstrate sensitivity to ultraviolet light spanning from room temperature down to cryogenic temperatures. Chapter 4 reports the fabrication and cryogenic optical characterization of lateral a-Se photodetectors incorporating a polyimide blocking layer and operated at high electric field. Measurements include low-photon sensitivity, direct response to 130 nm vacuum-ultraviolet excitation, linearity with photon flux prior to avalanche multiplication, and the effects of tellurium doping on avalanche onset and gain. Chapter 5 examines charge transport, impact ionization, and photogeneration in lateral a-Se devices operated over a broad range of electric fields, using the Onsager model for photogeneration, transport models including field-assisted hopping and thermally-assisted tunneling, and the Lucky–Drift model for impact ionization to describe the response evolution with temperature and field.
Keywords
amorphous selenium, photodetectors, LArTPC, cryogenic detectors, avalanche multiplication, charge transport
Disciplines
Other Physics
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Rooks, Michael, "Amorphous Selenium Photodetectors for Liquid Noble Detectors" (2026). Physics Dissertations. 188.
https://mavmatrix.uta.edu/physics_dissertations/188