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Dissertation
SiPM characterization and readout for nEXO & studying event topology in EXO-200
Doctor of Philosophy (Ph.D.), Drexel University
Dec 2025
DOI:
https://doi.org/10.17918/00011250
Abstract
The search for neutrinoless double-beta decay (0[nu][beta][beta]) seeks to study the nature of the neutrino and confirm the existence of physics beyond the Standard Model of Particle Physics. The EXO-200 experiment searched for 0[nu][beta][beta] in Xe-136 between 2011-2018 and, in the absence of a positive signal, set a lower limit for the decay's half-life at T^[0[nu][beta][beta]]_[1/2] > 3.5 x 10²⁵ yr at a 90% C.L. The proposed nEXO experiment will build on EXO-200's success with a design goal to reach a sensitivity to the half-life beyond 1028 years. To achieve its energy resolution and sensitivity goals, nEXO will utilize new detector technologies, including Silicon Photo-Multipliers (SiPMs), which have recently been developed to detect liquid xenon's vacuum ultraviolet scintillation light. SiPMs are beneficial for their single-photon detection ability, low noise, and low radioactivity. The nEXO collaboration has tested SiPMs from multiple suppliers and found that they meet the detector requirements, although testing is ongoing to determine the final supplier and design. This work describes test results from 2 prototype SiPM devices as well as the development of a LArASIC-based readout electronics system for nEXO's large-scale testing of SiPMs. nEXO's sensitivity relies in part on a solid understanding of signal and background events in the detector. In liquid xenon, double-[beta] decays are typically observed as a single energy deposit whereas background gamma events tend to scatter and create multiple deposits; however, in the EXO-200 experiment, about 10% of double-[beta] events were observed as multiple energy deposits which was attributed to bremsstrahlung emission. Both EXO-200 and nEXO use a topological discriminator to identify signal-like events with multiple deposits increasing the 0[nu][beta][beta] detection efficiency by about 10%. This work investigates in detail the event topology of signal and background events and attempts to benchmark simulations to EXO-200 data.
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Details
- Title
- SiPM characterization and readout for nEXO & studying event topology in EXO-200
- Creators
- Brady Eckert
- Contributors
- Michelle Dolinski (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University
- Number of pages
- xii, 99 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Arts and Sciences; Physics; Drexel University
- Other Identifier
- 991022150438604721