Nuclear reactors have played an essential role in developing our current understanding of neutrinos. The precision measurement of these high-flux, pure-flavor and controllable artificial neutrino sources shed lights on a wide range of fundamental questions in physics. Specifically, the Reactor Antineutrino Anomaly hints that there may exist a novel eV-scale sterile neutrino, which requires new physics beyond the Standard Model. Performing reactor neutrino spectrum measurements at very-short baseline will improve our imperfect understanding of antineutrino emission from fissile material.
CHANDLER is a new-generation neutrino experiment aiming for reactor antineutrino spectrum measurements, to test the eV-scale sterile neutrino oscillation hypothesis unambiguously. The second prototype detector, MiniCHANDLER, was deployed 25 meters from a $2.9~GW_{th}$ commercial nuclear reactor in North Anna, Virginia.
To fight against the overwhelming background arising from its surface-level deployment, CHANDLER detectors adopt a novel design using lithium-6 ($^6$Li) loaded zinc sulfide (ZnS) scintillator to tag neutron capture events, which significantly improves the IBD detection efficiency. The use of the Raghavan optical lattice brings enormous enhancement of light collection towards high energy resolution, which unlocks reconstruction of event topology to further suppress backgrounds. The ability of measuring reactor antineutrino spectra enables the potential application of CHANDLER technology in nuclear nonproliferation.
This thesis features the prototype detectors instrumentation, data analysis development and Monte Carlo study for the CHANDLER experiment during 2016 to 2020. The detector calibration and energy reconstruction with vertical muon forms a core piece of this thesis. We report our observation of IBD spectrum with 5.5$sigma$ significance with a four month deployment of the minimal shielded MiniCHANDLER prototype at North Anna. The application of separation cuts and topological selections in the analysis are instrumental for a segmented plastic scintillator detector. We also present our results from the proton scintillation quenching measurement at Triangle Universities Nuclear Laboratory, with the deployment of the first prototype detector, MicroCHANDLER, at a neutron beam. / Doctor of Philosophy / The sterile neutrino is a hypothetical particle yet to be observed, whose existence is suggested by a number of physics experiments with strong theoretical motivation. Due to the low chance of a neutrino interacting with matter, most neutrino detectors use a special process called inverse beta decay (IBD) to detect them. The CHANDLER experiment set out to measure antineutrinos produced by a reactor in the vicinity of its core. We found a significant signal of antineutrinos from our four-month deployment. This thesis details the technology and analysis that enables neutrino detection and improves detection efficiency. We also shows how we squeeze out the maximum information available to us from raw data, through the process called reconstruction. Other research topics related to the CHANDLER detector RandD are also included in this thesis.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/100738 |
| Date | 28 October 2020 |
| Creators | Li, Shengchao |
| Contributors | Physics, Link, Jonathan M., O'Donnell, Thomas, Sharpe, Eric R., Huber, Patrick |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/x-zip-compressed |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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