Birch, Harvey
(2020)
Development of the Optical Calibration System for the Outer Detector of the LUX-ZEPLIN Dark Matter Experiment.
Master of Philosophy thesis, University of Liverpool.
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Abstract
Discrepencies in cosmological observations of the universe indicate the existance of some kind of dark matter which makes up ∼26% of the energy density of the universe. It is theorised that the Weakly Interacting Massive Particle (WIMP) is a likely candidate for this unseen matter. The existance of WIMPs are predicted by both theories of the expanision of the early universe and extensions to the Standard Model of particle physics. LUX-ZEPLIN (LZ) is a second generation dark matter direct detection experiment searching for WIMPs using liquid xenon as target material. The addition of a three component veto system is one of the key aspects that distinguishes LZ from any other direct detection experiment to date. The veto system enables a more accurate discrimination of the background signals produced from detector components and the surrounding environment. One of the prominant backgrounds which produces WIMP-like signals in the dual phase time projection chamber are neutrons. The Outer Detector is one of the components of the veto system is used to characterise and reject such neutrons. The OD comprises of ten Ultra-Violet (UV) transparent acrylic tanks filled with gadolinium loaded liquid scintillator (GdLS) viewed by 120 photomultiplier tubes (PMTs). An Optical Calibration System has been developed to calibrate and monitor the performace of the Outer Detector PMTs and the degradation of the Gd-LS & UV - transparency of the acrylic. The Optical Calibration System has undergone extensive testing prior to installation. An understanding of how the electrical pulse sent to the LED corresponds to the intensity of the light emitted by the LED has been developed. A GUI has been produced to control the Optical Calibration System during calibration runs providing real time feedback to the controller. The inclusion of the veto system allows LZ to accurately reject background signals which would produce WIMP-like signals within the main detector volume. A correctly calibrated Outer Detector ensures that the experiment will be able to meet its projected sensitivity.
| Item Type: | Thesis (Master of Philosophy) |
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| Divisions: | Faculty of Science and Engineering > School of Physical Sciences |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 04 Sep 2020 11:05 |
| Last Modified: | 18 Jan 2023 23:39 |
| DOI: | 10.17638/03095465 |
| Supervisors: |
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| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3095465 |
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