Thesis Defense: Mitigating backgrounds and enhancing low-energy sensitivity in liquid xenon dark matter detectors

Speaker: Drew Ames (KIPAC) In Person and zoom

Ph.D. Candidate: Drew Ames
Research Advisor: Dan Akerib

Zoom Link: https://stanford.zoom.us/j/93014231272
Zoom Password: Email physicsstudentservices@stanford.edu for password

Dark matter direct detection experiments search for rare nuclear recoils produced by interactions between dark matter and ordinary matter. The LUX-ZEPLIN (LZ) experiment targets these events using a dual-phase liquid xenon time projection chamber (TPC) with a 7-tonne active mass. This talk presents work to improve the reach of LZ and future detectors by reducing radioactive backgrounds and enhancing sensitivity to low-energy signals. I describe the design and operation of a charcoal-based chromatography system that reduced krypton contamination in the LZ xenon supply to below 300 parts per quadrillion. I also present a study of electron emission from high-voltage electrodes, characterizing localized emitters and using coincident photon signals to identify individual background events. These techniques support LZ's low-energy, ionization-only analysis and contribute to the combined analysis of the first two science runs, which achieved world-leading sensitivity to dark matter masses above 10 GeV. Finally, I discuss efforts to expand sensitivity to low-mass dark matter through hydrogen doping, using the HydroX test platform to explore the feasibility of this technique for future xenon-based detectors.