DEPARTMENT OF PHYSICS DISSERTATION: Andrew Ames

Ph.D. Candidate:  Andrew Ames

Research Advisor:   Dan Akerib

Date:   June 10, 2025

Time:   12:30 PM PST

Location:  Varian 355

Zoom link:  https://stanford.zoom.us/j/93014231272

Password: Email physicsstudentservices [at] stanford.edu (physicsstudentservices[at]stanford[dot]edu) for password.

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

Abstract: 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.