SuperCDMS SNOLAB, HVeV Run 3, and Development of KIPM Detectors

Citation

Aralis, Taylor Benjamin (2024) SuperCDMS SNOLAB, HVeV Run 3, and Development of KIPM Detectors. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/gxjp-0863. https://resolver.caltech.edu/CaltechTHESIS:11272023-225643701

Abstract

Dark matter is the theorized source of many observed large-scale gravitational effects. It is dark in the sense that it lacks any heretofore measurable direct interaction with the electromagnetic spectrum. Being unable to rely on absorption, reflection, or emission of photons makes studying dark matter particularly challenging. Excluding neutrinos, which fail to explain the observed large-scale effects, dark matter has never been conclusively identified in a local laboratory experiment. There are many proposed models that could explain both our large-scale observations and our lack of local observations while still allowing for the possibility of local observation. Ultra-sensitive direct-detection experiments attempt to make precisely such observations. Confirmed detection of a new stable particle would provide important information for improving our understanding of both dark matter and cosmological models.

The SuperCDMS SNOLAB experiment is a direct-detection experiment designed with an initial focus on particle masses < 10 GeV. The experiment will measure both phonon and ionization signals in kg-scale semiconductor crystals held at cryogenic temperatures. In this thesis, I describe the experiment with emphasis on the ionization readout. I also detail the characterization process I performed on the ionization amplifier's low-power high-electron-mobility transistors (HEMTs).

SuperCDMS high-voltage eV-resolution (HVeV) detectors are gram-scale detectors designed to achieve single electron-hole-pair sensitivity. The first HVeV direct-detection search produced world-leading exclusion limits for dark-matter masses down to ~1 MeV. Here, I present my work analyzing the third search using such detectors. Run 3 was the first to include multiple detectors operated simultaneously and achieved an order of magnitude greater exposure than previous runs. I report the resulting exclusion limits for electron-coupled, dark-photon, and axion-like-particle dark matter.

Lastly, I discuss work performed at Caltech towards the development of kinetic-inductance phonon-mediated (KIPM) dark-matter detectors. KIPM detectors use frequency-multiplexed kinetic inductance detectors (KIDs) and have the potential for excellent event-position reconstruction and background rejection. KIPMs also present a clear path towards sub-eV resolution on event recoil energy. Such detectors could be used as part of a payload upgrade in SuperCDMS SNOLAB. KIPMs could also be used in smaller-scale experiments similar to SuperCDMS HVeV.

Thesis Files