Abstract

The axion is a hypothetical particle that may solve two major problems in physics: the strong CP problem in quantum chromodynamics (QCD) and the unknown particle nature of the dark matter. Axion haloscopes like the Axion Dark Matter eXperiment (ADMX) are capable of probing the region of parameter space where axions could constitute the dark matter. These experiments use a microwave resonant cavity in a strong magnetic field to convert axions into detectable photons when their Compton wavelength matches the resonant mode of the cavity. By moving a metal rod within the cavity volume, the resonant frequency can be tuned, and the experiment can sweep through axion parameter space. The expected signal power is typically ~10^-23 W, so superconducting amplifiers operating near the quantum limit are required to reach benchmark model KSVZ and DFSZ sensitivities. As haloscopes move to higher frequencies with smaller wavelengths, the cavity volume decreases, reducing the signal power and slowing down scan rates. In this thesis, I present work toward two complementary approaches to this problem: (1) the development, characterization, and operation of the cold electronics for ADMX as it advances toward a multicavity system, and (2) the design and initial testing of a smaller scale, but high sensitivity, helium-tuned experiment designed for squeezed vacuum scan speed enhancements.

Committee Chair

James Buckley

Committee Members

Erik Henriksen; Karthik Ramanathan; Kater Murch; P. S. Bhupal Dev

Degree

Doctor of Philosophy (PhD)

Author's Department

Physics

Author's School

Graduate School of Arts and Sciences

Document Type

Dissertation

Date of Award

4-27-2026

Language

English (en)

Author's ORCID

https://orcid.org/0000-0002-8072-3799

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