DEPARTMENT OF PHYSICS DISSERTATION DEFENSE: Nicholas Rapidis

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Title:  

Sub-μeV dark matter axion searches: design and realization

Abstract: 

The absence of charge-parity violation in the strong sector of the Standard Model — known as the strong CP problem — is one of the most significant fine-tuning problems in modern physics. As a problem that cannot be resolved using anthropic arguments, its only clear resolution arises from the introduction of a new massive scalar particle, the axion. The cosmological origins of the axion and its evolution also make it a very appealing dark matter candidate, thus solving another central problem in physics wherein ~80% of the mass in the universe exists in an undetected form of matter that is not predicted by the Standard Model. In this thesis, we present designs of new experiments that search for sub-μeV dark matter axions as part of the DMRadio program, namely DMRadio-m3, DMRadio-Core, and preliminary designs of DMRadio-GUT. These experiments use resonant LC circuits to search for dark matter axions utilizing their interaction with applied dc magnetic fields. We also present results from the realization of the DMRadio-50L experiment at Stanford, with a particular focus on the superconducting readout electronics and resonator components. The results from this thesis present substantial progress in the lab towards the first realization of a tunable lumped-element axion search while also providing a concrete roadmap for the experiments which will search for sub-μeV axions that can solve the strong CP problem and the dark matter problem.