The latest Snowmass and P5 High Energy Physics (HEP) reports, along with more recent community efforts, identify the search for QCD axion dark matter as a very important aspect of HEP Cosmic Frontier. The Generation 2 Axion Dark Matter eXperiment (ADMX-G2), sited at the University of Washington (UW), is based on the idea that if axions make up the dark matter in our Milky Way halo, they can be detected by their conversion into microwave photons within a high-Q cavity threaded by a large magnetic field. The signal power is of order of a yoctoWatt (10-24 Watts) of electromagnetic power, and signal detection therefore calls for deep cryogenic cooling and microwave amplifiers based on quantum electronics. Notably, this system recently demonstrated sensitivity to the very compelling but extraordinarily-feebly coupled DFSZ axion, by far the only experiment even close to achieving this sensitivity.

This grant supports the next stage in the approved ADMX-G2 experiment, for the UW-specific efforts to continue the axion search to higher frequencies. Specifically, this consists of the fabrication, installation, commissioning and operation of a series of cavity and electronics packages at the ADMX-G2 site at UW to reach frequencies up to 2 GHz. A separate research grant supports UW scientists.