Astrophysical and cosmological data point convincingly to a large component of cold dark matter in the Universe, but the nature of that dark matter is still unknown. Axions are possible dark matter candidates. This award will support the Axion Dark Matter eXperiment - High Frequency (ADMX-HF), which searches for Axions in the galactic halo. ADMX-HF extends the range of the ADMX experiment to the higher frequency band that probes both Axions with trace mass and Axions with sufficient mass to account for all the matter density in the Universe. ADMX-HF is therefore a uniquely powerful probe of Axion dark matter. Several new technologies have been developed in support of ADMX-HF. These have potential applications for high-precision measurements in other fields. The group has a history of employing undergraduates in the research, which provides training and experience in the areas of experimental control and data analysis software, mechanical and electronic assembly.
Axions in the galactic halo can be converted into a narrow-band microwave signal by an apparatus consisting of a microwave-cavity resonator permeated by a magnetic field. ADMX-HF is a small microwave cavity experiment that serves as both a pathfinder to take first data in the 10 to 100 micro-electronvolt range and as a test-bed for developing new cavities and quantum-limited photon detection schemes that could be migrated to the larger ADMX platform. All major systems have been constructed and are being integrated into the experiment with full commissioning to begin soon. During this award period ADMX-HF should transition to routine data-taking operation and probe the 16.5 to 66 micro-electronvolt range, bracketing the mass of the axion that corresponds to saturation of the matter density of the universe.