Status of the Axion Dark Matter Experiment -- High Frequency (ADMX-HF)

The axion is a well-motivated cold dark matter candidate first postulated to explain the absence of CP violation in strong interactions. Dark matter axions may be detected via their resonant conversion into photons in a high-$Q$ microwave cavity permeated by a strong magnetic field. The Axion Dark Matter eXperiment (ADMX) has used this technique to exclude axion models in the few $\mu$eV mass range. Much of axion dark matter parameter space has until recently been beyond the reach of experiment, but advances in amplifier technology have enabled quantum-limited axion detection around 20~$\mu$eV (5~GHz). ADMX-HF (high-frequency) at Yale, which recently took its first data, will have sufficient sensitivity to probe this region of parameter space. This talk will discuss the design, current status, and projected sensitivity of ADMX-HF, which serves as both an innovation test bed and a pathfinder search at high frequencies.