  Microwave cavities have been deployed to search for bosonic dark matter
candidates with masses of a few $\mu$eV. However, the sensitivity of these
cavity detectors is limited by their volume, and the traditionally-employed
half-wavelength cavities suffer from a significant volume reduction at higher
masses. ADMX-Orpheus mitigates this issue by operating a tunable,
dielectrically-loaded cavity at a higher-order mode, which allows the detection
volume to remain large. The ADMX-Orpheus inaugural run excludes dark photon
dark matter with kinetic mixing angle $\chi > 10^{-13}$ between 65.5 $\mu$eV
(15.8 GHz) and 69.3 $\mu$eV (16.8GHz), marking the highest-frequency tunable
microwave cavity dark matter search to date.
