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A Search for Dark Matter Axions with the Orpheus Experiment

Axions are well motivated particles that could make up most or all of the dark matter if they have masses below 100 $μ$eV. Microwave cavity techniques comprised of closed resonant structures immersed in solenoid magnets are sensitive to dark matter axions with masses of a few $μ$eV, but face difficulties scaling to higher masses. We present the a novel detector architecture consisting of an open, Fabry-Pérot resonator and a series of current-carrying wire planes, and demonstrate this technique with a search for dark matter axion-like particles called Orpheus. This search excludes dark matter axion-like particles with masses between 68.2 and 76.5 $μ$eV and axion-photon couplings greater than $4\times10^{-7} \mathrm{GeV}^{-1}$. We project that the fundamental sensitivity of this technique could be extended to be sensitive to couplings below $1\times10^{-15} \mathrm{GeV}^{-1}$, consistent with the DFSZ model of QCD axions.