Searching for low-mass axions using resonant upconversion
Catriona A. Thomson, Maxim Goryachev, Ben T. McAllister, E.N. Ivanov, P. A. Altin, Michael E. Tobar
Abstract
We present new results of a room temperature resonant AC haloscope, which searches for axions via photon upconversion. Traditional haloscopes require a strong applied DC magnetic background field surrounding the haloscope cavity resonator, the resonant frequency of which is limited by available bore dimensions. UPLOAD, the upconversion low-noise oscillator axion detection experiment, replaces this DC magnet with a second microwave background resonance within the detector cavity, which up-converts energy from the axion field into the readout mode, accessing axions around the beat frequency of the modes. Furthermore, unlike the DC case, the experiment is sensitive to a newly proposed quantum electromagnetodynamical axion coupling term ${g}_{aBB}$. Two experimental approaches are outlined---one using frequency metrology and the other using power detection of a thermal readout mode. The results of the power detection experiment are presented, which allows exclusion of axions of masses between $1.12\ensuremath{-}1.20\text{ }\text{ }\mathrm{\ensuremath{\mu}}\mathrm{eV}$ above a coupling strength of both ${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}$ and ${g}_{aBB}$ at $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}\text{ }\text{ }1/\mathrm{GeV}$, after a measurement period of 30 days, which is an improvement of 3 orders of magnitude over our previous result.