Searching for low-mass axions using resonant upconversion

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 gaBB. 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 1.12-1.20 μeV above a coupling strength of both gaγγ and gaBB at 3×10-6 1/GeV, after a measurement period of 30 days, which is an improvement of 3 orders of magnitude over our previous result.