Today we report in Physical Review Letters on a new method to constrain the conversion of axion-like particles into photons, measured using the superconducting resonant single particle detection circuit of one of our cryogenic Penning traps. By searching the noise spectrum of our fixed frequency resonant circuit for peaks caused by axion-to-photon conversion in the strong magnetic field of the Penning trap magnet, we are able to constrain the coupling of ALPs with masses around 2.7906-2.7914 neV to be gag<1*10-11 / GeV. This is more than one order of magnitude lower than the best laboratory haloscope and approximately five times lower than the CAST helioscope, setting limits in a mass and coupling range thatis not constrained by astrophysical observations. This approach can be extended to many other Penning trap experiments, and has the potential to provide stringent high-resolution limits in the low ma range. Using the existing technologies available in BASE and developing a purpose-built experiment, the detection bandwidth could be increased by a factor of >1000 at at least 100-fold improved detection sensitivity.
For details see: