While axions were originally proposed as a solution to the strong CP problem in quantum chromodynamics, it turned out that they can also act as dark matter candidates. As such, earth should constantly move through a halo of axion fields that can interaction with electromagnetic fields. The experimental idea of a cavity-based search experiment (or haloscope) is therefore to apply a strong magnetic field in a resonant electromagnetic cavity. Axion like particles can convert in the presence of this magnetic field into photons, governed by the axion-photon coupling constant, gayy.

The conversion probability of the axion to photons can be enhanced when the axion mass, ma, corresponds to the resonance frequencies of the cavity. The conversion probability of axion like particles into photons scales quadratically with the magnetic field strength with B2 and linearly with the volume. The available volume of the magnetic field also determines the shape of the cavity and thus its resonance frequency. Given that only one axion mass can be probed at one time, the resonance condition of the electromagnetic cavity must be tunable to probe a full band of different axion masses.