STAX. An Axion-like Particle Search with Microwave Photons

We discuss an improved detection scheme for a light-shining-through-wall (LSW) experiment for axion-like particle searches. We propose to use: gyrotrons or klystrons, which can provide extremely intense photon fluxes at frequencies around 30 GHz; transition-edge-sensors (TES) single photon detectors in this frequency domain, with efficiency $\approx1$; high quality factor Fabry-Perot cavities in the microwave domain, both on the photon-axion conversion and photon regeneration sides. We compute that present laboratory exclusion limits on axion-like particles might be improved by at least four orders of magnitude for axion masses $\lesssim 0.02$ meV.