Simulating MADMAX in 3D: requirements for dielectric axion haloscopes

Abstract

We present 3D calculations for dielectric haloscopes such as the currently envisioned MADMAX experiment. For ideal systems with perfectly flat, parallel and isotropic dielectric disks of finite diameter, we find that a geometrical form factor reduces the emitted power by up to 30 % compared to earlier 1D calculations. We derive the emitted beam shape, which is important for antenna design. We show that realistic dark matter axion velocities of 10 −3 c and inhomogeneities of the external magnetic field at the scale of 10 % have negligible impact on the sensitivity of MADMAX. We investigate design requirements for which the emitted power changes by less than 20 % for a benchmark boost factor with a bandwidth of 50 MHz at 22 GHz, corresponding to an axion mass of 90 µeV. We find that the maximum allowed disk tilt is 100 µm divided by the disk diameter, the required disk planarity is 20 µm (min-to-max) or better, and the maximum allowed surface roughness is 100 µm (min-to-max). We show how using tiled dielectric disks glued together from multiple smaller patches can affect the beam shape and antenna coupling.

Experimental determination of axion signal power of dish antennas and dielectric haloscopes using the reciprocity approach

“…Overall, the effect of the antenna-booster resonances on P sig seems tolerable. Extending the dielectric JCAP04(2024)005 haloscope to more disks comes with its own challenge of increasingly tighter tolerances on geometric inaccuracies [24]. In addition, it might not be practical to measure the electric field everywhere in a many disks setup especially when considering a cryogenic setup.…”

Physical signatures of fermion-coupled axion dark matter

“…There are a number of experimental details that we have neglected in this work, all of which could be addressed in a more detailed analysis, along the lines of refs. [163,164]. For simplicity, we have only considered transparent mode setups.…”

Axion dark matter: How to see it?

“…For realistic sensitivity to reach the QCD axion models, the MADMAX Collaboration proposed to build a large-scale dielectric haloscope experiment that features a 2-m-long 10-T dipole magnet, a boosting system consisting of 80 dielectric disks with 1-m 2 area, and a low-noise receiver chain. Recently, they demonstrated a first proof-of-principle realization of the booster setup of the haloscope using a copper mirror and up to five sapphire disks ( 69 ) and performed a dedicated 3D simulation study to investigate design requirements for the dielectric disk system ( 70 ).…”