Dark Matter Search
Axion-like particles (ALP) could constitute a significant fraction of dark matter. A spin-dependent coupling to ordinary matter then leads to the novel signature of an effective oscillating magnetic field that can be detected using nuclear magnetic resonance techniques.
Dark photon dark matter is a potential dark matter candidate, which could be described as a weakly coupled "hidden electric field", generated via kinetic mixing of the regular photon field and the dark photon field. The obeservable is a real electromagnetic field, which can be constrained via magnetic field measurements.
As a result, both dark matter candidates can be constrained via magnetic field measurements.
Towards an electrostatic storage ring for fundamental physics measurements
Storage ring precision experiments gain increasing attention to search for these couplings, as they provide alternative access via extreme measurement precision.
We are currently building a versatile, table-top sized electrostatic storage ring with 5.7 m circumference for non-relativistic polarized ions to search for EDMs as well as axion couplings.
The first implementation will be a demonstrator setup, operated at room temperature, suitable to store up to 109 ions in 200 bunches. The vacuum system will be set up next year and the ion source is currently being built.
Barium ion source: experimental progress
For the demonstrator setup, we plan to use barium ions from a laser ablation source. Ba+ has no nuclear spin and only one valence electron and can be polarized with 2 lasers. This makes it suitable to set new laboratory axion-electron couplings at a first "switch-on" of the storage ring. Therefore, the ion source is required to produce 10^6 ions per pulse with spot sizes of 100*10^-6 m or smaller. The vacuum system is setup in our lab right now and we are expecting to get barium ions beginning of next year.
Outdoor dark matter lab in Austria
We are currently establishing an outdoor lab in the Austrian alps. There the noise level is very low and therefore small magnetic fields can be measured with earth-field Rb magnetometers. As we do not need magnetic shielding there, we can constrain ALP couplings to electron spins as well as dark photon kinetic mixing.
Brandenstein, C. et al. Towards an electrostatic storage ring for fundamental physics measurements. Preprint at http://arxiv.org/abs/2211.08439 (2022)
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