A possible underground accelerator in the Dresden Felsenkeller

Abstract

Typical energies in an astrophysical scenario lie far below the Coulomb barrier. Therefore the cross section is tiny, and in an in-beam experiment the experimental counting rate in γ detectors is low. Often it is dominated by cosmic-ray induced background, even if suitable anticoincidence shields are applied. This problem can be overcome by placing the accelerator deep underground, where a sufficiently thick rock overburden attenuates cosmic rays. Based on the success of the LUNA 400 kV underground accelerator in Italy, several higher-energy underground accelerators are in the planning phase worldwide. All of them should be hosted in laboratories shielded by over 1000 m of rock, where cosmic-ray muons are negligible for the purposes of nuclear physics experiments. A preliminary background study indicates that a combined approach, using a shallow underground laboratory below 47 m of rock and an active shield to suppress surviving muons, results in a background level that is similar to deep underground sites.