Felsenkeller 5 MV underground accelerator: Muon, neutron, 𝛾-ray background and project status

Motivated by the success of the world's only underground ion accelerator, LUNA 0.4 MV in Italy, a project for a higher-energy underground accelerator is underway in Dresden. A 5\,MV Pelletron accelerator with double charging chains and provision for intensive ^1H^+, ^4He^+, and ^{12}C^+ beams based on external and internal ion sources is currently being installed in the Felsenkeller underground site in Dresden. Civil construction work in Felsenkeller will be completed in August 2017. The nine Felsenkeller tunnels are shielded from cosmic rays by 45\,m rock overburden, attenuating the background in radiation detectors. New data on the muon, neutron, and $\gamma$ background in Felsenkeller will be shown, and used for a discussion on the feasibility of low-background experiments there. The new accelerator will be open for outside users, and its most important experimental capabilities will be summarized.