The Felsenkeller underground ion accelerator is a 5 MV Pelletron accelerator originally produced by National Electrostatics (NEC) and commissioned in the Felsenkeller underground facility in 2019. It serves to provide accelerated charged particle beams for experiments in the Felsenkeller underground low-background facility. Typical ion beams (in brackets typical intensities and energies) include hydrogen (1-30 µA, 0.5-3 MeV), helium (1-30 µA, 0.5-5 MeV), carbon (1-30 µA, 1-15 MeV).

The accelerator can be used with either one of two ion sources: The external ion source is a 134-cathode SNICS cesium sputter ion source (NEC) and can provide negatively charged ions that are then stripped of some of their electrons in the nitrogen gas stripper of the accelerator terminal, for so-called tandem mode operation. The internal ion source is a radio frequency ion source (NEC) that is mounted directly on the 5 MV high voltage terminal and inserts its beam via an electrostatic deflector, for so-called single-ended operation.

The underground Felsenkeller site features a strong background reduction: 40x less muons, 180x less neutrons, 1000x less gamma signal with respect to the surface of the earth.

See https://www.hzdr.de/db/Cms?pNid=1029

Access is also available supported by the European Union (Transnational Access to Research Infrastructures), see http://chetec-infra.eu/tna/felsenkeller/

The Felsenkeller accelerator was jointly created by HZDR and TU Dresden (https://dresden-technologieportal.de/de/partner/view/id/1379). It is being used for the own research of the two partners and also made available for external users for scientific use, based on the recommendations by an international advisory board.