Nuclear astrophysics studies at the LENA facility: The γγ-ray detection system

The detection system of The Laboratory for Experimental Nuclear Astrophysics is described, including methods for measuring weak capture-γγ-ray resonances. Improved γγγγ-coincidence techniques are detailed, as well as the reduction of cosmic muon-induced background in the energy region of Eγ=0.6–9.0MeV by the use of compact cosmic muon anti-coincidence shields. These techniques reduced background count rates in the regions of Eγ=0.6Eγ=0.6–3.03.0 and 3.0–9.0 MeV with respect to unshielded singles count rates by factors of 3600 and 21, respectively.