Ultra-sensitive in-beam g-ray spectroscopy deep underground

Ultra-sensitive in-beam γ-ray spectroscopy studies for nuclear astrophysics are performed at the LUNA (Laboratory for Underground Nuclear Astrophysics) 400 kV accelerator, deep underground in Italy's Gran Sasso laboratory. By virtue of a specially constructed passive shield, the laboratory γ-ray background for Eγ < 3 MeV at LUNA has been reduced to levels comparable to those experienced in dedicated offline underground γ-counting setups. The γ-ray background induced by
an incident α-beam has been studied. The data are used to evaluate the feasibility of sensitive inbeam experiments at LUNA and, by extension, at similar proposed facilities.