Ultra-sensitive in-beam $ \gamma$ -ray spectroscopy for nuclear astrophysics at LUNA

Abstract

Ultra-sensitive in-beam $ \gamma$ -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 $ \gamma$ -ray background for $\ensuremath E_{\gamma}$ < 3 MeV at LUNA has been reduced to levels comparable to those experienced in dedicated offline underground $ \gamma$ -counting setups. The $ \gamma$ -ray background induced by an incident $ \alpha$ -beam has been studied. The data are used to evaluate the feasibility of sensitive in-beam experiments at LUNA and, by extension, at similar proposed facilities.