A new setup for the underground study of capture reactions

Abstract For the study of astrophysically relevant capture reactions in the underground laboratory LUNA a new setup of high sensitivity has been implemented. The setup includes a windowless gas target, a 4 π BGO summing crystal, and beam calorimeters. The setup has been recently used to measure the d(p,γ) 3 He cross-section for the first time within its solar Gamow peak, i.e. down to 2.5 keV c.m. energy. The features of the optimized setup are described.