A new measurement of the E1 amplitude in 12C(α,γ0)16O

The El amplitude of the transition to the ground state in the C-12(alpha, gamma)O-16 capture reaction was measured in the energy range E-cm=1.3 to 3.0 MeV using an intense C-12 beam in combination with a windowless He-4 gas target and an array of six 70% HPGe detectors. The detectors were placed in a ring-shaped geometry around the target at a distance of 17 cm on a plane perpendicular to the beam axis. A target length of 5.3 cm was defined by a 12.5 cm thick lead shielding. Passive and active shielding was used to achieve the necessary suppression of the beam induced and cosmic background. The results of this measurement and their extrapolation to the relevant energy during the helium burning phase in massive stars are reported.