A new measurement of the E1 amplitude in C-12(alpha,gamma(0))O-16

The El amplitude of the transition to the ground state in the C-12(alpha, g amma)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 t arget 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 achi eve the necessary suppression of the beam induced and cosmic background. Th e results of this measurement and their extrapolation to the relevant energ y during the helium burning phase in massive stars are reported.