Nuclear astrophysics with a recoil mass separator

Radiative capture reactions, like (α,γ)- and (p,γ)-reactions, are of great importance for the understanding of the different burning phases in stars. In most cases laboratory studies of some key reactions are very difficult due to the low cross section at the relevant Gamow energy where the stellar burning occurs. A new approach to measure these capture cross sections involves a two-sided differentially pumped gas target, a recoil mass separator, and a ΔE-E detector telescope (allowing for particle identification) as detection system. This combination allows a direct measurement of the produced recoils in inverse kinematics. The direct observation of the recoils requires an efficient recoil mass separator to filter out the incident beam particles from the recoils. The recoil separator must not only have a high filtering power but also a high transmission of the recoils (for the selected charge state) between the gas target chamber and the ΔE-E telescope. The feasibility of the separation of projectiles and recoils with a mass difference of 1 amu to 1 part in 1011 or more has been demonstrated in various experiments. A few of these experiments are discussed in this paper