Nuclear Astrophysics Experiments in Collaboration with Ruhr University

This paper reports on two nuclear astrophysics experiments performed in collaboration with Ruhr University. In a 12C+12C fusion reaction, the 12C(12C, α)20Ne and 12C(12C, p)23Na reactions were studied in the energy range of E = 2.10 MeV to 4.75 MeV using γ-ray spectroscopy. The deduced astrophysical S(E)* factor exhibited a new, strong resonance at E = 2.14 MeV, which lay at the high-energy tail of the Gamow peak. The resonance increased the reaction rate of the α-channel by a factor of five near T = 8 × 108 K. The electron screening in d(d, p)t was studied for a series of deuterated metal, insulator and semiconductor targets. Compared with the measurements performed with a gaseous D2 target, a large effect was observed in most metals, while a comparatively small effect was found in the insulators and semiconductors. Subsequently the temperature dependence of the electron screening in the d(d, p)t reaction was studied for the deuterated metals Pt and Co. Enhanced electron screening decreased with increasing temperature. These data represent the first observations of the temperature dependence of a nuclear cross section.