Surrogate Nuclear Reactions using STARS

The results from two surrogate reaction experiments using the STARS (Silicon Telescope Array for Reaction Studies) spectrometer are presented. The surrogate method involves measuring the particle and/or γ-ray decay probabilities of excited nuclei populated via a direct reaction. These probabilities can then be used to deduce neutron-induced reaction cross sections that lead to the same compound nuclei. In the first experiment STARS coupled to the GAMMASPHERE γ-ray spectrometer successfully reproduce surrogate (n,γ), (n,n'γ) and (n,2nγ) cross sections on 155,156Gd using Gd 3He-induced reactions. In the second series of experiments an energetic deuteron beam from the ESTU tandem at the Wright Nuclear Structure Lab at Yale University was used to obtain the ratio of fission probabilities for 238U/ 236U and 237U/ 239U populated using the 236,238U(d,d'f) and 236,238U(d,pf) reactions. Results from these experiments are presented and the implications for the surrogate reaction technique are discussed