Nuclear Astrophysics

Capture cross sections relevant to nucleosynthesis from statistical decay properties

For a full understanding of the evolution of elemental abundances a wealth of nuclear data is necessary. The production rates depend sensitively on the photon strength function (PSF) and nuclear level density (NLD) due to their central role in nuclear reactions. It has been shown that measured (n,γ) cross section data can be successfully reproduced by using the PSF and NLD data as input into cross section calculations. These cross-sections in turn are inputs into large network calculations to model the nucleosynthesis in astrophysical environments. Any unknown deviation from a smooth low-energy tail of the giant electric dipole resonance such as the pygmy dipole resonance can change the nuclear reaction rates in astrophysical environments significantly.

Over the last few years we have built up the necessary particle detection capabilities at iThemba LABS to perform resonance and photon strength function measurements in South Africa. Many of the interesting physics questions can currently not be answered because of the low statistics at high-γ ray energies due to the low-efficiency nature of germanium detectors. Large volume LaBr3:Ce detectors will complement the AFRODITE array to provide the necessary detection efficiency at high energies while the germanium detectors in 2017.