Measuring Stellar Fusion Cross Sections Underground

Daniel Bemmerer
Forschungszentrum Dresden-Rossendorf (FZD)


Due to the suppression by the Coulomb barrier, the cross sections of astrophysically relevant nuclear reactions are very low at the stellar energy. Therefore they can only be directly measured in a low-background environment. For more than a decade now, the LUNA collaboration has pursued this approach with a 0.4 MV accelerator in the Gran Sasso underground laboratory in Italy. It was highly successful in studying the nuclear physics of the Sun and of the Big Bang.

However, the energy range of LUNA is not sufficient to address the nuclear reactions of stellar helium and carbon burning and the neutron source reactions for the astrophysical s-process. Therefore, in the 2010 NuPECC Long Range Plan for nuclear physics in Europe, it is recommended to install one or more accelerators with higher energy underground.

I will discuss the methodology and main results of LUNA, and then review projects for new accelerators that are under discussion in Italy (Gran Sasso), Spain (Canfranc), Britain (Boulby), and recently also in Germany (Felsenkeller). Analogous efforts are being made in the US (DUSEL).