Felsenkeller 5 MV underground accelerator: Towards the Holy Grail of Nuclear Astrophysics 12C(α,γ)16O

Underground ion accelerator laboratories such as the LUNA 0.4 MV accelerator in Italy are indispensable in order to precisely measure charged particle induced nuclear reaction cross sections. The rock overburden attenuates the cosmic ray induced background and enables the measurement of very low interaction rates. The first of the new generation of higher-energy underground accelerators is the Felsenkeller 5 MV machine in Dresden/Germany, under construction and due to open late 2017. The cross sections of several nuclear reactions relevant to nucleosynthesis in a supernova and/or its precursor are not well known, with effects on the nucleosynthetic output of these events. Of these reactions, it is planned to study the 12C(alpha,gamma), 22Ne(alpha,gamma), 40Ca(alpha,gamma), and several other cases at Felsenkeller. The scientific motivation and state of work will be reviewed. It is hoped that the Felsenkeller accelerator will be widely used, including researchers from as many German universities as possible.