Neutron Sources in Stars, at the National Ignition Facility, and in the Underground

Neutrons are an important ingredient for the production of heavy elements. Without them nucleosynthesis processes such as the s-process or the r-process are not possible. While neutrons in explosive environments such as core collapse supernovae and merging neutron stars are the results of the disintegration of heavy nuclei at high density and temperature conditions, neutrons in cooler stellar or earth environments are based on specific nuclear reactions, mostly (α,n) reactions occurring on high abundance, low Z elements. Stellar helium burning is the natural site for neutron production in stellar interiors, where the dominant neutron sources are anticipated to be the 13C(α,n) and the 22Ne(α,n) reactions at stellar temperatures. Neither one of these reactions is well known at stellar energy conditions. Measuring the cross sections requires a background free environment deep underground. These environments, however are polluted by neutrons from (α,n) reactions on mineral materials containing 10,11B, 13C, 17,18O, 25,26Mg and possibly 29,30Si. The study of these reactions may also offer better insight into the understanding of the stellar plasma environment. This can be probed at the National Ignition Facility (NIF) at Livermore. This talk will focus on the scientific questions and challenges associated with the very low energy studies of the stellar neutron sources in deep underground and plasma environments.