Neutron spectroscopy and spectrum unfolding for nuclear reaction studies for RIB experiments.

Neutron spectroscopy is an important tool in the study of (p,n), (d,n), and (α,n) reactions, which probe single-particle states relevant to nuclear structure studies as well as reactions for heavy element nucleosynthesis. As the field of nuclear physics looks towards the next generation of radioactive beam facilities, such as FRIB, spectrum unfolding - an alternative method of neutron spectroscopy which is based on a detailed knowledge of the detector response- may offer a promising alternative to traditional time-of-flight methods. Spectrum unfolding has been well-tested for both continuous source measurements, such as ²⁵²Cf, and for normal kinematic reactions such as ¹⁸O(α,n)²¹Ne that provide discrete peaks. However, for inverse kinematic RIB experiments, the neutron spectrum is more complex, containing both the discrete reaction peaks of interest and a continuous neutron background from fusion evaporation in the target. Investigation of spectrum unfolding in this regime is being pursued via two methods; analysis of ²⁰Ne(d,n)²¹Na ReA6 beam data and simulations utilizing MCNP. In addition, LLNL is commissioning a new deuterated scintillator array for nuclear reaction studies. Details of this array and how it – and spectrum unfolding – will be used for experiments with RIBs will be discussed.