Early Nuclear Astrophysics Results from the FRIB Decay Station initiator (FDSi)

The study of exotic neutron-rich nuclei is key to the understanding of nuclear energy generation and nucleosynthesis in astrophysical environments. In addition to the various degrees of neutron-richness in the slow (s-), intermediate (i-), and rapid (r-) neutron capture processes, neutron-rich nuclei also play a role in electron degenerate environments where electron captures allow for the synthesis of very exotic nuclei. For example, understanding the thermal structure of accreted neutron star crusts in X-ray bursting systems is dependent on the details of nuclear energy release by subsequent electron captures on the ashes of X-ray bursts.

 

As nuclei become increasingly neutron-rich, now reachable by FRIB, the possible decay channels also increase, and the decay strength is fragmented amongst these different channels. Therefore, to properly understand the important decay channels for nuclear astrophysics, a complete spectroscopy of the beta-decay of very neutron-rich nuclei is critical for the accurate extraction of decay properties. The FRIB Decay Station initiator (FDSi) is a combination of different ancillary detectors, including high-purity Germanium detectors, neutron time-of-flight detectors and the high-efficiency, highly segmented total absorption spectrometer MTAS, that was designed with such complete spectroscopy in mind.

 

The FDSi has been used for several experiments since the operation of FRIB commenced. Preliminary nuclear astrophysics results from these experiments will be presented, and future possibilities will be discussed.