Beta-Delayed Neutron Measurements for R-Process Isotopes with BRIKEN*

Most of the unstable isotopes produced during the rapid neutron capture process (r-process) are expected to be $\beta$-delayed neutron emitters; a decay mode that populates neutron-unbound states in the daughter nuclei. The probability for $\beta$-delayed neutron emission is a key input for models of r-process nucleosynthesis in neutron star mergers and other astrophysical sites. $\beta$-delayed neutrons contribute to the density of free neutrons in the astrophysical environment, in particular during the late stages of the neutron capture phase of the r-process, and this decay mode also affects the final abundance of the elements produced once unstable isotopes have decayed to $\beta$-stability. A significant number of nuclei along the path of the r-process are finally within reach of decay experiments, thanks to a new generation of laboratories designed to produce intense beam of neutron-rich isotopes coupled with sensitive experimental setups. Beta-delayed neutrons at RIKEN (BRIKEN) is a setup for $\beta$-decay measurements at the Radioactive Isotope Beam Factory (RIBF) in RIKEN, Japan, which achieves a high detection efficiency with a state-of-the-art neutron detector based on $^{3}$He proportional counters. Since the first BRIKEN experiment, in 2017, our collaboration has studied $\beta$-delayed neutron emission in regions of the nuclear chart extending from cobalt (Z=27) to gadolinium (Z=64). The experiments covered regions that affect salient features of the r-process: the A=130 and the rare-earth elements abundance peaks. I will present the program of experiments of the BRIKEN collaboration, and discuss some of the first results and their impact in r-process models.