Direct measurement of beta-delayed neutron emission at and beyond doubly-magic $^{78}$Ni*

An experiment aiming to measure the beta-neutron-gamma decay properties of nuclei around $^{78}$Ni produced by in-flight fission of a $^{238}$U beam at 345 MeV/u and selected by means of BigRIPS was recently performed using the BRIKEN setup [1]. The BRIKEN detector is composed of the AIDA implantation-decay array [2] as well as 140 $^{3}$He tubes and 2 HPGe clovers. The counting efficiency of a single beta-delayed neutron (${\rm \beta_{1n}}$) is above 60 %. About 24 ${\rm \beta_{1n}}$ values have been measured for the first time between $^{76}$Co and $^{96}$Br including the ${\rm \beta_{1n}}$ for $^{78}$Ni [3]. Over 20 nuclei that are expected to exhibit ${\rm \beta_{2n}}$ emission are within the studied region. An analysis of nuclear structure effects responsible for the observed ${\rm \beta_{1n}}/{\rm \beta_{2n}}$ competition should now be possible as well as performing the r-process simulations with a greatly enhanced set of experimental ${\rm \beta_{xn}}$ values. An overview of experiment and a discussion of some preliminary result will be presented. [1] A. Tarifeno-Saldivia et al., IOP Jour. of Instr. 2016. [2] C. Griffin et al., in Proc. of NIC XIII Conf., 7-11 July 2014, Debrecen, Hungary. [3] K. Rykaczewski et al., experiment RIBF 127R, RIKEN RIBF, May/June 2017.