A Multi-Layered Approach to Multi-Neutron Filtering

MoNA (the Modular Neutron Array) is an array of 144 plastic scintillator detectors used to detect neutrons from the decay of neutron-unbound nuclei. As MoNA will soon be used at higher FRIB energies to investigate unbound nuclei that decay by two or more neutrons, it is important to accurately identify which hits in MoNA correspond to independent neutrons. We have developed a multi-layered approach for sorting out hit clusters (produced by np charge exchange protons creating additional light in adjacent bars) and causal events (occurring close enough in spacetime to be connected by a single scattered neutron) to properly assess the independent neutron multiplicity; for 2n data sets, our goal is to enhance the true 2 neutron signal and reduce the 1n signal to below 5%. We have used our filtering algorithm to produce E_decay plots from existing experimental data sets, and have seen higher 2n statistics and increased resolution, relative to traditional causality filters. Development of our sorting algorithm continues as we search for and identify additional sorting parameters that can also be used to recover 2n events which appear causally connected (and are therefore filtered out with the current algorithm), in order to provide higher 2 neutron statistics.