A New Dedicated Setup for Beta-Delayed Neutron Studies

Beta-delayed-neutron (βn) emitters are important to nuclear physics, including nuclear astrophysics and nuclear-reactor operations. Recent successes using recoil-ion time-of-flight spectroscopy to study βn precursors with the Beta Paul Trap (BPT) at ANL [1] have led to the development of a dedicated ion trap and detector system. This new setup is a radio-frequency quadrupole (RFQ) ion trap surrounded by a detector array, optimised to make highly selective measurements of βn emitters. Following β or βn emission, the recoiling daughter nucleus is detected in a microchannel plate (MCP) detector, and the β is detected in a dE-E plastic scintillator. The time difference between the detection of the β and the recoiling ion is used to distinguish β and βn events. This novel technique can be used to determine the neutron branch and neutron energy without requiring neutron detection. SIMION and GEANT4 are used to simulate previous BPT measurements using the new system, enabling optimisation of the detectors, geometry and measurement metrics. Simulation results will be presented. 

[1] R. M. Yee et al, PRL 110 (092501) 2013; J. M. Munson et al, NIM A898 (2018) 60-66