A new tool for (α,n) yield calculations and its implications for DEAP-3600

Neutron-induced nuclear recoils present one of the dominant backgrounds in many low-background experiments. These neutrons are largely radiogenic in origin, coming from fission and (α, n) reactions in detector components. The (α, n) neutron production rate in a material depends on its composition and the energies of the α decays inside of it. We present NeuCBOT, the Neutron Calculator Based on TALYS, a new tool for calculating the (α, n) yields and neutron energy spectra for materials exposed to a given set of α energies or α-emitting isotopes. We benchmark these calculations against measured yields and SOURCES-4C calculations. We discuss these yield calculations in the context of DEAP-3600, a Weakly Interactive Massive Particle dark matter detector at SNOLAB. Using NeuCBOT and Geant4 simulations, we predict the neutron-induced nuclear recoil background in DEAP-3600. We then present in-situ constraints on the neutron background rate in DEAP-3600, consistent with our prediction.