A New Tool for ($\alpha$,n) Yield Calculations and Radiogenic Neutron Backgrounds in 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 ($\alpha$,n) reactions in detector components. The ($\alpha$,n) neutron production rate in a material depends on the composition of the material as well as the energies of the $\alpha$ decays that occur within it. In this talk, we will present NeuCBOT, a new tool for calculating the ($\alpha$,n) yields and neutron energy spectra for arbitrary materials exposed to contamination from a given set of $\alpha$ energies or $\alpha$-emitting isotopes, and we will benchmark these calculations against calculations made by SOURCES-4A and various measured yields.
We will discuss these yield calculations in the context of DEAP-3600, a dark matter detector located at SNOlab, searching for nuclear recoils produced by Weakly Interacting Massive Particles. Using NeuCBOT and Geant4 simulations, we will predict the neutron-induced nuclear recoil backgrounds in DEAP-3600. We will then present in-situ measurements of neutron interactions in DEAP-3600 to show that these predictions are consistent with our observations, and that the neutron backgrounds are within the experiment's design goals.
I will be presenting a new neutron yield calculator, NeuCBOT, as well as discussing the expected neutron backgrounds in DEAP-3600, including in-situ limits on the neutron background rate, consistent with these predictions.