Evaluating SNO+ backgrounds through 222RN assays and the simulation of 13C(a, n)160 reactions during water phase

Abstract

SNO+ is a large multipurpose neutrino detector searching for rare interactions. Some backgrounds come from naturally occurring 222 Rn and its daughters within the 238 U chain. Under development are cryogenic trapping assay systems which will monitor the 222 Rn levels within scintillator, water, N 2 cover gas, and small detector materials. These systems can measure concentrations up to 8×10 −5 Rn atoms/L (1.6 × 10 −17 g 238 U/g LAB) within scintillator, and 4.75×10 −15 g are discussed within. 13 238 U/g H 2 O in water. The status of the assay systems C(α,n) 16 O reactions occur from 222 Rn’s progeny 210 Po, but Monte Carlo simulations predict < 0.4 events within the SNO+ fiducial volume of 5.5 m and 5 - 9 MeV region of interest over a 9 month running period within water.