222Rn measurements within the water phase of the SNO+ experiment

Abstract

The SNO+ experiment is a large multipurpose scintillator detector. In the first phase of the experiment, close monitoring is done to determine radioactivity background levels, in particular the monitoring of 222Rn as its presence can obscure or mimic physics data. This thesis focuses on a cryogenic technique used to collect and concentrate 222Rn in the water used for the SNO+ experiment. The target level for 222Rn using this system is 3.5 × 10−14 g 238U/gH2O equivalent for the initial water phase. The radon assay technique and resulting measurements are discussed. Further analysis was done to determine the content and locations of areas within the detector emitting higher than expected rate of events. This is informally known as the "hotspot" problem.