Neck sense rope system and leaching studies for SNO+.

Abstract

SNO+ is a multipurpose scintillation-based neutrino experiment which is located at SNO- LAB, Creighton mine, Sudbury. The primary scientific goal of the experiment is searching for the elusive process of neutrinoless double beta decay of 130Te. In addition to 0vbb decay, SNO+ will be able to detect low energy solar neutrinos, geo- and reactor- anti-neutrinos, as well as supernova neutrinos. During an initial water phase, it will also search for invisible modes of nucleon decay. This thesis briefly introduces neutrino physics and discusses the milestones in chapter 1. Chapter 2 discusses the SNO+ experiment in detail and outlines important developments in SNO+. Furthermore, chapter 3 and chapter 4 describe the two main projects that have been done by the author: i) leaching studies for the SNO+ experiment and ii) the neck sense rope system. Looking for rare events requires very stringent background limits. One of the sources of background originates from 222Rn daughters implanted into the inner surface of the SNO+ acrylic vessel. They can leach into the detector volume and increase the level of internal background. A leaching model has been developed by the author to estimate the activity and contribution to the backgrounds. The model is compatible with the measured value from a lead assay to within 1 sigma. The SNO+ sense rope system is a mechanical system which monitors displacement of the AV neck to within 2mm accuracy. The system has been calibrated and installed underground alongside with the sliding floor. Chapter 4 discusses the system, the performed calibration and the installation procedure in more detail.