Towards a Precise Energy Calibration of the CUORE Double Beta Decay Experiment

• Main Author: Dally, Adam G
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2014
• Subjects: Astrophysics; Low Temperature Physics; Nuclear engineering; Particle physics
• ISBN: 1321445113; 9781321445114

The mass of the neutrino may hold the key to many problems in cosmology and astrophysics. The observation of neutrino oscillations shows that neutrinos have mass, which was something that was not accounted for in the Standard Model of particle physics. This thesis covers topics relating to measuring the value of neutrino mass directly using bolometers. The first section will discuss the neutrino mass and different experiments for measuring the mass using bolometers. The mass of the neutrino can be measured directly from β-decay or inferred from observation of neutrinoless double beta decay (0νββ). In this work I present Monte Carlo and analytic simulation of the MARE experiment including, pile-up and energy resolution effects. The mass measurement limits of a micro-calorimeter experiments as it relates to the quantity of decays measured is provided. A similar simulation is preformed for the HolMES experiment. The motivation is to determine the sensitivity of such experiments and the detector requirements to reach the goal sensitivity. Another possible method for determining the neutrino mass is to use neutrinoless double beta decay. The second section will cover the Cryogenic Underground Observatory for Rare Events (CUORE) detector calibration system (DCS). CUORE is a neutrinoless double beta decay (0νββ) experiment with an active mass of 206 kg of 130Te. The detector consists of 988 TeO2 bolometers operating at 10 mK. The signature of 0 νββ decay is an excess of events at the Q-value of 2528 keV. Understanding the energy response is critical for event identification, but this presents many challenges. Calibration is necessary to associate a known energy from a γ with a voltage pulse from the detector. The DCS must overcome many design challenges. The calibration source must be placed safely and reliable within the detector. The temperature of the detector region of the cryostat must not be changed during calibration. To achieve this calibration sources must be cooled before before introducing them to the detector region. The highest acceptable temperature of the calibration sources are estimated using the Stephan-Boltzmann Law. The ability to cool the calibration sources to these temperatures was measured in several tests. The first test established the force required to cool the calibration sources within the time allotted. The second test established the time frame required for cooling the calibration sources to the required temperature. A model for ensuring the calibration sources are below the required temperature and recommended procedure for cooling the calibration sources is provided.