The Search for Periodic Modulations of Nuclear Decay Rates with the NEMO-3 Experiment and Development of the Light Injection Monitoring System for the SuperNEMO Experiment

Abstract

A search for periodic modulations of nuclear decay rates has been carried out using data from the NEMO-3 experiment. The Lomb-Scargle periodogram technique and it's error-weighted extension known as the Generalized Lomb-Scargle periodogram, both used in analyzing unevenly spaced time series, were applied to the Phase 2 data set spanning 6:0195 yrs. A study of double beta decay rates originating from 100Mo source foils has shown no evidence of periodic modulation between the sample frequency range of 0:083063 - 365:25 yrs^-1. Monte Carlo methods were used to test the sensitivity to detection of previously claimed modulations. For a yearly periodicity in decay rates, a limit has been set for the relative amplitude of such a modulation of 2.1% at the 90% condence level. In addition to this, a calorimeter monitoring system has been developed for the successor to NEMO-3. SuperNEMO is a next generation detector that will employ the same powerful approach to search for neutrinoless double beta decay with half-life sensitivities on the order of 1026 years corresponding to m < 50 meV. One of the most important features of any detector searching for 0\nu\beta\beta decay is its energy resolution and thus it's crucial to monitor and correct for any changes in this parameter over time. A Light Injection (LI) system has been developed to monitor and help calibrate the response of 712 SuperNEMO calorimeter modules over the lifetime of the experiment. The LI system will inject, via optical fiber, UV light from light emitting diodes into each calorimeter optical module to track its behavior between absolute calibration runs to a precision of 1%. In addition, the system can also be used to test the linearity of modules up to incident electron energies as high as 5 MeV.