PNNL

Abstract

The Majorana Collaboration is searching for the neutrinoless double-beta decay of the candidate nucleus 76Ge. The Majorana Demonstrator is an engineering eort that builds an array of germanium detectors and aims to deploy background reduction techniques suitable to field a 1-ton 76Ge-based search. Due to ultra low-background conditions, regular calibrations are needed to verify proper function of the detectors. Radioactive line sources are deployed around the cryostats containing the detectors so that it is possible to carry out hour-long energy calibrations. When measuring in low-background mode, these line sources have to be stored outside the shielding so they do not contribute to the background. The deployment and the retraction of the source are designed to be controlled by the data acquisition system and do not require any direct human interaction. In this paper, we detail the design requirements and implementation of the of the calibration apparatus providing sucient rate and energy spectra for the definition of pulse-shape cuts needed in the final analysis.