Status of the MAJORANA DEMONSTRATOR

TL;DR

The MAJORANA DEMONSTRATOR is a modular, ultra-low background germanium detector array designed to search for neutrinoless double beta decay, demonstrating scalable technology with low background rates to inform future large-scale experiments.

Contribution

This paper reports on the construction, deployment, and initial operation of the MAJORANA DEMONSTRATOR, showcasing its modular design and low-background performance as a step toward next-generation neutrino mass experiments.

Findings

Prototype module operated from 2014 to 2015

Module 1 assembled and being commissioned

Assembly of Module 2 in progress

Abstract

The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultra-low background, modular, HPGe detector array with a mass of 44-kg (29 kg 76Ge and 15 kg natGe) to search for neutrinoless double beta decay in Ge-76. The next generation of tonne-scale Ge-based neutrinoless double beta decay searches will probe the neutrino mass scale in the inverted-hierarchy region. The MAJORANA DEMONSTRATOR is envisioned to demonstrate a path forward to achieve a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value of 2039 keV. The MAJORANA DEMONSTRATOR follows a modular implementation to be easily scalable to the next generation experiment. First, the prototype module was assembled; it has been continuously taking data from July 2014 to June 2015. Second, Module 1 with more than half of the total enriched detectors and some natural detectors has been assembled and it is being commissioned. Finally, the assembly of Module 2, which will complete MAJORANA DEMONSTRATOR, is already in progress.