  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.
