The Majorana Demonstrator: First Module of Germanium Detectors Comes Online

The Majorana experiment begins its search for neutrinoless double-beta decay.

Image courtesy of Sanford Underground Research Facility
Assembly of the Majorana Demonstrator Module 1 detectors. Twenty-nine detectors are arranged in seven strings and mounted in an ultra-low-radioactivity copper cryostat. The array is assembled inside a nitrogen-purged glovebox to avoid exposure to naturally-occurring radon in the air.

The Science

The Majorana Demonstrator (MJD) has started its search for neutrinoless double beta decay, in a clean-room laboratory 4,850 feet underground in the Sanford Underground Research Facility in Lead, South Dakota. The first of two modules, containing over 22 kg of high purity germanium detectors, has been turned on.

The Impact

The Majorana experiment will search for neutrinoless double beta (0νββ) decay in germanium-76. Observation of this decay would have profound implications for our understanding of physics, by showing that lepton number conservation is violated, proving that the neutrino and the anti-neutrino are identical, and providing hints as to how the Big Bang produced more matter than it did antimatter.


To search for the neutrinoless double beta decay of germanium-76, Majorana uses detectors made from germanium enriched in the isotope 76Ge. In May 2015, the first full module containing 29 germanium detectors was installed in the lead/copper shield. A second module with another 30 detectors is currently being assembled and will be moved into the shield in late 2015. The Majorana Demonstrator (MJD) is located 4850 feet underground in the Sanford Underground Research Facility in Lead, SD. The deep location and an ultra-clean laboratory are required to eliminate “background” events that could be mistaken for the extremely rare 0νββ decays. The MJD project aims to demonstrate that extremely low background rates can be achieved, to prove the feasibility of a larger, more sensitive experiment proposed for the future.


David Radford
Physics Division, Oak Ridge National Laboratory


The Majorana Demonstrator project is funded by the Office of Nuclear Physics of the U.S. Department of Energy, and by the Particle Astrophysics Program of the National Science Foundation. Support was also provided by the Russian Foundation for Basic Research, and some early research and development work was supported by the U.S. Department of Energy through the Los Alamos National Laboratory Laboratory Directed Research and Development program and by the University of North Carolina.


N. Abgrall et al. (Majorana Collaboration), “The Majorana Demonstrator Neutrinoless Double-Beta Decay Experiment.” Advances in High Energy Physics 2014, 36543 (2014). [DOI: 10.1155/2014/365432]

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