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MAJORANA Detectors 

For more information, contact MAJORANA Collaboration Spokesperson: Steve Elliott (

Germanium detectors are a powerful tool in looking for the pair of electrons that are the “smoking gun” for neutrinoless double-beta decay. The main difficulty in a search like this is the presence of background events from the low levels of natural radioactivity which pervade our environment. These backgrounds could obscure any real double-beta decay events in the data stream. The excellent energy resolution of germanium detectors (their ability to measure energy deposition very precisely) removes many of these backgrounds.

Because the detectors themselves are semiconductor devices, they are exceptionally clean, further removing potential backgrounds. There is also a long history of analyzing signals from germanium detectors to glean specific information about the events that caused them. This capability will help reduce backgrounds even further. The MAJORANA collaboration plans to use devices known as “point contact detectors” in the upcoming phase of our experiment. 


The first phase of the MAJORANA experiment will be to deploy roughly 60 kg of germanium detectors at the Sanford Underground Laboratory in what we call a “Demonstrator Module.” The first half of the detectors will be fabricated from natural germanium, which is 7.44% 76Ge. We anticipate construction of this detector array beginning very shortly after the Sanford Underground Laboratory is ready, with production data taking to start roughly one year later. The second half of the DEMONSTRATOR will be detectors enriched to 86% in 76Ge. The enriched detectors will provide a much stronger double-beta decay signal, while the unenriched detectors will allow us to begin understanding MAJORANA backgrounds on a comparatively short timescale.