Neutrino Ettore Majorana Observatory

The Neutrino Ettore Majorana Observatory (NEMO experiment) is an international collaboration of scientists searching for neutrinoless double beta decay (0νββ). Observation of 0νββ would indicate neutrinos are Majorana particles and could be used to measure the neutrino mass. It is located in the Modane Underground Laboratory (LSM) in the Fréjus Road Tunnel. Data taking started in January 2003 and ended in January 2011. The NEMO-2 and NEMO-3 detectors produced measurements for double neutrino decays and limits for neutrinoless double-beta decay for a number of elements, such as molybdenum-100 and selenium-82. These double beta decay times are important contributions to understanding the nucleus and are needed inputs for neutrinoless decay studies, which constrain neutrino mass.

The NEMO collaboration remains active and is constructing an improved SuperNEMO detector.

Other 0νββ experiments use the same material for the source of double beta decays and the detector. This allows a large mass of source material to be used and thereby maximizes the sensitivity of the experiment, but limits its flexibility. NEMO takes a different approach, using thin foils of source material surrounded by a separate tracking calorimeter.

This allows the use of any source material which can be formed into a thin foil. Also, because its tracking is more accurate, it can reliably detect if two electrons come from the same place, thereby reducing false detections of double beta decays.

The experiment has a cylindrical shape with 20 sectors that contain different isotopes in the form of thin foils with a total surface of about 20 m². The main isotopes used for the neutrinoless double beta decay search are about 7 kg of enriched molybdenum-100 and about 1 kg of selenium-82. The experiment also contains smaller amounts of cadmium-116, neodymium-150, zirconium-96 and calcium-48 foils. Tellurium and copper foils are used for background measurements.

...
Wikipedia