The MAJORANA Collaboration
The MAJORANA project will search for neutrinoless double-beta decay by fielding an array of high-purity germanium (HPGe) detectors in ultra-clean electroformed-copper cryostats deep underground.
Many of the MAJORANA project’s R&D activities are taking place in the WIPP underground and will dramatically improve prospects for it and similar experiments to take place in the future. The MAJORANA experiments at WIPP are taking place in a different part of the mine than other similar experiments, near the underground’s air intake shaft in the western end of the facility.
HPGe detectors are ideal for such search because 76Ge (one of the naturally occurring isotopes of germanium) is an excellent candidate for neutrinoless double-beta decay. Recent advances in HPGe detector technology, in particular P-type Point-Contact (PPC) detectors, present exciting new techniques for identifying and reducing backgrounds to the neutrinoless double-beta decay signal. This should result in greatly improved sensitivity over previous generation experiments. The very low energy threshold attainable with PPC detectors also provides for a broader physics program including searches for dark matter and axions.
The MAJORANA DEMONSTRATOR is an R&D program that will field two modules each with roughly 20 kg of PPC detectors at Sanford Underground Laboratory in western South Dakota. The DEMONSTRATOR is itself an R&D project aimed at building a much larger experiment consisting of roughly 1000 kg of HPGe detectors.
Scientists involved with the the Majorana Project's Segmented Enriched Germanium Assembly (SEGA) and Multiple Element Germanium Array (MEGA) visit the WIPP underground.
The MAJORANA Collaboration includes research institutions and universities from around the globe, but most of the MAJORANA project's presence at WIPP is personnel from LANL. The project is named after Ettore Majorana, an Italian physicist who first speculated that a neutrino might be identical to its antiparticle. Understanding the electrically neutral, subatomic neutrino particle, and how rarely it interacts with other matter, has become one of the most intensive physics research projects ever attempted.
Beta decay happens when a neutron within a nucleus decays by emitting an electron and an anti-neutrino, and double-beta decay, first observed in 1986, is when it basically happens twice, simultaneously in the same nucleus. Researchers at WIPP and other locations are now looking for what’s called neutrinoless double-beta decay, meaning two electrons would be emitted, but the anti-neutrino from one of the beta decays would be absorbed by the other. This process could only occur if the electron neutrino has a nonzero mass and cannot be distinguished from its antiparticle.
MAJORANA’s presence at WIPP consists of prototype detectors and screening materials for radioactivity. The MAJORANA collaboration also electro-formed a small amount of ultra-clean copper in the WIPP underground as a proof of concept. In fact, some of the first electro-formed copper parts ever produced underground were produced at WIPP as part of the MAJORANA Project.