With the realization that neutrinos are massive, there is an increased interest in investigating their intrinsic properties. Understanding the neutrino mass generation mechanism, the absolute neutrino mass scale and the neutrino mass spectrum are some of the main focuses of future neutrino experiments. Experimental evidence of neutrinoless double-beta decay (NDBD) would definitively establish the Majorana nature of neutrinos while also providing information about the absolute neutrino mass.
This award will enable the Majorana Collaboration to carry out R&D activities related to the development of the proposed Majorana Demonstrator, a prototype Ge detector array that aims to prove the feasibility of building a future 1-tonne Ge NDBD experiment. The research would be conducted by the collaboration in two distinct areas: Ge detector development and the production and assay of ultra-low background materials. Building a NDBD experiment with the ability to probe neutrino mass in the inverted hierarchy region requires the combination of a large detector mass sensitive to NDBD, on the order of 1-tonne, and unprecedented background levels, on the order of or less than 1 count per year in the NDBD signal region. They plan to deploy and evaluate two different Ge detector technologies, one based on P-type material and the other on N-type.
Many of the initial suite of experiments being considered for DUSEL will directly benefit from the availability of ultra-clean materials with extremely small amounts of U and Th. Verifying the purity of materials requires sensitivities at the sub microBq/kg level. The development of enhanced sensitivity inductively coupled plasma mass spectrometry will benefit a broad set of applications and future experiments. The Ge detector development will benefit applications that require very low energy thresholds while also providing reduced backgrounds from associated detector components.
