Molybdenum-100 Reclamation and Purification for Neutrinoless Double-Beta Decay Experiments

Experiments probing the nature of the neutrino are searching for the rare nuclear process of neutrinoless double-beta decay (0?ßß). The state-of-the-art bolometer-based experiment is CUORE (Cryogenic Underground Observatory for Rare Events). Although CUORE is one of the most sensitive 0?ßß experiments to date, further background reduction is needed to clearly observe this rare process. The next generation 0?ßß detectors will be more sensitive, using detectors with particle identification to better reject background events. CUPID (CUORE Upgrade with Particle Identification) is a ton-scale 0?ßß experiment, including researchers from more than 30 institutions in 7 countries. CUPID will use molybdenum-100 containing scintillating bolometers as both the source and detector of 0?ßß events. The proposed SBIR program will further the partnership between RMD and MIT, working with the CUPID Collaboration. In our previous DOE-funded project, RMD developed the crystal growth and processing methods for lithium molybdate (LMO) scintillating bolometers of size and background-purity required for CUPID. The LMO crystals produced to date at RMD have utilized natural molybdenum, but the eventual crystals needed for CUPID will be enriched in 100Mo. Challenges in using enriched 100Mo for LMO scintillating bolometers include purification and reclamation. Suitable purity is needed for low-radioactivity background and strong scintillation signal. Reclamation of 100Mo from the residuals of crystal growth is required because of the significant expense and scarcity of enriched molybdenum. Thus, the goals of the proposed SBIR program are to develop chemical processes to reclaim molybdenum trioxide (100MoO3) from the LMO residuals and to purify the 100MoO3, making it suitable for subsequent LMO crystal growth. The efficacy of the developed chemical processes will be verified by growth and testing of LMO crystals needed for the CUPID experiment. The LMO crystals grown with purified MoO3 will be evaluated by chemical analysis and by cryogenic testing of the scintillating bolometers. Initial Phase-I work will use natural molybdenum. In the Phase-II project, we will scale-up and apply it to enriched 100MoO3 in sufficient volume to produce LMO crystals needed for CUPID.