Production of ultra-radio-pure NaI(Tl) crystals for Dark Matter search application whit the contribution of Ministero degli Affari Esteri e Cooperazione Internazionale
MAECI - PGR004136
Summary of the project
The aim of the project is to define a technological protocol and develop the technical tools compliant with the production of ultra-high purity NaI(Tl) scintillating crystals to be used as detectors in frontier astroparticle physics experiments, in particular the search for Dark Matter (DM) particles in our Universe. The results from astronomical observations accumulated in the last decades provide striking evidence for the existence of a large amount of dark (non-luminous) matter in the Universe. Despite dark matter’s dominance, its nature remains unknown. The discovery of DM particles through their direct detection would be an overwhelming achievement in the understanding of our Universe. Experiments that search for Dark Matter have to meet extremely stringent requirements for they need to isolate the very elusive DM signal from other spurious sources. Among such parasitic sources, the environmental radioactivity and the presence of trace radioactive contaminants in the detector’s material can strongly affect the experimental sensitivity. Scintillating crystals made of Thallium-doped Sodium Iodide (NaI(Tl) chemical formula) are excellent particle detectors, widely used in a variety of experimental applications. To be used as DM detectors, however, such crystals have to be produced with an extremely high level of radio-purity, not achievable by means of standard industrial techniques. Trace radioactive contamination in the crystals may come from natural, cosmogenic and anthropological sources. The path towards the production of ultra-high purity NaI(Tl) scintillating detectors includes the accurate selection, purification and careful monitoring of the raw materials, ancillaries, tools and facilities used for powder synthesis, crystal growth and final processing (cutting and polishing). To meet these goals, a strong partnership and an intense R&D activity is needed between the experimental groups and the company that owns the basic technology of crystal production.