Development of Low Background Sodium Iodide Scintillation Detectors for Dark Matter Research

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The origin of dark matter is one of the major scientific questions of our time. The DAMA/LIBRA experiment at the Underground Laboratory at Gran Sasso, Italy (LNGS) has reported a signal that is claimed to be evidence for dark matter in the form of elementary particles called Weakly Interacting Massive Particles (WIMPs). However, their results seem to be in conflict with other experiments that have searched for dark matter with null results. The situation will be unclear until an independent experiment with Sodium Iodide (NaI) detectors is done with lower background.This award will provide funds to develop low-background sodium iodide scintillation crystals for a sensitive dark matter search. Prior research, which was supported by an NSF EAGER grant, focused on the purification of precursor materials that are used for producing NaI powder. The activities planned with this award will be to a) address issues concerning the development of high purity low background NaI scintillation crystals grown with the high purity NaI powder and b) develop a sensitive method to measure the potassium radioactivity in the crystals to verify the very low levels needed for dark matter research. A possible second phase of research will be to deploy an array of such detectors in a low background environment that will allow a search for WIMP dark matter with lower background and higher sensitivity than achieved in the DAMA/LIBRA experiment.Broader impacts: Understanding the nature of dark matter would impact many fields of science from the largest scale of astronomy to the smallest scale of elementary particle physics. It is a mysterious form of matter that will connect to all fields once it is understood. In addition, the technology developed here, with demands on ultrapure materials, will benefit other fields that rely on such materials, such as semiconductors and nanotechnology devices.