DUSEL R&D for Measuring External Sources of Background (R&D) at Homestake for Double Beta Decay and Dark Matter Experiments

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Future DUSEL experiments will need to know the external sources of radioactivity including muon-induced neutrons at different levels of the DUSEL site. These external backgrounds, particularly fast neutrons and cosmogenic radioactivity from muon-induced processes, must be eliminated for underground experiments in pursuit of double beta decay, searches for dark matter candidates, and oscillations of low-energy neutrinos. This award will provide funds to measure such backgrounds with liquid scintillator, sodium iodide and germanium detectors. The results from such measurements will enable the experiments to be placed at different levels according to their designed sensitivity and shielding requirements. Measuring muon-induced neutron flux at the 300-ft level will enable one to benchmark Monte Carlo simulation codes for all incoming experiments. Measuring and understanding high energy neutron excitation of the shielding and detector materials for neutrinoless double-beta decay experiments are crucial for interpreting results and establishing shielding requirements. On the other hand, measuring partial gamma-ray cross sections provides useful data for benchmarking Monte Carlo simulation. These funds will provide the support needed to analyze existing data sets and to take more data.Among the broader impacts, it is noted that characterizing the DUSEL site is also useful to other DUSEL experiments, such as the underground nuclear astrophysics accelerator program and proton decay experiments. Knowledge gained from the proposed measurements can have wide-ranging application. The proposed research activities have impact on education and outreach by involving two undergraduate students from two institutions in two states.