Cosmogenic activation in materials at shallow depths

Decay products from long-lived radioactive isotopes produced by cosmogenic activation can be important sources of backgrounds in searches for dark matter and neutrino interactions. As experiments become larger and strive to search for rare-events, it is becoming increasingly important to store, assemble and fabricate the detector materials using methods that minimize above ground exposure to cosmic rays. This study is focused on the cosmic-ray muon-induced neutron flux and spectrum at shallow depths, particularly > 10 MeV neutrons that are relevant for tritium production in germanium (Ge) and silicon (Si), 39Ar production in argon, and cosmogenic activation in copper. Tritium production in the SuperCDMS Ge/Si detectors, that were stored underground for a number of years, is estimated. Also, cosmogenic activation in PNNL's shallow underground laboratory was studied for the materials germanium, copper, and argon.