Liquid Scintillator Anticoincidence Guard

Abstract

A study was undertaken to determine the reduction in cosmic ray background which can be obtained by anti‐coincidence techniques. A 50‐liter liquid scintillation detector was set to register all cosmic ray events depositing more than 10 MeV. With a minimum shielding over the detector's basement location of 60 g/cm², all but one in 10³ events were accompanied by a pulse greater than 100 keV in a 1500‐liter liquid scintillator anticoincidence guard. An additional 600 g/cm², in the form of 35 tons of concrete block and bags of iron ore over the detector and anti‐coincidence guard, reduced the unaccompanied events to 1 in 10⁴, or 7.7 counts/h through 0.35‐m² effective horizontal area.