Construction and performance of a large area liquid scintillator cosmic ray anticoincidence detector

Abstract

We describe details of the construction and performance of a large area cylindrical cosmic ray anticoincidence detector suitable for a medium energy neutrino experiment. The device provides 4π coverage with approximately 400 m 2 of liquid scintillator. Cosmic ray muons are rejected on-line with an inefficiency of ⋍ 10 −4 which is improved to a level of ⋍ 3 × 10 −6 or less with the application of off-line cuts. We also discuss the custom electronics used to operate and read out the device. Results from studies of the attenuation of neutral cosmic ray backgrounds by passive shielding are included.