Efficiency and Gamma Sensitivity of a Lithium Glass Neutron Detector

Neutron detectors are used in national security applications for detecting potential radioactive material entering the country.~ Due to the shortage of Helium-3 for neutron detectors, Lithium-6 glass scintillators could be a good material for a replacement detector.~ Lithium-6 has a large neutron capture cross section, which gives high neutron detection rates.~ Our detector is based on the fact that neutrons are captured by Lithium-6 which rapidly decays into an alpha particle and triton.~ Those particles induce scintillation in the glass scintillator and are detected in a photomultiplier tube.~ The orientation of the plastic and Lithium-6 glass changes the efficiency of the detector.~ Monte Carlo for Neutral Particles (MCNP) calculations have shown that increasing amounts of plastic provide more efficient neutron detection and that placing a layer of glass in the front of the detector is the ideal configuration. ~Homeland Security requires that a replacement for Helium-3 detectors must have low gamma sensitivity and high neutron detection efficiency.~ We are measuring the absolute gamma sensitivity of various arrangements of glass and plastic scintillator.~ Our goal is to meet the Department of Homeland Security requirement for gamma sensitivity of one part in 10,000.