The EJ-420 detector is an efficient detector of thermal neutrons in the presence of gamma radiation. The detector employs a lithium compound, whose Li content is enriched to 95% 6Li dispersed in a ZnS:(Ag) matrix. Efficient measurements of thermal neutron fluxes may be performed in the presence of gamma radiation as high as 107gamma rays per neutron.
In most applications, EJ-420 will give counting efficiencies up to 100% greater than those attainable with similar detectors based on 10B. The efficiency is dependent on the neutron energy and is approximately 30% for 0.1 eV neutrons and 60% for neutrons of energy 0.01 eV or less. The detection efficiency for thermal neutrons of about 0.025 eV is approximately 55%. The attainable detection efficiency in a particular application will, of course, also depend on the competing gamma ray background.