An observation on the response of small NE-213 scintillation detectors to high energy neutrons

At the University of Birmingham, dual parameter data acquisition has been used for neutron spectrometry with NE-213, to allow optimum separation of neutron and photon events in the scintillator. One persistent feature which has been encountered when using small (up to approximately 10 cm3) detectors and neutron energies above 10 MeV, is a ridge on the dual parameter response in-between the principal neutron and photon features. In dual parameter data collection, this does not present any particular problem since it can be included or excluded as required, but many laboratories favour single parameter data collection, particularly for use in the field. This short communication is an investigation of the origins and magnitude of this effect for a 2 cm diameter, 2 cm high right cylindrical cell of NE-213. It is however to be noted that similar effects have been observed for a 1.5 cm diameter by 1.5 cm high cylindrical cell.