Measurement of EJ-228 plastic scintillator proton light output using a coincident neutron scatter technique

Abstract

The light output function of the fast plastic scintillator EJ-228 was measured using a coincident neutron scatter measurement system and quasi-monoenergetic neutron beams produced by the tandem Van de Graaff accelerator at Triangle Universities Nuclear Laboratory. The measurement of scintillator light output using neutron scatter kinematics provides a model-independent determination of the light output function with quantifiable sources of uncertainty. Consequently, light output measurements performed using this method have a key advantage compared to other techniques: the characterization of the scintillating material depends only on the material itself and not on the size of the detector. This advantage is realized if the light output is defined as the absolute neutron light output relative to the absolute electron light output and two conditions are met: (1) the scintillator volume is fully illuminated and edge effects can be neglected during energy calibration measurements and light output measurements, and (2) the light attenuation length for scintillation photons in the material is long enough that the lowest energy interaction of interest produces a statistically significant number of scintillation photons for an interaction at any position in the scintillator volume. Commonly implemented measurement and analysis techniques for light output characterizations are explored and evidence of bias is provided for characterizations performed by analyzing the full-energy deposition edge of a light output spectrum.