  In this work, the simulation of optical photons is carried out in an
antineutrino detector module consisting of a plastic scintillator connected to
light guides and photomultipliers on both ends, which is considered to be used
for remote reactor monitoring in the field of nuclear safety. Using Monte Carlo
(MC) based GEANT4 simulation, numerous parameters influencing the light
collection and thereby the energy resolution of the antineutrino detector
module are studied: e.g., degrees of scintillator surface roughness, reflector
type, and its ap- plying method onto scintillator and light guide surface, the
reflectivity of the reflector, light guide geometries and diameter of the
photocathode. The impact of each parameter is inves- tigated by looking at the
detected spectrum, i.e. the number photoelectrons per depositing energy. In
addition, the average light collection efficiency of the detector module and
its spatial variation are calculated for each simulation setup. According to
the simulation re- sults, it is found that photocathode size, light guide
shape, reflectivity of reflecting material and wrapping method show a
significant impact on the light collection efficiency while scin- tillator
surface polishing level and the choose of reflector type show relatively less
impact. This study demonstrates that these parameters are very important in the
design of plastic scintillator included antineutrino detectors to improve the
energy resolution efficiency.
