Simulation study of a plastic scintillator for an electrical personal dosimeter

Plastic scintillators show several desired characteristics in dosimetry; especially tissue-equivalence is a definite advantage as an electrical personal dosimeter (EPD). The EPD based on an array-type Silicon Photomultiplier (SiPM) coupled to the polystyrene scintillator was proposed at the last time and has been improving. In this research, for the EPD application, the characteristics of plastic scintillator were studied through MCNP5 and LightTools simulation. For the reliable MCNP simulation, Gaussian energy broadening (GEB) was applied with the computed parameters from measured spectrum. The difference between simulation and measurement were 2.2% and 3.5% in terms of energy and FWHM each. To simulate the small-size effect in the plastic scintillator, the plastic scintillators of various sizes were simulated. The collapse of counting curve was shown in the MCNP simulation result. This was due to the escape of Bremsstrahlung photons and more clearly shown in the smaller scintillator, higher energy. In the LightTools simulation, the light collection efficiency of each size was simulated. Like the prediction, the efficiency decreased when the size of scintillator increased. The simulation results showed the plastic scintillator for the EPD must be small for the light collection, but also have minimum limit of size to avoid loss of count at the high energy.