Scintillation Efficiency and Position Sensitivity for Radiation Events in Plastic Scintillators

Plastic scintillators (PLSs) are potential materials for the development of a dosimeter based on linear energy transfer (LET) measurement for mixed radiation fields, such as the surroundings of accelerator facilities and in space because PLSs are composed mainly of hydrocarbon molecules, and have the effective atomic number and density similar to those of water and human tissues. In addition, PLSs have a wide range of application in particle physics experiments, owing to their response to all types of radiation (photon, neutron, and charged particles). To use PLSs in designing and constructing an LET spectrometer, essential characteristics of PLSs, such as light yields as a function of deposited energy and radiation species, and the position sensitivity to observe trajectories of incident radiation must be studied. Previously, we performed a procedure for determining the energy deposited in a PLS (EJ-200) for gamma rays from a 137 Cs radiation source using Compton Coincidence Technique. In that measurement, the scintillation efficiency, which was determined as a function of Compton electron energy, approaches a saturation value in the high-energy region and decreases in the low-energy region. The decrease in efficiency possibly suggests the nonproportionality between the light yield and deposited energy. In this paper, the scintillation efficiencies, as well as the absolute light yield of PLSs (EJ-200, EJ-212, and EJ-252) are investigated. In addition, the position sensitivity characteristic is studied by using a PLS rod, and photomultiplier tubes (PMTs) are attached to both ends of the rod, and the position of radiation incidence in the rod can be evaluated by using signals from the PMTs.