Organic plastic scintillators are attractive for several applications in medical dosimetry due to their high degree of water equivalence and their minimal perturbation of the radiation field. There is, however, a non-proportionality between the produced scintillation light and the absorbed energy for electrons below about 125 keV. This ionization quenching can be described by Birks formalism. In this work, a modified version of Birks formalism was developed. The model explicitly accounts for the light yield from secondary electrons and the model therefore can take advantage of the detailed electron spectra computed by Monte-Carlo techniques. The use of the model is demonstrated by comparison of modelling results and scintillator measurements of air kerma in a series of well-characterized, low energy x-rays beams with generating potentials from 60 kV to 300 kV (mean photon energies from 38 to 158 keV). The new model predicted the scintillator light production in good agreement with the experimental data. The model enables improved evaluations of the influence of quenching losses in MV photon beam dosimetry and other medical applications.
- Birks formalism
- Fiber-coupled organic plastic scintillators
- Ionization quenching
- Monte Carlo