Scintillation mechanism and efficiency of ternary scintillator thin films

The scintillation mechanism of ternary plastic scintillators, excited by ions, was studied in order to correlate the scintillation efficiency as a function of the thickness to the energy transfer process between the light emitters embedded in the polymer. A numerical model for describing the energy transfer from the matrix to the primary emitter, and from the primary emitter to the secondary one, was developed. The main parameters involved in this model are the mean free path of the polymer electronic excitation produced by the ionizing particle and the mean free path of the primary emitter photon. By this way, the total light yield as a function of the foil thickness was obtained. The theoretical curve was compared with the experimental results obtained from NE102 thin films of different thickness. The samples were excited with a particles irradiated by an ²⁴¹Am source, and the emission intensity as a function of the wavelength was collected by an optical spectrometer equipped with a nitrogen cooled CCD. By interpolating the light intensity of the two emitters as a function of the thickness, the two mean free paths involved in the energy transfer processes were calculated. From the experimental and interpolation data, it was evidenced that the overall photon number as a function of the thickness exhibits a local maximum at 40 μm, which corresponds to the ion range into PVT.