Measurement of time performances of the fast component of plastic scintillator fluorescence

Described is a spectrometer with three counters in a telescope, operating in a single-photon regime, developed for studying the processes of energy transformation in plastic scintillators beginning from the moment of a charged particle getting into a telescope. Considered are the method and results of measuring the time performance (rise time constant and decay time) of the fluorescence fast component for five types of polystyrene scintillators with different additions. The measurements have been performed using photomultipliers. The samples of 1x50x50 mm scintillators were exposed to electrons from a strontium-90 β-source with a maximum energy of 2.26 MeV. Cherenkov light was used as a zero-time reference in time-distribution measurements. The rise time constant of a scintillator with 2-phenyl-5(4-biphenyl) 1,3,4 oxadiazol (PBD) addition is about 60 ps and the decay time of this scintillator is equal to 1.4 ns. Typical time spectra, obtained from the experimental results and on the base of calculations, are presented. It is pointed out that fluorescence amplitude of a scintillator with PBD addition is two times greater than that of a scintillator with p-terphenyl+POPOP