Measuring the light collection time in plastic scintillators

The results of design and experimental determinations of the time of light collection in plastic scintillators on the photocathode of a photomultiplier (PM) are given. The scintillators were excited by short electron pUlses. Dimensions of the scintillators varied in the range from 2 to 100 mm. The energy of an electron beam was equal to 100 keV the beam current pulse duration was 0.1 ns, beam current was up to 10-6 A, frequency of current pulse repetition was up to 1.0 MHz, aperture of an electron beam was 1 to 2 mm. Measur ement have been conducted with SDP, SPS-B9 and SPS-B7 scintillators coated with hight-reflecting (white) and light-absorbing (black) enamel as well as with non-colored polished scintillators. The data obtained show that the light collection time depends not only on the type of coating but on the scintillator type and presence of optical contact as well. It is concluded that the true light collection times for the investigated scintillators are comparable with the time resolution of a PM and can essentially affect the time resolution of a scintillation detector