Study of polystyrene scintillators-WLS fibers elements and scintillating tile-WLS prototypes for New CHOD detector of CERN NA-62 experiment
In the paper the light output and the time resolution of polystyrene scintillators-WLS samples have been measured with use wavelength shifting (WLS) fiber readout. The samples of different thickness (7-30 mm) have been made in the shape of bricks and plates with the areas of 25×80 and 108×134 (268) of mm$^2$ respectively. Besides samples of “ordinary” scintillator with additions of 2% p-Terphenyl + 0,05% POPOP, the rapid ultraviolet scintillator with one 2% additive PBD was used. For the light collection were used WLS-fibers BCF92, Y11 and scintillation fiber SCSF-78M as re-emitting. The fibers were glued into the grooves on the front surface of scintillators. As the photo detectors silicon photomultipliers (SiPM) were used, which were produced by CPTA (Russia) and SensL (Ireland). It is shown that the dependence of light output on the thickness of scintillator is nonlinear and close to the power function with ½ index, which is also confirmed by the calculations carried out by Monte Carlo. The measured value of a light output makes it possible to obtain time resolution of about 0.5 ns. The best result (0.22 ns) of the time resolution with the MIP detection is obtained for the pair of ultraviolet scintillator and SCSF-78M fiber.
IHEP, Protvino, RF