Parameters of various types of light guides for large area scintillation counters

The properties of a variety of different light guides used in conjunction with a large area scintillator have been studied. The performance of a Y7 wavelength-shifter bar, a fishtail, a separated twisted and an all area coupled twisted lucite light guide were compared. Various parameters of the counters, including the number of photoelectrons, the detection efficiency, the attenuation length, the time resolution and the effective light velocity were measured. The detection efficiency for minimum ionizing particles is near 100% for each of the four types of light guides. The best performance was found for the all area coupled twisted guide. For this, we observe an average of 50 photoelectrons per minimum ionizing particle and a mean time resolution (sigma) of 0.4ns. The absorption length for scintillation light in Y7 was determined and a decay time spectrum consisting of two exponential components has been measured. A Monte Carlo simulation of photon transmission in the counters has been done; the measured results on the performance of the various counter configurations agree well with the predictions of the simulation.