Light yield of Kuraray SCSF-78MJ scintillating fibers for the Gluex barrel calorimeter

Over three quarters of a million 1-mm-diameter 4-m-long Kuraray double-clad SCSF-78MJ (blue-green) scintillating fibers have been used in the construction of the GlueX electromagnetic barrel calorimeter for the Hall D experimental program at Jefferson Lab. The quality of a random sample of 4750 of these fibers was evaluated by exciting the fibers at their mid point using a 90Sr source in order to determine the light yield using a calibrated vacuum photomultiplier as the photosensor. A novel methodology was developed to extract the number of photoelectrons detected for measurements where individual photoelectron peaks are not discernible. The average number of photoelectrons from this sample of fibers was 9.17±0.6 at a source distance of 200 cm from the PMT.