Attenuation length and spectral response of Kuraray SCSF-78MJ scintillating fibres

Over three quarters of a million, 4-m long Kuraray double-clad SCSF-78MJ (blue–green) scintillating fibres have been used in the construction of the GlueX electromagnetic barrel calorimeter, as part of the Hall D experimental program at Jefferson Lab. The response and quality of a random sample of 4750 of these fibres have been evaluated by employing a 373-nm UV LED to stimulate the fibres along their length and reading out the light using a spectrophotometer and a photodiode in order to extract the spectral response and the attenuation length, respectively. Single exponential fits to the spectral response in the 100–280 cm distance from the light source yielded an average bulk attenuation length and standard deviation of (387±26) cm. Double-exponential fits to the spectral response over the entire 4-m length also allowed the extraction of long and short wavelength components at (486±54) cm and (75±22) cm, respectively. Finally, diameter uniformity measurements were carried out. The quality assurance results confirmed that the fibres were of high quality and complied with GlueX specifications.