MODELING AND SCANNING OF LIGHTGUIDES FOR PB/SCIFI CALORIMETERS

Calorimeters containing embedded arrays of scintillating fibers often require uniform-acceptance lightguides to gather, mix and transport light from the end face of the module to a photo-sensitive detector. To optimize such devices, we have built a flexible lightguide scanning station which imitates the distribution of light coming from an array of scintillating fibers. This system has been used to map the photocathode response of photomultiplier tubes, the transmission uniformity of lightguides and the performance of detector-lightguide combinations. Additionally, we have developed a ray-trace modeling program which accurately reproduces the experimental results. These tools are described in the context of our own application-specific examples, while their general nature makes them attractive in other situations where lightguides are involved. Finally, the effect of lightguide non-uniformity is evaluated in order to estimate the systematic contribution to the calorimeter energy resolution description.