A HPMT based set-up to characterize scintillating crystals

We have developed a fully automatic measurement set-up, capable of measurin g light yields arising from scintillating crystals in a linear range of abo ut four orders of magnitude. The photodetector is a hybrid photomultiplier tube specially developed to optimize linear range and photon detection. Cry stal and photodetector are temperature controlled by a closed water circuit , as this is essential when measuring low light yield scintillating crystal s with a marked temperature dependence of their light yield. Gamma sources can be placed either on top or on the side of the crystal. In this latter c ase, the source can be automatically moved by a computer-controlled step mo tor to provide a uniformity profile of the light yield along the crystal. T agged and not-tagged operation modes are possible. The whole set-up is comp uter-controlled in an effort to provide fast and reliable measurements, to characterize many crystals per day. This is important for the quality contr ol of the lead tungstate crystals that will be applied in the electromagnet ic calorimeter of the CMS-detector at the LHC at CERN. (C) 1999 Elsevier Sc ience B.V. All rights reserved.