Light collection uniformity of lead tungstate crystals for the CMS electromagnetic calorimeter

摘要

A technique has been developed to measure the light collection uniformity of lead tungstate crystals for the CMS electromagnetic calorimeter. The use of a hybrid photomultiplier tube allows a precision measurement despite the intrinsically low light yield. It is found that shading the chamifered edges of the crystals with a pencil can achieve a reduction in the front-non-unifortnity of approximately 0.1%/X-0. Similar effects are observed by de-polishing the chamfers. (c) 2004 Elsevier B.V. All rights reserved.