Super radiation hard vacuum phototriodes for the CMS endcap ECAL

摘要

The energy resolution sigma/E of the electromagnetic calorimeter (ECAL) in the energy range of 50-500 GeV is defined mainly by two terms: stochastic alpha/rootE and constant C. The photoreadout of the CMS Endcap ECAL consists of vacuum phototriodes (VPT), which are broadening a signal from n(p) photoelectrons characterized by the excess noise factor F = n(p)(sigma/E)(2). The technical specification of the CMS ECAL requires the value of F to be smaller than 4 in the CMS LHC environment during 10 years of detector operation. In this paper we present results of the VPT performance study in a magnetic field up to 4T, in a gamma radiation field of 0-50 kGy and in a neutron fluence of 7 x 10(15) n/cm(2). The standard phototriodes FEU-188 with faceplates from UV glass used in CMS ECAL as well as VPTs with super radiation hard cerium-doped glasses were investigated at the Co-60 gamma facility, a neutron generator and a nuclear reactor in the Petersburg Nuclear Physics Institute (PNPI). The dependence of the VPT gain and the excess noise factor in magnetic fields on the fine-mesh plane orientation has also been studied. (C) 2004 Published by Elsevier B.V.