Upgrade of the monitoring system of LHCb ECAL

Abstract

The LHCb ECAL is a shashlik calorimeter of 6016 cells, covering 7.68×6.24 m 2 area. To monitor the readout chain of each ECAL cell, the LHCb ECAL is equipped with a LED based monitoring system. During the LHC Run I (2009-2012 it was found that the precision of the monitoring suffers from the radiation degradation of transparency of polystyrene clear fibers used to transport the LED light to the ECAL photomultipliers. In order to improve the performance of the monitoring system, and especially in view of significant increase of LHCb working luminosity foreseen after 2018, the present plastic fibers have been replaced by radiation hard quartz fibers. The design of the upgraded version of the LHCb ECAL monitoring system is described here. The usage and performance of the new system for the ECAL calibration during the LHCb Run II are discussed.