Development of high resolution and radiation hard electromagnetic calorimeter for the DVCS experiment

Abstract

The electromagnetic calorimeter for the Deeply virtual Compton Scattering (DVCS) experiment requires high energy resolution and radiation hardness. The calorimeter for the experiment will be assembled using 1080 PbWO4 crystals supported by a carbon fiber structure. In order to achieve an energy resolution of ~ 1.3 % for 7 GeV gamma-rays, the thickness of the carbon structure was decided to be 0.5 mm based on Geant4 Monte-Carlo simulation. The detector will be operated in a harsh radiation environment (~ 5 Gy/hr), which will induce a severe decrease of the PbWO4 light transmission. For this reason, an optical bleaching method, based on the use of blue LEDs and quartz optical fiber will be used to regularly recover the crystals. For the radiation hard crystals, we found that the damage from 30 Gy of ionizing irradiation can be recovered by 2 hours of optical bleaching with 1 mm and 800 m diameter fibers. In this communication, we will present the current status of the detector R&D and construction, as well as simulation results of its performance