The Electromagnetic Calorimeter for the PANDA Target Spectrometer

Abstract

The future experiment with a next generation detector will focus on hadron spectroscopy. It will use cooled anti-proton beams with a momentum between 1.5 GeV/c and 15 GeV/c interacting with various targets. This allows to directly form all states of all quantum numbers and measure their widths with an accuracy of a few tens of keV. The experiment will be located at the exceptional Facility for Anti-proton and Ion Research in Germany (FAIR), which is currently under construction. The electromagnetic target calorimeter of the experiment has the challenging aim to detect high energy photons with excellent energy resolution over the full dynamic range from 15 GeV down to a few tens of MeV within a 2 T solenoid. The target calorimeter itself is divided into a barrel and two endcaps. The individual crystals will be read out with two precisely matched large area avalanche photo diodes. In the very inner part of the forward endcap vacuum phototetrodes will be used instead. To reach the demands of the experiment, improved PbWO4 (PWO) scintillator crystals, cooled down to −25°C have been chosen. They provide a fast decay time for highest count rates, short radiation length for compactness, improved light yield for lowest thresholds and excellent radiation hardness [1]. The main part of the 15,740 crystals needed have been produced by the Bogoroditsk Plant of Technochemical Products (BTCP) in Russia. After stopping their business, a new potential producer for the missing 41% of crystals have been found. The company Crytur in Czech Republic provided 150 promising preproduction crystals so far. Except some of the very first produced crystals, all samples exceed the required high quality parameters. Most of them have already been used for the first major assembly stage of assembling one of the 16 barrel slice segments, which will be presented as well.