Electromagnetic Calorimeters
Belarusian and Russian scientists
take part in the program of heavy scintillating crystals (PWO). The
electromagnetic calorimeter based on the PWO crystals was proposed by
the RDMS scientists in 1994. Five years later, after research and
development, the performance of the crystals required by the experiment,
including the radiation hardness, have been achieved at a plant in
Bogoroditsk. The quality control system ACCOS for the produced crystals
has been developed by the RDMS scientists and delivered to CERN.
RDMS continues studies of the fundamental properties of the crystals.
JINR and institutes from Armenia and Belarus take part in the
sub-project of the preshower detector SE. The preshower detector is
located in front of the electromagnetic calorimeter. Its role is
to resolve the photon from the neutral pion, and to measure the
coordinates of the photon. The detector consists of two absorbers
and two layers of silicon detectors (X, Y).
The combined thickness of the
absorbers is 3 X0
(they guarantee 95% conversion probability);
the strip width of the silicon detectors is 2 mm.
Fig. 6 shows the results of the studies of the SE+ECAL system of
detectors. The results meet the requirements of the project.
Numerous studies have been
performed to check the radiation hardness of the full-scale detectors.
The results demonstrate a stable performance of the detectors after
a radiation exposure corresponding to 10 years of operation under
the real conditions of the experiment. Mass-production of the silicon
strip detectors is under way in cooperation with ELMA, Zelenograd,
and CERN. Presently, a 30% of detectors have been produced.
Fig. 4:
a)Energy resolution of the electromagnetic calorimeter with the preshower detector;
b) Spatial resolution of the preshower detector
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