Speaker
Fulvio Tessarotto
(INFN Triest)
Description
A fast photon detection system has been designed and built for the upgrade
of COMPASS RICH-1, a large size gaseous RICH in use at the COMPASS
Experiment at CERN SPS since 2001 and successfully operated in its
upgraded version during the 2006 run. The aim of the upgrade was to make
RICH-1 adequate for high rate operation: the photon detectors of the central
region have been replaced by a new system based on MAPMTs coupled to
individual fused silica lens telescopes and fast read-out electronics while in
the peripheral regions the existing MWPCs with CsI photocathodes have
been equipped with a new read-out system, based on the APV chip. The
telescopes are characterized by a large image demagnification factor with
minimal distortion and large angular acceptance. Accurate coupling to high
sensitivity front-end electronics allowed overcoming the potential problem
represented by the wide dynamical range of PMT responses to single
photoelectrons, while keeping the noise rates and the channel cross-talk at
a negligible level. The high rate capability and the good intrinsic PMT time
resolution are fully exploited by signal digitization via a system based on the
F1 TDC. We present the photon detection design and the constructive
aspects, the test beam and laboratory studies, as well as the preliminary
characterization of the system in the COMPASS experimental environment,
where about 60 photons per ring at saturation have been routinely
obtained. It will be shown that, with this upgrade, COMPASS RICH-1 is
entering the era of the fast RICH counters, suitable for high rate operation.
Primary author
Fulvio Tessarotto
(INFN Triest)
