Development of a Read-out System with a PWO based Electro-Magnetic Calorimeter for the ALICE Experiment at LHC

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We have successfully developed a photon readout system of a newly developed lead-tungstate crystal for the Photon Spectrometer (PHOS) in the ALICE experiment at CERN-LHC. The PHOS is an electromagnetic calorimeter consisting of 17,920 channels of detector element based with a PWO crystal, and is designed to achieve the finest energy resolution and the best two-track resolution among EM-calorimeters for GeV particles so far built. The readout system is composed of an avalanche photo-diode (APD), a preamplifier board, a front-end electronics (FEE) board which is equipped with several functions of a pulse shaper, a pulse form digitizer, a digital data processor, a level-0 and -1 trigger processor, and a data transfer bus driver. The APD and preamplifier board has been designed, tested and fabricated in Japan. The APD/preamplifier sample has been used in a 256 channel prototype calorimeter and tested at CERN-PS and SPS in 2005-06. They showed an excellent performance as is designed and preliminary approved for mass-production. The FEE board was designed and tested in cooperation with groups from CCNU and WUST at Wuhan, China, since they are charged in the FEE board mass-production. A technical review of the readout system was held in May 2005, and Toru Sugitate presented its status and readiness as one of presenters. The approval for mass-production of the entire system has been officially given in Oct. The Grant-In-Aid project has then been successfully completed and we are ready for the PHOS construction. Based on this successful achievement, a new Grant-in-Aid has been proposed for a construction of the PHOS detector and studies of quark-gluon-plasma physics via the photon channel in ALICE at LHC.