Development and construction of a Time Of Flight(TOF) system for charged hadron identification in ALICE at LHC

The Time Of Flight (TOF) system of the ALICE (A Large Ion Collider Experiment) apparatus at CERN-LHC (Large Hadron Collider), is especially devoted to the particle identification (PID) of charged hadrons in an intermediate range of momenta. The base detector for TOF is the Multigap Resistive Plate Chamber (MRPC), characterized by an intrinsic time resolution below 50 ps and efficiency well over 99%. The assembling procedures, the tests of mechanics, cooling and electronics of the 8 meters long TOF "supermodules", together with the performance tests before installation in the experimental area and the commissioning steps after the installation, are presented. An analysis on the cluster-pads has been performed with the data of the first cosmic runs, in order to improve the tracking reconstruction made with the tracker system (Inner Tracking System,ITS and Time Projection Chamber, TPC) of ALICE.