The MRPC-based ALICE Time-Of-Flight detector: Commissioning and first performance

The ALICE Time-Of-Flight (TOF) detector is a cylindrical array with a total area of about 150 m2 and more than 153,000 readout channels; it will allow charged hadron separation for momentum up to a few GeV/c. The very good performance required for such a system has been achieved by means of the Multigap Resistive Plate Chamber (MRPC) whose time resolution is better than 50 ps with an overall efficiency close to 100%. The TOF detector is fully installed since April 2008; it has successfully been operated during cosmic ray data taking. The very good stability, noise level and time performance are reported here. The status of the calibration and the first physics results with the TOF detector are given.