Construction and test of the first two sectors of the ATLAS barrel liquid argon presampler

The electromagnetic (e.m.) calorimeter of the ATLAS experiment for the Large Hadron Collider will be a sampling liquid argon accordion calorimeter. To achieve sufficient energy resolution, it is necessary to correct for the energy loss in the material upstream of the calorimeter. For this purpose, a separate presampler detector fixed on the inner face of the e.m. calorimeter, in the same cryostat, is being built by the ATLAS collaboration. Two presampler sectors have already been built and tested in their final version. The geometry of the detector and the various steps of its construction are reviewed. The hardware performance of the detector measured both at CERN and at the ISN-Grenoble (specific test bench) is discussed. It is concluded that the presampler will adequately fulfill its role for future operation at the CERN Large Hadron Collider.