Construction of the ALICE silicon pixel detector and prototype performance in test beam

Abstract

The Silicon Pixel Detector (SPD) forms the two innermost layers of the Inner Tracking System (ITS) of the ALICE experiment at the CERN LHC. The SPD consists of 120 detector modules (half-staves) on two barrel layers with 107 pixel cells and a total silicon surface of 0.2 m 2. The SPD is severely constrained in terms of material budget, dimension and volume of the whole system. The SPD design, the main system components and the current status of the project are overviewed. The automated equipment and the procedure for the assembly of the half-staves are illustrated. The results of the data analysis of a test beam performed with single assemblies at the SPS in 2003 are reported. It is shown that efficiency and spatial resolution are in good agreement with the design specifications and satisfy the ALICE requirements.