Studies of radiation effects in the NA60 silicon pixel detectors

NA60 is a fixed target experiment at the CERN SPS, which studies dimuon production in proton- and ion-induced collisions. Downstream of the target system a silicon pixel telescope made with p-on-n silicon sensors measures the charged tracks originating from the interactions. During the 2003 data taking period with indium–indium collisions at 158 GeV per incident nucleon, a significant radiation dose with a very inhomogeneous distribution has been accumulated in the pixel telescope, leading to partially type-inverted silicon sensors. Measurements of the depletion voltage and leakage current performed during this run are shown and compared with simulation results. It is also shown that the operation of partially type-inverted sensors poses no major problem.