STEPS TOWARDS THE USE OF SILICON DRIFT DETECTORS IN HEAVY-ION COLLISIONS AT LHC

The inner tracking system of the ALICE detector for Pb-Pb collisions a t the LHC require a very good granularity in the innermost planes, due to the high particle density, up to 8000 particles per unit of rapidi ty. The silicon drift detectors are a very good candidate for this app lication, but up to now no large system using this technology has been industrially produced and operated in experiments. One of the first s teps towards large scale production is the study of the doping uniform ity in commercially available Si wafers. The understanding of doping f luctuations is of fundamental importance since they introduce deviatio ns of the electron trajectories from the expected ones. In addition, i t is also necessary to know the changes possibly introduced by differe nt processing steps in the resistivity profiles. We report here the re sults of measurements of resistivity profiles for NTD silicon wafers b oth before and after processing.