ALICE silicon drift detector: qualification procedure of the mass production

Abstract

Large area, 7.25 /spl times/ 8.76 cm/sup 2/ silicon drift detector (SDD) has been developed for the ALICE experiment at CERN. The final detector design features elements devoted to allow controlled operational conditions and good production yield. The point-like arrays of injection electrodes on board, have shown the ability to trace with the needed frequency and precision the changes in drift speed induced by temperature variations in the different operating conditions. The design characteristics of the integrated on board high voltage divider, as well as of the guard electrodes, should ensure for 10 years operation a suitable voltage distribution along the drift direction without applying to an external support. Special care has been put in the choice of the base NTD wafer material. It is now of paramount importance to thoroughly verify the characteristics of each single detector before integration in the final layout. Dedicated testing facilities have been developed to select from the mass production 260 detectors that will equip the two cylindrical layers which are part of the ALICE inner tracking system. We find in the first qualification batches for mass production the confirmation of the design and technological characteristics that we have obtained in the pre-series detectors. We report on the testing facilities and procedures, the detector selection criteria and the test results.