Hamamatsu APD for CMS ECAL: quality insurance

The Hamamatsu Photonics S8148 large area Avalanche Photo Diodes (APD) were designed for the crystal electromagnetic calorimeter of the CMS setup at LHC in a close collaboration of Hamamatsu Photonics and CMS APD group (PSI, Northeastern University and University of Minnesota). All essential parameters of these devices are controlled by the producer and are fairly stable during the mass production, except the radiation hardness. To insure 99.9% reliability of APDs in the radiation hard environment of LHC, the CMS APD group had to invent a dedicated screening procedure. The details of this procedure and some results of the screening are discussed