Author/Authors :
Grahl، نويسنده , , J. and Kronquist، نويسنده , , I. and Rusack، نويسنده , , R. and Singovski، نويسنده , , A. and Kuznetsov، نويسنده , , A. and Musienko، نويسنده , , Y. and Reucroft، نويسنده , , S. K. Swain، نويسنده , , J. and Deiters، نويسنده , , K. T. Ingram، نويسنده , , Q. and Renker، نويسنده , , D. and Sakhelashvili، نويسنده , , T.، نويسنده ,
Abstract :
The photo detectors of the CMS electromagnetic calorimeter have to operate in a rather hostile environment, in a strong magnetic field of 4 T and under unprecedented radiation levels. Avalanche Photo Diodes (APDs) have been chosen to detect the scintillation light of the 62,000 lead tungstate crystals in the barrel part of the calorimeter. After a 6 year long R&D work Hamamatsu Photonics produces APDs with a structure that is basically radiation hard. Only a few percent of the delivered APDs are weak due to defects at the surface caused by dust particles in the production process. Since a reliability of 99.9% is required, a method to detect weak APDs before they are built into the detector had to be developed. The described screening method is a combination of 60Co irradiations and annealing under bias of all APDs and irradiations with hadrons on a sampling basis.
Keywords :
Avalanche photodiode , Calorimeter , Photo detector , Radiation hardness
