Radiation damage study of a Geiger-mode avalanche photo-diode (MPPC) using a pion beam at TRIUMF*

Silicon solid state Geiger-mode avalanche photo-diodes (MPPC) are now available from a several manufacturers. They offer several advantages compared to a conventional PMT -- small size, weight, and even cost. However such solid state devices are also much more susceptible to radiation damage. Previous studies of a Hamamatsu S10362 400 pixel detector have shown significant radiation damage after exposure to 100M protons ($\sim$50 MeV). We have studied the signal deterioration and dark current during irradiation by a 130 MeV/c pion beam at TRIUMF. The results for a total exposure of 5000M pions will be presented.