DAMAGE OBSERVED IN SILICON DIODES AFTER LOW-ENERGY PION IRRADIATION

We present results of irradiation tests performed in the pion beam of the Paul Scherrer Institute. Our results confirm the prediction, that the Delta-resonance is reflected as an enhancement of the damage cause d by low energy pions. At the peak of the Delta-resonance we measure a damage constant 1.5 times higher than generally adopted for neutrons and high energy protons. This result means that the lifetime of silico n detectors close to the vertex at LHC experiments will be limited by the pion background. We predict type inversion of high resistivity det ectors to occur after two months of full luminosity and the depletion voltage to reach 200 V within the first four years, even if the detect ors are operated at 0 degrees C.