Bulk radiation damage in silicon detectors and implications for LHC experiments

Bulk radiation damage to high resistivity n-type silicon detectors was studied with incident pi(+) (190 MeV) and protons (500, 647 or 800 MeV). Silicon bulk damage constants were extracted based on proton fluences, phi up to similar to 8x10(13) cm(-2) and for pi(+) fluences up to similar to 3x10(13) cm(-2). Although the measured damage constants for pi(+) and for proton irradiations were different, a simple empirical relationship was proposed to relate the pi(+) and proton radiation damage data. In addition: (a) Activation time constants for reverse annealing were determined at four temperatures between 0 degrees C and 50 degrees C. (b) 8 silicon detectors were exposed to a second proton fluence of similar to 3x10(13) cm(-2). The resulting changes in the effective dopant concentration, N-eff, were consistent with a model where the bulk radiation effects were purely additive. (c) Following reverse annealing the bulk radiation damage to high resistivity n-type silicon detectors was consistent with the simple functional form: N-eff(phi)=N-eff(0)e(-c phi)-(g(c)+g(y))phi, with c, g(c) and g(y) damage coefficients measured for pi(+) and proton radiation. The measured damage coefficients were used to provide predictions for the depletion voltage for the innermost pixel and silicon strip layers in the large detectors at the LHC.