Simulation of Radiation Damage Effects on Planar Pixel Guard Ring Structure for ATLAS Inner Detector Upgrade

We use ac and dc technology computer assisted design simulations to study the effects of radiation damage in the planar pixel sensors of the ATLAS inner detector upgrade, in particular on the active area and breakdown protection of different multiguard rings structure. Using a model of defect introduction into silicon band gap that agrees well with simulation up to fluences of $10^{15} \rm{n}_{eq}/cm^2$, we simulated how high radiation damage phenomena like space-charge sign inversion and double-junction formation affects the efficiency of different models of multiguard ring structures in n-type and p-type bulk. Depletion potential, potential distribution on guard rings, breakdown voltage, and leakage current were extracted from simulations to compare the behavior of the different models.