Early stage of reverse annealing and projections for LHC experiments

Summary

Reverse annealingof radiation damage in silicon bulk has been studied with emphasis on its implications on LHC experiments. Predictions were shown to depend critically on the model used for reverse annealingdynamics. A set of 8p ⁺-n-n ⁺ pad detectors was irradiated with neutrons to fluences from 2 × 10¹³ to 2 × 10¹⁴ n/cm^-2. Time-development of defects at 20 °C for 100 days covered the expected annealingat LHC. A linear parameterization of this initial stage of reverse annealingwith a slope parameter was used. The fluence dependence of the slope clearly proved that reverse annealingis indeed a first-order process. A large spread was observed in the slope even with identically treated detectors from the same production batch, the mean value correspondingto a reverse annealingtime constant of 476 days. Two pad detectors were irradiated to 4 × 10¹³ n/cm^-2 and reverse annealingmeasured for a month at 60°C. A fit with two exponentials was shown to adequately describe reverse annealingup to completion.