Update of the annealing scenario for irradiated silicon p-in-n microstrip sensors

Abstract

The configuration of almost all silicon microstrip sensors instrumenting the tracker detectors of the current experiments in LHC is with readout from implanted p-strips on n-type silicon bulk (from 300 to 400μm thick). The performance of these sensors will change with the irradiation and the time after irradiation (annealing). The effect of the annealing on the performance of the tracking devices has been a source of concern for the experiments due to the rise of the full depletion voltage with time. The experiments have anticipated to suppress annealing effects by keeping the sensors at low temperature also outside operation time. In fact, a scenario that allows a certain amount of annealing could be advantageous for running the silicon sensors towards the end of the experiment lifetime when the readout signal starts to be sensitively degraded. A new set of measurements of the full depletion voltage and charge collection as a function of annealing time with miniature silicon microstrip sensors is presented here and discussed in view of possible annealing scenarios.