Accelerated annealing of n + -p strip detectors irradiated with pions

TLDR: In this article, the authors presented charge collection measurements with silicon detectors with implanted n-type readout strips in p-type silicon bulk (n+p) and observed that irradiation of these detectors with pions results in only ~ 30% of the increase of VFD seen after irradiation with neutrons to the same NIEL equivalent fluence.

Abstract: Charge collection measurements with silicon detectors with implanted n-type readout strips in p-type silicon bulk (n+-p) are presented. Detectors were irradiated with 191 MeV pions at the Paul Scherrer Institute (PSI) in Villigen in Switzerland. Signals induced by electrons from 90Sr source were measured with SCT128 chip. Collected charge and detector current were measured after several annealing steps summing up to over 10000 minutes at 60?C. It was observed that irradiation of these detectors with pions results in only ~ 30% of the increase of Vfd seen after irradiation with neutrons to the same NIEL equivalent fluence. Charge multiplication effects in pion irradiated detectors were seen only after long accelerated annealing time. Both effects are consistent with smaller space-charge introduction rates after irradiation with charged hadrons, characteristic for oxygenated detector material. It was confirmed that, at sufficient bias voltage, reverse annealing after pion irradiation does not represent a problem for application of these detectors in trackers at upgraded LHC.