Measurement of anomalously high charge collection efficiency in n+p strip detectors irradiated by up to 1016 neq/cm2

Micro-strip detectors made by implanting n-type readout strips on p-type silicon bulk (n+p) are promising candidates for tracking detectors for applications in extremely high radiation fields such as those expected in experiments at Super-LHC. In this paper, we present measurements of signals in n+p strip detectors caused by fast electrons from a 90Sr source and read out by an SCT128A chip. Detectors were irradiated with reactor neutrons up to 1016 neq/cm2. The collected charge was measured at different bias voltages, and measurements were taken up to very high voltages of 1700 V. We measured the most probable value of collected charge as high as before irradiation with detectors irradiated up to 3×1015 neq/cm2. Excellent performance with nearly 50% of the charge collected was also obtained with the detector irradiated to 1016 neq/cm2.