Radiation damage in the LHCb VELO1

The VErtex LOcator (VELO) is a silicon strip detector designed to reconstruct particle tracks and vertices produced by proton–proton interactions near to the LHCb interaction point. The excellent track resolution and decay vertex separation provided by the VELO are essential to all LHCb analyses. For the integrated luminosity delivered by the LHC up to the end of 2011 the VELO is exposed to higher particle fluences than any other silicon detector of the four major LHC experiments. These proceedings present results from radiation damage studies carried out during the first two years of data taking at the LHC. Radiation damage has been observed in all of the 88 VELO silicon strip sensors, with many sensors showing evidence of type-inversion in the highest fluence regions. Particular attention has been given to the two n+-on-pn+-on-p sensors as this type of sensor is one of the leading candidates for the LHC silicon detector upgrades.

► Silicon sensor radiation damage studies from the LHCb VELO.
► We investigate the change in silicon sensor properties as a function of fluence.
► Type inversion has been observed in the majority of sensor inner regions.
► Unexpected decrease in depletion voltage is observed for n-in-p type sensors.