Charge collection efficiency measurements for segmented silicon detectors irradiated to 1x1016 n cm−2

Plans are well advanced for a phased upgrade program of the large hadron collider (LHC) at CERN. An improvement of nearly a factor of ten to reach a luminosity close to 10³⁵ cm² s^-1 is the target of the upgraded machine, called the super LHC (SLHC). The innermost tracker devices in the SLHC will be exposed to hadron radiation doses in excess of 1times10¹⁶ n_eq cm^-2. The detectors to be used in the tracker system of the SLHC experiments need therefore to be qualified to these extreme fluences. Segmented n-strip silicon detectors made with thin (140 mum) and standard (300 mum) p-type substrates have been irradiated with neutrons to different fluences up to 1times10¹⁶ n cm^-2 and characterised in term of charge collection efficiency measurements using high speed (40 MHZ) analogue electronics. These measurements are the first direct comparison between the charge collection performances of thin and thick silicon microstrip devices as a function of different fluences relevant to future supercolliders. They also set a reference for the maximum collected charge by segmented sensors made in planar technologies (microstrip and pixel detectors) at these extreme doses, allowing for predictions on the functionality of silicon detectors that can operated in the inner tracking system of SLHC experiments.