Performance of P-type micro-strip detectors after irradiation to 7.5×1015 p cm2

Exploiting the advantages of reading out segmented silicon from the n-side, we have produced test detectors with LHC pitch but 1-cm-long strips which even after proton irradiation at the CERN PS (24 GeV protons) to 7.5×10¹⁵ cm^-2 show signal to noise greater than 8:1 using LHC speed electronics. This dose exceeds by a factor of 2 that required for a replacement of the ATLAS semiconductor tracker to cope with an upgrade of the LHC to a Super-LHC with ten times greater luminosity. These detectors were processed on p-type starting material of resistivity ∼2 kΩcm and, unlike n-in-n designs, only required single-sided processing. Such technology should therefore provide a relatively inexpensive route to replacing the central tracking at both ATLAS and CMS for Super-LHC (SLHC). The shorter strip length is required to limit the noise. Even at these extreme doses 30% of the nonirradiated signal is seen. This 7000 e^- signal (in 280-μm-thick sensors) is very competitive with the postirradiation performance of other, more exotic detector options . The hit density expected at a SLHC would anyway require a scaling down of the sense element length (for a given pitch) to retain an occupancy of less than 1% in the layers of the central tracker. We therefore propose such a "short-strip" design as a possible low cost and easily implemented route to achieving the requirements for very high luminosity tracking at an upgraded LHC.