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 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 10 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. The shorter strip length is required to limit the noise. Even at these extreme doses 30% of the non-irradiated signal is seen. This 7000e^- signal (in 280 μm thick sensors) is very competitive with the post irradiation performance of other, more exotic detector options. The hit density expected at a Super-LHC 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 ´stripsel´ design as a possible low cost and easily implemented route to achieving the requirements for very high luminosity tracking at an upgraded LHC.