Studies on charge collection of p-type silicon detectors under neutron irradiation expected for Super-LHC

The existing technology used in the ATLAS Tracker is at the limit for performances of 10 years of running at a LHC peak luminosity of 10³⁴ cm^-2s^-1. The operation under an upgraded luminosity of 10³⁵ cm^-2s^-1 (Super-LHC) will imply a corresponding increase of the radiation dose. The expected dose for the inner detector tracker at the Super-LHC is up to 1 × 10¹⁶ equivalent neutron cm^-2 in comparison with a dose of 1 × 10¹⁵ equivalent neutron cm^-2 at the LHC after the envisaged 10 years of operation. So, the classic concept of p-on-n silicon microstrip detector as used in the current Semiconductor Tracker (SCT) in ATLAS needs to be abandoned for the Super-LHC. Investigations with n-on-p silicon sensors are showing arguments in favor of implementing these technologies in harsh radiation environment as the Super-LHC. This paper reports about studies with p-type sensors undergoing high radiation doses of neutrons in terms of their charge collection efficiency. A significant contribution to the radiation damage to the sensors in the tracker volume is due to backscattered neutrons so it is important to know the sensor performance under this kind of irradiation. Microstrip sensors from two different suppliers have been tested and a new analogue acquisition system called ALIBAVA system has been used to carry out the measurements.