THE ATLAS TRACKER UPGRADE: SHORT STRIPS DETECTORS FOR THE sLHC

It is foreseen to increase the luminosity of the Large Hadron Collider (LHC) at CERN around 2018 by about an order of magnitude, with the upgraded machine dubbed Super-LHC or sLHC. The ATLAS experiment will require a new tracker for sLHC operation. In order to cope with the order of magnitude increase in pile-up backgrounds at the higher luminosity, an all silicon detector tracker is being designed. As the increased luminosity will mean a corresponding increase in radiation dose, a new generation of extremely radiation hard silicon detectors is required. A massive R&D program is underway to develop silicon sensors with sufficient radiation hardness. New front-end electronics and readout systems are being designed to cope with the higher data rates. The challenges of powering and cooling a very large strip detector will be discussed. Ideas on possible schemes for the layout and support mechanics will be shown. Planar detectors to be made on p-type wafers in a number of different designs have been developed. These prototype detectors were then produced by a leading manufacturers and irradiated to a set of fluences matched to sLHC expectations. The irradiated sensors were subsequently tested with LHC-readout-electronics in order to study the radiation-induced degradation, and determine their performance after serious hadron irradiation of up to 10(15) n(eg)cm(-2). The signal suffers degradation as a function of irradiation. It is however evident that sufficient charge can still be recorded even at the highest fluence. We will give an overview of the ATLAS tracker upgrade, in particular focusing on innermost silicon strip layers. We will draw conclusions on what type and design of strip detectors to employ for the upgrades of the tracking layers in the sLHC upgrades of LHC experiments.