The ATLAS Transition Radiation Tracker and recent developments in $p^{+}$n silicon strip detectors for LHC

The ATLAS Collaboration is building, as a part of its tracking system, a 370000 straw drift tube detector, the Transition Radiation Tracker, that provides flexible level-2 triggering, robust pattern recognition and good electron/pion separation. We discuss the final design choices that will ensure reliable operation over the experiment lifetime in the harsh LHC environment, with particular emphasis on high counting rate and detector ageing issues. We also discuss recent developments in single-sided p/sup +/n silicon strip detectors optimised for capacitively-coupled read-out with single strip threshold binary electronics. Results on high voltage operation capability and on the use of a novel biasing technique, making use of implanted bias resistors, after irradiation up to a fluence of 3*10 /sup 14/ cm/sup -2/ 24 GeV protons, are presented. (6 refs).