Autocalibration: The Influence of the\\ Track Incidence Angles and a New Method

The calibration of the space-time relationship r(t) of the Monitored Drift Tube Chambers in ATLAS will have to be done with the chambers' own data because no external reference detector will be available. Techniques for this so-called ``autocalibration'' have been worked on since the early days of ATLAS preparation. It is a known problem that speed and precision of autocalibration convergence depend crucially on the range of track incidence angles. This note presents an algebraic approach to this dependence. We shall investigate under which conditions autocalibration has enough information to determine the r-t relationship uniquely. A new technical realization will be introduced which is designed for making optimal use of all available information. Finally we determine the spread of track incidence angles for each ATLAS MDT chamber, and discuss the achievable calibration precision. Our calculations are based on the detector response for the gas Ar/CO$_{2}$ (93/7).