Precision Muon Tracking Detectors and Readout Electronics for Operation at 
Very High Background Rates at Future Colliders 

Oliver Kortner, Hubert Kroha, Sebastian Nowak, Robert Richter, Philipp Schwegler

Max-Planck-Institut fuer Physik, Munich

The experience of the ATLAS muon spectrometer shows that drift-tube chambers provide highly reliable precision muon tracking 
over large areas. The ATLAS muon chambers are exposed to unprecedentedly high background of photons and neutrons 
induced by the proton collisions. Still higher background rates are expected at 
future high-energy and high-luminosity colliders. Drift-tube detectors with 15 mm tube diameter 
have been developed for such conditions. Tests at the Gamma Irradiation Facility at CERN showed that the rate capability 
is improved by more than an order of magnitude compared to the MDT chambers as space charge effects are strongly suppressed 
and operation with minimal electronics deadtime is possible. The performance of the sMDT chambers with new readout 
electronics optimized for high rate operation at minimum deadtime will be discussed. Several full-scale sMDT chambers 
have been constructed with an unprecedentedly high sense wire positioning accuracy of 10 microns and installed in the 
ATLAS muon spectrometer. The chamber design and assembly methods have been optimized for large-scale production, 
reducing considerably cost and construction time while maintaining the high mechanical accuracy and reliability. Precise 
mounting of optical sensors for the chamber alignment monitoring system is integral part of the assembly procedure.