Precision muon tracking detectors and read-out electronics for operation at very high background rates at future colliders

The experience of the ATLAS MDT 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 beyond HL-LHC. Therefore, drift-tube detectors with 15 mm tube diameter (30 mm in ATLAS), optimised for high rate operation, have been developed for such conditions. Several such full-scale sMDT chambers have been constructed with unprecedentedly high sense wire positioning accuracy of better than 10 μm. The chamber design and assembly methods have been optimised for large-scale production, reducing considerably cost and construction time while maintaining the high mechanical accuracy and reliability. Tests at the Gamma Irradiation Facility at CERN showed that the rate capability of sMDT chambers is improved by more than an order of magnitude compared to the MDT chambers. By using read-out electronics optimised for high counting rates, the rate capability can be further increased.