Performance of a wall-less drift chamber for muon detection

We present results on an intensive study of a muon detector prototype designed for an experiment at the LHC. The chamber has eight layers of drift tubes measuring one projection of a muon track, and was tested with cosmic and beam muons and in a magnetic field. Single hit detection efficiencies of 99.9% for all gas mixtures and single hit resolutions of 190 μm for the preferred gas mixture of Ar/CO2 80% / 20% were achieved. In a magnetic field of 3 T the single hit resolution with this gas mixture decreased by 10%.