First Results from the Cosmic-Ray Test-Facility at LMU Munich

A cosmic-ray test-stand for MDT chambers has been installed at the University of Munich. Three BOS chambers stacked on top of each other were operated simultaneously. All chambers show proper operational behaviour: in all of their tubes the rate of accidental hits was small and the length of their drift-time spectra agreed within 1,6~$ns$ and better inside each triple layer of tubes. Tracks reconstructed in the uppermost and lowest chamber were used to measure the ATLAS z-coordinate of the anode wires and the distance of the tube layers in the chamber in the middle. Comparisons with the measurement of the x-ray tomograph show that both quantities can be determined with an accuracy of 10~$\mu m$ after a data-acquisition time of 20 hours.