Experience gained in the certification of Seattle MDT ATLAS end-cap chambers

ATLAS monitored drift tube (MDT) chambers are composed of precision muon drift tubes assembled into arrays to form base chambers. Each tube wire in a chamber is located to a precision of 25 microns to provide large area precision chambers for the measurement of muons produced in high-energy collisions at the LHC. Following the completion of 80 MDT base chambers we have been through a process at Seattle and CERN of certifying their operational readiness for ATLAS. The certification process involved a recheck of the gas tightness, the addition of the high voltage and signal electronics cards, the cabling, the testing and conditioning for dark current at high voltage and ultimately collecting millions of cosmic ray events for each MDT. This paper reviews the results, the problems and the repairs performed during the certification. Analysis of the cosmic ray events provides an insight into occasional anomalies in tube function.