The co-evaporation system, shown above, is capable of depositing thin films simultaneously from three sources: 2 electron beam guns and 1 thermal boat. It has been used to deposit thin Y-Ba-Cu-O superconducting thin films. The system was constructed by Scofield and his students in 1988 around a 24-in. diameter bell jar and a liquid nitrogen-cooled diffusion pumping system. The three sources are controlled in feed-back loops by three inficon XTC deposition controllers. In addition to the three evaporation sources the system has a gas inlet which has been used for evaporating in an oxygen background pressure. The system also contains a residual gas analyzer for monitoring gas constituents.