Beam seal for line narrowed production laser

Ultraviolet lasers are widely used in industry. Important examples are current use of KrF and ArF excimer lasers (and the currently scheduled use of F excimer lasers) for lithographic fabrication of integrated circuits. These lasers typically operate 24 hours a day, 7 days per week 365 days per year with only short down times for maintenance. A gas discharge modular laser with beam train isolation between laser chamber module and front and rear optics which define the laser resonant cavity. Beam train isolation units isolates the beam train from atmospheric air while permitting quick and easy removal of the laser chamber without disturbing the optics of the resonant cavity. In preferred embodiments, metal bellows units are bolted at only side so that the chamber module can be removed and replaced without unbolting the bellows unit.