Laser gas purifying apparatus

Claim 1

Apparatus for purifying gas of an excimer laser wherein laser gas is passed out of the resonant cavity through an outlet port, transferred to gas-cleaning means, and returned to the resonant cavity through an inlet port, said apparatus comprising: a first closed cycle system comprising a first conduit system coupled between the outlet and inlet ports of said laser including in the order named first valve means, pump means for conveying gas through said conduit system, a cooling trap and second valve means, said first and second valve means when open connecting said laser in said first conduit system for circulating laser gas from said outlet port, through said cooling trap and back to said inlet port, and when closed disconnect said first conduit system from said laser, and a second conduit system including third valve means connected to said first conduit system which when said third valve means is closed provides a second closed cycle system including said pump means and said cooling trap, but not said first and second valve means, for recirculating laser gas through said cooling trap independently of the laser.