Providing of gases for an excimer laser

Claim 1

In a method for reducing the expenditure of a heavy rare gas in an excimer laser system utilizing in a laser chamber a lasing mixture of a diluent rare gas, a heavy rare gas and a halogen gas in given percentages which includes the steps of continuously evacuating the lasing mixture from the laser chamber, removing from the evacuated lasing mixture any halogen compounds formed by lasing action in the laser chamber to provide a cleansed lasing mixture and feeding the cleansed lasing mixture back into the laser chamber, the improvement comprising adding to the fed back cleansed lasing mixture a supplemental lasing material comprising a gas mixture of the diluent rare gas, the heavy rare gas and the halogen gas, the percentage of halogen gas in the range of 3% to 15%, the percentage of diluent rare gas in the range of 60% to 97% and the percentage of heavy rare gas in the range of 0.3% to 25% of the mixture but with the percentages of the diluent rare gas to heavy rare gas being in substantially the same ratio of said given percentages of said rare gases.