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Abstract

An excimer laser apparatus is provided with a compact high efficiency dust particle removal means which is capable of maintaining the windows clean with only a small volume of purging gas, and which prevents deterioration of aperture masks without having to increase the cavity length or risking the possibility of leakage from piping connections. The excimer laser apparatus uses, as dust particle removal means, filters (13a and 13b) made of metal or ceramic which is non-reactive with fluorine. A ground potential dust collector can be provided at a downstream side of a static dust particle remover, having an anode and a cathode, for collecting any dust particles which have passed through the static dust particle remover. In addition, clean laser medium gas can be introduced into subchambers (14a and 14b) through gas introducing passages (11a and 11b) provided in the walls of the housing (1) and then into the laser chamber (12) through labyrinths (8a and 8b) without disturbing the clean gas which stays near the internal surfaces of the windows (6a and 6b).

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First Claim