Patent ID: 7545842

Claim:
A pre-ionizer for a gas-discharge laser, said gas discharge laser including a sealed metal housing containing the laser gas, said housing being at ground potential, said housing including a planar wall having an aperture formed therein to accommodate the pre-ionizer, said pre-ionizer comprising: a metal body having a passage extending therethrough, said metal body being sealably connectable to the wall of the housing adjacent said aperture and being at ground potential; a membrane of a dielectric material sealably retained within the metal body and closing the passage through the metal body, said membrane having a planar region; and a single planar electrode retained within the metal body, in face to face contact with the planar region of said dielectric membrane on one side thereof and electrically isolated from the metal body and connectable to an RF power supply such that a discharge can be created in the region of the passage of the metal body adjacent the membrane on the side opposite the electrode, wherein the passage through the metal body has, in sequence of position, a first portion having a first diameter, a second portion having a second diameter less than the first diameter, and a third portion having a third diameter less than the second diameter, wherein the dielectric membrane is a base portion of a circular dielectric crucible including a raised rim portion having a diameter greater than the third diameter such that the crucible covers the third portion of the passage, wherein the crucible is retained in the second portion of the aperture though the metal body by a cylindrical retaining sleeve bearing on the rim portion of the crucible, the retaining sleeve including a flanged portion having a diameter greater than the second diameter.