Flowing gas laser discharge tube structure

Abstract

A co-axial laser tube structure of the kind used in a flowing gas laser has an inner axially extending tube for confining the flowing gas in a discharge region, a single pin cathode mounted adjacent the hot end of the inner tube, a single pin anode mounted intermediate the cool end and the hot end of the inner tube, a gas entrance orifice for permitting gas to flow from the exterior tube into the interior of the tube at the location of the anode electrode means, and an outer tube which is separate from and which extends co-axially with the inner tube. The outer tube is made of plastic and conducts flowing gas along the outside of the inner tube from the cool end to the gas entrance orifice. The co-axial laser tube structure includes tube installation and mounting means effective to permit installation and/or replacement of the inner and outer tubes without the need for subsequent adjustment or bore registration of the tubes. The inner surface of the inner tube is frosted to minimize parasitic modes which could be produced by diffracted light impinging on the inside surface of the inner tube at a grazing angle and also for decreasing the boundary layer of thickness to improve turbulence in the gas flow between the anode and the cathode. The installation and mounting means include shaft seals, chamfers and related O-rings which are effective to hold the co-axial laser tube structure in registration with the bore without over contraint. The centering ring at the hot end of the inner tube has an aperature which shadows the glass tube from any diffracted light of the laser beam. This centering ring has an inner gas flow opening which is curved with a sufficiently large radius to eliminate any turbulence in the gas flow through the opening. A downstream diffuser recovers some velocity head of the gas flowing through the centering ring.