Existing laser systems have an optical resonator structure in which an active gas lasing medium, such as a gaseous mixture of CO.sub.2, N.sub.2 and He is excited to produce a beam of coherent radiation. Precise optical components including mirrored surfaces at either end of the resonator cavity are exposed to the gas lasing medium. It is critical to the laser resonator and optical components thereof that the lasing medium be maintained at a predetermined temperature, in the range of 20.degree.-30.degree. C.
Prior laser resonators have controlled the temperature of the lasing medium by using heat exchangers having concentrically arranged tube-in-tube constructions with the gas lasing medium flowing through the inner tube or primary chamber and the stabilizing heat-exchange fluid, such as oil or water, flowing through an outer secondary chamber between the inner tube and a metal outer casing.
Contamination of the gas lasing medium is a major problem and adversely affects the useful life of optical resonator components. Such contamination occurs in the circulation of the lasing gas from the resonator structure through fittings, hose connections, heat exchangers and pumps, and a principal source of such contamination has been in the primary or first heat exchanger in which the high temperatures implied upon the gas in the resonator are reduced back into the range of ambient temperatures. The inner gas conveying tube in an existing primary heat exchanger for a laser resonator is believed to have been constructed of PVC (polyvinyl chloride) tubing from which oxides or like contaminates are induced into the gas lasing medium. Since the lasing medium is recirculated from the heat exchanger to the resonator cavity for reuse, such contaminates have been deposited on mirrored optical surfaces and substantially reduced the efficiency of the laser, thereby necessitating the frequent replacement of optical components. This causes downtime for replacement of the optical components with an incident loss of production time and great expense.
The contamination problem has not been solved heretofore. Filtering the gas lasing medium using a micron filtering arrangement does not effectively remove such contaminates, and acceptable substitutes for the primary PVC temperature controller (not contributing to the contamination problem) have not been available.
Replacement of the primary temperature controller (inner tube) is also complex due to unique assembly problems. The laser may be installed near structural walls or other obstructions, which limits access essentially to one end of the exchanger since the inner and outer tubes in this heat exchanger are typically in the magnitude of 12 feet in length. The assembly operation is relatively simple if a PVC inner tube is used since connections, joints, etc. may be easily glued. However, if non-contaminating materials are used, the assembly and installation becomes critical. For example, if glass is used for the inner tube (primary chamber) as in the present invention, the approximately 12 foot long glass inner tube must be slid down the entire length of the approximately 12 foot long outer metal casing and channeled through openings in the heat exchanger manifold at both ends. Moreover, compatible end caps, connectors, fittings, etc. must be used to complete the flow of the gas lasing medium. Such a temperature controller meeting these criteria has heretofore not been available.