A laser has at least two coaxial electrode tubes spaced apart to provide a laser cavity therebetween and a cooling system including cooling coils about the outer surface of the outer electrode and about the inner surface of the inner electrode and in heat exchange contact therewith. Support pipes are provided about the outside of the outside cooling coil and about the inside surface of the inner cooling coil. The cooling coils are deformed into improved heat exchange contact with the electrode tubes by internal pressure and may be softened by annealing or the like before the application of the deformation pressure.