Abstract: A gas laser with a discharge bore defined by a single-bore extruded ceramic discharge tube is disclosed. An outer tube is located over the discharge tube so as to define an annular space therebetween. Caps are located over both ends of the tubes and each cap is provide with at least one gas transport passage so the discharge bore and the annular space are in communication. The annular space is filled with electrically insulating, thermally conducting components such as washers, baffles and ceramic granules. When the laser is in operation the annular space serves as a gas return path so a uniform equilibrium pressure is maintained in the discharge bore. The components in the annular space inhibit the flow of electrical current in the space so all of the current flow is through the discharge bore so as to excite the gas therein. The components in the annular space also provide a thermally conductive path between the discharge tube and the outer tube to diffuse heat away from the discharge bore.