Abstract: An internal mirror metal vapor laser, and in particular, a helium-cadmium laser discharge tube, which is economical, compact and has a relatively long operating and shelf life, typically of 10,000 hours. A positive column helium-cadmium laser tube of the consumable type and having optical resonator mirrors integral with the tube ends to hermetically seal the tube is provided which includes a relatively large volume cadmium reservoir capable of containing sufficient cadmium for life times exceeding ten thousand hours. A resistive heater is applied to the cadmium reservoir for controlling the cadmium vapor pressure. A heat sunk diffusion confinement section and a cataphoretic confinement section are provided adjacent one end mirror and a heat sunk diffusion confinement section is provided adjacent the other end mirror to protect the end mirrors from condensing cadmium vapor.