Aerothermic characterization of a high-power fast axial flow CO 2 laser

Abstract

Because the structure of the flow in glow discharge tubes for high-power CO 2 lasers is one of the main physical processes to control in order to avoid arcing, an experimental procedure for studying the velocity and temperature fields in such tubes was performed. Two kinds of injection system have been studied. For the first one, the gas mixture is injected by a single sonic nozzle located on the axis of the tube. Because the power of the laser may be increased by associating several tubes in line, the other injection system consists of a series of 12 holes radially arranged in order to move injectors away from the axis. For both cases, the axial mean time velocity profile was measured (without electric discharge) using a laser Doppler anemometry technique in several sections of the discharge tube. The temperature field was investigated during the discharge by using a special thermofluorescent probe. It is found that turbulence facilitates the homogenization of the discharge.