The influence of tube-plate electrodes on the laser mode of a fast-transvere- flow C02 laser
The distribution of the electric field of a tube-plate transversal flow discharge C02 laser is numerically solved. It is helpful to understand the formation and improvement of the laser mode.
An analytical approach to the design of electrodes in high-power, fast-transverse-flow CO2 lasers
Abstract Usually, the design of the electrodes of fast-transverse-flow CO 2 lasers relies more on experimental data than on theoretical analysis. Traditional systems sustain a stable, high-power discharge but the current distribution generates a peaked, non-uniform small-signal-gain pattern. We present a theoretical model suitable for the design of electrodes that achieves a quasi uniform gain distribution. The analysis, based on a two-temperature model and the gas-transport equations, computes the electron density that supports a flat gain pattern. Combining the desired electron density with the electron-balance equations, the model determines the required electric field. The results were used to design a new set of electrodes for a home-made fast transverse flow CO 2 laser. A stable, large volume discharge ( 4 × 8 × 90 cm 3 ) with very good uniformity was obtained. The resulting gain distribution was registered in a bi-dimensional map. The peak gain rose from 1.2 m - 1 , attained with the old electrode set, to 1.6 m - 1 with the new one and the gain showed a homogeneous profile.
Relationship of optical and acoustic emissions to laser weld penetration
Detection and analysis of optical, acoustic and plasma charge emissions from laser beam welds is a promising approach for quality monitoring. In this work, the airborne acoustic and optical-wavelength electromagnetic (light) emissions from laser welds were studied. A matrix of travel speed and CO 2 laser power settings was used to generate bead-on-plate welds in cold-rolled low-carbon steel sheet metal. The power/travel matrix-generated welds having partial penetration, moderate full penetration (visually sound welds) and excessive penetration (relatively wide weld beads with undercut due to drop-through of the molten pool). The intensity of the light emitted from the weld area was found to vary with process parameters, exhibiting a local minimum for moderately full-penetration welds. The RMS amplitude of the acoustic energy was found to have a local maximum for these same moderate full-penetration conditions. The relationship between the optical and acoustic signals was investigated and it was found that the acoustic signal was approximately proportional to the time derivative of the optical signal. The front-side light emission signal was also found to vary inversely with backside light emission.