Experiments performed over the past year have involved the use of near-diffraction-limited lasers at power levels up to 20 kW for welding applications. This is a substantially higher power level than used in all previously reported experiments. As a result of the higher powers, significantly deeper penetration has been achieved. The optical cavity for the lasers used in these tests was an unstable oscillator, producing a near-diffraction-limited output with an obscuration of approximately 50 percent. The measured penetration for these tests is in reasonably good agreement with established correlations for vacuum electron beam welding data, indicating a strong similarity between the two types of welding. It is shown that a power of 2-4 kW is needed to produce thermally efficient welds in low-thermal-diffusivity plate materials such as 1/2-in stainless steel, and that higher powers are needed for the more highly conducting metals.

Deep penetration welding with high-power CO 2 lasers

A physico-mathematical model of rocket exhaust plumes

Mode-control experiments at a 30-kW CW power level with an unstable resonator at a high Fresnel number were performed on a gas dynamic laser. Near- and far-field intensity distributions were obtained that are consistent with theoretical values for an approximately twice diffraction-limited beam. Under these conditions, the output power was more than half of the maximum multi-mode power.

Performance of an unstable oscillator on a 30-kW CW gas dynamic laser

Processes of collisional redistribution of vibrational energy prevail over specific chemical reaction mechanisms in the determination of vibrational energy distributions in present hydrogen halide CW chemical lasers. Despite the resultant relatively modest departures from the Maxwell-Boltzmann form for the distribution of energy among the vibrational levels of product molecules, selective vibrational energy transfer to a second molecule (e.g., CO 2 ) can be an effective method for the production of complete population inversion by the energy release of chemical reactions. This concept has been the basis for the development of the transfer chemical laser (TCL) during the past three years. A summary of recent progress in the development of CW and pulsed DF-CO 2 transfer chemical lasers is presented. An experiment designed to produce multikilowatt supersonic DF-CO 2 chemical laser operation with full atmospheric recovery in the exhaust gases is discussed. Recent measurements of key vibrational energy transfer processes are reviewed; such measurements have greatly clarified the kinetic aspects of the HF, DF, HF-CO 2 , DF-CO 2 , HCl-CO 2 and HBr-CO 2 chemical lasers. The very large values for these key rates (corresponding to about 20 to 200 collisions) can be attributed to energy transfer to rotation under the influence of a sizable attractive intermolecular potential well and enhanced repulsion at close range.

MD1 - The transfer chemical laser: A review of recent research

In a laser machining system, gas is injected while air is inducted from the rear of a plurality of injection nozzles (9 c) disposed in the space between the machining head (3) and the workpiece (M) and disposed at stipulated intervals in the direction in which the laser light passes, so as not to disturb the machining gas, thus preventing the adhesion of dust arising during laser machining to optical components (31, 32) within the head (3) A light receptor (4) that receives light reflected or dispersed due to adhered contamination is disposed upstream of the optical components (31, 32) within the head (3), and a determination part (6) compares the light reception value against a preset threshold value

Method and device for prevention of adhesion of dirt and contamination on optical parts in laser beam machine

In a high powered laser system it is proposed that combustion gases be bled off from a gas turbine engine and their composition adjusted by burning extra fuel in the bleed gases or adding extra substances. Suitable aerodynamic expansion produces a population inversion resulting in laser action in the CO2 species. Alternatively, bleed gases may be taken from the high pressure compressor of the gas turbine engine and an appropriate fuel burnt therein. If required, other adjustments may also be made to the composition and the resulting gaseous mixture subjected to aerodynamic expansion to induce laser action as before.

Norman Thomas Jewell

Papers

Gas dynamic lasers