Gas Transport Laser Research Articles

Radiation Power Control of the Industrial CO<sub>2</sub> Laser Excited by а Nonself-Sustained Glow Discharge by Changing the Frequency of Ionization Pulses

The article describes radiation power control of industrial CO2 lasers of Lantan series excited by а nonself-sustained glow discharge in the automatic mode. These lasers are closed-cycle fast gas-transport lasers excited by a nonself-sustained glow discharge with ionization by periodic-pulsed capacitively coupled auxiliary discharge. In this case, ionization and conductivity are provided by periodic-pulsed capacitively coupled discharge. The energy contribution to molecular oscillations is provided by the passage of the main discharge current through the plasma with electron density given by ionization. This permits easy laser power control, provides excellent optical homogeneity and stability of an active volume together with high laser efficiency. A system of a nonself-sustained glow discharge with ionization by periodic-pulsed capacitively coupled auxiliary discharge, the stages of creation and brief characteristics of the Lantan series lasers is presented. The method of controlling the power of laser radiation by changing the frequency of the ionization pulses is determined. This control method allows operating of the laser in continuous and in pulse-periodic modes with adjustable pulse ratio and pulse duration, and also provides switching from one mode to another. In the continuous mode, the radiation power is controlled by changing the frequency of ionization pulses, which are high voltage pulses with duration of 100 ns, given with the frequency of 1-5 kHz. Pulse-periodic radiation control is performed by modulating ionization pulses that consists of pulses being delivered in batches. The frequency of the pulses in a batch determines the radiation power in a pulse. The frequency of the batches following is the frequency of the pulse mode, and the length of the batch determines the pulses duration. Based on the experimental data, the dependence of the radiation power on the ionization pulses frequency was determined. An experimental system is presented and the measuring accuracy of the laser radiation power and the frequency of ionization pulses is determined. Data acquiring and processing of experimental results were performed using the NI 6008 USB data acquisition device in the LabVIEW programs of National Instruments. To study the dependence of the laser power on Мехатроника, автоматизация, управление, Том 21, № 4, 2020 231 the frequency of the ionization pulses, a regression analysis method was applied. Studies have shown that the dependence of the laser power on the ionization pulses frequency is linear in a wide range of parameters. The equation of the direct regression is calculated. The confidence estimates of the coefficients of the direct regression and the confidence estimates of the deviation of the theoretical direct regression from the empirical one are calculated with a confidence level of 95%.

Off-Axial, Gas-Jet-Assisted, Laser Cutting of 6.35-mm Thick Stainless Steel

A dual gas-jet, laser-cutting technique involving coaxial and off-axial oxygen gas flows was developed to cut 6.35-mm thick AISI 304 stainless steel plates with a 1.2-kW CO2 gas transport laser at a cutting speed of 12.7 mm/sec (30 in./min). Under identical process conditions, the single, coaxial gas jet could not cut the stainless steel although the cutting speed was reduced to 2.11 mm/sec (5 in./min). Thresholds of off-axial nozzle diameter, gas-impinging angle, oxygen pressure, and other process parameters were determined to obtain clean-cut edge quality (average dross height 0.25 mm). Experimental data coupled with a fluid-dynamics model of gas flow were presented to show the effectiveness of the dual gas-jet, laser-cutting method in achieving the maximum machining rate without deteriorating the quality of cut.

Development of a high power gas transport CO 2 laser with with cylindrical geometry

The aim of this work is to report the achievement of a light weight, compact, high power CO 2 laser which can be used in industry. The construction and operation of a CO 2 gas transport laser with cylindrical geometry and two parallel electrical discharges are presented. Using a 600 mm diameter, 1400 mm length, 250 kg laser head, we have obtained more than 1.6 kW laser power with 2% stability and 2 mrad full angle divergence. For comparison the results are presented for one electrical discharge laser.

Simple and economic compressors for large-volume gas transport laser systems

Design, construction, and operational details of a simple and efficient axial flow compressor, suitable for large closed-cycle gas transport laser applications is described. These compact and high performance devices are easily assembled from standard low-cost industrially available components. Performance achieved is as good as that of commercial units, but at an order of magnitude lower cost.

Formation of austenite in laser-processed Fe-0.2%C-20%Cr alloy

Laser surface alloying of chromium on a 0.2% C steel was performed using a 1200 W continuous wave CO 2 gas transport laser to produce an alloy containing 20% Cr. The effects of rapid melting and subsequent quenching on the microstructure and microhardness of this alloy were then investigated. A single-pass laser melting was employed to produce a penetration depth of 600 μm. The microstructure, characterized by scanning and thin foil transmission electron microscopy, consisted of austenite needles embedded in a ferritic matrix. The factors governing the formation of austenite and its substructure are discussed and some evidence for the mechanism is presented.

200 W KrF gas transport laser

This paper describes the design and operation of a closed cycle, gas transport, krypton fluoride laser which has generated an average output power of over 200 W while operating at a pulse repetition rate of 1 kHz.

Laser beam interaction with plastics

An efficient and clean laser process is reported which was developed to replace the mechanical skiving utilized for selectively removing plastic material over metal composites, leaving substrate materials undamaged and undelaminated. A CO2 continuous-wave gas transport laser, with laser intensities exceeding 5×104 W/cm2, was utilized to establish the procedure. The parameters of the appropriate physical model for the material removal are calculated.

GAIN AND SATURATION IN TRANSVERSE FLOWING CO2–N2–He MIXTURES

Gain and saturation are investigated in a kW CO2–N2–He gas-transport laser. The active medium flows at 35 m/sec transverse to the probe laser beam. Gain falls exponentially downstream of the excitation region with a characteristic decay distance of 7 cm, giving a decay time of approximately 2 msec. A saturation parameter of approximately 250 W cm2 is determined. This large value is due to rapid flow which sweeps the molecules through the laser beam in a time shorter than the upper state relaxation time.