High-speed measurement of plasma temperature in CO2 laser welding

Abstract

A new method for a high-speed measurement of the plasma temperature has been proposed to characterise the fluctuated plasma state in CO2 laser welding. Monochromatic photographs of two different spectral lines were taken simultaneously in less than 10 ms with a combination of a splitter, two monochrometers, two image intensifiers and two high-resolution CCD cameras. The temperature of a stably induced pure argon plasma was determined by off-axis maximum emission technique (Larenz method) and ArII/ArI relative intensity technique to confirm the validity of the proposed method. The result showed a good agreement with each other. The distributions of the plasma temperature were measured using this method under various welding conditions. The effect of welding variables on the laser power absorption in the plasma has also been evaluated on the basis of inverse Bremsstrahlung.A new method for a high-speed measurement of the plasma temperature has been proposed to characterise the fluctuated plasma state in CO2 laser welding. Monochromatic photographs of two different spectral lines were taken simultaneously in less than 10 ms with a combination of a splitter, two monochrometers, two image intensifiers and two high-resolution CCD cameras. The temperature of a stably induced pure argon plasma was determined by off-axis maximum emission technique (Larenz method) and ArII/ArI relative intensity technique to confirm the validity of the proposed method. The result showed a good agreement with each other. The distributions of the plasma temperature were measured using this method under various welding conditions. The effect of welding variables on the laser power absorption in the plasma has also been evaluated on the basis of inverse Bremsstrahlung.