Spectroscopic measurements of laser induced plasma during welding with CO2 laser

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Abstract
Results of spectroscopic measurements of laser‐induced plasma under welding conditions are presented. Welding was performed with the use of a continuous‐wave CO2 laser operating at a power of 2 kW. Argon or helium was used as a shielding gas. The welding metal was stainless steel or titanium. Emission spectra from plasma were measured with a spectrograph and 1254 Silicon Intensified Target detector connected to the optical multichannel analyzer. The plasma electron temperatures were determined from the relative intensities of spectral lines and the electron densities were determined either from Stark broadening of atomic line or the absolute intensity of ionic line. The distributions of the electron temperature and density over the metal surface are presented and the influence of a shielding gas on plasma parameters is demonstrated. The plasma parameters obtained were used to calculate the absorption of a laser beam in the plasma over the metal surface. No significant absorption was found in our experimental conditions.