ABSORPTION OF CO2-LASER BEAM IN RELATION TO LASER CUTTING PROCESS

The absorption of incident laser beam is important when the quality of the laser machining is concerned, since the surface plasma acts as a medium between the workpiece and a laser beam. In the present study, t he measurement of electron number density and temperature is carried o ut using a Langmuir probe. Effective absorption coefficients due to el ectron-ion and electron-neutral collisions as well as photoionization processes are dealt with analytically using the Maxwell's equations. T he validity of classical treatment for the electron-neutral collision in relation to absorption is introduced and discussed. Consequently, t he absorption coefficients due to these processes are computed within the frame of the data obtained from the present work. The study is ext ended to include the transmittance of He-Ne laser beam through the sur face plasma generated during laser beam-workpiece interaction. It is f ound that the electron-ion collision is the dominant mechanism in the absorption process. The present data indicates that about 85% of the r eference He-Ne is absorbed at the location close to the irradiated spo t center in the plasma, therefore, the attenuation, scattering and def lection of the reference beam is mainly due to vapor atoms than the ch arged particles.