Distribution of the intensity absorbed by the keyhole wall in laser processing

The distribution of the energy flux absorbed by the wall is investigated after the laser beam undergoes multiple diffuse and specular reflections in a hemispherical cavity. The laser beam is characterized by different energy distribution parameter, wavelength, and polarization. Inverse Bremsstrahlung absorption within the plasma and Fresnel absorption on the cavity wall are taken into account. Scattering within the plasma, radiation absorption due to surface temperature and alternation of polarization in the process of multiple reflections are assumed to be negligible. The analytic model is derived and compared with the Monte Carlo method. The influences of wavelength, polarization, inverse Bremsstrahlung absorption coefficient and material property on the absorbed intensity are discussed. (C) 2003 Published by Elsevier B.V.