Discrete ray model and technique for laser beam absorption modeling

We present a mathematical model of laser radiation absorption in a laser target and describe a corresponding numerical algorithm. The model is developed using a geometrical optics principles. The model application range is extended by taking into account a number of effects that go beyond the geometric optics approximation. To this end we approximate a plasma medium near a "critical density" surface as a set of plane layers. This allows us to construct a simple and sufficiently accurate method for the calculation of laser radiation absorption and reflection processes taking place in the "critical density" region as well as to take into account the dependence of radiation-matter interaction processes on the polarization direction etc. The developed technique is fitted to the radiative-gasdynamics numerical code. It is based on the analytical solution to differential equations corresponding to the optical "ray" model of the laser energy radiation flux. The solution is obtained under the assumption that the squared refractive index gradient has a constant value in any computational mesh cell. The convergence rate of the proposed technique is estimated through numerical experiments.