Theoretical model of absorption of laser light by a plasma

Abstract

A simple model of laser light absorption is described. The absorption mechanism is mainly inverse bremsstrahlung, but a crude description of resonance absorption is also included. The intensity and the wavelength dependence are emphasized, but the model takes into account the target material composition, the laser pulse length, and the focal spot radius. Plane and spherical expansion are treated. Results range from short‐wavelength, low‐intensity regime, where inverse bremsstrahlung absorption is total, to long‐wavelength high‐intensity regime, where inverse bremsstrahlung absorption is negligible. Scaling laws concerning absorption, electron temperature, and electron kinetic pressure are given in the two limiting regimes. A characteristic flux Φ^*, or, alternatively, a characteristic wavelength λ^* is defined which separates the two regimes, the other parameters being held constant.