ABSORPTION OF LASER-LIGHT IN OVERDENSE PLASMAS BY SHEATH INVERSE BREMSSTRAHLUNG

The original sheath inverse bremsstrahlung model [P. J. Catto and R. M . More, Phys. Fluids 20, 704 (1977)] is modified by including the vxB term in the equation of motion, as the evanescent magnetic field in an overdense plasma is greater than the corresponding electric field. It is shown that the present results are significantly different from th ose derived without the vxB term. The vxB term is also important in in terpreting the absorption mechanism. If the vxB term were neglected, t he absorption of the light would be incorrectly interpreted as an incr ease in the transverse components of the canonical momentum, in the ca se of a normally incident laser light. It is also shown that both the sheath inverse bremsstrahlung and the anomalous skin effect are limiti ng cases of the same collisionless absorption mechanism. Results from particle-in-cell (PIG) plasma simulations are compared with the absorp tion coefficient calculated from the linear theory. Finally, the effec ts of finite density gradients are investigated by PIC simulations. (C ) 1995 American Institute of Physics.