COMPUTATIONAL SIMULATION OF COLLISIONAL AND COLLISIONLESS PLASMA KINETICS UNDER ACTION OF LASER RADIATION

M.G. Keidzhyan, M.F. Ivanov, A.V. Ivlev
VANT. Ser.: Mat. Mod. Fiz. Proc 1997. Вып.1. С. 53-54.

      This work studies interactions of powerful laser radiation with supercritical density plasma. At radiation rates of 10¹⁶ W/cm² the plasma dynamics under irradiation is severely non-linear, while at rates of 10¹⁸ W/cm² and higher relativistic effects become essential which motivates employment of computer experiment methods.
      To model processes (rates of 10¹⁸W/cm² and higher, the collisionless case, this work uses the developed electromagnetic codes implementing the particle method in the 2-D and 2^1/2D-gepmetry with account of electron relativism and ion mobility. The following was considered within a wide initial data range: normal and oblique radiation incidence; cases of planar and focused waves at various polarizations; evolution of processes on the density gradient. Some new effects were considered, such as generation of high-energy (MeV) electron fluxes on the boundary, generation of long-lived eddy structures in the plasma volume, excitation of higher harmonics on the boundary and, hence, laser radiation travel into dense plasma, essential dependence of dynamic processes on radiation polarization. Intense evolution of instabilities occurring on the density gradient was found to lead to generation of spatial structures in plasma. For oblique radiation incidence non-linear processes of plasma wave excitation and energy transfer to plasma are considered.
      To model kinetic processes (at rates up to 10¹⁶ W/cm²) with account of Coulomb collisions, developed computer codes are used which are based on Langevin equations stochastically equivalent to the original Focker-Plank equation. The collision effect on radiation absorption processes was analyzed.