A review is presented on our recent Vlasov-Fokker-Planck(VFP)simulation code development and applications for high-power laser-plasma interactions.Numerical schemes are described for solving the kinetic VFP equation with both electronelectron and electron-ion collisions in one-spatial and two-velocity(1D2V)coordinates.They are based on the positive and flux conservation method and the finite volume method,and these twomethods can insure the particle number conservation.Our simulation code can deal with problems in high-power laser/beam-plasma interactions,where highly non-Maxwellian electron distribution functions usually develop and the widely-used perturbation theories with the weak anisotropy assumption of the electron distribution function are no longer in point.We present some new results on three typical problems:firstly the plasma current generation in strong direct current electric fields beyond Spitzer-H¨arm’s transport theory,secondly the inverse bremsstrahlung absorption at high laser intensity beyond Langdon’s theory,and thirdly the heat transport with steep temperature and/or density gradients in laser-produced plasma.Finally,numerical parameters,performance,the particle number conservation,and the energy conservation in these simulations are provided.
By one-dimensional Vlasov-Poisson simulation,the critical initial state marking the transition between the Landau scenario,in which the electric fields definitively damped to zero and the O'NEIL scenario,in which the Landau damping is stopped after a certain damping stage,is studied.It is found that the critical initial amplitude ε can only exist when the product of the wave number(k m) and the electron thermal velocity(v th) is moderate,that is,0.2 < k m v th < 0.7.Otherwise,no critical initial amplitude is found.The value ε increases with the increase in k m for a fixed v th,and also increases with the increase in v th for a fixed k m.When k m v th is fixed,the value ε also changes with the wave number and the electron thermal velocity,even though the damping rate and the oscillation frequency are the same in this case.
