We investigate collision characteristics of micro-sized particles (diameter less than 100 microns) via numerical simulations and experiments. Discrete element method (DEM) simulations, based on improved hard-sphere model, are performed to explore effect of initial velocity, surface energy, size, mass concentration, and wind speed on cohesive collisions and non-cohesive collisions between micro-sized particles. Aggregation and settlement process are considered as well. It is found that simulated cohesive collision rate agrees with experimental results of self-settlement of micro-sized particles.

For energy deposition of fast electrons in high density plasma, a relativistic Fokker-Planck equation in three-dimensional momentum space is introduced. It includes both binary collision and contribution from plasma collective response. Numerical method as well as kinetic code of the equation is developed. Typical energy deposition cases are presented with comparison with stopping power model. Energy deposition of fast electrons with energy from 0.5 MeV to 3.5 MeV in 300 g·cm^-3 DT plasma are simulated. It shows that scattering angle ϕ plays minor role on range and penetration depth of energy deposition of fast electrons.

We study numerical method for relativistic Vlasov equation and present a scheme for computing Vlasov equation based on Cartesian-spherical coordinate system, which can be used to reduce number of numerical grid for momentum space. Furthermore, a 4th order non-splitting finite volume scheme is proposed in order to solve momentum parts of relativistic Vlasov equation. In test problems, especially relativistic Landau problem, laser-plasma interaction are solved by using the scheme. We confirm the scheme with theoretically analysis as well as numerical comparison with results of PIC method.

We analyze effect of a small-bandwidth linear frequency chirp on growth of Raman instability with coupled relativistic Maxwell-fluid equations.It is shown that threshold of Raman backward scattering is increased by frequency chirp with no dependence on the sign of chirp.And growth rate of Raman forward scattering increases(decreases) for a positive(negative) chirp.In addition 1D3V particle-in-cell simulations are performed.It shows agreement with theoretical analysis.

A 2(1/2) dimensional particle simulation code PLASIM (Plasma and Simulator) is developed with the purpose of studying the interaction of laser and plasma.The algorithm of the code is introduced.A main characteristics of the code is that it can simulate collision effects by adopting β-particle cloud.Another characteristics is that electrons and ions are both relativistic. So the computation results are more believable when incident laser is ultra-intense.

Two kinds of parallel 2(1/2)-dimensional particle simulation algorithm is designed.One of the algorithm codes is constructed under the distributed-memory process system.One 3-Dimensional Maxwellian velocity algorithm is presented and the Lindman absorbent boundary condition is generalized.The parallel efficiency is tested and analyzed. As an example,the result of the channel effect in plasma by ultrahigh laser is given.

The 3-D Fast Multipole Method, a kind of gridless particle simulation method, is described and improved to obtain higher accuracy. A spherical particle with reduced dimensional motion model is presented. As examples, the spatial distribution of the potential in dust plasma and the instability produced by electrons streaming through ions are simulated. The results of simulations are in agreement with the theory.

A first-order algorithm of numerical solution is developed for systems simultaneously driven by correlated additive noise and multiplicative noise,both in the case that the multi-plicative noise is of white and of colored noise.As an example,the steady state probability distribution of bistable model is computed.Results verifies that this algorithm is applicable.

The distinguishing features of the two-dimensionl particle simulation program developed for research on laser-plasma interaction are described.

The excitation of plasma waves, the acceleratioin of electrons and the generation of suprathermal electrons in the processes of laser plasma resonant absorption have been simulated using the developed two dimensional multi time scale fully electromagnetic relativistic particle simulation computer code. The simulation results prove to be reasonable through theoretical analyses.

Based on the physical model and the calculation method proposed in references[1,2] by anthors,a calculation program of XQMA of micre-particle specimens by using Monte Carlo simulation was made.A series of theoretical formulae for the electron scattering and the production, absorption and fluorescence of characteristic X-rays in particles were given.The datum documents are established in the program.The softwa-re has the ability of automatically treating data,and it can also be applied to the XQMA of block specimens and thin film specimens.