Particle-in-Cell Simulation of Expansions of Dense Plasma Sources for X-Ray Laser Systems

概要

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A numerical model based on the particle-in-cell (PIC) simulation method is applied to C5+ high density plasma expansions. Spherical, cylindrical, and planar expansions are simulated and compared for two cases of initial conditions. In the first, a compact plasma cloud of 22 nm in diameter (width) with the ion density n i0 = 1029 m-3 and the ion and electron temperatures kT i0=kT e0= 10 keV is modeled, while in the second an inflated cloud of 20 µm diameter (width) with n i0 = 1025 m-3 and kT i0=kT e0= 100 eV is considered. The expansion wave-front is shown to have a double layer structure which rapidly decays with time. The electrons that are diffused beyond the plasma core, are divided into two groups; runaway electrons and captured ones. The split of temperatures which are based on different components of the particle velocity, demonstrate nonequilibrium nature of expansion. The density and temperatures drop rapidly all over the cloud volume during the compact plasma expansion. In the inflated cloud, there exists a core where the plasma density remains unchanged, while the temperature is gradually decreasing. The geometry dependence of the expanding plasma characteristics is also discussed.
1997-07-15