Plasma hydrodynamic model

Earlier calculation on many electron atomic systems under plasma was performed by Stewart and Pyatt [58], who estimated the variation of IP of several atoms using a finite temperature TF model. Applications of the density functional theory on these systems were reviewed by Gupta and Rajagopal [57], The calculations on many electron systems are mostly concerned with the hot and dense plasmas with the application of the IS model, or from general solutions of the Poisson equation for the potential function. The discussions using the average atom model in Section 3.3, Inferno model of Liberman in 3.4, STA model in 3.5, hydrodynamic model in... 

The hydrodynamic model is based on a sufficiently high collision probability under thermodynamic equilibrium. This condition is fulfilled only at p > 1 mbar, i.e., at high pressures above the typical PLD film deposition conditions, or at the beginning of plasma expansion, at high plasma density (small target to substrate distance). 

Several different models for (k,CO) were explored by them, including the (local) Drade model, a hydrodynamic model, and the Lindhard-Mermin dielectric function. At low frequencies, much below the plasma frequency, they found that the imaginary part of the polarizability was actually enhanced, but that at higher frequencies this enhancement was not as pronounced. The enhancement was attributed to the excitation of particle-hole pairs in the metal. 

The experimental results were analyzed using an integrated approach. To obtain the temporal evolution of the temperature and the density profiles of the bulk plasma, the experimental hot-electron temperature was used as an initial condition for the 1D-FP code [26]. The number of hot electrons in the distribution function were adjusted according to the assumed laser absorption. The FP code is coupled to the 1-D radiation hydrodynamic simulation ILESTA [27]. The electron (or ion) heating rate from hot electrons is first calculated by the Fokker-Planck transport model and is then added to the energy equation for the electrons (or ions) in ILESTA-1D. Results were then used to drive an atomic kinetics package [28] to obtain the temporal evolution of the Ka lines from partially ionized Cl ions. 

The radiation-hydrodynamic simulation includes the Quotidien EOS [29] and Ion EOS based on the Cowan model [30], For the electron component, a set of fitting formulae derived from the numerical results from the Thomas-Fermi model and a semi-empirical bonding correction [31] are adopted. The effective Z-number of the partially ionized plasma is obtained from the average atom model. Radiation transport is treated by multigroup diffusion. 

The pres it understanding of processes in the interior of stars is the result of combined efforts from many scientific disciplines such as hydrodynamics, plasma physics, nuclear physics, nuclear chemistry and not least astrophysics. To understand what is going on in the inaccessible interior of a star we must make a model of the star which explains the known data mass, diameter, luminosity, surface temperature and surface composition. The development of such a model normally starts with an assumption of how elemental conqx)sition varies with distance from the center. By solving the difierential equations for pressure, mass, tenq>erature, luminosity and nuclear reactions from the surface (where these parameters are known) to the star s center and adjusting the elemental composition model until zero mass and zero luminosity is obtained at the center one arrives at a model for the star s interior. The model developed then allows us to extrapolate the star s evolution backwards and forwards in time with some confidence. Figure 17.4 shows results from such modelling of the sun. 

In conjunction with the above experiments, hydrodynamic computer models have been developed to provide a detailed description of the liner motion [18]. The effect of the compressibility of the liner fluid becomes particularly important in thick liners moving at high velocity. If the turnaround time is much less than the transit time of a sound wave through the liner, compression waves will be set up which modify the motion and can cause severe shock loading of the driving mechanism. It is desirable to operate a reactor under conditions where these waves are not significant, and this sets an upper limit on the final pressure to which the plasma may be compressed. 

A complete description of the operation of a Linus reactor requires a compressible hydrodynamic treatment of the liner motion incorporating non-linear magnetic diffusion at the inner surface, coupled self-consistently to a plasma model which includes transport and fusion energy release. It should be three-dimensional to account for the axial contraction of the plasma, it should include the effect of neutron and breramstrahlung heating on the magnetic diffusion in the liner, and should also treat the evaporation of lithium from the liner and its diffusion into the plasma. 

New advanced fs-lasers have recently been found to produce less buffer-gas plasma above the sample surface and especially at reduced pressure, and thus allow more accurate determinations of Cu and Zn in brass samples to be performed than with ns pulses [586]. The hydrodynamic expansion of the plasma, as studied by fluorescence measurements at different heights above the samples and with different delays, was found to be in agreement with the results of calculations based on a modified point-blast model [587]. 

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