Using the chemical-picture representation of plasmas as a mixture of various ions and free electrons, a consistent description of thermodynamics of dense multicharged-ion plasmas is being developed that involves the effects of Coulomb non-ideality and degeneracy of plasma electrons; contribution of the excited ion states (on the base of the superconfiguration approach) that may exist under an appropriate truncation of ion energy spectra due to plasma effects; hard-sphere-model representation of the finite-volume effects of plasma ions with the model parameters (effective ion sizes) corresponding to superconfigurations yielding the greatest contribution to partition functions. We present the calculated data for average ionization, Grüneisen coefficient, and specific heat of aluminum and iron plasmas at temperatures of 0.03-3 keV and densities 10 IntoductionConsistent modeling of thermodynamic properties of dense plasmas in the warm-dense-matter (WDM) domain -at temperatures T ≥ E F (E F -Fermi energy) and densities ρ about or lower than normal solid density ρ 0 -is still one of the challenging problems to be addressed. Such plasmas are produced from interactions of intense radiation fluxes and particle beams in numerous present-day experimental studies on high-energy-density physics (HEDP). Therefore, this problem receives much attention in the leading national laboratories running HEDP research. These plasmas are characterized by strong Coulomb interactions, partial degeneracy of plasma electrons, presence of internal degrees of freedom due to the atomic-shell structure of multielectron ions (shell effects), perturbations of bound ionic states by plasma microfields, and the finite-ion-volume effects at high plasma densities. The lack of systematic experimental data in this range of plasma parameters strongly impedes derivation of the first-principles and semiempirical Equation-of-State (EOS) models.Though one can simulate dense-plasma EOS by using well-developed and practically conceivable cell models [1], those models intrinsically fail to represent self-consistent converse effect of inter-ionic Coulomb correlations on the equilibrium electron distribution in a cell and therefore on the total thermodynamic functions [2]. This, however, can be done within the framework of chemical-picture (CP) approach [2-4] enabling to consider Coulomb interactions between all the charged particles and obtain both appropriate direct corrections to EOS and the shift of ionization equilibrium. It is also worth noting that apart from its traditional application to low-density plasmas, the CP-approach admits extrapolation to reasonably nonideal dense gas and expanded-metal plasmas in the density range 0.1 ≤ ρ/ρ 0 ≤ 1 [2] we are interested in.Recently, P. Hakel et al.[4] developed a CP-model of nonideal plasmas allowing for strong coupling of charged particles with analytic fits obtained from the hypernetted-chain and Monte Carlo simulations [5] and finite ion sizes by using multicomponent hard-sphere model of Mansoori [6]. The cont...
We propose a dynamic model of the electron projector of an electron-ray tube, developed using the method of large particles and using statistical methods for modeling the cathode.In recent years the method of large particles has received widespread application in numerical modeling of motions characterized by large deformations, displacements of the medium, nonstationarity, and nonlinearity of the processes that occur in the mechanics of solid media.This method makes it possible to obtain the dynamics of the evolution of the phenomenon, the characteristic properties of the currents that arise in the medium when the interval of variation of the medium itself is large, the shape of the body, and other parameters. At the same time applications of electron optics in microelectronics, diagnostics of materials, and the treatment of surfaces in connection with the development of technology using sharply focused electron beams of various powers, all require a dynamic description of the processes in electron projectors and electron-optic systems. The method of large particles happens to be effective for solving this class of problems; it was the method applied to create the dynamic model. The papers [1][2][3] give an application of the method of large particles for intensive electron beams in modeling klystrons, magnetrons, transport systems, and other electrophysical devices.The basis of the mathematical model in our case was the solution of a self-consistent problem that presumes a solution of the system of equations of motion of particles subject to the three-dimensional charge fields created by the particles themselves and external electrostatic fields determined by solving the Poisson and Laplace equations respectively. The electron tiux that is modeled was replaced by a group of macroparticles with an automatically varying enlargement factor coinciding at a given instant of time with the cells of an imposed N x N Euler grid. The computation process consists of repeated steps on time, at each of which the fields being accounted for were computed with a stationary grid; in solving the equations of motion a redistribution of particles in space was carried out, i.e., new coordinates and velocities of the particles were determined using their values at the preceding step, and the anode current, variation of the flux, leakage currents, and the geometric and current characteristics of the beam were found. In determining the parameters of the model that effect the discretization of space and timc the space-time step, it was assumed that the distance traversed by a particle in one time step did not exceed the step in the space grid. The time step remained constant during the count of the entire model; it was chosen from the condition of precision in the solution of the equations of motion and was written in accordance with the geometric dimensions of the region being studied and the average velocity of the particles in the volume. The space step varied over the whole length of the electron-optical system depending on the num...
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