Particle dynamics during adiabatic expansion of a plasma bunch

The renormalization-group approach is used to obtain an exact solution to the self-consistent Vlasov kinetic equations for plasma particles in the quasi-neutral approximation. This solution describes the one-dimensional adiabatic expansion of a plasma bunch into a vacuum for arbitrary initial particle velocity distributions. Ion acceleration is studied for two-temperature Maxwellian and super-Gaussian initial electron distributions, which predetermine distinctly different ion spectra. The solution found is used to describe the acceleration of ions of two types. The relative acceleration efficiency of light and heavy ions as a function of atomic weights and number densities is analyzed. The solutions obtained are of practical importance in describing ion acceleration during the interaction of an ultrashort laser pulse with nanoplasma, for example, cluster plasma or plasma produced when thin foils are irradiated by a laser.     

Permittivity of plasma and nonstationary theory of nonlocal transport

A regular procedure is proposed for finding the solution to a linearized kinetic equation for charged particles with the Landau collision integral in a plasma with large Z. The expression for longitudinal permittivity of a collisional plasma, which is obtained using this procedure for the entire range of frequencies and wavenumbers, as well as the collision parameter, is transformed to the known expressions in the corresponding asymptotic limits. The nonlocal transport equations for small perturbations are also formulated for arbitrary relations between the characteristic space and time scales of the plasma; these relations considerably extend the limits of applicability for previously developed theories.     

Extraction of niobium with phenol-formaldehyde resol oligomer Yarrezin B from peroxide solutions

Extraction of niobium by nitrogen-containing phenol-formaldehyde resol oligomer Yarrezin B from peroxide sulfate solutions was studied. The stoichiometry of extraction was determined. The structure of the extracted complex Nb(O₂)(OH)O₂R(OH)N was predicted by molecular mechanics (MM) and molecular dynamics (MD) methods and the semiempirical ZINDO/1 method (single-point calculations) with the use of the HyperChem Release 8.0.4 program package.     

Optimization of the generalized method of Hermitian and skew-Hermitian splitting iterations for solving symmetric saddle-point problems

An algorithm for solving a nonsingular symmetric system of linear equations with a saddle point is examined. This algorithm has two constant iteration parameters and is an extension of the algorithm of Hermitian and skew-Hermitian splitting iterations (the HSS algorithm). Analytical formulas are derived for the optimal values of the iteration parameters. The formulation of the optimization problem is a classical one for the saddle-point problems. The results obtained are sharp.     

Ultrashort-laser-pulse absorption with spatial dispersion and nonlocal transport effects

We study ultrashort-laser-pulse absorption and plasma heating at a sharp plasma–vacuum interface using advanced models for all-range plasma permittivity and nonlocal heat transport. The electron response includes both collisional and collisionless dissipative effects in the plasma of an arbitrary ion charge. We show that nonlocal electron heat transport is important for correct determination of the value of electron temperature and spatial temperature profile. Nonlocal electron heat flux comes into play after electrons heat up to temperatures of the order of 1 keV and to temperatures several times less for low-density targets.     

Direct acceleration of electrons by radially polarized laser pulse

Direct electron acceleration by highly focused ultrahigh-power laser pulses of radial polarization in the ultrarelativistic mode was studied. The mode at which the focusing spot size appears of the same order as the laser radiation wavelength was considered. Electromagnetic fields were calculated using exact Stratton-Chu diffraction integrals. Calculations showed that, as for the case of linear polarization, too sharp focusing (in the diffraction limit) is not optimum for electron acceleration, despite the strong axial field namely in the case of a submicrometer laser spot. At the same time, the case of moderate focusing is more attractive for electron acceleration.     

Synthesis of n-methyl-3-carboxy-2-chloro-dibenzo[<Emphasis Type="Italic">c,f</Emphasis>][1,4,5]oxa-thiazepine s,s-dioxide and its derivatives

A new dibenzo-condensed oxathiazepinecarboxylic acid was obtained starting from the methyl ester of 2,4-dichloro-5-chlorosulfonylbenzoic acid. Derivatives were obtained from N-phenylamide and N-methylamide of 2,4-dichloro-5-chlorosulfonylbenzoic acid. Methods for the preparation of the starting aromatic sulfonyl chlorides were proposed.     

Electron transport and permittivity in a plasma with an arbitrary ionic charge

Based on the solution of a linearized kinetic equation for electrons with a Landau collision integral, we develop a theory of electron transport for small perturbations in a completely ionized plasma with an arbitrary ionic charge that is free from any constraints on the characteristic perturbation time and length scales. We calculate the potential and vortex electron fluxes for an arbitrary electron collision frequency that allow the spatial and temporal nonlocal transport to be described. We also derive expressions for the longitudinal and transverse electron permittivities of a collisional plasma with an arbitrary ionic charge that are suitable for describing the plasma response to small perturbations with an arbitrary frequency and wave vector. Using the transverse permittivity, which allows the absorption of an electromagnetic wave to be described in the entire range of plasma parameters (from the strongly collisional to the collisionless one), as an example, we provide a detailed comparison with previously known models.     

Kinetic susceptibility and transport theory of collisional plasmas

A system of nonlocal electron transport equations for electrostatic perturbations in (omega,k) space in a high-Z plasma is derived from the Fokker-Planck equation for arbitrary relations between the time, space, and collisionality scales. The closed scheme for obtaining the longitudinal plasma susceptibility epsilon(omega,k) in the entire (omega,k) plane is proposed. Regions in the (omega,k) plane have been mapped for problems such as the relaxation of the local temperature enhancement with a time-dependent heat conductivity. The electron dielectric permittivity has been calculated over the entire range of parameters, including the transition region between Vlasov and Fokker-Planck equation solutions.     

Forward ion acceleration in thin films driven by a high-intensity laser

A collimated beam of fast protons, with energies as high as 1.5 MeV and total number of greater, similar10(9), confined in a cone angle of 40 degrees +/-10 degrees is observed when a high-intensity high-contrast subpicosecond laser pulse is focused onto a thin foil target. The protons, which appear to originate from impurities on the front side of the target, are accelerated over a region extending into the target and exit out the back side in a direction normal to the target surface. Acceleration field gradients approximately 10 GeV/cm are inferred. The maximum proton energy can be explained by the charge-separation electrostatic-field acceleration due to "vacuum heating."