G A Vergunova

Calculation of optical characteristics of nonequilibrium plasma

A collisional-radiative model has bene developed to calculate the physical and optical characteristics of thermodynamical nonequilibrium plasma. The mean charge of plasma ions, the ionization-state density, radiative energy losses, line ratios, the opacities and the emissivities have been calculated for the steady-state optically transparent plasma, which contains aluminum or copper multi charged ions, in a broad range of plasma densities and temperatures. The comparison shows that our result agree satisfactorily with the calculation results of other authors and with the experimental data.

Mean opacities of LTE plasmas: detailed configuration accounting versus other approaches

The hydrodynamic-radiation codes are used for a simulation of mean Rosseland and Planck opacities from different models similar to Hartree-Fock model, average ion model, detailed configuration accounting model, and so on. At present the necessity in such a data is high especially for plasma of mixture of ions. In this work we present the results on a comparison of mean opacities calculated by means of various codes and models. The calculations were carried out for the local thermodynamic equilibrium (LTE) plasmas of various chemical elements and mixtures. The models under consideration are the DESNA model and the THERMOS, JIMENA (analytical opacity formula), and the LEDCOP codes. The main results and conclusions about applicability of each of the approaches based on the comparison are presented for LTE plasma on Be, C, Al, SiO2. After verification, the results of the DESNA model calculations will be used to create the database on mean opacities in a broad range of plasma density and temperature for various materials, including the case of non-LTE plasma.

Direct drive targets for the megajoule facility UFL-2M

Development of direct drive target schemes for the megajoule facility is a topical problem of up-to-date inertial fusion physics. The choice of possible schemes and solutions depends essentially on the irradiation conditions. The installations both running (NIF) and under construction (LMJ) are destined to the 3ω irradiation in PDD (polar direct drive) configuration. The UFL-2M installation that is under construction is based on 2ω irradiation and a symmetrical scheme of direct drive target irradiation. Under these conditions possible schemes for direct drive targets demonstrating the ignition and the achievement of gain G=10÷20 are considered in this report. At the same time, the possibilities are analyzed for the target compression and ignition with a reliability reserve at the conditions that can deviate from the standard ones, and if our understanding of the physics of the processes is not completely adequate to the physics of the real processes.

Analysis of the symmetry of the direct-drive target implosion under laser pulse of a megajoule scale

The class of direct-drive targets for the laser pulse of a megajoule scale is considered in the work. A distinctive feature of the design of these targets is a relatively low aspect ratio (outer DT-shell radius/shell thickness, A ~ 10) to provide greater compression stability. The irradiation of the target surface is carried out by the shaped laser pulse on 2ω of Nd-laser. The influence of laser energy absorption inhomogeneity on the parameters of compression and burning of thermonuclear fuel on the final stage of implosion is studied in the work based on 1D and 2D numerical calculations. The results of 2D modeling show that in the case of targets offset from the point of beams crossing significantly greater reduction in the neutron yield is observed than in the case when only irregularities caused by the geometry of irradiation by the finite number of beams are taken into account.

Spectral emissivities and opacities of plasma at laserinteraction with targetsof various chemical composition

In the present work a theoretical model of plasma absorption and emission is developed and applied to explanation of some experimentally observed spectra from laser-produced plasmas under conditions being of interest for the ICF as well. The targets for ICF contain the layers of various materials: Be, Al, Cu, SiO2, agar (C12H18O9)n, and others. Of interest is the code, calculating the optical characteristics of plasma of a complicated chemical composition in a broad range of plasma conditions (density and temperature). This spectroscopic modeling has been performed by a collisional-radiative model DESNA for non-LTE mixtures involving detailed structure of excited levels of all charge states from a neutral atom to a fully ionized ion. In the paper we present some new results of theoretical investigation of x-ray emission in the conditions close to real experiments on interaction of short and powerful laser pulses with targets. The simulation and available experimental results are in good enough agreement for various target materials (C, Al, Cu).

Gamma-ray generation in the picosecond-laser plasma with taking into account the prepulse influence

The picosecond laser pulse interaction with different targets was studied on the NEODIM installation. THE processes in laser-produced plasma were considered theoretically and by numerical calculations by RAPID-SP and RADIAN codes with taking into account the pre-pulse with energy contrast of the factor 103-104. Interpretation of the experiments, estimations and numerical results for plasma and electromagnetic fields parameters, fast electron and (gamma) -radiation are presented in this work.