J.G. Rubiano

An effective analytical potential including plasma effects

Abstract In this work, we have developed a method to build an effective analytical potential for ions in slightly nonideal plasmas. This proposed potential is obtained from an analytical isolated potential with one or two parameters depending on the total number of electrons of the ion. The plasma effects are included by means of the linearized Debye–Huckel approximation taking into account the reaction of the plasma-charge density to the optical electron. Due to the influence of the plasma over the atomic potential, this permits to obtain level energies and wave functions as a function of the inverse of Debye radius, the quantum numbers, the nuclear charge, the bound electron number and the ionization state of the ion. Also, we compare the analytical effective potential proposed in this paper with other ones very well known in the available literature.

A screened hydrogenic model using analytical potentials

The screened hydrogenic model and analytical potentials are tools widely used for atomic calculation of dense plasma physics. In this paper, we present a simple method to obtain screened hydrogenic energy levels and wave functions from analytical potentials for ions. Atomic data obtained using this model are compared satisfactorily with results of similar models and of more sophisticated self-consistent codes.

ANALYTICAL EXPRESSIONS FOR THE n-ORDER MOMENTA OF CHARGE DISTRIBUTION FOR IONS

Abstract In this work a family of four analytic expressions for the n-order momenta of the charge distribution for ions, 〈rn〉, depending on three, two, or one parameters will be presented. These expressions are derived through the use of electronic charge densities obtained from a family of four analytical potentials. The parameters in the expressions were obtained for ions in the ground state from helium to uranium isoelectronic sequences. The use of these parameters allows to find analytical expressions for the 〈rn〉 as functions of the nuclear charge, Z, only. Finally, the results obtained are compared with results computed by different methods.

Determination of corona, LTE, and NLTE regimes of optically thin carbon plasmas

In this work is accomplished the determination of the corona, local and non-local thermodynamic equilibrium regimes for optically thin carbon plasmas in steady state, in terms of the plasma density and temperature using the ABAKO code. The determination is made through the analysis of the plasma average ionization and ion and level populations. The results are compared whit those obtained applying Griem’s criterion. Finally, it is made a brief analysis of the effects of the calculation of level populations assuming different plasma regimes in radiative properties, such as emissivities and opacities.

Determination and analysis of plasma parameters for simulations of radiative blast waves launched in clusters of xenon and krypton

In this work several relevant parameters and properties for krypton and xenon plasmas are analyzed, such as, for example, the average ionization, the plasma thermodynamic regimes, the radiative power losses and the mean opacities. This analysis is performed in a range of density and temperature typically found in laboratory experiments to generate radiative blast waves in laser-heated clustered plasmas. A polynomial fit of those parameters is also presented. Finally an analysis of the thermal cooling instability is performed.

Calculation of the radiative opacity of laser-produced plasmas using a relativistic-screened hydrogenic model

Abstract In this work, we use a relativistic-screened hydrogenic model to compute the radiative opacity of laser-produced plasmas. The model is based on a set of screening charges which allow one to easily calculate atomic properties of isolated ions. These screened charges have been fitted to a fourth-order polynomial depending on the nuclear charge Z for ground and single excited states of ions belonging to the isoelectronic sequences comprised between He-like to U-like. In the opacity model used, ionic populations are obtained by solving the Saha equation including degeneracy corrections. Bound–bound transitions are determined using a Voigt profile for line shape, which includes natural, collisional, Doppler and UTA widths. Bound–free and free–free opacities are evaluated using the Kramer cross-sections with appropriate corrections. Scattering processes are computed through the use of the Thomson formula with corrections. The results are compared with other screened hydrogenic models and more sophisticated self-consistent codes.

Developments and comparison of two denim opacity models

Abstract Local Thermodynamic Equilibrium (LTE) opacity codes have been developed at DENIM during the last years. JIMENA 1 , 2 is an opacity code that solves self-consistently, for each temperature and density, the radial Dirac equation with a local spherically symmetrical potential. Very recently we have developed a new opacity code, called ANALOP, that uses an analytical potential [3] , which can include density and temperature effects for atomic data calculations. Opacities are determined with these two codes for selected elements at different plasma conditions.

Natural radioactivity measurements of beach sands in Gran Canaria, Canary Islands (Spain)

Concentrations of natural radionuclides (226)Ra, (232)Th, (40)K and man-made (137)Cs in most important tourist Gran Canaria beaches have been determined using a high-purity Germanium detector to analyse their radiological hazard. Average values of the activity concentrations of (226)Ra, (232)Th and (40)K were 17.6±1.4, 21.3±1.8 and 480±22 Bq kg(-1), respectively. Observed activity concentration values of (137)Cs were practically negligible from a radiological protection point of view. The results of this paper were compared with others published in the bibliography for beaches and coastal sediments of different countries. The mean external air absorbed dose rate was 43.9±2.8 nGyh(-1), which resulted in an outdoor annual effective dose below the world average. Also, the radium equivalent and the external hazard index were calculated. Results from Gran Canaria beaches showed the low levels of radioactivity, indicating no significant radiological risk related to human activities in the area.

Development of an analytical potential to include excited configurations

Excited configurations are very important in dense plasma physics. In this work we propose a new analytical potential for excited configurations obtained from another one for ground configuration. With this potential several atomic magnitudes have been calculated for ions in excited configurations analyzing what kind of excited configurations introduce more influences in those magnitudes. Using this potential, atomic data generated are satisfactorily compared with those obtained using other analytical potential using sophisticated self-consistent codes, and with others available in the bibliography.

Influence of atomic kinetics in the simulation of plasma microscopic properties and thermal instabilities for radiative bow shock experiments

Numerical simulations of laboratory astrophysics experiments on plasma flows require plasma microscopic properties that are obtained by means of an atomic kinetic model. This fact implies a careful choice of the most suitable model for the experiment under analysis. Otherwise, the calculations could lead to inaccurate results and inappropriate conclusions. First, a study of the validity of the local thermodynamic equilibrium in the calculation of the average ionization, mean radiative properties, and cooling times of argon plasmas in a range of plasma conditions of interest in laboratory astrophysics experiments on radiative shocks is performed in this work. In the second part, we have made an analysis of the influence of the atomic kinetic model used to calculate plasma microscopic properties of experiments carried out on magpie on radiative bow shocks propagating in argon. The models considered were developed assuming both local and nonlocal thermodynamic equilibrium and, for the latter situation, we have considered in the kinetic model different effects such as external radiation field and plasma mixture. The microscopic properties studied were the average ionization, the charge state distributions, the monochromatic opacities and emissivities, the Planck mean opacity, and the radiative power loss. The microscopic study was made as a postprocess of a radiative-hydrodynamic simulation of the experiment. We have also performed a theoretical analysis of the influence of these atomic kinetic models in the criteria for the onset possibility of thermal instabilities due to radiative cooling in those experiments in which small structures were experimentally observed in the bow shock that could be due to this kind of instability.