accedaCRIShttps://accedacris.ulpgc.es/jspuiThe accedaCRIS digital repository system captures, stores, indexes, preserves, and distributes digital research material.Fri, 09 Aug 2024 16:33:52 GMT2024-08-09T16:33:52Z50101Analysis of radiative opacities for optically thin and thick astrophysical plasmashttp://hdl.handle.net/10553/57432Title: Analysis of radiative opacities for optically thin and thick astrophysical plasmas
Authors: Espinosa Vivas, Guadalupe; Rodríguez Pérez, Rafael; Gil, Juan Miguel
Abstract: The resolution of the radiative transfer equation in radiation-hydrodynamic simulations of astrophysical plasmas require radiative opacities. In this work, an analysis of the monochromatic and multigroup opacities of an astrophysical plasma mixture has been carried out. The study has been made in ranges of electron temperatures and densities of 1−1000 eV and 1011−1020 cm−3, respectively, a wide range of plasma conditions that can be found in several astrophysical scenarios where local and non-local thermodynamic regimes are attained. Collisional-radiative calculations were performed to obtain the plasma level populations and the monochromatic opacities in that range of plasma conditions, covering both thermodynamic regimes. Since the astrophysical mixture includes chemical elements from hydrogen to iron, their contribution to the total opacity will depend on the plasma conditions and we have made a characterization of their contribution as a function of the electron density and temperature and also of the photon frequency. Multigroup and gray approaches are commonly used in the radiative transfer equation in radiation-hydrodynamic calculations. We have analyzed the influence of the number of the groups in the accuracy of the multigroup opacities and we have showed that, for a given plasma condition, the opacity of the multicomponent plasma in the gray approach may be considerably influenced by only some of the contributing elements, due to the influence of the weighting function in the mean, which can lead to great differences with respect to the monochromatic opacity. Finally, since there are situations in which the self-absorption of the plasma radiation becomes relevant due to the dimensions of the plasma, we have performed an analysis of the influence of the radiation trapping in the monochromatic and multigroup opacities in terms of the plasma conditions and the width of the plasma slab, assuming the plasma with planar geometry and we have also studied the departures of the local thermodynamic regime.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10553/574322019-01-01T00:00:00ZStopping power of a helium plasma under LTE or NLTE conditionshttp://hdl.handle.net/10553/42019Title: Stopping power of a helium plasma under LTE or NLTE conditions
Authors: González-Gallego, Luis; Barriga-Carrasco, Manuel D.; Gil, Juan Miguel; Rodríguez, Rafael; Espinosa, Guadalupe
Abstract: In this work, the stopping power of a partially ionized helium plasma due to its free and bound electrons is analyzed for an electron temperature and density in which local thermal equilibrium (LTE) or non-local thermal equilibrium (NLTE) regimes can be possible. In particular by means of collisional-radiative models, the average ionization of the plasma as well as the abundances of different helium species (HeI, HeII, and HeIII) are analyzed in both LTE and NLTE thermodynamic states. The influence of this ionization and of the different ion abundances on the stopping power of the helium plasma is shown to be quite significant. Finally, our theoretical model is compared with experimental results on slowing down of swift argon ions in helium plasma.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/10553/420192018-01-01T00:00:00ZRadiative properties for astrophysical plasma mixtures in nonlocal thermodynamic equilibriumhttp://hdl.handle.net/10553/42201Title: Radiative properties for astrophysical plasma mixtures in nonlocal thermodynamic equilibrium
Authors: Rodriguez, Rafael; Espinosa, Guadalupe; Miguel Gil, Juan
Abstract: Radiative properties play a pivotal role in astrophysical plasma flows and are needed in radiation-hydrodynamic simulations in order to understand their behavior and also to interpret the plasma emission spectra, which are valuable diagnostic tools. Radiative properties of astrophysical plasma mixtures have been commonly calculated for low-density optically thin plasmas assuming coronal equilibrium and for high density assuming local thermodynamic equilibrium. However, there are wide ranges of conditions in which these thermodynamic regimes are not achieved and the plasma is in the nonlocal thermodynamic equilibrium regime. In the present work, a study of the plasma radiative properties of oxygen and iron and an astrophysical plasma mixture in nonlocal thermodynamic steady-state equilibrium is carried out. The ranges of electron temperatures and densities considered are 1-1000 eV and 10(11)-10(20) cm(-3), respectively. In the study, departures from coronal and local thermodynamic equilibria in terms of the density and temperature are also analyzed. Large differences in the radiative properties that can reach two orders of magnitude when the plasma is far from these thermodynamic regimes are obtained. These analyses are done assuming the plasma to be optically thin. A brief study of the influence of the plasma self-absorption in the radiative properties of oxygen and iron is made. For that purpose, the plasma is assumed with planar geometry and the study is performed in terms of the width of the plasma slab and electron temperature and density.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/10553/422012018-01-01T00:00:00ZAnalysis of microscopic properties of radiative shock experiments performed at the Orion laser facilityhttp://hdl.handle.net/10553/41936Title: Analysis of microscopic properties of radiative shock experiments performed at the Orion laser facility
Authors: Rodriguez, R.; Espinosa Vivas, Guadalupe; Gil, J. M.; Suzuki-Vidal, F.; Clayson, T.; Stehlé, C.; Graham, P.
Abstract: In this work we have conducted a study on the radiative and spectroscopic properties of the radiative precursor and the post-shock region from experiments with radiative shocks in xenon performed at the Orion laser facility. The study is based on post-processing of radiation-hydrodynamics simulations of the experiment. In particular, we have analyzed the thermodynamic regime of the plasma, the charge state distributions, the monochromatic opacities and emissivities, and the specific intensities for plasma conditions of both regions. The study of the intensities is a useful tool to estimate ranges of electron temperatures present in the xenon plasma in these experiments and the analysis performed of the microscopic properties commented above helps to better understand the intensity spectra. Finally, a theoretical analysis of the possibility of the onset of isobaric thermal instabilities in the post-shock has been made, concluding that the instabilities obtained in the radiative-hydrodynamic simulations could be thermal ones due to strong radiative cooling.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/10553/419362018-01-01T00:00:00ZEnergy loss of Fe ions in He plasmas at different thermodynamic stateshttp://hdl.handle.net/10553/42190Title: Energy loss of Fe ions in He plasmas at different thermodynamic states
Authors: Barriga-Carrasco, Manuel D.; González-Gallego, Luis; Miguel Gil, Juan; Rodriguez, Rafael; Espinosa, Guadalupe
Abstract: In this work, we analyze the thermodynamic states of the helium plasma and their influence on the stopping power calculations which are needed for obtaining the energy loss of the iron beams traversing them. The analysis is made in ranges of plasma free electron densities (10(15)-10(19) cm(-3)) and temperatures (1-10 eV) of experiments with iron beams at 6 and 4.3 MeV/u energies. For this purpose, we use Saha-Boltzmann equations for local thermal equilibrium (LTE) and a collisional-radiative model for non-local thermal equilibrium (NLTE) in steady-state situation implemented in a computer code. For the highest temperatures and free electron densities, LTE and NLTE models provide quite similar results for the average ionization and ion abundances. When the opacity effects are taken into account in the NLTE simulations, the optically thick simulations provide fairly similar results to those of the LTE model. The plasma thermodynamic states have a direct impact on the calculation of the energy loss. The differences on the plasma stopping power between considering it in LTE or in NLTE may entail a 10% of the total stopping for the experiments analyzed in the electron density region of 10(18) -10(19) cm(-3). These differences can be around 27% for plasmas with smaller electron density of 10(17) cm(-3) and around 42% for plasmas with an electron density of 10(15) cm(-3). New experiments would be appreciated to be made in a future to corroborate the latest calculations.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/10553/421902018-01-01T00:00:00ZMonochromatic and mean radiative properties of astrophysical plasma mixtures in nonlocal thermodynamic equilibrium regimehttp://hdl.handle.net/10553/55027Title: Monochromatic and mean radiative properties of astrophysical plasma mixtures in nonlocal thermodynamic equilibrium regime
Authors: Rodríguez Pérez, Rafael; Espinosa, Guadalupe; Gil, Juan Miguel; Beltrán, Pablo R.
Abstract: Radiative‐hydrodynamics and radiative transfer simulations of astrophysical plasmas require the determination of radiative properties. However, most of the plasma radiative properties are calculated assuming the plasma in coronal equilibrium or local thermodynamic equilibrium regimes that is often not the case for many scenarios. In this work, we present nonlocal thermodynamic equilibrium calculations of radiative opacities of Fe and S and of an astrophysical plasma mixture for temperatures larger than 100 eV. We also analyze the departure from local thermodynamic equilibrium simulations.
Wed, 01 Jan 2020 00:00:00 GMThttp://hdl.handle.net/10553/550272020-01-01T00:00:00ZGeneration and Parametrization of Mean Plasma Radiative Properties Databases for Astrophysics and Nuclear Fusion Applicationshttp://hdl.handle.net/10553/69817Title: Generation and Parametrization of Mean Plasma Radiative Properties Databases for Astrophysics and Nuclear Fusion Applications
Authors: Rodríguez, Rafael; Espinosa, Guadalupe; Gil, Juan Miguel; Beltrán, Pablo R.
Abstract: In plasmas found in nuclear fusion energy and astrophysics, radiative properties play a pivotal role and they are needed in radiation hydrodynamic simulations of these plasmas. However, their calculation is a very complex problem involving very long computational times. One of the solutions is to perform parametrizations of the plasma radiative properties as a function of the plasma conditions which leads to considerable reductions in computational costs. In this work, we present models to generate and parametrize radiative properties databases as a function of plasma conditions which are valid for any plasma thermodynamic regime.
Wed, 01 Jan 2020 00:00:00 GMThttp://hdl.handle.net/10553/698172020-01-01T00:00:00ZSimulation of the ion beam-plasma interaction processes for point-like ions in doped DT plasmashttp://hdl.handle.net/10553/69982Title: Simulation of the ion beam-plasma interaction processes for point-like ions in doped DT plasmas
Authors: Beltrán, Pablo R.; Gil, Juan Miguel; Rodríguez, Rafael; Espinosa, Guadalupe; Barriga-Carrasco, Manuel D.
Abstract: The purpose of this work is to study the interaction between an ion beam and a doped deuterium-tritium (DT) plasma in a fast ignition nuclear fusion context. In order to analyze the influence of the dopants in the interaction process, we present a physical model to carry out spatial-temporal simulations of the stopping of an ion beam interacting with a doped plasma target, the plasma heating processes, and the formation of the ignition regions. We perform a set of numerical experiments where different concentrations of dopants are added to a fully ionized DT plasma. These simulations allow us to characterize the increase in the stopping power and the maximum temperatures achieved with the presence of impurities, as well as the reduction of the heated and ignition regions. This reduction in the ignition region indicates difficulties for the formation of an efficient hot spot when there are dopants in the DT plasma.
Wed, 01 Jan 2020 00:00:00 GMThttp://hdl.handle.net/10553/699822020-01-01T00:00:00ZInfluence of atomic kinetics in the simulation of plasma microscopic properties and thermal instabilities for radiative bow shock experimentshttp://hdl.handle.net/10553/36016Title: Influence of atomic kinetics in the simulation of plasma microscopic properties and thermal instabilities for radiative bow shock experiments
Authors: Espinosa, G.; Rodríguez, R.; Gil, J. M.; Suzuki-Vidal, F.; Lebedev, S. V.; Ciardi, A.; Rubiano, J. G.; Martel Escobar, Pablo
Abstract: 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
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10553/360162017-01-01T00:00:00ZBound electron stopping power model of partially stripped ions in partially ionized plasmashttp://hdl.handle.net/10553/58366Title: Bound electron stopping power model of partially stripped ions in partially ionized plasmas
Authors: Gil de la Fe, Juan Miguel; Beltran, Pablo R.; Rodriguez, Rafael; Espinosa, Guadalupe; Barriga-Carrasco, Manuel D.; Gonzalez-Gallego, Luis
Abstract: In this work, an expression for the bound electron stopping power of partially ionized highly energetic ions for partially ionized plasmas in the context of the Bethe approximation, in both local thermodynamic equilibrium and nonequilibrium, is presented and studied. The mean excitation energy of the stopping power incorporates a detailed description of the bound electron states of both the ion beam and plasma under different thermodynamic regimes. In the analysis carried out, we focus our attention on fully stripped ion beams in partially ionized aluminum plasmas. The temperature and electron density ranges considered were 4-100 eV and 10(16)-10(22) cm(-3), respectively.
Wed, 01 Jan 2020 00:00:00 GMThttp://hdl.handle.net/10553/583662020-01-01T00:00:00Z