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Journal Article•DOI•

Comparing plasma population kinetics codes: Review of the NLTE-3 Kinetics Workshop

TL;DR: It was found that good agreement between codes and with experiments is observed near closed shells, but significant differences exist otherwise, or when density effects are important, as well as plans for the next workshop and for a kinetics database.
Abstract: Comparison of plasma population kinetics codes, which has become an important tool for their testing and verification, was the subject of the third Non-LTE Code Comparison Workshop held at the National Institute of Standards and Technology in December 2003. The motivations for the workshop are presented here, together with its technical organization. The cases studied range from carbon to gold, and include both steady-state and time-dependent calculations. The set of results represents the current capabilities in kinetics modeling, and illustrates the effectiveness of this workshop approach to code comparisons. It was found that good agreement between codes and with experiments is observed near closed shells, but significant differences exist otherwise, or when density effects are important. On a more general level, we discuss how to meaningfully compare kinetics data. We conclude with plans for the next workshop and for a kinetics database.
Citations
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Journal Article•DOI•
TL;DR: In this paper, a simple screened-hydrogenic model was proposed to calculate ionization balance with sufficient accuracy, at a low enough computational cost for routine use in radiation-hydrodynamics codes.

166 citations

Journal Article•DOI•
TL;DR: In this article, a hybrid approach is proposed to treat atomic structure and rates in collisional-radiative models, combining the completeness of highly averaged models with the accuracy of detailed models.

159 citations

Journal Article•DOI•
TL;DR: The High Flux Model (HFM) as discussed by the authors was used in the National Ignition Campaign (NIC) gas-filled/capsule-imploding hohlraum energetics campaign.

148 citations

08 Jul 2009
TL;DR: In this paper, a simple screened-hydrogenic model was proposed to calculate ionization balance with surprising accuracy, at a low enough computational cost for routine use in radiation-hydrodynamics codes.
Abstract: The last few years have seen significant progress in constructing the atomic models required for non-local thermodynamic equilibrium (NLTE) simulations. Along with this has come an increased understanding of the requirements for accurately modeling the ionization balance, energy content and radiative properties of different elements for a wide range of densities and temperatures. Much of this progress is the result of a series of workshops dedicated to comparing the results from different codes and computational approaches applied to a series of test problems. The results of these workshops emphasized the importance of atomic model completeness, especially in doubly excited states and autoionization transitions, to calculating ionization balance, and the importance of accurate, detailed atomic data to producing reliable spectra. We describe a simple screened-hydrogenic model that calculates NLTE ionization balance with surprising accuracy, at a low enough computational cost for routine use in radiation-hydrodynamics codes. The model incorporates term splitting, {Delta}n = 0 transitions, and approximate UTA widths for spectral calculations, with results comparable to those of much more detailed codes. Simulations done with this model have been increasingly successful at matching experimental data for laser-driven systems and hohlraums. Accurate and efficient atomic models are just one requirement for integrated NLTE simulations. Coupling the atomic kinetics to hydrodynamics and radiation transport constrains both discretizations and algorithms to retain energy conservation, accuracy and stability. In particular, the strong coupling between radiation and populations can require either very short timesteps or significantly modified radiation transport algorithms to account for NLTE material response. Considerations such as these continue to provide challenges for NLTE simulations.

141 citations

Journal Article•DOI•
TL;DR: The Los Alamos suite of relativistic atomic physics codes is a robust, mature platform that has been used to model highly charged ions in a variety of ways The suite includes capabilities for calculating data related to fundamental atomic structure, as well as the processes of photoexcitation, electron-impact excitation and ionization, photoionization and autoionization within a consistent framework as discussed by the authors.
Abstract: The Los Alamos suite of relativistic atomic physics codes is a robust, mature platform that has been used to model highly charged ions in a variety of ways The suite includes capabilities for calculating data related to fundamental atomic structure, as well as the processes of photoexcitation, electron-impact excitation and ionization, photoionization and autoionization within a consistent framework These data can be of a basic nature, such as cross sections and collision strengths, which are useful in making predictions that can be compared with experiments to test fundamental theories of highly charged ions, such as quantum electrodynamics The suite can also be used to generate detailed models of energy levels and rate coefficients, and to apply them in the collisional-radiative modeling of plasmas over a wide range of conditions Such modeling is useful, for example, in the interpretation of spectra generated by a variety of plasmas In this work, we provide a brief overview of the capabilities within the Los Alamos relativistic suite along with some examples of its application to the modeling of highly charged ions

130 citations

References
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Journal Article•DOI•
TL;DR: In this article, the authors presented new and updated calculations of the ionization equilibrium for all the elements from H to Ni and collected for these elements all the data available in the literature for the ionisation and radiative plus dielectronic recombination rates.
Abstract: We present in this paper new and updated calculations of the ionization equilibrium for all the elements from H to Ni. We collected for these elements all the data available in the literature for the ionization and radiative plus dielectronic recombination rates. In particular, the dielectronic rates have been fitted with a single formula and the related coefficients are tabulated. Our results are compared with previous works.

1,041 citations

Journal Article•DOI•
TL;DR: H ULLAC as mentioned in this paper, an integrated code for calculating atomic structure and cross sections for collisional and radiative atomic processes, is based on relativistic quantum mechanical calculations including configuration interaction.
Abstract: We describe H ULLAC , an integrated code for calculating atomic structure and cross sections for collisional and radiative atomic processes. This code evolved and has been used over the years, but so far, there was no coherent, comprehensive, and in-depth presentation of it. It is based on relativistic quantum mechanical calculations including configuration interaction. The collisional cross sections are calculated in the distorted wave approximation. The theory and code are presented, emphasizing the various novel methods that has been developed to obtain accurate results very efficiently. In particular we describe the parametric potential method used for both bound and free orbitals, the factorization–interpolation method applied in the derivation of collisional rates, the phase amplitude approach for calculating the continuum orbitals and the N JGRAF graphical method used in the calculation of the angular momentum part of the matrix elements. Special effort has been made to insure the simplicity of use, which is demonstrated in an example.

437 citations

Journal Article•DOI•
TL;DR: In this article, the authors follow and continue the line of Bibermanl, Fujimoto, and Seaton by trying to find a classification in these results and find a (analytical) relation between the atomic state distribution function and the underlying plasma properties.

308 citations

Journal Article•DOI•
TL;DR: In this article, a fully time-dependent collisional-radiative (CR) model for stripped ions of carbon recombining in a cold dense plasma demonstrates an order of magnitude faster recombination of He-like ions.
Abstract: In a recombining plasma the metastable states are known to accumulate population thereby slowing down the recombination process. We show that an account of the doubly excited autoionizing states, formed due to collisional recombination of metastable ions, results in a significant acceleration of recombination. A fully time-dependent collisional-radiative (CR) modeling for stripped ions of carbon recombining in a cold dense plasma demonstrates an order of magnitude faster recombination of He-like ions. The CR model used in calculations is discussed in detail.

162 citations

Journal Article•DOI•
TL;DR: The field has reached a threshold at which better organization becomes crucial and new methods of verifying and validating complex codes are mandatory if computational science is to fulfill its promise for science and society.
Abstract: The field has reached a threshold at which better organization becomes crucial. New methods of verifying and validating complex codes are mandatory if computational science is to fulfill its promise for science and society.

158 citations