Calculation of mean excitation energies of 3d-elements and their cations

Sauer, Stephan P. A.; Sabin, John R.

doi:10.1080/00268976.2020.1823508

Cited by 4 publications

(4 citation statements)

References 56 publications

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“…where N is the number of electrons bound to the considered ion, r i is the radial coordinate of the ion, ρ (r i ) is the electron density distribution, which is assumed to be spherically symmetric around the nucleus, ω 0 (r i ) is the local plasma frequency of the electron gas in the ion [42] and F is a correction factor derived by fitting the LPA to the results from Sauer et al [28,29]:…”

Section: Appendix B Meementioning

confidence: 99%

“…This requires the mean excitation energy (MEE) for tungsten ions, which is not available neither from measurements nor from present ab-initio theoretical calculations. MEE was calculated with an approach based on the local plasma approximation (LPA) corrected to fit the results from Sauer et al [27][28][29]. More detailed comments on the selection of ADAS coefficients and MEE calculation can be found in appendices A and B.…”

Section: Tungsten Impuritiesmentioning

confidence: 99%

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First numerical analysis of runaway electron generation in tungsten-rich plasmas towards ITER

Walkowiak,

Hoppe,

Ekmark

et al. 2024

Nucl. Fusion

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The DREAM code was extended to include tungsten impurities in disruption simulations with the aim of studying the runaway electron (RE) generation. This study investigates RE current sensitivity on the following plasma parameters and modelling choices: tungsten concentration, magnetic perturbation strength, electron modelling, thermal quench time and tokamak geometry - ITER-like or ASDEX-like. Our investigation shows that a tungsten concentration below 10-3 does not cause significant RE generation on its own. However, at higher concentrations it is possible to reach a very high RE current. Out of the two tested models of electrons in plasma: fluid and isotropic (kinetic), results from the fluid model are more conservative, which is useful when it comes to safety analysis. However, these results are overly pessimistic when compared to the isotropic model, which is based on a more reliable approach. Our results also show that the hot-tail RE generation mechanism is dominant as a primary source of RE in tungsten induced disruptions, usually providing orders of magnitude higher RE seed than Dreicer generation.We discuss best practices for simulations with tungsten-rich plasma, present the dependance of the safety limits on modelling choices and highlight the biggest shortcoming of the current simulation techniques. The obtained results pave the way for a wider analysis of tungsten impact on the disruption dynamics, including the mitigation techniques for ITER in the case of strong contamination of the plasma with tungsten.

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Section: Appendix B Meementioning

confidence: 99%

Section: Tungsten Impuritiesmentioning

confidence: 99%

First numerical analysis of runaway electron generation in tungsten-rich plasmas towards ITER

Walkowiak,

Hoppe,

Ekmark

et al. 2024

Nucl. Fusion

View full text Add to dashboard Cite

show abstract

“…Its determination from first principles calculations is a considerable challenge, so except for elements that do not require relativistic corrections, hω Z0,s is generally obtained from empirical laws constrained by measurements for neutral atoms only [55][56][57][58]. Recent advanced calculations carried out by a non-relativistic multi-configurational self-consistent field (MCSCF) code have allowed us to estimate hω Z0,s for all ionization states of the elements lighter than argon Z s ⩽ 18 [14,15,59]. Although this result represents considerable progress, the accurate determination of hω Z0,s for many higher-Z elements, such as tungsten, is still missing, which makes it difficult to study the impact of inelastic processes by electronion interaction in a hot plasma.…”

Section: Mean Excitation Energymentioning

confidence: 99%

“…Even if the atomic processes that must be described in the CODE and LUKE kinetics codes are rather similar, some differences specific to hot plasmas must be investigated. Indeed, while the atomic physics of argon and elements with lower Z s values has been thoroughly studied by quantum nonrelativistic codes describing the ground-state and mean excitation energies for different ionization states [12][13][14][15], the knowledge of atomic properties for metallic elements with higher Z s values, and in particular for tungsten, is much more sparse. This is a consequence of the relativistic effects and the resulting complex orbital coupling, which must be fully incorporated in quantum calculations, making them considerably more difficult.…”

Section: Introductionmentioning

confidence: 99%

A unified description of atomic physics for electron Fokker–Planck calculations

Savoye-Peysson,

Mazon,

Bielecki

et al. 2023

Nucl. Fusion

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Most of the realistic kinetic calculations for tokamak plasmas require now to incorporate the effect of partially ionized high-Z elements arising either from uncontrolled influxes of metallic impurities like tungsten in high input power regimes or from mitigation of runaway electrons generated after possible major disruptions by massive gas injection. The usual electron-ion Fokker-Planck collision operator must be therefore modified, since all atoms in the plasma are not fully ionized, as it can be considered for light elements. This represents a challenge, in order to perform fast but also accurate calculations, regardless the types of elements present in the plasma, but also their local levels of ionization, while covering a wide range of electron energies in a consistent way, from keV to tens of MeV in plasmas whose electron temperature may itself vary from few eV to several keV. In this context, a unified description of the atomic models is proposed, based on a multi-Yukawa representation of the electrostatic potential calibrated against results obtained by advanced quantum calculations. Besides the possibility to improve the description of inner and outer atomic shells in the determination of the atomic form factor, this model allows to derive analytical formulations for both elastic and inelastic scattering which can be then easily incorporated in kinetic calculations. The impact of the number of exponentials in the description of the atomic potential is discussed, and the comparison with simple or advanced atomic models is also performed.

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Mean total and orbital excitation energies of atomic ions in two approaches of the Thomas–Fermi theory

Cabrera‐Trujillo

Cruz

2022

Advances in Quantum Chemistry

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Calculation of mean excitation energies of 3d-elements and their cations

Cited by 4 publications

References 56 publications

First numerical analysis of runaway electron generation in tungsten-rich plasmas towards ITER

First numerical analysis of runaway electron generation in tungsten-rich plasmas towards ITER

A unified description of atomic physics for electron Fokker–Planck calculations

Mean total and orbital excitation energies of atomic ions in two approaches of the Thomas–Fermi theory

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