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The proportions of nl (n = 4 − 10) energy levels to the total cross-section in EA processes of the ground state W 38+ .
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In this manuscript, we present our calculations of detailed electron-impact single ionization cross-sections for tungsten ions, spanning charge states W38+− W45+. The level-to-level distorted-wave method implemented in the flexible atomic code (FAC) was used for calculation. Comparison between the present level-to-level distorted wave treatment and...
Citations
... [3] Among the various ionization processes in fusion plasma, electron-impact single ionization (EISI) stands as the most dominant. [4,5] Therefore, comprehensive knowledge of ionization cross sections for tungsten ions, extending up to the highest charge states, is essential for fusion plasma modeling. ...
... [18] The CADW method was employed to investigate electron-impact single ionization (EISI) for the ground state of all charged states of W ions. [16] Additionally, the level-to-level distorted wave (LLDW) method is widely applied in calculations, such as the investigation of EISI cross sections for W 38+ -W 45+ using the LLDW method. [5] Our research group conducted detailed theoretical calculations and investigations on the electron-impact ionization of W 4+ , W 5+ , and W 17+ using the LLDW method, considering both direct ionization (DI) and excitation autoionization (EA) contributions. [2,19] Jonauskas et al. meticulously reevaluated the EISI cross section of W 5+ , both through rigorous experimentation and comprehensive theoretical analy-sis. ...
The electron-impact single ionization cross section for W ⁸⁺ ion has been calculated using flexible atomic code, employing the level-to-level distorted-wave approximation. This calculations takes into account contributions form both direct ionization (DI) and excitation autoionization (EA). However, the theoretical predictions, based solely on the ground state, tends to underestimated the experimental values. This discrepancy can be mitigated by incorporation contributions from excited states. We extended the theoretical analysis, including the contributions from the long-lived metastable states with lifetimes exceeding 1.5 × 10 ⁻⁵ s. We employed two statistical models to predict the fraction of ground state ions in the parent ion beam. Assuming a 79% fraction of parent ions in ground configuration, the experiment measurements align with the predictions. Furthermore we derived the theoretical cross-section for the ground state as correlated plasma rate coefficients, and compared it with existing data. Despite the uncertainty in our calculations, our results are still acceptable.
... Later on, the EISI data for W 5+ [10] and W 7+ [11] were studied by LLDW method with special attention on the contribution of the metastable states. Apart from this, in one of our papers, the EISI cross sections for W 38+ -W 45+ with LLDW method [12] have been reported. In the very recent effort, He et al performed experimental measurements and theoretical calculations of cross sections on high charge states of W ions with q = 66-71 [13], which filled the gap in experimental studies of W ions with q > 20. ...
This study focuses on the significance of suprathermal (‘hot’) electrons in the tokamak device. Hot electrons, which follow a non-Maxwellian energy distribution, are high-energy electrons that exert a substantial influence on various processes taking place within the plasma. Our aim was to investigate the influence of non-Maxwellian distribution on the rate coefficients of highly charged tungsten ions. This paper presents Maxwellian and non-Maxwellian electron impact ionization rate coefficients for W46+ to W55+ ions. The cross sections were calculated using the fully relativistic flexible atomic code (FAC) with level-to-level distorted-wave method. We found that even for a small fraction of hot electrons, the contribution of hot electrons to the rate coefficients is still dominant at low bulk temperature.
L-shell electron-impact ionization (EII) cross sections for highly charged tungsten ions were measured at incident electron energies of 29.10 and 38.92 keV using the Shanghai-EBIT. Resolved x-rays from radiative recombination (RR) processes were recorded with a high-purity Ge detector in a static electron energy scanning mode. Absolute EII cross sections were obtained by normalizing to the theoretical RR cross sections. The experimental results were compared with the calculated results using the relativistic distorted-wave method implemented in the flexible atomic code and the relativistic Lotz semi-empirical equation. The measurements showed general agreement with the calculated results by two theoretical methods for Li- to N-like W ions. The experimental uncertainties are not sufficiently small to discern the two theoretical results. Furthermore, the influence of Breit interaction on the EII cross sections of open L-shell tungsten ions was studied, and the effect is small but non-negligible. The measured EII cross sections of open L-shell tungsten ions would contribute to fusion plasma studies.
