Duck-Hee Kwon

Bio: Duck-Hee Kwon is an academic researcher. The author has an hindex of 3, co-authored 3 publications receiving 33 citations.

Dielectronic recombination of Cu-like W45+

Abstract: We have investigated dielectronic recombination (DR) for Cu-like W45+ forming Zn-like W44+ by theoretical calculation using the flexible atomic code based on an independent process, isolated resonance, and distorted wave approximation. We have focused on the effect of configuration mixing involving double electron core excitation as well as single electron core excitation on the DR via 3 d 9 4 l 4 l ′ 4 l ″ and 3 p 5 3 d 10 4 l 4 l ′ 4 l ″ resonances by inner-shell core excitation Δ n c = 1 . About 20% and over 100% changes in Maxwellian rate coefficient are shown at high energies over 200 eV and at low energies near the threshold, respectively, by the configuration mixing. Non-resonant stabilizations (NRS) and decays to autoionizing levels possibly followed by cascades (DAC) to non-closed inner-shells 3 d 9 4 l 4 l ′ 4 l ″ are also considered. The NRS and DAC effect on the DR Maxwellian rate coefficient is relatively smaller than the configuration mixing effect and is less than ~ 20 % . Particular attention has been paid to the DR via 3 d 10 4 lnl ′ resonances by valence-shell core excitation Δ n c = 0 which was not considered in the previous work (Behar et al., 1997 [4] ). The 3 d 10 4 lnl ′ resonances very dominate the DR at low energies below ~ 100 eV . Δ n c = 2 core excitations are small but not negligible ( ~ 10 % ) relatively at high energy range around 10 keV. Our total DR rate coefficient shows the difference with the recombination coefficient on the ADAS database obtained by using a simple semiempirical formula over order of magnitude at low energies and about 30–50% at 2–7 keV energy range where W45+ is abundant.

Dielectronic recombination of Ni-, Cu-, and Zn-like tungsten ions

Abstract: Dielectronic recombination (DR) for Ni- and Zn-like Wq+ (q=46, 44) has been investigated extending the previous theoretical methodology (Kwon and Lee, 2016 [6] ) applied for Cu-like W45+ which treats configuration mixing (CM) between resonances, non-resonant stabilization to non-closed inner-shells and decays to autoionizing levels possibly followed by cascades. For W46+ DR via 3 [ s , p , d ] 17 4 lnl ′ and 3 [ s , p , d ] 17 5 lnl ′ resonances ( Δ n c = 1 , 2) are included to the total Maxwellian rate coefficient. CM between 3 p 6 3 d 9 4 lnl ′ and 3 p 5 3 d 10 4 lnl ′ resonances largely changes low energy DR near the threshold. For W45+ radiative decay channels 3 d 10 4 l ′ n ′ l ′′ ( 4 n ′ n ) of DR via 3 d 10 4 lnl ′ resonances ( Δ n c = 0 ) which were missed in our previous calculation (Kwon and Lee, 2016 [6] ) are included and the rate coefficient is revised. For W44+ CM involving double electron core excitation is taken into account. All non-negligible core excitations Δ n c = 0 of 4 s , Δ n c = 1 of 4 s , 3 d , and 3 p , and Δ n c = 2 of 4 s , 3 d , and 3 p are included to the total DR rate coefficient for W44+. Our total DR rate coefficients for Wq+ ( q = 46 − 44 ) are compared with available previous ab initio predictions by other level-to-level calculations and by a configuration-averaged level group calculation, and with ADAS data by semiempirical formula in detail.

Dielectronic recombination of lowly charged tungsten ions Wq+(q=5−10)

Abstract: Dielectronic recombination (DR) rate coefficients for the ground levels of low ionization state W q + ( q = 5 − 10 ) ions have been obtained by an ab-inito level-by-level calculation using the flexible atomic code (FAC) based on relativistic jj coupling scheme and independent process, isolated resonance, distorted wave approximation. The radiative transition calculation in the original FAC has been adapted into parallel programming for time effective dealing with so many resonance levels of the complex open 4f, 5p, or 5d-shell structure ion. Core excitations Δ n c = 0 , 1 of 4f, 5p, and 5d (W 5 + ), Δ n c = 2 of 4f, and Δ n c = 0 of 4d (W 7 + ), and 5s (W 8 + ) are included to the total DR rate coefficient. The core excitations Δ n c = 0 , 5p → 5l and Δ n c = 1 , 4f → 5l mainly contribute to the total DR rate coefficients. The strong resonances involved in the DR are analyzed and the total DR rate coefficients are compared with available previous ab-initio predictions and with ADAS data by a simple semiempirical formula.

A Decade with VAMDC: Results and Ambitions

Abstract: This paper presents an overview of the current status of the Virtual Atomic and Molecular Data Centre (VAMDC) e-infrastructure, including the current status of the VAMDC-connected (or to be connected) databases, updates on the latest technological development within the infrastructure and a presentation of some application tools that make use of the VAMDC e-infrastructure. We analyse the past 10 years of VAMDC development and operation, and assess their impact both on the field of atomic and molecular (A&M) physics itself and on heterogeneous data management in international cooperation. The highly sophisticated VAMDC infrastructure and the related databases developed over this long term make them a perfect resource of sustainable data for future applications in many fields of research. However, we also discuss the current limitations that prevent VAMDC from becoming the main publishing platform and the main source of A&M data for user communities, and present possible solutions under investigation by the consortium. Several user application examples are presented, illustrating the benefits of VAMDC in current research applications, which often need the A&M data from more than one database. Finally, we present our vision for the future of VAMDC.

Highly Charged Ions in Magnetic Fusion Plasmas: Research Opportunities and Diagnostic Necessities

Abstract: Highly charged ions play a crucial role in magnetic fusion plasmas. These plasmas are excellent sources for producing highly charged ions and copious amounts of radiation for studying their atomic properties. These studies include calibration of density diagnostics, x-ray production by charge exchange, line identifications and accurate wavelength measurements, and benchmark data for ionization balance calculations. Studies of magnetic fusion plasmas also consume a large amount of atomic data, especially in order to develop new spectral diagnostics. Examples we give are the need for highly accurate wavelengths as references for measurements of bulk plasma motion, the need for accurate line excitation rates that encompass both electron-impact excitation and indirect line formation processes, for accurate position and resonance strength information of dielectronic recombination satellite lines that may broaden or shift diagnostic lines or that may provide electron temperature information, and the need for accurate ionization balance calculations. We show that the highly charged ions of several elements are of special current interest to magnetic fusion, notably highly charged ions of argon, iron, krypton, xenon, and foremost of tungsten. The electron temperatures thought to be achievable in the near future may produce W70+ ions and possibly ions with even higher charge states. This means that all but a few of the most highly charged ions are of potential interest as plasma diagnostics or are available for basic research.

Dielectronic recombination of lanthanide and low ionization state tungsten ions : W13+ - W+

Abstract: The experimental thermonuclear reactor, ITER, is currently being constructed in Cadarache, France. The reactor vessel will be constructred with a beryllium coated wall, and a tungsten coated divertor. As a plasma-facing component, the divertor will be under conditions of extreme temperature, resulting in the sputtering of tungsten impurities into the main body plasma. Modelling and understanding the potential cooling effects of these impurities requires detailed collisional-radiative modelling. These models require a wealth of atomic data for the various atomic species in the plasma. In particular, partial, final-state resolved dielectronic/radiative recombination (DR/RR) rate coefficients for tungsten are required. In this manuscript, we present our calculations of detailed DR/RR rate coefficients for the lanthanide-like, and low ionization stages of tungsten, spanning charge states W$^{13+}$ to W$^{1+}$. The calculations presented here constitutes the first detailed exploration of such low ionization state tungsten ions. We are able to reproduce the general trend of calculations performed by other authors, but find significant differences ours and their DR rate coefficients, especially at the lowest temperatures considered.

Partial and total dielectronic recombination rate coefficients for W55+ to W38+

Abstract: Dielectronic recombination (DR) is the dominant mode of recombination in magnetically confined fusion plasmas for intermediate to low-charged ions of W. Complete, final-state resolved partial isonuclear W DR rate coefficient data is required for detailed collisional-radiative modelling for such plasmas in preparation for the upcoming fusion experiment ITER. To realize this requirement, we continueThe Tungsten Project by presenting our calculations for tungsten ions W55+ to W38+. As per our prior calculations for W73+ to W56+, we use the collision package AUTOSTRUCTURE to calculate partial and total DR rate coefficients for all relevant core-excitations in intermediate coupling (IC) and configuration average (CA) using κ-averaged relativistic wavefunctions. Radiative recombination (RR) rate coefficients are also calculated for the purpose of evaluating ionization fractions. Comparison of our DR rate coefficients for W46+ with other authors yields agreement to within 7-19% at peak abundance verifying the reliability of our method. Comparison of partial DR rate coefficients calculated in IC and CA yield differences of a factor ∼ 2 at peak abundance temperature, highlighting the importance of relativistic configuration mixing. Large differences are observed between ionization fractions calculated using our recombination rate coefficient data and that of Putterich et al [Plasma Phys. and Control. Fusion 50 085016, (2008)]. These differences are attributed to deficiencies in the average-atom method used by the former to calculate their data.