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Spectroscopic studies of emissions released from tungsten ions combined with a pellet injection technique have been conducted in the Large Helical Device. The tungsten Unresolved Transition Array (UTA) spectrum was observed in the wavelength ranges of extreme ultraviolet (EUV) 6–60 Å and 130–340 Å, and the electron temperature dependence of the UTA spectral shape was investigated in the electron temperature region < 4.3 keV. The UTAs of W24+–W33+ at 20–33 Å, W37+–W42+ at 45–47 Å, W27+–W29+ at 48–55 Å, and W7+– W27+ at 170–210 Å were observed. Unidentified UTAs were also found at 230–270 Å and 280–320 Å. As the electron temperature increased further above 4 keV, the W37+–W42+ UTA at 45–47 Å was maintained, while the other UTAs became less intense., source:T Oishi et al 2023 J. Phys.: Conf. Ser. 2439 012005, source:https://doi.org/10.1088/1742-6596/2439/1/012005, identifier:0000-0002-1171-8603

Datasets of oscillator strength spectra, photoabsorption cross sections, and mass absorption coefficients are evaluated for 9 atoms (H, He, Li, N, O, Ne, Na, Cl, and Ar) and 23 molecules (H2, N2, O2, CO, NO, HCl, H2O, CO2, N2O, NO2, H2S, SO2, O3, NH3, CH4, C2H2, C2H4, C2H6, CH3OH, C6H6, SiH4, SF6, and C60), which are based on the data compiled by Berkowitz [Atomic and Molecular Photoabsorption: Absolute Total Cross Sections (Academic Press, 2002)]. The atomic number of adopted atoms is up to 18 (Ar) and that of constituent atoms of adopted molecules is not larger than 17 (Cl). For these atoms and molecules, experimental data are plenty to construct a reliable oscillator strength spectrum over the entire energy region. Datasets reported here are presently the most reliable because Berkowitz adopted cross sections after severe consideration of existing experimental data. The oscillator strengths are selected to satisfy the several sum rules and other theoretical bound conditions

Energies, E1, M1, E2, M2 transition rates, oscillator strengths, and lifetimes from relativistic configuration interaction calculations are reported for the states of the 2p6, 2p53s, 2p53p, and 2p53d, configurations in all Ne-like ions between Mg III and Kr XXVII. Core-valence and core-core correlation effects are accounted for through SD-expansions to increasing sets of active orbitals. The Breit interaction and leading QED effects are included as perturbations. The results are compared with experiments and other recent benchmark calculations. In Mg III, Al IV, Si V, P VI, S VII, and Ar IX, for which experimental energies are known to high accuracy, the mean error in the calculated energies is only 0.011%.

We present the energy dependence of the intensity ratio between the 3s3p3P2—3s3d3D3 transition at 233.9 Å and the 3s3p1P1—3s3d1D2 transition at 243.8 Å in Fe xv studied with an electron beam ion trap over an energy range that spans resonance excitation regions. Clear resonance structures are observed in the electron energy range of 400–600 eV. The energy dependence obtained in the experiment is compared with a collisional-radiative model calculation, including resonance excitations, and overall agreement is found. It is shown that the ratio strongly reflects the population of the 3s3p3P2 metastable state, which is the lower state of the 233.9 Å transition., source:Hiroyuki A. Sakaue et al 2023 ApJ 943 14, source:https://doi.org/10.3847/1538-4357/aca895, identifier:0000-0003-2209-3255

source:https://www.iaea.org/publications/12222/atomic-and-plasma-material-interaction-data, identifier:0000-0001-7544-1773

The electron correlation effects and Breit interaction as well as Quantum Electro-Dynamics (QED) effects were expected to have important contribution to the energy level and transition properties of heavy highly charged ions. The ground states [Ne]3s 23p 63d 2 and first excited states [Ne]3s 23p 53d 3 of W54+ ion have been studied by using Multi-Configuration Dirac-Fock method with the implementation of Grasp2K package. A restricted active space method was employed to investigate the correlation contribution from different models. The Breit interaction and QED effects were taken into account in the relativistic configuration interaction calculation with the converged wavefunction. It is found that the correlation contribution from 3s and 3p orbital have important contribution to the energy level, transition wavelength and probability of the ground and the first excited state of W54+ ion., source:Ding, X., Sun, R., Koike, F. et al. Correlation, Breit and Quantum Electrodynamics effects on energy level and transition properties of W54+ ion. Eur. Phys. J. D 71, 73 (2017). https://doi.org/10.1140/epjd/e2017-70829-y, source:https://doi.org/10.1140/epjd/e2017-70829-y

We present an investigation of previously unidentified visible lines for W8+ and W9+ from the spectra observed using an electron-beam ion trap. The analysis is based on collisional-radiative (CR) modeling with fine-structure sublevel population kinetics. To ensure the identification of lines done by the CR model, we have also performed an accurate calculation of transition energies and transition probabilities within the multiconfigurational Dirac-Fock approach using grasp2018. In the spectrum, most of the observed lines are assigned as magnetic dipole transitions belonging to the first two lower-lying configurations of these ions., source:Priti, Momoe Mita, Daiji Kato, Izumi Murakami, Hiroyuki A. Sakaue, and Nobuyuki Nakamura Phys. Rev. A 102, 042818 – Published 23 October 2020, source:https://doi.org/10.1103/PhysRevA.102.042818, identifier:0000-0001-6263-6563

We present a direct observation of the M1 transition between the fine structure splitting in the 4f135s25p6 2F ground term of W VIII. The spectroscopic data of few-times ionized tungsten ions are important for the future ITER diagnostics, but there is a serious lack of data. The present study is part of an ongoing effort to solve this problem. Emission from the tungsten ions produced and trapped in a compact electron beam ion trap is observed with a Czerny–Turner visible spectrometer. Spectra in the EUV range are also observed at the same time to help identify the previously-unreported visible lines. The observed wavelength 574.47±0.03 nm (air), which corresponds to the fine structure splitting of 17,402.5 ± 0.9 cm −1 , shows reasonable agreement with the previously reported value 17,410 ± 5 cm −1 obtained indirectly through the analysis of EUV spectra [Ryabtsev et al., Atoms 3 (2015) 273]., source:Mita, M.; Sakaue, H.A.; Kato, D.; Murakami, I.; Nakamura, N. Direct Observation of the M1 Transition between the Ground Term Fine Structure Levels of W VIII. Atoms 2017, 5, 13. https://doi.org/10.3390/atoms5010013, source:https://doi.org/10.3390/atoms5010013

Tungsten spectra in visible, vacuum ultra-violet (VUV) and extreme ultra-violet (EUV) wavelength ranges have been studied in LHD, EAST and HL-2A toroidal devices for magnetic-confinement fusion research. Tungsten spectra from low-ionized tungsten ions are observed in VUV and EUV ranges, e.g. W VI at 605.926 Å and W VII at 216.219 Å and 261.387 Å, and Doppler temperature of the W5+ ion and edge tungsten influx rate of the W6+ ion are analyzed. Ionization stages of unresolved transition array mainly consisting of W24+-W33+ ions at 15–70 Å are determined at each small wavelength interval of 0.1 Å based on radial profile measurement. The density profile is analyzed for W24+ and W27+ ions in addition to highly ionized ions, e.g. W44+ and W45+. Several magnetic dipole forbidden lines are observed, e.g. W XXVII and W XXVIII, and the density profile is also analyzed for W27+ ions. Contributions are made on tungsten diagnostics for fusion research through the present studies., source:https://doi.org/10.1007/978-981-16-7691-8_2, identifier:0000-0003-4139-7721

We present a laser induced breakdown spectrum of Er II in the near ultraviolet region. To use the spectrum for the evaluation of the transition probabilities, an alloy target with a low content of Er was used to suppress the self-absorption. From the linearity of the Boltzmann plot obtained by using the sensitivity corrected experimental intensity and existing transition probability data, the local thermal equilibrium condition of the plasma and the reliability of the transition probability data are confirmed. The linear function obtained in the Boltzmann plot is used for the determination of a previously unreported transition probability for the line at 393.863 nm., source:Appl. Sci. 2022, 12(4), 2219; https://doi.org/10.3390/app12042219, source:https://doi.org/10.3390/app12042219

The National Institute for Fusion Science (NIFS) has compiled and developed atomic and molecular numerical databases for various collision processes and makes it accessible from the internet to the public. The database contains numerical data of cross sections and rate coefficients for electron collision or ion collisions with atoms and molecules, attached with bibliographic information on their data sources. The database system provides query forms to search data, and numerical data are retrievable. The graphical output is helpful to understand energy dependence of cross sections and temperature dependence of rate coefficients obtained by various studies. All data are compiled mainly from published literature, and data sources can be tracked by the bibliographic information. We also have data of sputtering yields and back-scattering coefficients for solid surfaces collided by ions in the database. All data in the database are applicable to understand atomic and molecular processes in various plasmas, such as fusion plasma, astrophysical plasma and applied plasma, as well as for understanding plasma–surface interaction in plasmas., source:Atoms 2020, 8(4), 71; https://doi.org/10.3390/atoms8040071, source:https://doi.org/10.3390/atoms8040071, identifier:0000-0001-7544-1773

We report recent results of extreme ultraviolet (EUV) spectroscopy of highly charged heavy ions in plasmas produced in the Large Helical Device (LHD). The LHD is an ideal source of experimental databases of EUV spectra because of high brightness and low opacity, combined with the availability of pellet injection systems and reliable diagnostic tools. The measured heavy elements include tungsten, tin, lanthanides and bismuth, which are motivated by ITER as well as a variety of plasma applications such as EUV lithography and biological microscopy. The observed spectral features drastically change between quasicontinuum and discrete depending on the plasma temperature, which leads to some new experimental identifications of spectral lines. We have developed collisional-radiative models for some of these ions based on the measurements. The atomic number dependence of the spectral feature is also discussed., source:C Suzuki et al 2017 Plasma Phys. Control. Fusion 59 014009, source:https://doi.org/10.1088/0741-3335/59/1/014009

Quantitative tungsten study with reliable atomic modeling is important for successful achievement of ITER and fusion reactors. We have developed tungsten atomic modeling for understanding the tungsten behavior in fusion plasmas. The modeling is applied to the analysis of tungsten spectra observed from plasmas of the large helical device (LHD) with tungsten pellet injection. We found that extreme ultraviolet (EUV) emission of W24+ to W33+ ions at 1.5–3.5 nm are sensitive to electron temperature and useful to examine the tungsten behavior in edge plasmas. We can reproduce measured EUV spectra at 1.5–3.5 nm by calculated spectra with the tungsten atomic model and obtain charge state distributions of tungsten ions in LHD plasmas at different temperatures around 1 keV. Our model is applied to calculate the unresolved transition array (UTA) seen at 4.5–7 nm tungsten spectra. We analyze the effect of configuration interaction on population kinetics related to the UTA structure in detail and find the importance of two-electron-one-photon transitions between 4p54dn+1– 4p64dn−14f. Radiation power rate of tungsten due to line emissions is also estimated with the model and is consistent with other models within factor 2., source:Citation I. Murakami et al 2015 Nucl. Fusion 55 093016, source:https://doi.org/10.1088/0029-5515/55/9/093016, identifier:tungsten atomic model, EUV spectra, impurity behavior

Ejected material from neutron star mergers gives rise to electromagnetic emission powered by radioactive decays of r-process nuclei, the so-called kilonova or macronova. While properties of the emission are largely affected by opacities in the ejected material, available atomic data for r-process elements are still limited. We perform atomic structure calculations for r-process elements: Se (Z = 34), Ru (Z = 44), Te (Z = 52), Ba (Z = 56), Nd (Z = 60), and Er (Z = 68). We confirm that the opacities from bound–bound transitions of open f-shell, lanthanide elements (Nd and Er) are higher than those of the other elements over a wide wavelength range. The opacities of open s-shell (Ba), p-shell (Se and Te), and d-shell (Ru) elements are lower than those of open f-shell elements, and their transitions are concentrated in the ultraviolet and optical wavelengths. We show that the optical brightness can be different by $\gt 2$ mag depending on the element abundances in the ejecta such that post-merger, lanthanide-free ejecta produce brighter and bluer optical emission. Such blue emission from post-merger ejecta can be observed from the polar directions if the mass of the preceding dynamical ejecta in these regions is small. For the ejecta mass of 0.01 ${M}_{\odot }$, observed magnitudes of the blue emission will reach 21.0 mag (100 Mpc) and 22.5 mag (200 Mpc) in the g and r bands within a few days after the merger, which are detectable with 1 m or 2 m class telescopes., source:Citation Masaomi Tanaka et al 2018 ApJ 852 109, source:https://doi.org/10.3847/1538-4357/aaa0cb, identifier:0000-0001-8253-6850

We report a population kinetics study on line emissions of the Pm-like Bi22+ performed by using a collisional-radiative (CR) model. Population rates of excited levels are analyzed to explain the population trapping in the 4f135s2 state which causes the loss of the 5s − 5p resonance lines in emission spectra. Based on the present analysis, we elucidate why the population trapping is not facilitated for a meta-stable excited level of the Sm-like Bi21+. The emission line spectra are calculated for the Pm-like isoelectronic sequence from Au18+ through W13+ and compared with experimental measurements by electron-beam-ion-traps (EBITs). Structures of the spectra are similar for all of the cases except for calculated W13+ spectra. The calculated spectra are hardly reconciled with the measured W13+ spectrum using the compact electron-beam-ion-trap (CoBIT) [Phys. Rev. A 92 (2015) 022510]., source:Daiji Kato, Hiroyuki A. Sakaue, Izumi Murakami, Nobuyuki Nakamura, Population trapping: The mechanism for the lost resonance lines in Pm-like ions, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 408, 2017, Pages 16-20., source:https://doi.org/10.1016/j.nimb.2017.05.029

Tungsten W46+ lines were successfully observed in the extreme ultraviolet (EUV) wavelength range of 7 ∼ 8 Å in the Large Helical Device (LHD). Tungsten ions are distributed in the neutral beam injection (NBI) heated LHD plasma by injecting a pellet consisting of a small piece of tungsten metal wire enclosed by a carbon tube. While the electron temperature has a sudden drop due to the pellet injection, it can be recovered by applying electron cyclotron heating (ECH) together with continuous NBI heating. It is found that a W46+ line at 7.93 Å is emitted when the central electron temperature ranges around 3.4 keV with relatively high intensity and is isolated from other intrinsic impurity lines. The 7.93 Å line consists of two lines of forbidden transitions which are blended with each other; an electric quadrupole (E2) transition at 7.928 Å and a magnetic octupole (M3) transition at 7.938 Å. Observation of W46+ lines in the stellarator experiments is reported for the first time in the present study while the lines have been already observed in several tokamak experiments. The electron temperature dependence of the emission intensity of the 7.93 Å line agreed well with that of the fractional abundance of W46+ ions calculated using the ionization and recombination rate coefficients available in the ADAS database under the assumption of the collisional ionization equilibrium. The 7.93 Å line observed in this study will be used as tools for further spectroscopic researches, such as the measurements of spatial profile of W46+ ions using a space-resolved EUV spectrometer developed in LHD., source:Citation Tetsutarou Oishi et al 2021 Phys. Scr. 96 025602, source:https://doi.org/10.1088/1402-4896/abd0ba, identifier:0000-0002-1171-8603

Visible magnetic-dipole (M1) lines can serve as a novel diagnostic mean of tungsten in ITER and future DEMO reactors. Here a local tungsten density in core plasmas of the large helical device (LHD) is successfully assessed with the measurement of visible M1 lines emitted by W26+ and W27+. By such a measurement, (i) the radial profile of total tungsten density in the LHD core plasmas with a line-averaged electron density of ∼4 × 1019 m−3 and central electron temperature of ∼1 keV is found to be a hollow, and (ii) the total tungsten density is found to be decreased in the whole region with an increase in the electron temperature due to the onset of reheat mode. The scheme with visible M1 lines used in the present work can be also applied for the tungsten density measurement at the ITER edge plasma., source:Citation Daiji Kato et al 2021 Nucl. Fusion 61 116008, source:https://doi.org/10.1088/1741-4326/ac22d1, identifier:0000-0002-5302-073X

0000-0001-7544-1773, The National Institute for Fusion Science (NIFS) has compiled and developed atomic and molecular numerical databases for various collision processes and makes it accessible from the internet to the public. The database contains numerical data of cross sections and rate coefficients for electron collision or ion collisions with atoms and molecules, attached with bibliographic information on their data sources. The database system provides query forms to search data, and numerical data are retrievable. The graphical output is helpful to understand energy dependence of cross sections and temperature dependence of rate coefficients obtained by various studies. All data are compiled mainly from published literature, and data sources can be tracked by the bibliographic information. We also have data of sputtering yields and back-scattering coefficients for solid surfaces collided by ions in the database. All data in the database are applicable to understand atomic and molecular processes in various plasmas, such as fusion plasma, astrophysical plasma and applied plasma, as well as for understanding plasma–surface interaction in plasmas.

0000-0001-7544-1773