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A robust method for determining the electron temperature and density of atmospheric-pressure non-equilibrium argon plasmas is reported. The methodology is based on the analysis of the continuum and line spectra of the plasma. Assuming that the electron energy distribution function (EEDF) is expressed as a two-temperature generalized EEDF (GEEDF), the gamma value of the GEEDF is determined through a grid search of the continuum spectrum analysis given by the bremsstrahlung process, which minimizes the mean-squared logarithmic error (MSLE). In addition, the relationship between the gamma value and the electron temperature and density is determined. Utilizing this relationship, the electron temperature and density are determined by minimizing the MSLE between the excited-state densities obtained from the line spectrum analysis and numerically calculated using the collisional-radiative model. This methodology yielded results that satisfied both continuum and line spectrum analyses. In addition, the same analysis was conducted either by continuum spectrum analysis or by line spectrum alone to compare the results. [ABSTRACT FROM AUTHOR]

D2 molecular band emission observed at a wavelength range of λ∼557−643nm is utilized to measure electron density, ne, in D plasmas of the PISCES-A and PISCES-RF linear plasma devices. The D2 band is divided at λ=593nm to make an intensity ratio, D2L (∼557–593nm)/D2R (∼593–643nm), where D2L consists predominantly of the g3Σg+3dσ, h3Σg+3sσ, i3Πg3dπ, j3Δg3dδ → c3Πu2pπ transitions, while D2R mainly includes the d3Πu3pπ → a3Σg+2sσ Fulcher band emission. It is experimentally found that D2L/D2R depends strongly on ne with little Te dependence in ranges of ne∼(0.031−6.1)×1018 m−3 and Te∼2.3−13.9eV. This observed trend is consistent with collisional-radiative model calculations using Yacora on the Web.

The wavelengths and transition rates of W40+-W42+ ions within the range of 40–140 Å, have been calculated using the Flexible Atomic Code of the Dirac-Fock-Slater method with a central potential. We investigated the charge state distribution of W38+-W45+ ions at different temperatures by constructing an appropriate rate equation and demonstrate the importance of the dielectronic recombination process. Additionally, we simulated the emission spectra of W40+-W42+ ions in a Tokamak plasma environment using collisional-radiative modeling. Our findings demonstrate strong agreement with experimental results and other related theoretical investigations. Finally, we propose certain pairs of transition lines as diagnostic tools for plasma temperature and density, leveraging the correlation between line intensity ratio and electron temperature and density. [ABSTRACT FROM AUTHOR]

In this work, a krypton gas impurity seeding experiment was conducted in a Large Helical Device. Emission lines from the Na-like Kr ion in the extreme ultraviolet wavelength region, such as 22.00 nm, 17.89 nm, 16.51 nm, 15.99 nm, and 14.08 nm, respective to 2 p 6 3 p (2 P 1 / 2 o) − 2 p 6 3 s (2 S 1 / 2) , 2 p 6 3 p (2 P 3 / 2 o) − 2 p 6 3 s (2 S 1 / 2) , 2 p 6 3 d (2 D 3 / 2) − 2 p 6 3 p (2 P 3 / 2 o) , 2 p 6 3 d (2 D 5 / 2) − 2 p 6 3 p (2 P 3 / 2 o) , and 2 p 6 3 d (2 D 3 / 2) − 2 p 6 3 p (2 P 1 / 2 o) transitions, are observed. In order to generate a theoretical synthetic spectrum, an extensive calculation concerning the excitation of the Kr 25 + ion through electron impact was performed for the development of a suitable plasma model. For this, the relativistic multiconfiguration Dirac–Hartree–Fock method was employed along with its extension to the relativistic configuration interaction method to compute the relativistic bound-state wave functions and excitation energies of the fine structure levels using the General Relativistic Atomic Structure Package-2018. In addition, another set of calculations was carried out utilizing the relativistic many-body perturbation theory and relativistic configuration interaction methods integrated within the Flexible Atomic Code. To investigate the reliability of our findings, the results of excitation energies, transition probabilities, and weighted oscillator strengths of different dipole-allowed transitions obtained from these different methods are presented and compared with the available data. Further, the detailed electron impact excitation cross-sections and their respective rate coefficients are obtained for various fine structure resolved transitions using the fully relativistic distorted wave method. Rate coefficients, calculated using the Flexible Atomic Code for population and de-population kinetic processes, are integrated into the collisional-radiative plasma model to generate a theoretical spectrum. Further, the emission lines observed from the Kr 25 + ion in the impurity seeding experiment were compared with the present plasma model spectrum, demonstrating a noteworthy overall agreement between the measurement and the theoretical synthetic spectrum. [ABSTRACT FROM AUTHOR]

The wavelengths and transition rates of W ^40+ -W ^42+ ions within the range of 40–140 Å, have been calculated using the Flexible Atomic Code of the Dirac-Fock-Slater method with a central potential. We investigated the charge state distribution of W ^38+ -W ^45+ ions at different temperatures by constructing an appropriate rate equation and demonstrate the importance of the dielectronic recombination process. Additionally, we simulated the emission spectra of W ^40+ -W ^42+ ions in a Tokamak plasma environment using collisional-radiative modeling. Our findings demonstrate strong agreement with experimental results and other related theoretical investigations. Finally, we propose certain pairs of transition lines as diagnostic tools for plasma temperature and density, leveraging the correlation between line intensity ratio and electron temperature and density.

An inverse model based on a low-pressure helium collisional-radiative (CR) model was developed. Parts of the rate coefficients were recalculated from the cross-sections. The dominant processes in the revised model were extracted to simplify the calculation and to develop an inverse model. The model can calculate the electron density and temperature of low-pressure helium plasma by inputting the population densities of levels 3 1 S , 3 3 S , and 3 1 D , which can be measured by optical emission spectroscopy (OES) measurement in the visible wavelength range. The results demonstrate that the electron temperature obtained by the model is extremely close to the original value in the CR model. The output values of the electron density were of the same order and magnitude as the input values. The electron density and temperature measured by OES measurement in the experiment using the developed inverse model are consistent with the results measured by the probe method. [ABSTRACT FROM AUTHOR]

In this manuscript, we present our calculations of detailed electron-impact single ionization cross-sections for tungsten ions, spanning charge states W 38 + − W 45 + . 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 previous configuration-averaged calculations has been performed for the W 45 + ion, and we explore the possible reason for the difference observed between two calculations. We demonstrate the importance of radiative damping on the total electron-impact ionization cross-section for the W 43 + ion. Present calculations provide missing cross-sections for W 38 + − W 45 + . The data obtained are expected to be useful for modeling plasmas for fusion applications, especially for the ITER community. [ABSTRACT FROM AUTHOR]

Thermal helium beam diagnostics using the line ratio spectroscopy method are widely used to infer temperature and density in fusion-relevant edge plasmas. These diagnostics consist of an observational system which measures emitted line radiation from either intrinsic or injected helium plasma impurities. These spectral features are then compared to the output of a collisional-radiative model to infer plasma parameters (Te, ne) from the observed helium radiation. In order to investigate the systematic uncertainties of such a diagnostic, we present the results of a Bayesian treatment of a helium collisional-radiative model (Schmitz et al., 2008) using synthetic data modeled after an existing system on the plasma experiment Wendelstein 7-X (Barbui et al. 2016). From this study, we present a new method for comprehensively combining measurement uncertainties with underlying atomic rate parameter uncertainties in the inference of plasma parameters. Finally, we also demonstrate the utility of this Bayesian approach in targeting sensitivities within the model, allowing determination of high-priority atomic data for future refinement and comparison between differing atomic models.

To evaluate the impact of transport of metastable, vibrationally excited states of the hydrogen molecule in dense and cold plasmas each vibrational state must be simulated as an individual species. Eirene neutral gas simulations of a one‐dimensional flux‐tube using a metastable‐resolved model indicate a 30–50% decrease in the effective dissociation rate compared to simulations using a metastable‐unresolved setup, which consider a single molecular species. Zero‐dimensional Eirene simulations omitting transport effects predict a 25–65% decrease in the effective dissociation rate due to differences between the metastable‐unresolved AMJUEL and the metastable‐resolved H2VIBR rates available in Eirene. The exclusion of molecular hydrogen depletion via electronically excited states and vibrational transitions v→v±N,N>1 from the metastable‐resolved rates reduce the effective dissociation rate. By accounting for the difference caused by the different collisional‐radiative treatment of the metastable‐resolved rates compared to the metastable‐unresolved rates, transport effects are expected to be relevant under detached divertor conditions. It is, however, not possible to individually assess the role of the collisional‐radiative processes and transport on the effective dissociation rate using the currently available atomic and molecular rates for the metastable‐resolved and metastable‐unresolved Eirene setups. [ABSTRACT FROM AUTHOR]

A high-temperature air collisional-radiative model considering both vibrational and electronic excited states is established to investigate the plasma characteristics along the stagnation-line in the post-shock flow by coupling with the one-dimensional flow model. The results obtained by the model are in reasonable agreement with the experimental data and previous calculation results. The evolutions of different temperatures and energy relaxation processes are analyzed in detail for the height of 76.42 km and Mach number of 40.58. The vibrational and electronic excited modes play a critical role on the energy transfer. The vibrational excitation processes under heavy-particle impact can transfer the translational energy to the vibrational mode, then to the electrons by the vibrational de-excitation processes. The excitation of atoms by heavy-particle impact can gain energy from the translational mode, and the de-excitation processes of high-lying excited states under electron impact result in the energy transfer to electrons. The elastic collisions also play a role on the direct transfer from translational energy to electrons. The calculations are performed for a wide range of flight altitudes and Mach numbers to investigate the thermochemical state and energy relaxation. By comparing the energy transfer processes under different altitudes and Mach numbers, it is found that the energy transfer is dominated by vibrational processes for the low-Height low-Mach condition, and the contribution of electronic excited mode is negligible. The division of thermochemical state and chemical reactions in the Height-Mach number diagram is obtained, which provides the basis for the selection of thermochemical model required for atmospheric reentry calculation. • A CR model coupled with 1D flow model is established to study energy relaxation. • The vibrational and electronic excited modes are critical for the energy transfer. • Analysis of energy relaxation is done in a wide range of heights and Mach numbers. • The division of thermochemical state in Height-Mach number diagram is obtained. [ABSTRACT FROM AUTHOR]

Thin films are used in various industrial fields, namely in the manufacture of solar cells, flat screens and in improving the physical properties of material surfaces. In thin film deposition processes, the degree of equilibrium and other plasma characteristics such as the nature, density and temperature must be identified in order to understand the occurrence of various phenomena. In this work, the main focus is on studying the spatial distributions of densities of excited states of Ar* (3p54s (1sx: x = 2-5)), as well as the relative contributions of processes such as the electron impact effect, the radiative de-excitation, the diffusion phenomena of metastable states and the Penning ionization in the population and depopulation of different argon atoms states. For this purpose, a Collisional-Radiative Model (CRM) including 41 states was applied using specified parameters in RF magnetron sputtering plasma. These parameters include electron temperature, electron and ion densities of argon. The rate equations of the state densities led to a matrix system that was solved numerically by iterative Gauss-Seidel Method. The results show that the axial distributions of different excited states and those on the cathode side are slightly larger than those found on the anode side, and they show also that both densities are less than at the reactor center. For metastable states 3p54s (1s5, 1s3), the Penning ionization is important, but it is not important for resonant states 3p54s (1s4, 1s2). Different densities of the excited states are not symmetrical with respect to the center of the reactor due to the existence of a magnetic field at the cathode. [ABSTRACT FROM AUTHOR]

A series of experiments is described which were conducted to measure the absolute spectral irradiances of laser plasmas created from metal targets over the wavelength region of 123–164 nm by two separate 1.0 μm lasers, i.e., using 100 Hz, 10 ns, 2–20 kHz, 60–100 ns full-width-at-half-maximum pulses. A maximum radiation conversion efficiency of ≈3%/2 π sr is measured over a wavelength region from ≈125 to 160 nm. A developed collisional-radiative solver and radiation-hydrodynamics simulations in comparison to the spectra detected by the Seya–Namioka-type monochromator reveal the strong broadband experimental radiations which mainly originate from bound–bound transitions of low-ionized charges superimposed on a strong continuum from a dense plasma with an electron temperature of less than 10 eV. [ABSTRACT FROM AUTHOR]

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 previous configuration-averaged calculations has been performed for the W45+ ion, and we explore the possible reason for the difference observed between two calculations. We demonstrate the importance of radiative damping on the total electron-impact ionization cross-section for the W43+ ion. Present calculations provide missing cross-sections for W38+− W45+. The data obtained are expected to be useful for modeling plasmas for fusion applications, especially for the ITER community.

A fluid collisional-radiative model for H2 has been implemented in the edge-fluid code UEDGE and compared to the kinetic neutral code EIRENE on a simple, 2D, orthogonal domain with a constant, static plasma distribution. The novel CRUMPET Python tool was used to implement dissociation and energy rate coefficients that consider molecular-assisted processes, binding energy, and radiation due to molecular processes into the UEDGE fluid molecular model. The agreement between the fluid and kinetic molecular models was found to be within 20% when corresponding rates were used in UEDGE and EIRENE for a domain with absorbing boundaries. When wall recycling was considered, EIRENE predicted up to a factor of 2.2 higher molecular densities than UEDGE at T

An rovibrationally resolved collisional‐radiative model of molecular hydrogen (K. Sawada and M. Goto, Atoms 4: 29, 2016) is included in the authors' neutral transport code for large helical device (LHD) plasmas. The spatial distributions of the electron temperature and density, including the divertor and divertor leg regions, are given to the code. The molecules released from the graphite divertor target are tracked. The initial rotational and vibrational states of the released molecules are provided by simulation using a molecular dynamics model. The rovibrational population produced in an LHD plasma is evaluated. [ABSTRACT FROM AUTHOR]

A volume and a twin surface dielectric barrier discharge (VDBD and SDBD) are generated in different nitrogen–oxygen mixtures at atmospheric pressure by applying damped sinusoidal voltage waveforms with oscillation periods in the microsecond time scale. Both electrode configurations are located inside vacuum vessels and operated in a controlled atmosphere to exclude the influence of surrounding air. The discharges are characterised with different spatial and temporal resolution by applying absolutely calibrated optical emission spectroscopy in conjunction with numerical simulations and current–voltage measurements. Plasma parameters, namely the electron density and the reduced electric field, and the dissipated power are found to depend strongly on the oxygen content in the working gas mixture. Different spatial and temporal distributions of plasma parameters and dissipated power are explained by surface and residual volume charges for different O2 admixtures due to their effects on the electron recombination rate. Thus, the oxygen admixture is found to strongly influence the breakdown process and plasma conditions of a VDBD and a SDBD. [ABSTRACT FROM AUTHOR]

The attachment mode of arc on anode is closely related to the non‐equilibrium chemical kinetics process of the anode region of arc. In this paper, the detailed chemical reaction mechanisms in the flow‐affected region for both diffuse and constricted argon arc attachments are investigated by means of one‐dimensional discharge coupled with a single‐fluid, two‐temperature model. The collisional‐radiative model is used to examine the chemical reaction processes occurring in the anode region, including the arc centreline and fringe region. The numerical results are validated by comparison with available experimental data. The obtained radial distributions of electron temperature, electron density, excited states densities, ionization, and recombination processes reveal that different mechanisms dominate the diffuse and constricted arc‐anode attachments. [ABSTRACT FROM AUTHOR]

Optical emission spectroscopy has been widely used in low-temperature argon plasma diagnostics. A coronal model is usually used to analyze the measured line ratios for diagnostics with a single temperature and density. However, many plasma processing conditions deviate from single temperature and density, optically thin conditions, or even coronal plasma conditions due to cascades from high-lying states. In this paper, we present a collisional-radiative model to investigate the validity of coronal approximations over a range of plasma conditions of Te = 1–4 eV and Ne = 108–1013 cm−3. The commonly used line ratios are found to change from a coronal limit where they are independent of Ne to a collisional-radiative regime where they are not. The effects of multiple-temperature plasma, radiation trapping, wall neutralization, and quenching on the line ratios are investigated to identify the plasma conditions under which these effects are significant. This study demonstrates the importance of the completeness of atomic datasets in applying a collisional-radiative model to low-temperature plasma diagnostics.

The intensity ratio of Fe XIV 264.765A/274.203A is useful to determine the electron density of solar corona, and the relationship between the electron density and the intensity ratio obtained from a model should be evaluated using laboratory plasmas to estimate the electron density more precisely. We constructed a new collisional–radiative model (CR-model) for Fe XIV (an Al-like iron ion) by considering the processes of proton-impact excitation and electron-impact ionization to the excited states of a Mg-like iron ion. The atomic data used in the CR-model were calculated using the HULLAC atomic code. The model was evaluated based on laboratory experiments using a compact electron beam ion trap, called CoBIT, and the Large Helical Device (LHD). The measured Fe XIV 264.785 Å/274.203 Å line intensity ratio with CoBIT was 1.869 ± 0.036, and it agreed well with our CR-model results. Concurrently, the measured ratio using LHD was larger than the results of our CR-model and CHIANTI. The estimated electron densities using our CR-model agreed with those from CHIANTI within a factor of 1.6–2.4 in the range of ne≈1010−11cm−3. Further model development is needed to explain the ratio in a high-electron density region.

This article presents the calculation results on the conversion efficiency (CE) of 1.064 μm laser-produced plasmas (LPPs) extreme-ultraviolet (EUV) tin (Sn) light sources with the Gaussian and a triangular-flat-topped like laser pulse temporal shapes. The computational model includes a collisional-radiative model and 1D hydrodynamics code that predicts reported experimental and theoretical results on the CE of 1.064 μm and 10.6 μm LPP EUV sources with the planar and mass-limited spherical Sn targets. The calculations for the case of a spherical target reveal that an optimum triangular-flat-topped like laser pulse generates a higher CE compared to the Gaussian pulse, especially, for the longer laser pulse duration than ≈ 30 ns. The study demonstrated that a rising intensity rate of the laser pulse has a vital role to optimize the CE as well as to prolong the in-band (13.5 ± 0.135 nm) spectral emission of a small Sn spherical target. The model predicts a ≈ 30 ns rising time duration for a linearly increasing intensity of triangular-flat-topped 1.064 μm laser pulse is necessary to obtain a maximum CE with a typical ≈ 40 μm diameter liquid Sn droplet.

A series of experiments is described which were conducted to measure the absolute spectral irradiances of laser plasmas created from metal targets over the wavelength region of 123–164 nm by two separate 1.0 μm lasers, i.e., using 100 Hz, 10 ns, 2–20 kHz, 60–100 ns full-width-at-half-maximum pulses. A maximum radiation conversion efficiency of ≈3%/2πsr is measured over a wavelength region from ≈125 to 160 nm. A developed collisional-radiative solver and radiation-hydrodynamics simulations in comparison to the spectra detected by the Seya–Namioka-type monochromator reveal the strong broadband experimental radiations which mainly originate from bound–bound transitions of low-ionized charges superimposed on a strong continuum from a dense plasma with an electron temperature of less than 10 eV.

Highlights • Diagnostics of electron temperature and density for low temperature Ar plasma by an optical emission spectroscopy combined with a collisional-radiative (CR) model has been investigated and compared with a Langmuir probe diagnostics. • The CR model considers two-temperature electron energy distribution function and an escape factor for finite cylinder geometry in a capacitively-coupled plasma and an inductively-coupled plasma. • Two-temperature EEDF model works well with the non-Maxwellian plasmas and the finite-cylinder escape factor gives plasma emission spectra close to the measured spectra. Abstract Reliability of electron temperature and density diagnostics by an optical emission spectroscopy and a collisional radiative modeling is investigated by being compared with a Langmuir probe diagnostics for capacitively-coupled and inductively-coupled Ar plasmas in the ranges of electron temperature 1.2–2.2 eV and density 4.0 × 10 9 − 8.0 × 10 11 cm − 3. Particular attention has been paid to radiation trapping and electron energy distribution function (EEDF) regarding the modeling. It is found that the two-temperature EEDF model gives better agreement of electron temperature diagnostics with the Langmuir probe measurement for non-Maxwellian plasma. The radiation trapping with an escape factor for finite size cylinder geometry reduces the discrepancy between the modeled and measured spectral line intensities compared to an escape factor for plane parallel geometry, specially for the optically thick 811.5 nm transition to the metastable level whose population depends on the diffusion rate. [ABSTRACT FROM AUTHOR]

The properties and spectrum of the highly charged tungsten ions draw more and more attention, due to its potential application in the next generation fusion reactor. The transition wavelength and rate of the magnetic-dipole transition between the levels of the ground configuration of W53+ ion in the range of 10 − 20 nm were calculated by Dirac–Fock–Slater (DFS) method with a local central potential and Multi-Configuration Dirac-Hartree-Fock (MCDHF) method, respectively. The results are consistent with the previous EBIT experimental data and other theoretical data. A collisional-radiative model was constructed, and the spectrum of magnetic-dipole transition of W53+ ion observed on EBIT (Y. Ralchenko et al., Phys. Rev. A. 83 , 032517, 2011) was reproduced theoretically. Another two new transitions near the wavelength of 16.683 nm and 18.018 nm are also assigned to the M1 transition of W53+ ion. • The EBIT spectrum of W53+ ion was reproduced and analyzed by CRM with accurate atomic data. • The new M1 transition between the ground configuration of W53+ ions were assigned to the experimental spectrum. • The MCDHF transition wavelength was used instead of DFS results to get better agreement with the experiments. [ABSTRACT FROM AUTHOR]

Plasmas of a variety of types can be described by the collisional radiative (CR) model developed by Colombant and Tonan. From the CR model, the ion distribution of a plasma at a given electron temperature and density can be found. This information is useful for further simulations, and due to this, the employment of a suitable CR model is important. Specifically, ionization bottlenecks, where there are enhanced populations of certain charge states, can be seen in these ion distributions, which in some applications are important in maintaining large amounts of a specific ion. The present work was done by implementing an accepted CR model, proposed by Colombant and Tonon, in Python and investigating the effects of variations in the ionization energy and outermost electron subshell occupancy term on the positions of ionization bottlenecks. Laser Produced Plasmas created using a Nd:YAG laser with an electron density of ∼ne = 1021 cm−3 were the focus of this work. Plots of the collisional ionization, radiative recombination, and three-body recombination rate coefficients as well as the ion distribution and peak fractional ion population for various elements were examined. From these results, it is evident that using ionization energies from the NIST database and removing the orbital occupancy term in the CR model produced results with ionization bottlenecks in expected locations.

A detailed-level collisional-radiative model for the M1 transition spectrum of the Ca-like W 54+ ion as observed in an electron beam ion trap (EBIT) was constructed based on atomic data calculated by the relativistic configuration interaction method and distorted wave theory. The present calculated transition energy, rate and intensity of W 54+ M1 transitions are compared with previous theoretical and experimental values. The results are in reasonable agreement with the available experimental and theoretical data. The synthetic spectrum explained the EBIT spectrum in the 12–20 nm region, while a new possibly strong transition has been predicted to be observable with an appropriate electron beam energy. The present work provides accurate atomic data that may be used in plasma diagnostics applications. [ABSTRACT FROM AUTHOR]

A detailed level collisional-radiative model of the E1 transition spectrum of Ca-like W 54+ ion has been constructed. All the necessary atomic data has been calculated by relativistic configuration interaction (RCI) method with the implementation of Flexible Atomic Code (FAC). The results are in reasonable agreement with the available experimental and previous theoretical data. The synthetic spectrum has explained the EBIT spectrum in 29.5–32.5 Å , while several new strong transitions has been predicted to be observed in 18.5–19.6 Å for the future EBIT experiment with electron density n e = 10 12 cm −3 and electron beam energy E e = 18.2 keV. [ABSTRACT FROM AUTHOR]

We report a population kinetics study on line emissions of the Pm-like Bi 22+ performed by using a collisional-radiative (CR) model. Population rates of excited levels are analyzed to explain the population trapping in the 4 f 13 5 s 2 state which causes the loss of the 5 s − 5 p 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 Bi 21+ . The emission line spectra are calculated for the Pm-like isoelectronic sequence from Au 18+ through W 13+ 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 W 13+ spectra. The calculated spectra are hardly reconciled with the measured W 13+ spectrum using the compact electron-beam-ion-trap (CoBIT) [Phys. Rev. A 92 (2015) 022510]. [ABSTRACT FROM AUTHOR]

A method for determining the electron temperature and electron density in a plasma is proposed that is based on minimization of the difference between the experimental relative intensities of the spectral argon (Ar) lines and those same intensities calculated with the aid of the collisional-radiative model. The model describes the kinetics of the ground state and 40 excited states of the Ar atom and takes into account the following processes: excitation and deactivation of the states of the atom by electron impact, radiative decay of the excited states, self-absorption of radiation, ionization of excited states by electron impact, and quenching of metastable states as a consequence of collisions with the chamber walls. Using the given method, we have investigated the plasma of a magnetron discharge on a laboratory setup for intermediate-frequency magnetron sputtering for a few selected operating regimes. [ABSTRACT FROM AUTHOR]

Employing the independent-process and isolated-resonance approximations using distorted-waves (IPIRDW), we have performed a series of calculations of the resonance-enhanced electron-impact excitations (EIE) among 27 singly excited levels from the n ≤ 6 configurations of Cu-like gold (Au, Z = 79 ). Resonance excitation (RE) contributions from both the n = 4 → 4 − 7 and n = 3 → 4 core excitations have been considered. Our results demonstrate that RE contributions are significant and enhance the effective collision strengths (ϒ) of certain excitations by up to an order of magnitude at low temperature (10 6.1 K), and are still important at relatively high temperature (10 7.5 K). Results from test calculations of the resonance-enhanced EIE processes among 16 levels from the n ≤ 5 configurations using both the Dirac R -matrix (DRM) and IPIRDW approaches agree very well with each other. This means that the close-coupling effects are not important for this ion, and thus warrants the reliability of present resonance-enhanced EIE data among the 27 levels. The results from the collisional-radiative model (CRM) show that, at 3000 eV, near where Cu-like Au is most abundant, RE contributions have important effects (up to 25%) on the density diagnostic line intensity ratios, which are sensitive near 10 20 cm − 3 . The present work is the first EIE research including RE contributions for Cu-like Au. Our EIE data are more accurate than previous results due to our consideration of RE contributions, and the data should be helpful for modeling and diagnosing a variety of plasmas. [ABSTRACT FROM AUTHOR]

• K-shell x-ray spectra of hot krypton plasmas were simulated by using a collision-radiative model, for which the atomic parameters were generated by using the flexible atomic code (FAC). • Effects of the generalized Breit interaction (GBI) on the atomic parameters and the K-shell x-ray spectra of hot krypton plasmas have been investigated, and thus the GBI effect on the accuracy of the plasma diagnostics has been estimated. • This work will contribute to plasma diagnostics in fusion science, due to that the krypton is used as a tracer to obtain the temperature and density in the inertial confinement fusion experiments, and it is used as a coolant in magnetic confinement fusion experiments. K -shell spectra are widely used for the plasma diagnostics in fusion science and astrophysics. Here, we report on a theoretical investigation of the relativistic and QED effects, i.e., the Breit interaction (BI) or the generalized Breit interaction (GBI), on the simulation of K -shell x-ray spectra of hot krypton plasmas. The simulation was conducted using a collisional-radiative model, for which the atomic parameters were generated by using the flexible atomic code. As expected, the present work shows that the BI and GBI produce similar effects for such a light element as krypton, which maximum difference of 3.7% in the emission spectra. When comparing to results calculated with just the Coulomb interaction, the GBI affects the specific line intensity by up to 15%, thus bringing about approximately 4%, 13% uncertainties for deducing the electron density and temperature of plasmas, respectively. [ABSTRACT FROM AUTHOR]

The question of the Local Thermodynamic Equilibrium (LTE) of laser-induced plasmas is crucial regarding the Laser-Induced Breakdown Spectroscopy (LIBS) technique. The most relevant way to assess theoretically the possible departure from LTE is to develop state-to-state models of the chemical species involved. The present paper illustrates such an elaboration in the case of aluminum and tungsten. Based on this state-to-state approach, the two collisional-radiative models CoRaM-Al and CoRaM-W are elaborated. They include elementary processes under electron and heavy particle impact in thermal non-equilibrium, spontaneous emission, radiative recombination and thermal Bremsstrahlung. These models are applied to the case of ultrashort laser-induced plasmas expanding in an argon gas at different pressure, for which a relevant collisional-radiative model is also elaborated to predict the propagation of the shock wave. The laser conditions are close to those used for a typical LIBS analysis under ultrashort regime. At high argon pressure (10 5 Pa), the relaxation of the plasma takes place according to a rather low departure from LTE, as revealed by the thorough examination of the Boltzmann plots derived from the state-to-state models. This relaxation occurs at temperature higher for aluminum than for tungsten, but close to 10,000 K from 200 ns. Conversely, at low pressure (10 Pa), the extinction of the plasma is observed at ∼ 500 ns, just after a phase corresponding to significant departure from equilibrium. These results support the idea of the choice of short gate delays close to the laser pulse for the LIBS characterization of tungsten matrices in tokamak-like conditions. [ABSTRACT FROM AUTHOR]

The theoretical visible transitions and spectra of W13+ ion from the Electron Beam Ion Trap are investigated by constructing and solving a collisional-radiative model (CRM) within the Quasi-Steady-State approximation. The necessary atomic data for constructing the CRM have been calculated using the relativistic configuration interaction (RCI) method and distorted wave approximation. The present results are in reasonable agreement with the available experimental observations and theoretical calculations. The relative intensities of the M1 transitions between the ground and low-lying excited fine-structure levels have been found to strongly depend on the electron density from n e =109 cm−3 to n e =1012 cm−3, which might be useful for the future diagnosis of the electron density of the plasma. • The experimental visible spectrum of W13+ ion was analyzed by the collisional radiative modeling with accurate atomic data. • The M1 transition between the ground and excited configuration of W13+ ions were assigned to the experimental spectrum. • The dependence of the spectrum intensity on the electron density was explained. [ABSTRACT FROM AUTHOR]

We present Dédale, a fast code implementing a simplified non-local-thermodynamic-equilibrium (NLTE) plasma model. In this approach, the stationary collisional–radiative rates equations are solved for a set of well-chosen Layzer complexes in order to determine the ion state populations. The electronic structure is approximated using the screened hydrogenic model (SHM) of More with relativistic corrections. The radiative and collisional cross-sections are based on Kramers and Van Regemorter formula, respectively, which are extrapolated to derive analytical expressions for all the rates. The latter are improved thereafter using Gaunt factors or more accurate tabulated data. Special care is taken for dielectronic rates which are compared and rescaled with quantum calculations from the Averroès code. The emissivity and opacity spectra are calculated under the same assumptions as for the radiative rates, either in a detailed manner by summing the transitions between each pair of complexes, or in a coarser statistical way by summing the one-electron transitions averaged over the complexes. Optionally, n ℓ -splitting can be accounted for using a WKB approach in an approximate potential reconstructed analytically from the screened charges. It is also possible to improve the spectra by replacing some transition arrays with more accurate data tabulated using the SCO-RCG or FAC codes. This latter option is particularly useful for K-shell emission spectroscopy. The Dédale code was used to submit neon and tungsten cases in the last NLTE-8 workshop (Santa Fe, November 4–8, 2013). Some of these results are presented, as well as comparisons with Averroès calculations. [ABSTRACT FROM AUTHOR]

In this study, we used optical emission spectroscopy (OES) as a diagnostic tool in a Duo-Plasmaline surface-wave discharge. Argon plasma emission is recorded in order to calculate the electron density n e and the electron temperature T e in argon gas at a pressure range of 10–30 Pa. To describe argon emission, a corona model using different line ratios is compared to a more complete collisional-radiative model (CRM). It has been found that metastable states play an important role in the population model via electron impact excitation and radiation trapping and should be taken into account for the considered pressure range. The obtained parameters are in the range of 1.4 eV for the electron temperature and 5 × 1016 m−3 for the electron density. [Display omitted] • Development and comparison of emission models for argon Duo-Plasmaline plasma. • Assessment of importance of each process included in the emission model. • Comparison with experimental 2p lines in optical emission spectrum. • Calculation of electron temperature and density by experimental fitting. [ABSTRACT FROM AUTHOR]

Beyond the experimental studies, the assessment of the ability of ultra-short (femto or picosecond) laser pulses to provide correct estimates of the elemental composition of unknown samples using laser-induced breakdown spectroscopy requires the modeling of a typical situation. The present article deals with this modeling for aluminum in nitrogen. A spherical layer model is developed. The central aluminum plasma is produced by the ultra-short pulse. This plasma is described using our collisional–radiative model CoRaM-Al in an upgraded version involving 250 levels. Its expansion and relaxation take place in nitrogen, where the formation and the propagation of a shock wave are taken into account. In this shocked nitrogen layer, the equilibrium conditions are assumed. Mass, momentum and energy conservation equations written under an Eulerian form are used to correctly model the global dynamics. Energy losses are due to radiative recombination, thermal Bremsstrahlung and spontaneous emission. These elementary processes are implemented. The only input parameters are the pulse energy E 0 , the ablated mass M of the sample and the pressure p 0 of the surrounding gas. The equilibrium composition involving N 2 , N, N 2 + , N + and free electrons of the shocked nitrogen layer is calculated from the thermodynamic database of our collisional–radiative model CoRaM-N 2 . The conditions E 0 = 10 mJ and M ≃ 10 − 10 kg corresponding to a 532 nm laser pulse are chosen. The model assumes the initial equilibrium of the aluminum plasma produced by the laser pulse absorbed by the sample. Then, owing to the significant overpressure with respect to the background gas ( p 0 is assumed atmospheric), the surrounding gas starts to be compressed while the propagation of a shock wave takes place. The shock layer maximum pressure is obtained at approximately 20 ns. At this characteristic time, the nitrogen pressure is around 400 times the atmospheric pressure. A shock velocity of 7 km s − 1 is predicted. The central plasma is characterized by a rapidly decreasing pressure, which leads for a while to a very low temperature (3500 K) with respect to the initial one (65,000 K). Then, the aluminum plasma is in a moderate nonequilibrium situation for Al. For Al + , the nonequilibrium degree is higher and the excited states are very weakly populated. Then, the aluminum plasma temperature increases due to the compression by the shock layer. Later, the pressure converges to p 0 owing to the momentum transfer with the shock layer, and the shock velocity decreases. The central plasma progressively tends to equilibrium. A maximum expansion of approximately 1 mm in radius and a lifetime of 40 μs are predicted for the aluminum plasma. [ABSTRACT FROM AUTHOR]

A novel rovibrationally resolved collisional-radiative model of molecular hydrogen that includes 4,133 rovibrational levels for electronic states whose united atom principal quantum number is below six is developed. The rovibrational X 1 Σ g + population distribution in a SlimCS fusion demo detached divertor plasma is investigated by solving the model time dependently with an initial 300 K Boltzmann distribution. The effective reaction rate coefficients of molecular assisted recombination and of other processes in which atomic hydrogen is produced are calculated using the obtained time-dependent population distribution.