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The spatially-resolved electron temperature, rotational temperature, and number density of the two metastable Ar 1 s levels were investigated in a miniature RF Ar glow discharge jet at atmospheric pressure. The 1 s level population densities were determined from optical absorption spectroscopy (OAS) measurements assuming a Voigt profile for the plasma emission and a Gaussian profile for the lamp emission. As for the electron temperature, it was deduced from the comparison of the measured Ar 2 p i &rarr, 1 s j emission lines with those simulated using a collisional-radiative model. The Ar 1 s level population higher than 10 18 m - 3 and electron temperature around 2.5 eV were obtained close to the nozzle exit. In addition, both values decreased steadily along the discharge axis. Rotational temperatures determined from OH(A) and N 2 (C) optical emission featured a large difference with the gas temperature found from a thermocouple, a feature ascribed to the population of emitting OH and N 2 states by energy transfer reactions involving the Ar 1 s levels.

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.

Тонкі плівки використовуються в різних галузях промисловості, а саме у виробництві сонячних елементів, плоских екранів та для поліпшення фізичних властивостей поверхонь матеріалів. У процесах осадження тонких плівок ступінь рівноваги та інші характеристики плазми, такі як природа, густина і температура, повинні бути визначені, щоб зрозуміти появу різних явищ. У роботі основна увага приділяється вивченню просторових розподілів густин збуджених станів Ar* (3p54s (1sx: x = 2-5)), а також відносних внесків таких процесів, як бомбардування електронами, випромінювальне дезбудження, явища дифузії метастабільних станів та іонізація Пеннінга в популяції та депопуляції різних станів атомів аргону. Для цього радіаційну модель зіткнень (CRM), яка включала 41 стан, було застосовано з використанням заданих параметрів у плазмі високочастотного магнетронного розпилення. Ці параметри включають температуру електронів, густини електронів та іонів аргону. Кінетичні рівняння густин станів привели до матричної системи, яка була розв'язана чисельно за допомогою ітераційного методу Гауса-Зейделя. Результати показують, що осьові розподіли різних збуджених станів та станів на катоді трохи більші, ніж на аноді; вони також показують, що обидві густини менші, ніж у центрі реактора. Іонізація Пеннінга важлива для метастабільних станів 3p54s (1s5, 1s3), але не важлива для резонансних станів 3p54s (1s4, 1s2). Різні густини збуджених станів не є симетричними відносно центру реактора через наявність магнітного поля на катоді. 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.

A new thermal helium beam diagnostic has been implemented as plasma edge diagnostic at the ASDEX Upgrade (AUG) tokamak. The helium beam is built to measure the electron density ne and temperature Te simultaneously with high spatial and temporal resolution in order to investigate steady-state as well as fast transport processes in the plasma edge region. For the thermal helium beam emission line ratio spectroscopy, neutral helium is locally injected into the plasma by a piezo valve. This enabled the measurement of the line resolved emission intensities of seven He i lines for different plasma scenarios in AUG. The different line ratios can be used together with a collisional-radiative model (CRM) to reconstruct the underlying electron temperature and density. Ratios from the same spin species are used for the electron density reconstruction, whereas spin mixed ratios are sensitive to electron temperature changes. The different line ratios as well as different CRMs are tested for their suitability for diagnostic applications. Furthermore their consistency in calculating identical parameters is validated and the resulting profiles are compared to other available diagnostics at AUG. EUROfusion Consortium 633053 US Department of Energy DE-SC00013911 and DE-SC0014210

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.

An atmospheric pressure nitrogen/argon plasma flows at high velocity through a water-cooled test-section in which it is forced to recombine within 250 μs. At the test-section inlet, the plasma is in Local Thermodynamic Equilibrium (LTE) at about 7200 K. Because recombination rates are finite, the plasma reaches a state of chemical nonequilibrium at the exit of the test-section, at a temperature of about 4715 K. At the test-section exit, the radiation emitted by the plasma, measured by emission spectroscopy, shows significant departures from equilibrium in the populations of the excited electronic states of nitrogen (N2 B3Πg, N2 C3Πu) and of the nitrogen ion N 2 + B 2 Σ u + . This experiment is thus proposed as a test-case to validate collisional-radiative (CR) models. A vibrationally specific CR model is then used to predict the emission of these states. The rate coefficients of the model are calculated with the Weighted Rate Coefficient method based on elementary cross-section data. These rates depend explicitly on the kinetic temperatures of electrons (Te) and heavy species (Tg). The predictions of the CR model are in good agreement with the measured vibrational population distribution in the N2 B state. A method is then proposed to determine ground state nitrogen atom densities based on the measured vibrational population distribution of the N2 B state.

A zero-dimensional collisional–radiative (CR) model, coupled self-consistently with the electron Boltzmann equation, has been applied to the description of a metallic-laser induced plasma at experimental conditions typical of LIBS experiment. To take in account expansion effects, the experimental temperature and total number density as function of time have been used as input data. Plasma composition and the simultaneous time evolution of both heavy particle level distributions and the electron energy distribution function have been calculated by taking into account the most relevant collisional and radiative processes. This approach estimates the hierarchy of the elementary processes during the expansion and possible deviations from LTE conditions. The comparison of the experimental and theoretical results shows a good agreement, but at the same time new questions arise on the analysis of spectroscopic results and on the assumption generally made in LIBS.

We present a collisional-radiative approach of the theoretical analysis of laser-induced breakdown spectroscopy (LIBS) plasmas. This model, which relies on an optimized effective potential atomic structure code, was used to simulate a pure aluminum plasma. The description of aluminum involved a set of 220 atomic levels representative of three different stages of ionization (Al 0 , Al + and Al ++ ). The calculations were carried for stationary plasmas, with input parameters ( n e and T e ) ranging respectively between 10 13–18 cm − 3 and 0.3–2 eV. A comparison of our atomic data with some existing databases is made. The code was mainly developed to address the validity of the local thermodynamic equilibrium (LTE) assumption. For usual LIBS plasma parameters, we did not reveal a sizeable discrepancy of the radiative equilibrium of the plasma towards LTE. For cases where LTE was firmly believed to stand, the Boltzmann plot outputs of this code were used to check the physical accuracy of the Boltzmann temperature, as it is currently exploited in several calibration-free laser-induced breakdown spectroscopy (CF-LIBS) studies. In this paper, a deviation ranging between 10 and 30% of the measured Boltzmann temperature to the real excitation temperature is reported. This may be due to the huge dispersion induced on the line emissivities, on which the Boltzmann plots are based to extract this parameter. Consequences of this fact on the CF-LIBS procedure are discussed and further insights to be considered for the future are introduced.

The emission characteristics of an ultraviolet-visible pulsed multi-ionic xenon laser were studied through time-resolved spectroscopy and the results were interpreted using a collisional-radiative theoretical model. This analysis includes more than 20 laser lines belonging to several ionic species (Xe III-VIII). Depending on the experimental conditions, different temporal distributions of the laser lines and their corresponding spontaneous emissions can be observed. In particular, laser emission presents temporal oscillations near threshold. Pumping processes for the laser transitions have been analyzed by using this model. Relativistic Hartree-Fock calculations of laser level lifetimes and radiative transition probabilities were performed. Experimental laser gain for several transitions were obtained and compared with the theoretical values derived from the calculations.

A brief overview is given of theoretical results for electron-impact ionization of atoms and ions. A description is given of the main theoretical methods, along with the databases where the data are archived. It is shown that for light species, ground and metastable ionization cross sections are in reasonable agreement with experiment when non-perturbative data are used for the near neutrals and distorted wave data are used for ions greater than a few times ionized. Some discrepancies between theory and experiment still remain for systems with open d and open p subshells. The sensitivity of ionization rate coefficients to the near threshold part of the ionization cross section is shown. The role of excited states in effective ionization rate coefficients is demonstrated and recent excited state ionization cross section results for H, He, He+, B2+ and Ne are presented.