Calculation of total thermal conductivity of ionized gases
Boltzmann equation for calculating transport coefficients and thermal conductivity of partially ionized gases
Ahtye, W. F.↗
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Electrical and thermal properties of plasmas.
Current density and heat flux expressions in terms of transport coefficients of partially ionized gas, noting thermoconductivities
PLASMA DENSITY↗
Fifth and sixth approximations to the electron transport coefficients.
Electron transport coefficients of partially ionized argon extended to 5th and 6th Chapman-Enskog-Burnett approximations
Devoto, R. S.↗
Thermal diffusion in the topside ionosphere for mixtures which include multiply-charged ions.
Thermal diffusion coefficient for fully ionized plasma containing mixture of arbitrary charge ions in topside ionosphere
Schunk, R.↗
Thermal diffusion in the F2-region of the ionosphere
Thermal diffusion effects on F 2 region ion densities, deriving diffusion coefficients for partially ionized atomic oxygen plasma
Schunk, R. W.↗
Computer modeling of pulsed CO2 lasers for lidar applications
The object of this effort is to develop code to enable the accurate prediction of the performance of pulsed transversely excited (TE) CO2 lasers prior to their construction. This is of particular benefit to the NASA Laser Atmospheric Wind Sounder (LAWS) project. A benefit of the completed code is that although developed specifically for the pulsed CO2 laser much of the code can be modified to model other laser systems of interest to the lidar community. A Boltzmann equation solver has been developed which enables the electron excitation rates for the vibrational levels of CO2 and N2, together with the electron ionization and attachment coefficients to be determined for any CO2 laser gas mixture consisting of a combination of CO2, N2, CO, He and CO. The validity of the model has been verified by comparison with published material. The results from the Boltzmann equation solver have been used as input to the laser kinetics code which is currently under development. A numerical code to model the laser induced medium perturbation (LIMP) arising from the relaxation of the lower laser level has been developed and used to determine the effect of LIMP on the frequency spectrum of the LAWS laser output pulse. The enclosed figures show representative results for a laser operating at 0.5 atm. with a discharge cross-section of 4.5 cm to produce a 20 J pulse with aFWHM of 3.1 microns. The first four plots show the temporal evolution of the laser pulse power, energy evolution, LIMP frequency chirp and electric field magnitude. The electric field magnitude is taken by beating the calculated complex electric field and beating it with a local oscillator signal. The remaining two figures show the power spectrum and energy distribution in the pulse as a function of the varying pulse frequency. The LIMP theory has been compared with experimental data from the NOAA Windvan Lidar and has been found to be in good agreement.
Spiers, Gary D.↗
The influence of autoionization accompanied by excitation on the dielectronic recombination and the ionization equilibrium of silicon ions
The dielectronic recombination rate coefficients have been calculated for the various ionization stages of silicon. Account has been taken of all stabilizing radiative transitions and all autoionization processes which involve a single-electron electric-dipole transition of the recombining ion core. For certain ions the dielectronic recombination rates, although still larger than the direct radiative recombination rates, are found to be substantially reduced when account is taken of the effects of a previously neglected autoionization process in which the excited recombining ion core undergoes a delta n = 0 transition to a lower excited state. The temperatures at which these ions have their maximum abundance in corona equilibrium are significantly reduced when use is made of the new dielectronic recombination rates. Calculations are also presented for the total rates of radiative energy loss from isothermal steady-state plasmas due to the line and continuum emission of silicon ions.
Jacobs, V. L.↗
Approximations for proton excitation of coronal ion fine structure
Explicit approximations that yield proton excitation cross sections and rate coefficients for fine-structure transitions in a wide variety of ions over the low and intermediate energy ranges are obtained in terms of the electric quadrupole transition probability and quadrupole radial integral of a given ion. The range of applicability of these approximations is discussed, and comparisons are made with available cross sections and rate coefficients. Values of quadrupole radial integrals are given for ground configurations of even-Z elements in higher stages of ionization. Proton excitation rate coefficients are computed for coronal transitions involving fine-structure levels in the ions Fe XIII, Fe XV, Fe XVIII, Fe XXI, and Ca XIII.
Kastner, S. O.↗
Comparison of vibration dissociation coupling and radiative heat transfer models for AOTV/AFE flowfields
A series of detailed studies comparing various vibration dissociation coupling models, reaction systems and rates, and radiative heating models has been conducted for the nonequilibrium stagnation region of an AFE/AOTV vehicle. Atomic and molecular nonequilibrium radiation correction factors have been developed and applied to various absorption coefficient step models, and a modified vibration dissociation coupling model has been shown to yield good vibration/electronic temperature and concentration profiles. While results indicate sensitivity to the choice of vibration dissociation coupling model and to the nitrogen electron impact ionization rate, by proper combinations accurate flowfield and radiative heating results can be obtained. These results indicate that nonequilibrium effects significantly affect the flowfield and the radiative heat transfer. However, additional work is needed in ionization chemistry and absorption coefficient modeling.
Carlson, Leland A.↗
Silicon surface damage due to gamma radiation.
Silicon surface damage, discussing low energy gamma irradiation effect on bulk lifetime and recombination velocity
GAMMA RADIATION↗
Atomic Data for the CHIANTI Database
The CHIANTI spectral code consists of an atomic database and a suite of computer programs to calculate the optically thin spectrum of astrophysical objects and to carry out spectroscopic plasma diagnostics. The database includes atomic energy levels, wavelengths, radiative transition rates, collisional excitation, ionization and recombination rate coefficients, as well as data to calculate free-free, free-bound and two-photon continuum emission. In recent years, we have been pursuing a program to calculate atomic data for ions whose lines have been observed in astrophysical spectra but have been neglected in the literature, and to provide CHIANTI with all the data necessary to predict line intensities. There are two types of such ions: those for which calculations are available for low-energy configurations but not for high-energy configurations (i.e., C-like, N-like, O-like systems), and ions that have never or only seldom been studied. This poster will summarize the current status of this project and indicate the future activities .
Bhatia, Anand K.↗
CHIANTI-An Atomic Database for Emission Lines. XV. Version 9, Improvements for the X-Ray Satellite Lines
CHIANTI contains a large quantity of atomic data for the analysis of astrophysical spectra. Programs are available in IDL and Python to perform calculation of the expected emergent spectrum from these sources. The database includes atomic energy levels, wavelengths, radiative transition probabilities, rate coefficients for collisional excitation, ionization, and recombination, as well as data to calculate free–free, free–bound, and two-photon continuum emission. In Version 9, we improve the modeling of the satellite lines at X-ray wavelengths by explicitly including autoionization and dielectronic recombination processes in the calculation of level populations for select members of the lithium isoelectronic sequence and Fe XVIII–XXIII. In addition, existing data sets are updated, new ions are added, and new total recombination rates for several Fe ions are included. All data and IDL programs are freely available at http://www.chiantidatabase.org or through SolarSoft, and the Python code ChiantiPy is also freely available at https://github.com/chianti-atomic/ChiantiPy.
X-rays (general)↗
Collisional excitation rate coefficients for Fe XI
It is pointed out that electron collisional rate coefficients for iron ions are important atomic data for studies of both laboratory and astrophysical plasmas. Datla et al. (1975) have measured the ionization and relative excitation rate coefficients for Fe VIII, Fe IX, and Fe X. The present investigation is concerned with the relative excitation rate coefficients for Fe XI. Absolute intensities of VUV transitions 3s2 3p3 3d-3s2 3p4, 3s 3p5-3s2 3p4, and 3s2 3p3 4s-3s2 3p4 in Fe XI are measured and interpreted in terms of excitation rate coefficients. Data regarding the Fe XI line intensities and plasma parameters, and the relative excitation rate coefficients for Fe XI are provided in tables.
Wang, J.-S.↗
The effects of spatial nonuniformities on high temperature microwave breakdown
Effects on high temperature microwave antenna breakdown of ionization frequency, collision frequency, diffusion coefficient, and breakdown parameters
Light, G. C.↗
Consistent transport coefficients in astrophysics
A consistent theory for dealing with transport phenomena in stellar atmospheres starting with the kinetic equations and introducing three cases (LTE, partial LTE, and non-LTE) was developed. The consistent hydrodynamical equations were presented for partial-LTE, the transport coefficients defined, and a method shown to calculate them. The method is based on the numerical solution of kinetic equations considering Landau, Boltzmann, and Focker-Planck collision terms. Finally a set of results for the transport coefficients derived for a partially ionized hydrogen gas with radiation was shown, considering ionization and recombination as well as elastic collisions. The results obtained imply major changes is some types of theoretical model calculations and can resolve some important current problems concerning energy and mass balance in the solar atmosphere. It is shown that energy balance in the lower solar transition region can be fully explained by means of radiation losses and conductive flux.
Fontenla, Juan M.↗
The ionization equilibrium of astrophysically abundant elements
The paper presents new calculations of ionization equilibrium fractions of 11 abundant elements (C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni) as functions of temperature. Convenient coefficients for fitting the rates of collisional ionization, radiative recombination, and dielectronic recombination are also tabulated. Many of the ionization rates are based on recent experimental measurements of cross sections for collisional ionization and autoionization following inner-shell excitation. These rates are used elsewhere in computations of nonequilibrium ionization, radiative cooling, radiative shock models, and plasma emission diagnostics.
Shull, J. M.↗
Shock tube study of ionization rates of NaCl-contaminated argon
Electron density, electron temperature, and concentration of excited sodium atoms are measured in the weakly ionized regime behind a shock wave in impure argon in a shock tube using microwave techniques and spectrally resolved radiometry. Evidence is presented to show that an apparent increase in the rate of ionization is due to electron detachment of negative chlorine ions produced from sodium chloride vapor contained as an impurity. To be consistent with this chemical model, rate coefficients are found in the temperature range between 5500 and 8600 K for the dissociation of NaCl into an ion pair, dissociation of NaCl into a neutral pair, and electron detachment of a negative chlorine ion. Electron temperature is lower than heavy-particle temperature by roughly 1000 K. The electron-argon impact-ionization rate coefficient is a weak function of electron temperature in contradiction to expectation.
Schneider, K.-P.↗
Iron ionization and recombination rates and ionization equilibrium
In the past few years important progress has been made on the knowledge of ionization and recombination rates of iron, an astrophysically abundant heavy element and a major impurity in laboratory fusion devices. We make a critical review of the existing data on ionization and dielectronic recombination and present new computations of radiative recombination rate coefficients of Fe(+14) through Fe(+25) using the photoionization cross sections of Clark et al. (1986). We provide analytical fits to the recommended data (direct ionization and excitation-autoionization cross sections; radiative and dielectronic recombination rate coefficients). Finally we determine the iron ionic fractions at ionization equilibrium and compare them with previous computations as well as with observational data.
Arnaud, M.↗