Accuracy of K-shell spectra modeling in high-density plasmas

Study of atomic spectroscopy and electron collision process in non-ideal classical plasmas

This manuscript presents an approach to the calculation of atomic properties and the electron collision excitation process in a non-ideal classical plasma, based on the relativistic distorted wave methodology. The method incorporating the pseudopotential obtained from a sequential solution of the Bogolyubov chain equations, that yields modification term to the calculation of the central field potential, is employed to characterize the interactions among the charged particles in plasmas. The bound/continuous state wave functions and the electron collision excitation matrix elements are determined using the aforementioned pseudopotential within a relativistic Dirac–Coulomb atomic structure framework. Systematic investigations on the effects of non-ideality of plasma on the electronic structures, radiative properties, and excitation cross sections within a selected temperature and density range are carried out in the specific cases of H atom and Ca18+ ion as they make it possible to reproduce the reference data well and thus to conclude with the reliability of the (present) method developed. Apart from its fundamental importance, this study is essential for several applications, especially for the analysis of atomic processes in non-ideal plasmas, and offers a new perspective for the calculation of atomic properties under different conditions in various astrophysical and laboratory plasmas.

Theoretical evaluation of excitation cross section and fluorescence polarization of a solid-density Si plasma

In this article, a fully relativistic approach is proposed to precisely predict the electronic structures, spectral properties, cross sections, and degrees of linear polarization of light emitted after excitation of plasma-embedded ions by electron impact, taking into account the plasma shielding effects on the atomic structures and collision dynamics, in addition to the contributions of Breit interaction and quantum electrodynamics effects. The scheme employs the effective shielding potential deduced from a solution of Poisson equation, based on the self-consistent field ion-sphere simulations to explain the interactions among the charged particles, where the perturbation correlation Dirac–Coulomb Hamiltonian is constructed. The simple and understandable form makes it a good substitute for complex self-consistent field calculation. As an illustrative example, a comparative investigation regarding the influences of different plasma temperature and density parameters on the level energies, transition rates, integrated total/magnetic sublevel cross sections, and linear polarizations of the radiation following electron-impact excitation of Si XIII (a solid-density Si plasma) is carried out. Numerical results show that the plasma density effect can significantly affect the atomic structures and collision cross sections, yet has limited influence on the polarization characteristics. A comparison of our calculations with other results, when available, is made. The advanced approach presented here not only opens a novel window for exploring the atomic dynamics processes in hot and/or dense plasmas, but also provides important information about polarization of the line emission. This study is beneficial for the high energy density physics, laser-produced plasmas, and astrophysical applications.

Intensity limits for propagation of 0.527 microm laser beams through large-scale-length plasmas for inertial confinement fusion

We have established the intensity limits for propagation of a frequency-doubled (2omega, 527 nm) high intensity interaction beam through an underdense large-scale-length plasma. We observe good beam transmission at laser intensities at or below 2x10(14) W/cm(2) and a strong reduction at intensities up to 10(15) W/cm(2) due to the onset of parametric scattering instabilities. We show that temporal beam smoothing by spectral dispersion allows a factor of 2 higher intensities while keeping the beam spray constant, which establishes frequency-doubled light as an option for ignition and burn in inertial confinement fusion experiments.

Efficient multi-keV X-ray sources from Ti-doped aerogel targets

We have measured the production of hnu approximately 4.7 keV x rays from low-density Ti-doped aerogel (rho approximately 3 mg/cc) targets at the OMEGA laser facility (University of Rochester), with the goal of maximizing x-ray output. Forty OMEGA beams (lambda(L)=0.351 microm) illuminated the two cylindrical faces of the target with a total power that ranged from 7 to 14 TW. The laser fully ionizes the target (n(e)/n(crit)</=0.1), and a laser-bleaching wave excites, supersonically, the high-Z emitter ions in the sample. Ti K-shell x-ray emission was spectrally resolved with a two-channel crystal spectrometer and also with a set of filtered aluminum x-ray diodes; both instruments provide absolute measurement of the multi-keV x-ray emission. We find between 40 and 260 J of output with 4.67</=hnu</=5.0 keV.

Spectroscopy of heliumlike argon resonance and satellite lines for plasma temperature diagnostics

The n=2-1 spectral emission pattern of heliumlike argon, together with the associated satellite emission originating from lithiumlike argon have been measured with high-resolution x-ray spectroscopy at the Berlin electron-beam ion trap. The observed line intensity across a wide range of excitation energies was weighted by an electron-energy distribution to analyze as a function of plasma temperature the line ratios between KLL dielectronic recombination satellites, in particular the j+z, j, and k satellites, and the w-resonance line. A good agreement between various theoretical models is found, supporting the method of line-ratio measurement as a temperature diagnostic for plasmas. A value for the so-called R-line ratio is determined and calculations with the HULLAC suite of codes predict it to be electron density independent over a wide range.

K-shell spectroscopy of an independently diagnosed uniaxially expanding laser-produced aluminum plasma

We present detailed spectroscopic analysis of the primary K-shell emission lines from a uniaxially expanding laser-produced hydrogenic and heliumlike aluminum plasma. The spectroscopic measurements are found to be consistent with time-dependent hydrodynamic properties of the plasma, measured using Thomson scattering and shadowgraphy. The K-shell population kinetics code FLY with the measured hydrodynamic parameters is used to generate spectra that are compared to the experimental spectra. Excellent agreement is found between the measured and calculated spectra for a variety of experimental target widths employed to produce plasmas with different optical depths. The peak emission from the hydrogenic Lyman series is determined to be from a temporal and spatial region where the hydrodynamic parameters are essentially constant. This allows a single steady-state solution of FLY to be used to deduce the electron temperature and density, from the measured line ratios and linewidths, for comparison with the Thomson and shadowgraphy data. These measurements are found to agree well with time-dependent calculations, and provide further validation for the FLY calculations of the ionization and excitation balance for a K-shell aluminum plasma. We also discuss the possible application of this data as a benchmark for hydrodynamic simulations and ionization/excitation balance calculations.

X-ray emission of a xenon gas jet plasma diagnosed with Thomson scattering

We present the results of a benchmark experiment aimed at validating recent calculation techniques for the emission properties of medium and high-Z multicharged ions in hot plasmas. We use space- and time-resolved M-shell x-ray spectroscopy of a laser-produced gas jet xenon plasma as a primary diagnostic of the ionization balance dynamics. We perform measurements of the electron temperature, electron density, and average charge state by recording simultaneous spectra of ion acoustic and electron plasma wave Thomson scattering. A comparison of the experimental x-ray spectra with calculations performed ab initio with a non-local-thermodynamic-equilibrium collisional-radiative model based on the superconfiguration formalism, using the measured plasma parameters, is presented and discussed.