Ionization distributions and radiation spectra of a dense plasma driven by intense ion beams are studied by solving stationary rate equations. Expressions for the rate coefficients are derived. Optically thin plasmas of hydrogen and carbon are considered neglecting hydrodynamic motion. Results on level populations versus temperature, on power balance and equilibrium states, and also on emission spectra are given. In particular, the transition from beam-determined plasma states to thermal equilibrium states is discussed. Beam parameters are chosen close to those in experiments now being planned.

Stimulated Brillouin and Raman scattering are of considerable interest because of their importance to basic nonlinear plasma physics phenomena and to laser-driven inertial confinement fusion. Induced scattering can be substantial for high intensity (I), long wavelength (λ) lasers because the instability growth rates depend exponentially on Jλ2, and also for short wavelength, long scalelength (L) laser/plasma interaction because of nearly homogeneous or large convective gain conditions. Experimental results from both KrF and CO2 laser/plasma interaction studies are presented to illustrate important wavelength dependent features of induced scattering such as the nature of the instability (absolute, convective), threshold, spectra, reflectivity and saturation effects. Backscattering characteristics have been measured for solid target plasmas (aluminum, gold) produced by KrF laser pulses focused to intensities <1014 W/cm2 and gas targets (hydrogen, oxygen) by CO2 laser pulses at intensities <1013 W/cm2. Collisional absorption dominates the KrF laser experiments, whereas particle heating and increased Landau damping dominate the CO2 laser experiments. Current theoretical work concerned with nonlinear effects in Langmuir wave localization, wave collapse and particle heating (generating characteristic high temperature electrons) is also presented.

A time-dependent collisional radiative model, based on a five-charge state at any spacetime point in the plasma, is elaborated in order to follow the basic atomic physics processes in a plasma undergoing ionization and recombination. This model can either be used independently or be included in a magnetohydrodynamics code of a transient plasma. In the latter case, the efficiency of the model makes it particularly useful in saving computing time of hydrodynamic codes developed in connection with ion-driven fusion.

The development of a hydrodynamic instability in laser targets is studied by means of a 2-D numerical code “ATLANT”. During the linear stage, the perturbations grow as:

In the nonlinear stage the growth rate of the Rayleigh-Taylor instability is reduced, and new harmonics are generated. The effect of the nonuniformity of the laser irradiation has been investigated for long-wave and short-wave perturbations. The growth rate of short-wave perturbations may be effectively decreased by means of symmetrical pre-pulses.

The main objective of this work is to find analytical formulas for the oscillator strength f of hydrogen-like ions. It is well known that f is proportional to the energy of the transitions between eigenstates (ΔE), and to the square of the R matrix. Therefore, the problem of calculating f can be reduced to finding analytical expressions for both parameters, ΔE and R. Hence these expressions would be in accordance with quantum results based on more sophisticated calculations.

Laser-produced plasmas have many properties similar to, or which can be scaled to, those encountered in space, magnetospheric, ionospheric, and astrophysical situations. We describe several such experiments performed with the PHAROS III Nd-laser facility at NRL.

Frequency-dependent opacities are determined for high-Z plasma taking into account splitting of the energy levels with orbital quantum number l. The energy levels are calculated with the help of the screened hydrogenic model generalized by Perrot for l splitting. Oscillator strengths for bound-bound and bound-free transitions are computed from hydrogenic wave functions with two different screened nuclear charges. The average atom model is used to determine the plasma state, with provision for continuum lowering and pressure ionization. Explicit results for extinction coefficients of gold plasma with ρ = 0.1 g/cm3 and T = 100−500 eV are compared with calculations neglecting l splitting. Considerably enhanced absorption at lower photon energies (50–300 eV) is obtained when taking l splitting into account. Planck and Rosseland mean opacities are also calculated and compared with data contained in the SESAME opacity library. Remarkable agreement is found without any artificial line broadening or band smearing.

Thermal energy transport in laser-irradiated glass microshells coated with polystyrene/metal layers seems to be dominated by hot spots. These are connected with filaments which are enhanced by hydrodynamic instability of the Rayleigh-Taylor type.

We present results from non-LTE line radiation transport calculations for high-temperature, optically thick plasmas with densities ∼1016-1020 ions/cm3. The calculations are based on an escape probability radiative transport model in which the atomic rate equations are solved self-consistently with the radiation field. Steady-state ionization and excitation populations are determined by detailed balancing of atomic processes, with photoexcitation effects included. Atomic data are computed using a combination of Hartree-Fock, semiclassical impact-parameter, and distorted-wave calculations. Our results indicate that the reabsorption of line radiation significantly alters the level populations and reduces the radiation flux from several types of fusion-related plasmas. We also compare our results with those obtained from multigroup radiation diffusion calculations, and discuss the ramifications of our results for ICF target chamber plasmas.

Tritium self-heats at a rate of 97 W/mole because of its β activity. This energy drives preferential sublimation of solid T2 or DT from regions where a layer is thicker and warmer to regions where the layer is thinner and colder. A frozen tritium layer inside an isothermal container approaches isotropy exponentially with a time constant as short as 14.4 minutes. Targets Isotropized by Radioactively Induced Sublimation (IRIS) and sized for an ICF reactor demonstrate high gain and offer real fabrication advantages.

A formulation of radiative transfer is discussed describing energy flow in a turbulent mixture in the vicinity of a Rayleigh–Taylor unstable interface, as might be extant in an ICF pellet. Included in this discussion are (1) the method of smoothing and the Liouville master equation approaches in the case of Markovian statistics as the description of the fluid mixing, (2) the use of asymptotics to derive various limiting descriptions of the Markov model, (3) the use of the theory of alternating renewal processes to obtain an integral equation formulation for non-Markovian statistics, and (4) the reduction of this non-Markovian integral formulation to integro-differential equations of the generic transport form, with statistical effects represented by pseudoscattering terms.

We present a theoretical approach to the thermodynamic properties of nonideal plasmas consisting of neutral atoms, multiply charged ions, and free electrons. Starting with the free energy, we describe the ionization equilibrium of this system by a coupled set of mass action laws (Saha equations). Our model of interaction takes into account Coulomb forces between all charged particles and hard-core forces between all heavy particles and the electrons. The influence of multiple ionization and different interaction parts on plasma composition, mean charge, and equation of state is discussed for xenon. Finally, we show the potential occurrence of the plasma phase transition.

The paper describes different types of plane targets, the method for obtaining metal microballoons from Au, Ag, and Cu with diameters of 600–1200 μm and wall thickness of 5–20 μm, and spherical cascade and cannonball type targets.

The pump wave reflected from the overdense plasma may play an important role in the dynamics of stimulated Brillouin scattering. The particular case of Double Stimulated Brillouin Scattering (DSBS) suggested by Zozulya, Silin, & Tikhonchuk [Sov. Phys. JETP 59, 756 (1984)] is studied here in detail. In DSBS the incident pump wave and the reflected pump wave scatter from a common ion acoustic wave. Some steady state properties of DSBS are reviewed. The analysis of DSBS dynamics is based on a series of ‘numerical experiments’.At small pump intensities the system asymptotically approaches a true steady state. When the intensity is increased the solution turns into a regular pulse train with intensity dependent period. Connections between the pulses and soliton-like solutions of a damped sine-Gordon equation are discussed.

Collision times in plasmas are usually defined in connection with the time evolution of the ensemble-averaged scattering angle . Extrapolating the short-time behaviour ϑshort(t), one obtains the collision time tc by setting ϑshort(tc) = π/2. We have shown with the help of computer simulations that this procedure is ambiguous, as we can clearly distinguish three regimes for ϑ(t). There is always an initial ballistic regime with ϑ(t) ∝ t with dominant pairwise interactions. This lasts up to times α/υth where α is the mean distance between the particles and υth their mean velocity. This is followed by a diffusive regime with ϑ(t) ∝ t½, which is characterized by many small-angle scattering events. Eventually, this diffusion will lead to a uniform distribution of the directions of the velocity. So ϑ(t) will saturate towards π/2 in a third asymptotic regime. For large plasma parameters Γ ≫ 1, this asymptotic behaviour will be modulated by a damped oscillation of ϑ(t) with the plasma frequency. For such strongly coupled plasmas the diffusive regime is suppressed and one observes a direct transition from the initial ballistic to the asymptotic collective regime characterized by the plasma oscillation. Parameters such as the diffusion constant and the transition times are estimated with the help of analytical models.