This paper summarizes the results of several laser–plasma-interaction experiments using multikilojoule lasers, and considers their implications for laser fusion. The experiments used 1·06-, 0·53-, 0·35-, and 0·26-μm light to produce relatively large, warm, planar plasmas and to study the effect of laser wavelength and density-gradient scale length on the Stimulated Raman Scattering and on the scattering of light at frequencies near the incident laser frequencey by Stimulated Brillouin Scattering or other processes. The results of these experiments suggest that some laser wavelength between 0·2 and 0·6 μm will be required for high-gain laser fusion.

Recent advances in X-ray laser research have significantly increased the possibilities for X-ray laser applications. In this paper, we report the first demonstration of pointing and focusing of a soft X-ray laser beam. A LLNL selenium soft X-ray laser at 206 and 209 Å was used in these experiments. Two state of the art 76 mm diameter multilayer mirrors were used to collimate and refocus the laser onto a set of cross hairs which were constructed from 100 μm diameter wires. The cross hairs were located 4.6 m from the X-ray laser source. Results show that the laser can be pointed to within 75 μrad and focused to a 235 μm diameter spot. It is expected that eventually spot sizes near 100 μm and flux levels of 100J/cm2 at X-ray irradiances up to 1012W/cm2 can be provided to a remote application, using a similar beam relaying system.

When viewed from outer space, the earth's magnetic field does not resemble a simple dipole, but is severely distorted into a comet-shaped configuration by the continuous flow of solar wind plasma. A complicated system of currents flows within this distorted magnetic field configuration called the ‘magnetosphere’ (See figure 1). For example, the compression of the geomagnetic field by the solar wind on the dayside of the earth is associated with a large-scale current flowing across the geomagnetic field lines, called the ‘Chapman-Ferraro’ or magnetopause current. The magnetospheric system includes large-scale currents that flow in the ‘tail’, the ring current that flows at high altitudes around the equator of the earth, field-aligned ‘Birkeland’ currents that flow along geomagnetic field lines into and away from the two auroral regions, and a complex system of currents that flows completely within the layers of the ionosphere, the earth's ionized atmosphere. The intensities of these various currents reach millions of amperes and are closely related to solar activity. The geomagnetic field lines can also oscillate, like giant vibrating strings, at specified resonant frequencies. The effects of these vibrations, sometimes described as ‘standing Alfvén waves’, have been observed on the ground in magnetic field recordings dating back to the beginning of the century. Observations of currents and waves with satellite-borne magnetic field experiments have provided a new perspective on the complicated plasma processes that occur in the magnetosphere. Some of the new observations are described here.

The formation conditions of a cryogenic target with a quality fusion cryolayer were found. The special device for the injection of the cryotarget into the ICF focus was devised.

The process of induced bremsstrahlung is studied and it is found that anisotropy in the electron distribution can lead to the amplification of radiation. The gain rate is ,Λ where ν is the electron-ion collision frequency, ωp and ω the plasma and radiation frequency, and Λ a numerical factor which is positive only for anisotropic distributions.

We demonstrate that 100% absorption of an unpolarized monochromatic light can be achieved in a plasma with a density profile characterized by a presence of a cavity and a steep density gradient across the critical region. These profiles can occur in a laser produced plasma due to the radiation pressure effects. The conditions were found when both s- and p -polarizations of the electromagnetic radiation which is obliquely incident upon a stratified plasma are totally absorbed at same angle of incidence. The effect is due to simultaneous excitation of surface and guided modes which are eigenmodes of the considered plasma structure. When these modes are excited some additional conditions must be satisfied which allow for full compensations of all dissipative processes by the radiation energy inflow.

The purpose of this paper is to demonstrate how the MHD equilibrium theory can be used to describe the global magnetic field configuration of Earth's magnetosphere and its time evolution under the influence of magnetospheric convection. The MHD equilibrium theory represents magneto-hydrodynamics in the slow-flow approximation. In this approximation time scales are long compared to typical Alfvén wave travel times, and plasma flow velocities are small compared to the Alfvén speed. Under those conditions, the inertial term ρ(dv/dt) in the MHD equation of motion is a small second order term which can be neglected. The MHD equilibrium theory is not a static theory, though, because time derivatives and flow velocities remain first order quantities in the continuity equation, in the thermodynamic equation of state, and in the induction equation. Therefore one can compute slowly time-dependent processes, such as magnetospheric convection, in terms of series of static equilibrium states. However, those series are not arbitrary; they are constrained by thermodynamic conditions according to which the magnetosphere evolves in time.

It is an interesting question, whether or not the magnetosphere, driven by slow, lossless, adiabatic, earthward convection of magnetotail flux tubes, can reach a steady state. There exist magnetospheric equilibria in which magnetotail flux tubes satisfy the steady-state condition d/dt (Pρ−γ) = 0. Those configurations exhibit a deep magnetic field minimum in the equatorial plane, near the inner edge of the tail plasma sheet. The magnetosphere becomes tearing-mode unstable in the neighborhood of such a minimum, thus leading to periodic onsets of substorms in the inner plasma sheet. This explains why distinct magnetic field minima have not been observed in this region. Magnetic substorms seem to be an inevitable element of the global convection cycle which inhibit the establishment of an ultimate steady state.

MHD equilibria discussed in this paper result from linear and non-linear solutions to the two-dimensional Grad-Shafranov equation for isotropic thermal plasma pressure.

The quantitative analysis of the collisional line broadening and the ionization state distributions for determining optical properties of aluminum plasmas are the main goal of this paper. In a preliminary analysis, results from an average atom model are compared with those from detailed configurations, assuming LTE conditions. The sensitivity to these physical aspects in the extinction coefficient and in the Rosseland and Planck mean opacities are carefully studied.

The spatial and temporal behaviour of the X-ray gain in laser-produced plasmas is investigated theoretically. Hydrodynamical 1–D simulations of plasma heating and expansion for different laser parameters are combined with calculations of the corresponding density distributions for the ionic states in the plasma. The interesting energy level populations in hydrogen-like ions are found with radiation reabsorption taken into account. Results will be presented for cylindrical C and Al targets for the 3→2 (C) and 4→3 (C, Al) transitions. It is shown that the reabsorption of the Lα-line reduces the value of the gain for the 3→2 transition and modifies its spatial and temporal distribution.

It is demonstrated that finite pressure gradients can be maintained in the lowest free energy state (‘relaxed state’) of a plasma configuration. The pressure forces are supported by the Magnus Force in a compressible adiabatic plasma if mass motions are considered. It has been demonstrated elsewhere that these forces can be of the same order of magnitude as the Lorentz forces in some laboratory plasmas.

Many experiments show features of the Raman spectrum at variance with the predictions of conventional theory. One persistent discrepancy, the cut-off in the spectrum of scattered light at about 1·5λ0, led Simon and Short to postulate that the scattered spectrum is not Raman light as such, but derives from enhanced Thomson scattering from plasmas in which a population of suprathermal electrons is present. We describe a set of simulations which model the propagation of a light wave through a plasma characterized by two electron temperatures with the hot electron fraction varying between 0 and 0·05. The results show that enhanced Thomson scattering will contribute to the spectra observed in some experiments at least and confirm the contention that the spectrum of the scattered light is not especially sensitive to the width of the suprathermal electron feature. We have also examined the effect of a finite quiver velocity on the enhanced Thomson spectrum as a function of the population of suprathermal electrons, in particular its effect on the wavelength bands.

Electrical quasi-neutrality is not a general property of a thermalized self-gravitating plasma. If the massive component of a two-component plasma consists of charged macroscopic solid grains for which the charge-to-mass ratio is of order then self-gravitation and thermalization lead to substantial large-scale charge separation. An alternative statement of the condition for substantial equilibrium charge separation is that the Jeans length and Debye length of the plasma are similar.

We consider a system of condensations in such a plasma and show that properties of the system are similar to observed properties of the system of galaxies.

This paper presents an analysis for focusing of an intense proton beam by a self-magnetic field. In this analysis, the self-magnetic field is used in a positive sense for beam focusing. The computation employs an equation for the beam trajectory in which the effect of the self-magnetic field is included. The results show that it is possible to use the self-magnetic field for the good beam focusing.

The following errors were found in the article “Nuclear Driven Flashlamps”, by M. A. Prelas, F. P. Boody, G. H. Miley and J. F. Kunze, Lasers and Particle Beams, 6(1), 25 (1988):

Error 1 Page 29, Paragraph 2, Line 14—

Error 2 Page 35, Equations on page should be

Error 3 Page 37, Table 5, the bottom of Table 5 should read

* experimental data

Error 4 Page 44, Equations 19 and 20 should be

Error 5 Page 44, Equation 21 should be

Error 6 Page 44, Equation 26 should be

Error 7 Page 50, Equation 36 should be

Error 8 Page 55, Section 6. Production Chemicals should be

6.1 Production of Chemicals

Error 9 Page 56, Equation 38 should be

Error 10 Page 56, Section 6.2, paragraph 3, line 5, eg should be

Eg

The influence of ponderomotive force-induced plasma motion on filamentation is examined, using both linear and non-linear descriptions. Although the time asymptote of the process is identical to the stationary convective amplification of filaments, the dynamics of the plasma response may have a serious impact on the transient behaviour of filamentation. The plasma motion contains large amplitude oscillations of inhomogeneities in the laser beam with maxima that substantially exceed the asymptotic value and temporary growth of the very narrow filaments, which cannot be amplified in the stationary approximation.