Gold cavity targets were irradiated with λ = 0.44 μm laser light at intensities ≤ 2.6 ×1013 W/cm2. The outward motion of the cavity wall was investigated by simultaneous optical and x-ray shadowgraphy. The wall motion is attributed to the pressure generated by an ablative heat wave, driven by the soft x-rays in the cavity. The observed transparency of the cavities for the x-rays used for shadowgraphy allowed the determination of the density profile of the cavity wall which decays possibly due to fragmentation.

Experimental data are reported on second harmonic generation (SHG) during the interaction between a Nd laser beam (20 ns pulse-duration and peak intensity 1013 W/cm2) and a plasma of density 1019 cm−3 produced in helium. The behavior of self-focusing and the onset of steep plasma gradients under the same experimental conditions have been previously characterized by independent techniques as already reported. In the light of these former findings, the observed SH magnitude, emission pattern and time dependence are briefly discussed and compared with expectations.

The typical target structure of the inertial confinement fusion by using the ion beams as the energy driver, and its optimized parameters are shown in this paper. The phenomenon occurring at the fuel implosion in the target, from which the thermonuclear fusion output energy of 2·5 GJ is released, is analyzed, and the requirements for the driver beam are summarized.

The realization of an ideal volume compression of laser-irradiated fusion pellets (by C. Yamanaka) opens the possibility for an alternative to spark ignition proposed for many years for inertial confinement fusion. A re-evaluation of the difficulties of the central spark ignition of laser driven pellets is given. The alternative volume compression theory, together with volume burn and volume ignition (discovered in 1977), have received less attention and are re-evaluated in view of the experimental verification by Yamanaka, generalized fusion gain formulas, and the variation of optimum temperatures derived at self-ignition. Reactor-level DT fusion with MJ-laser pulses and volume compression to 50 times the solid-state density are estimated. Dynamic electric fields and double layers at the surface and in the interior of plasmas result in new phenomena for the acceleration of thermal electrons to suprathermal electrons. Double layers also cause a surface tension which stabilizes against surface wave effects and Rayleigh–Taylor instabilities.

A one-dimensional Lagrangian code is used to model the interaction of laser light with plasma. The equation of state used is a realistic, piecewise analytic fit, which allows simulations starting from normal density and temperature conditions. The atomic physics required in the code (ionization, radiation rate, and opacities) is interpolated from tables generated using a non-LTE hydrogenic atom model. Radiation transport is treated approximately using a new, numerically efficient recursive algorithm. Results from numerical simulations are compared with recent X-ray measurements from Al, Ti, and Fe plasmas. The code is also used to investigate the X-ray conversion efficiency and the effect of radiation transport on the mass ablation rate and ablation pressure.

The coupling of a large amplitude plasmon, generated by the beat-wave process, to ion acoustic waves may lead to modulational or decay instabilities, which are investigated here. A general dispersion relation obtainable from Zakharov equations predicts large growth rates (∼ωpi) for short wavelength modulations. To avoid these, extremely short pulse lengths are required in the beat-wave experiments. Due to the very long wavelength of the beat-plasmon, the decay instability is not likely below the ke V-temperatures.

The flux transport effect on the radiation-induced plasma density profile and ablative flow outside the resonance layer in steady state in one dimensional spherical geometry studied. The numerical predictions conclude the existence of plateau-like plasma density profile rather than overdense bump formation in the underdense plasma. The plasma density profile, though retaining its shape, becomes more pronounced as the heat flux is increased. However, the length of the plasma density plateau is found to be quite small when compared with the isothermal case.

Nd: YAG laser action controlled by a solid target-plasma reflectivity is reported. A quasi-continuous mode-locking pulse train consisting of 26 ± 4 ps pulses was observed using a two-stage laser amplifier and a carbon target. A single pulse energy of 0.2 mJ and a peak power density at the target of about 1011 W/cm2 were measured.

An investigation into the feasibility of using a laser-generated plasma source of soft X rays as a laboratory based instrument for biological imaging and microlithography is presented. A preliminary characterization of the source has been carried out with carbon, copper and aluminum targets with specific interest in generating a monochromatic source of soft X rays in the ‘water window’. Measurements of X-ray production with respect to angular distribution, effects of cratering and different focusing conditions are reported. Initial conclusions on the optimization of the source for use in biological imaging are drawn.

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.

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.

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 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.

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.

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.

Inverse bremsstrahlung absorption in the spherical, quasi-steady corona of a weakly nonuniform laser-irradiated target is considered. Here we have assumed that laser irradiation is almost spherical, justifying a linear analysis in terms of spherical harmonics. Our analysis is applicable for low intensities and short wavelength pulses. Complete results for ablation pressure, mass flow rate, and critical surface location are given in terms of Legendre index.

A mechanism of trapping and entrainment of electromagnetic (EM) field pulses into supercritical regions of an inhomogeneous plasma by ion-acoustic waves is considered.

The mass ablation rate and ablation pressure on laser-irradiated spherical microshells were measured using the space-resolved X-ray spectroscopy. A new method for the study of the ablation by means of the Doppler shifted X-ray images is proposed. The time-resolved measurements of X-ray emission from layered microtargets allow us to determine the heat front penetration through the microshell wall.