A magnetically insulated diode with an active anode source has been developed which produces a high-quality intense ion beam. The anode plasma of annular shape is produced independently of the main diode power pulse by the inductive breakdown of a radially expanding gas cloud supplied by a fast puff valve and nozzle configuration. The diode was developed on a 1010-W pulsed power generator that typically produces 150-kV, l-μs pulses. Prompt ion beam turn-on was attained in this diode when an adequate delay between pulsing the plasma source and delivering the diode power pulse was chosen. The neutral atom density in the diode accelerating gap was sufficiently low that the presence of the neutrals did not limit the beam pulse duration. When the puff valve was filled with H2 gas, a pure proton beam was produced, within the 20% uncertainty of the measurement technique. Proton beam pulses longer than 1 μs and current densities higher than 100 A/cm2 at 70–150 keV were generated.

The Al–Mg photoresonant X-ray laser scheme study was carried out on the 1.4-MA GIT-4 generator with a 1.7-cm separation between the liner axis and the Mg target. The radiation power in the pumping line was (2–3).109 W/cm and the radiation power within the 45–60–A range was 3.11010 W/cm. The Mg VI and MG VII lines were found by the grating spectrograph.

A paraxial theory of relativistic self-focusing of a Gaussian laser beam in plasmas, when the nonlinear part of the effective dielectric constant is arbitrarily large, is presented. The plasma is taken to be homogeneous without any density fluctuations being necessary. The approach of Akhmanov et al. based on the WKB and paraxial ray approximations has been followed. It is seen that the saturating nature of nonlinearity leads to two values of critical power of the beam (Pcrl and Pcr2) for self-focusing. When the power of the beam P lies between the two critical values (i.e., Pcr1 < P < Pcr2), the medium behaves as an oscillatory waveguide; the beam first converges and then diverges, converges again, and so on. For P > Pcr2 the beam first diverges, then converges, then diverges, and so on. Because the relativistic mechanism is instantaneous, the theory is applicable to the understanding of selffocusing of laser pulses also.

The design scheme of a radially convergent 30-, 70-, or 100-μs e-beam-pumped laser with 9 or 18 1 excited volume is described. Amplitude, temporal, and spectral characteristics of the laser output, as well as laser thresholds in (Ar–Xe, He–Ar–Xe, He–Ne–Ar, and He– Ne–Ar–H2) gas mixtures have been investigated. The distribution of the specific deposited energy over the laser chamber cross section has been calculated by the Monte Carlo method. The small signal gain and unsaturable loss values of the active medium were measured for a Penning plasma Ne laser at λ = 0.585 μm.

Zero-dimensional numerical computation of electrical discharge-pumped excimer lasers is extended to a one-dimensional model that is used to study the effects of the density perturbations of the background neutral gas and the nonuniform predischarge (which means preionization in this paper) electron density on the transition of the uniform discharge to the nonuniform prestage state leading to the onset of arc formation (which is not included in this particular model). It was found that a local density depression of 1% or an enhancement of the local electric field of 1% can increase the local energy input by several hundred percent. The initial electron density perturbations, on the other hand, are found to modify the energy input by the same order of magnitude as the initial perturbations.

Inertial confinement fusion (ICF) targets can be imploded by heavy-ion beams (HIBs) in order to obtain a highly compressed fuel microsphere. The hydrodynamic efficiency of the compression can be optimized by tuning the ablation process in order to produce the total evaporation of the pusher material by the end of the implosion. Such pusherless compressions produce very highly compressed targets for relatively short confinement times. However, these times are long enough for a fusion burst to take place, and burnup fractions of 30% and higher can be obtained if the volume ignition requirements are met. Numerical simulations demonstrate that targets of 1-mg DT driven by a few MJ can yield energy gains of over 70. Although direct drive is used in these simulations, the main conclusions about volume ignition are also applicable to indirect drive.

A new method of intense relativistic electron beam modulation at frequencies up to ∼1 GHz is suggested. Current modulation is provided by using the azimuthal magnetic field of the beam to control the beam reflection from the magnetic mirror. The results of computer simulations for a 2-MeV, 20–50-kA beam are presented.

Rayleigh-Taylor (RT) and Richtmyer–Meshkov (RM) instabilities at the pusher–fuel interface in inertial confinement fusion (ICF) targets may significantly degrade thermonuclear burn. Present-day supercomputers may be used to understand the fundamental instability mechanisms and to model the effect of the ensuing mixing on the performance of the ICF target. Direct three-dimensional numerical simulation is used to investigate turbulent mixing due to RT and RM instability in simple situations. A two-dimensional turbulence model is used to assess the effect of small-scale turbulent mixing in the axisymmetric implosion of an idealized ICF target.

The production of a long scale-length plasma of electron density 1020–1021 cm-3, measuring 10 X 0.5 mm using a laser-heated capillary discharge is reported. X-ray spectroscopic measurements have been performed which show that the plasma constituents can be varied by changing the material that lines the exit slit of the device. The capillary thus provides a useful source of large underdense plasmas created from solid materials suitable for laser-plasma interaction studies. Numerical simulations consistent with spectroscopic studies suggest that temperatures up to about 700 eV were achieved following irradiation of these plasmas by high-power laser light.

Although synchrotron radiation is thought to be well understood in a theoretical sense, the practicalities of controlling a synchrotron source sometimes seem difficult. Often the output spectrum contains sharp peaks, especially at the high-frequency end of the spectrum. These spikes are unwanted because they rob power from desired frequency intervals, and unexpected because idealized theory predicts a quite smooth spectrum. In the face of such difficulties, it has been natural to suspect some sort of engineering shortfall. But the present paper argues that the spectral structure may point instead to an imperfection of theory.