Recent advances of the photon kinetic theory are illustrated here, with examples taken from plasma physics (forward Raman scattering), and from nonlinear optics (self-phase modulation). This theory can provide a unified view of nonlinear optical phenomena involving photon beams with an arbitrary spectrum.

The concept of fast ignition of precompressed pellets for inertial confinement fusion is presented and the main approaches are discussed. Numerical simulations of fast coronal ignition and the peculiarities of this scheme are considered in detail. Particular attention is devoted to the energy transport in the pellet corona. It is shown that fast coronal ignition will be successful only if the energy deposition by the fast electrons is anomalous over a sufficiently extended overdense region. Alternative schemes are briefly discussed.

The structure of large clusters such as neutral clusters, metallic clusters, and clusters ion is investigated. Furthermore, the electron distribution of large clusters when they are irradiated by an intense ultrashort laser pulse is treated. The cluster excitation results from the interaction of the electron subsystem with the laser field. Analyzing the quantum metallic cluster proves that its properties differ essentially from the properties of a classical small metallic sphere. The eigen frequency of the surface oscillation of a cluster is obtained and it is shown that it is lower than Mie frequency because of Thomas–Fermi screening.

Energetic ion beams are produced during the interaction of ultrahigh-intensity, short laser pulses with plasmas. These laser-produced ion beams have important applications ranging from the fast ignition of thermonuclear targets to proton imaging, deep proton lithography, medical physics, and injectors for conventional accelerators. Although the basic physical mechanisms of ion beam generation in the plasma produced by the laser pulse interaction with the target are common to all these applications, each application requires a specific optimization of the ion beam properties, that is, an appropriate choice of the target design and of the laser pulse intensity, shape, and duration.

Modern experimental methods and instruments for X-ray spectral investigation of hot dense plasma provide complex information on environmental conditions in extreme states of matter. The basic spectroscopic conceptions for K-shell plasma diagnosis are outlined, the main characteristics of toroidally bent crystal spectrometers and vertical-dispersion instruments are briefly reviewed. Selected applications (monitoring and optimization of the emission from the femtosecond-laser-produced plasmas, characterization of colliding laser-exploded foils, spectral line merging, and continuum lowering in constrained-flow plasmas) demonstrate the usefulness of advanced spectroscopic methods for plasma diagnostics and fundamental research.

The Rayleigh–Taylor instability (RTI) of a laser-accelerated ablative surface of a thin plasma layer in an inertial fusion energy (IFE) target with incompressible electrically conducting plasma in the presence of a transverse magnetic field is investigated using linear stability analysis. A simple theory based on Stokes-lubrication approximation is proposed. It is shown that the effect of a transverse magnetic field is to reduce the growth rate of RTI considerably over the value it would have in the absence of a magnetic field. This is useful in the extraction of IFE efficiently.

In the laser–plasma interaction experiments, self-focusing and filamentation affect quite a large number of other parametric processes including stimulated scattering processes. Nonlinearity considered in the present problem is the collisional type. The coupling between the main beam, ripple, and excited electron plasma wave is strong. Authors have investigated the growing interaction of a rippled laser beam with an electron plasma wave leading to enhanced Raman scattering. An expression for scattered power is derived and the effect of the externally applied magnetic field on the enhancement of scattered power is observed. From computational results, it is observed that the effect of increased intensity of the main beam leads to suppression of power associated with the Raman scattered wave.

Relativistic laser–plasma interaction, subsequent superhot electron transport, superhot electron energy deposition, and the overall implosion process are key subjects for fast ignition. All these phenomena couple with each other, and more studies by simulations are essential. We have a plan to simulate the whole of fast ignition self-consistently with four individual codes. Four codes are integrated into one big system in the Fast Ignition Integrated Interconnecting code project. In a first stage of this project, we integrate the Arbitrary Lagrangian Eulerian (ALE) hydro code with the collective particle in cell (PIC) code. The PIC code obtains density profile at maximum compression from the ALE hydro code to introduce imploded plasma into a PIC system, and we can simulate interaction between ignition laser and realistic plasma. We have evaluated reflected laser spectrum and electron energy distribution, and found many differences between the realistic plasma profile and the conventional one in PIC simulations.

Multiple ionization of large clusters when they are irradiated by an intense ultrashort laser pulse is investigated. Different mechanisms, responsible for cluster ionization, are investigated. It is found that the ionization of large clusters, irradiated by a strong intense ultrashort laser pulse, is realized by means of the surface thermoemission.

The electron-beam-pumped KrF laser installation GARPUN with a 100-J output energy and long 100-ns pulse duration has been used to investigate laser–target interactions in a broad range of laser intensities for small (150 μm) and large (∼1 cm) irradiated spots. For higher intensities (up to 5 × 1012 W/cm2), a conical shock wave was generated in condensed matter by megabar pressure at the ablation front. It propagated with a supersonic velocity in a quasisteady manner together with a conical shock wave inside a target. Evaporated target material moving with a velocity of ∼50 km/s formed an extended plasma corona of ∼5 mm length with an electron temperature of ∼100 eV. Emission spectra of plasma have been investigated in the extreme UV range 120–250 Å. For lower intensities (108–109 W/cm2), planar shock waves in normal density air were produced with initial velocities up to 4 km/s in the forward direction and 7 km/s in the opposite direction toward incident radiation. In rarefied air, the forward shock wave kept velocities constant whereas the backward ones were accelerated up to 30 km/s. Planar compression waves in transparent condensed matter were also demonstrated propagating with sonic velocity.

Experimental investigations of heavy-ion-generated shock waves in solid, multilayered targets were performed by applying a Schlieren and a laser-deflection technique. Shock velocity and the corresponding pressures, temporal and spatial density profiles inside the material compressed by multiple shock waves, and details of the shock dynamics were determined. Important for equation-of-state and phase transition studies, such experiments extend their relevance to inertial confinement fusion and astrophysical fundamental research.

The article presents the multigroup kinetic approximation of radiation transport in hohlraum systems. The view factor-based method of numerical solution is proposed. Its advantages are a detailed account of the problem geometry and accurate handling of the solution angular anisotropy and discontinuities. The method is computationally efficient and easily parallelizable. Coupled to the kinetic + hydro description of the wall dynamics, it represents a powerful tool for integrated investigation of the systems with strongly inhomogeneous optical properties.

This article presents a numerical and theoretical study of the generation and propagation of oscillation in the semiclassical limit ħ → 0 of the nonlinear paraxial equation. In a general setting of both dimension and nonlinearity, the essential differences between the “defocusing” and “focusing” cases are observed. Numerical comparisons of the oscillations are made between the linear (“free”) and the cubic (defocusing and focusing) cases in one dimension. The integrability of the one-dimensional cubic nonlinear paraxial equation is exploited to give a complete global characterization of the weak limits of the oscillations in the defocusing case.

This article reports on experimental studies of subnanosecond electron beams formed in air under atmospheric pressure. An electron beam with an amplitude of ∼170 A with a duration at FWHM of ∼0.3 ns has been obtained. Based on beam temporal characteristics and discharge spatial characteristics, the critical fields were supposed to be reached at plasma approach to anode. Simultaneously, the sharp high-energy pulse of e-beam current is generated. Of critical importance is the cathode type and occurrence on the cathode of plasma protrusions. It is shown that to get maximum amplitude of the electron beam in the gas diode, the discharge in the gas diode should be volumetric.

Measurements of the ion emission from targets irradiated with neodymium glass and iodine lasers were analyzed and a very significant anomaly observed. The fastest ions with high charge number Z, which usually are of megaelectron volt energy following the relativistic self-focusing and nonlinear-force acceleration theory, were reduced to less than 50 times lower energies when 1.2 ps laser pulses of about 1 J were incident. We clarify this discrepancy by the model of skin depth plasma front interaction in contrast to the relativistic self-focusing with filament generation. This was indicated also from the unique fact that the ion number was independent of the laser intensity. The skin layer theory prescribes prepulse control and lower (near relativistic threshold) laser intensities for nonlinear-force-driven plasma blocks for high-gain ignition similar to light ion beam fusion.

A large amplitude Trivelpiece–Gould (TG) mode, in a strongly magnetized beam–plasma system, parametrically couples to a beam space charge mode and a TG mode sideband. The density perturbation associated with the beam mode couples with the electron oscillatory velocity, due to the pump wave, to produce a nonlinear current, driving the sideband. The pump and the sideband waves exert a ponderomotive force on the electrons with a component parallel to the ambient magnetic field, driving the beam mode. For a pump wave having k0·v0b0/ω0 < 0, where ω0, k0 are the frequency and the wave number of the pump, and v0b0 is the beam velocity, the sideband is frequency upshifted. At low beam density (Compton regime) the growth rate of the parametric instability scales as two-thirds power of the pump amplitude, and one-third power of beam density. In the Raman regime, the growth rate scales as half power of beam density and linearly with pump amplitude. The background plasma has a destabilizing role on the instability.