We present some experimental results which demonstrate the presence of electric inhibition in the propagation of relativistic electrons generated by intense laser pulses, depending on target conductivity. The use of transparent targets and shadowgraphic techniques has made it possible to evidence electron jets moving at the speed of light, an indication of the presence of self-generated strong magnetic fields.

This paper deals with the realization of a CA model of the physical interactions occurring when high-power laser pulses are focused on plasma targets. The low-level and microscopic physical laws of interactions among the plasma and the photons in the pulse are described. In particular, electron–electron interaction via the Coulomb force and photon–electron interaction due to ponderomotive forces are considered. Moreover, the dependence on time and space of the index of refraction is taken into account, as a consequence of electron motion in the plasma. Ions are considered as a fixed background. Simulations of these interactions are provided in different conditions and the macroscopic dynamics of the system, in agreement with the experimental behavior, are evidenced.

We present the design of a single-shot third-order autocorrelator that can be used to measure optical pulse lengths of ultrashort pulses within a fixed time window on a single-shot basis. It has a number of advantages over traditional second-order autocorrelation devices, namely a more direct and accurate measurement of pulse shape, the ability to differentiate temporal activity ahead and behind the pulse, and an increased dynamic range. The design is linear and is, in principle, no more difficult to construct and operate than a second-order autocorrelator.

As a basis for this review the results of the investigations of a number of processes occurring at different stages of the fast z-pinch evolution, beginning with the electric explosion of a wire and ending with hot spot formation, have been assumed. At the same time the experimental results whose significant part had been obtained when investigating the explosion of thin aluminum and composite (W-Al-W; W-SiO2-W) wires at the high-current SIGNAL accelerator (∼220-kA current, ∼50-ns rise time) have been used.

The X-ray emission from hollow atoms produced by collisions of multiply charged ions accelerated by a short pulse laser with a solid or foil is studied theoretically. The possibility of obtaining a high conversion efficiency X-ray source in an ultrafast atomic process (∼1 fs) is demonstrated using the multistep-capture-and-loss (MSCL) model. Such an X-ray source has a clear advantage for the spectral range around a few kiloelectron volts over the conventional Kα X-ray source. Namely, the number of X-ray photons increases as the laser energy becomes larger and could reach 3 × 1011 photons for a laser energy of about 10 J.

Wire array z pinches on the Z accelerator provide the most intense laboratory source of soft X rays in the world. The unique combination of a near-Planckian radiation source with high X-ray production efficiency (10 to 15% wall plug), large X-ray powers and energies (>100 TW, ≥0.8 MJ in 6 ns to 7 ns), large characteristic hohlraum volumes (0.5 to >10 cm3), long pulse lengths (5 to 20 ns), and low capital cost (<$50–$100/radiated Joule) may make z pinches a good match to the requirements for driving high-yield scale (>200 MJ yield) ICF capsules with adequate radiation symmetry and margin. The z-pinch-driven hohlraum approach of Hammer et al. (1999) may provide a conservative and robust solution to the requirements for high yield, and is currently being studied on the Z accelerator. This paper describes a multiple-region, 0-D hohlraum energetics model for z-pinch-driven hohlraums in four configurations. We observe consistency between the model and the measured X-ray powers and hohlraum wall temperatures to within ±20% in X-ray flux, for the four configurations. The scaling of pinch energy and radiation-driven anode-cathode gap closure with drive current are also examined.

We report on a new technique that we used to accurately time the velocity of a cluster beam. It involves deflecting particles away from their usual beam path by scattering with an ablation plume. We were able to time the occurrence of a C60 cluster beam to better than 0.2%. This technique was critical in recent light-force polarizabilities experiments.

We use both a Fourier-transform-based analysis and time-retrieval calculations to get time-resolved measurements of the reflectivity and the phase shift of a chirped probe pulse interacting with a fs-laser-produced plasma by spectral interferometry in a single shot. We have devised a novel dual-quadrature Mach–Zehnder configuration in which wavefront division is used to obtain spatial fringes from the perturbed and unperturbed probe simultaneously. We demonstrate the capability of this technique with fully analyzed experimental data on the interaction of a femtosecond laser with C3H6 and C samples, showing 35-fs time resolution.

The influence of absorption and ionization on high-order harmonic generation in a gas-filled hollow fiber is analyzed within the framework of slowly varying envelope approximation. Harmonic spectra and pressure dependencies are calculated for high-order harmonic generation in hollow fibers filled with different rare gases. Ionization of the gas filling the fiber gives rise to self-phase modulation of the pump pulse, changing the phase mismatch within the pump pulse and shifting the maxima in pressure dependencies of high-order harmonics.

The production of highly charged ions in a CO2 laser-generated plasma is compared for different laser pulse-time structures. The work was performed at the CERN Laser Ion Source, which has the aim of developing a high current, high charge-state ion source for the Large Hadron Collider (LHC). When an intense laser pulse is focused onto a high-Z metal target, the ions expanding in the plasma plume are suitable for extraction from the plasma and matching into a synchrotron. For the first time, a comparison is made between free-running pulses with randomly fluctuating intensity, and mode-locked pulse trains with a reproducible structure and the same energy. Despite the lower power density with respect to the mode-locked pulse train, the free-running pulse provides higher charge states and higher yield.

In the past few years, long-implosion-time (150 ns to 200 ns) z pinches have made significant progress in terms of their ability to make kilovolt X rays or to produce high-power subkilovolt emissions. These advances are enabling the community to utilize lower-cost pulsed power designs for high current X-ray facilities. The advances will be reviewed in historical context in this paper, plus some new physics regimes and understanding resulting from this work will be highlighted.

X-ray emission spectra in the 5–22 nm range were recorded from planar and structured (meshlike groove surface) gold targets at 45° and 90° to the laser axis. A laser beam of 10-ns duration with EL ≤ 700 mJ and 1.06-μm wavelength was used for the experiment. Experimental results indicate an enhanced X-ray yield from a structured target as compared to a planar target under identical experimental conditions. Increased X-ray emission is attributed to plasma confinement and the possibility of conversion of kinetic energy into localized thermal energy of the plasma. Results are analyzed explicitly on the incident laser energy.

Charged transparent macroparticles of silicium carbide of radius r = 0.5 μm are submitted to the repeated radiation pressure of a laser beam which follows the sides of a square 3.5 × 3.5 m, using total reflection on three prisms. The macroparticles follow a closed path since they are deflected by a strong electric field, using magnetic insulation. After 4650 revolutions, velocities up to 106 km/s can be reached.

Harmonics spectra in an n-type InP bulk semiconductor showing up to the 13th harmonic are reported. The external field is linearly polarized with the frequency ν = 100 GHz. Calculations are based on a Monte Carlo simulation for the electron motion in the conducting band and on an electrodynamics equation for the harmonics generation. The effect of a significant reduction of efficiency in the generation of particular harmonics is found, and is traced back to a sort of alternating field Gunn effect. A short analysis of the different physical mechanisms giving rise to harmonics generation is presented.

A theoretical model for a multicascade liner system is proposed with a view to reduce the growth rate of Rayleigh-Taylor (R-T) instability and to calculate the fusion parameters of a dense θ-pinch plasma. The dynamics of such plasma has been described using the modified snow-plow model for sinusoidal and t1/3 types of discharge current profiles. Numerical results demonstrate that the thermonuclear fusion parameters can be achieved for a dense θ-pinch deuterium-tritium (D-T) fiber plasma for an optimum choice of shell thickness. The relevance of this kind of study is possible use of gas-liner and staged pinches as an alternative source of thermonuclear fusion.

A study of angular distribution of X-ray line radiation emitted from a laser-produced plasma is presented. Plasma was produced by irradiating a planar magnesium target using single laser pulses of 6 J, 4.5 ns (FWHM) from an Nd:glass laser system. Angular distribution of X-ray emission in the spectral range of 7–10 Å was recorded using a single X-ray crystal spectrograph. X-ray emission intensity for different resonance lines is observed to decrease up to an angle of ∼45° with respect to target normal, followed by a significant increase at higher angles. The observed departure of angular distribution from a monotonically decreasing behavior is broadly in agreement with the calculations of the escape factor of the radiation at different angles from a thick disk-shaped plasma using a spectroscopic code RATION.

When a laser pulse impinges on a molecule which is invariant under certain symmetry operations selection rules for harmonic generation (HG) arise. In other words, symmetry controls which channels are open for the deposition and emission of laser energy—with the possible application of filtering or amplification. We review the derivation of HG selection rules and study numerically the interaction of laser pulses with an effectively one-dimensional ring-shaped model molecule. The harmonic yields obtained from that model and their dependence on laser frequency and intensity are discussed. In a real experiment obvious candidates for such molecules are benzene, other aromatic compounds, or even nanotubes.

In this article, we study the effect of various parameters on the estimation of radiation temperature inside an indirect drive ICF hohlraum and also study the hydrodynamics of aluminum and gold foils driven by the hohlraum radiation. A multigroup one-dimensional, radiation hydrodynamic code is used for this study. Opacities are calculated using a screened hydrogenic average atom model. We also investigate the opacities of Au-Sm and Au-Gd mixtures. It is shown that the mixing of two high Z materials can lead to an enhancement in the Rosseland means, which is of direct interest in indirect-drive inertial confinement fusion. The radiation temperature inside a cylindrical hohlraum is seen to be strongly dependent on the number of frequency groups used. One group radiation transport underpredicts the radiation temperature. It is shown that erroneous results can be obtained if the space mesh in the hohlraum wall is not fine enough. The spectrum of the radiation inside the hohlraum is seen to be different from Planck, especially in the high-energy range. This may lead to preheating of the target. Hydrodynamics of an aluminum foil driven by the hohlraum radiation is also presented in this article. A scaling law for the radiation-driven shock-wave speed in the gold foil is obtained.

Characteristic X-rays generated by high-intensity laser interaction with solids were investigated and used for determining the resulting hot electron populations. Spectrally as well as spatially resolved data are evaluated for this purpose. The experimental data were compared with Monte Carlo simulations to determine the electron energy distribution and geometric features of the electron beam. These results are in good agreement with PIC simulations. The self-generated low-resistivity channel of the electron beam results in a distinct difference in the generated rear-side X-ray spot when the electron beam propagates in an insulator rather than a metal. Self-generated electric fields prevent electron propagation into the vacuum. This fact is used for demonstrating photopumping of cobalt with copper Kα radiation, an experiment relevant to innershell X-ray laser schemes. The emission of cobalt is compared with that of nickel, which is not photopumped by copper Kα, and is found to be enhanced by a factor of 2.5.

Charge-exchange collisions are one of the effective pumping methods for soft X-ray lasers. Experiments are performed to investigate charge-exchange collisions between highly charged Mg ions in colliding laser-produced magnesium plasmas. Pinhole photography and XUV spectroscopy are used as diagnostic tools. Spectroscopic studies show selective population of n = 3 levels of Mg IX ions, which results in enhancement of respective line intensities. Theoretical calculations also give a large cross section as high as 10−15 cm2 for these charge-exchange collisions when the relative velocities of the colliding ions are of the order of 107 cm s−1. XUV pinhole pictures are taken in early stages, which give more insight into the expansion dynamics of the colliding magnesium plasmas.