The temporal contrast is classified into two main regimes, the nanosecond-scale and the picosecond-scale contrast prior to the main pulse. The Lund terawatt laser system is shown to be improved on the nano- and picosecond-scale by a factor of 10 and 50, respectively, when it was optimized for contrast but not for energy. Calculations are also presented to emphasize the role of angular dispersion on the picosecond contrast. Finally we show a compromise between the duration and contrast of femtosecond laser pulses amplified in an optical parametric (chirped pulse) amplifier.

Success in inertial confinement fusion (ICF) requires sophisticated, characterized targets. The increasing fidelity of three-dimensional (3D), radiation hydrodynamic computer codes has made it possible to design targets for ICF which can compensate for limitations in the existing single shot laser and Z pinch ICF drivers. Developments in ICF target fabrication technology allow more esoteric target designs to be fabricated. At present, requirements require new deterministic nano-material fabrication on micro scale.

In order to develop a high repetition rate X-ray lasers, the longitudinal-pumped transient collisional excitation (TCE) X-ray laser is one of the most effective pumping schemes. The high directive Ni-like Mo 18.9 nm soft X-ray laser pumped by modest laser energy has already been demonstrated by using the tabletop size Ti:sapphire/Nd:glass laser system that delivering energy of 150 mJ in 475 fs at the center wavelength of 1054 nm. The total energy in the pre-pulse and the main pulse was 150 mJ, which will make possible multi-hertz operation. To pursue the high repetition rate of the laser-driven TCE X-ray laser, we have designed a new 20 TW Ti:Sapphire laser system (600 mJ, 30 fs, 10 Hz). Special attention was paid to improve the contrast ratio, control of pulse shape as well as phase by an acoustic optic programmable dispersive filter (AOPDF) and 1 kHz preamplifier. Preliminary data have shown good laser characteristics. As the preliminary experiments, we have investigated high order harmonics generation from low-density laser plasma by using the solid target irradiated by a femtosecond laser pulse. The highest order was the 51st. harmonic at wavelength of 15.61 nm.

For achieving practically useful laser fusion energy generation, it is necessary to have a M-J laser system with a repetition rate over 10 Hz. We believe that a beam combination method using stimulated Brillouin scattering phase conjugate mirrors (SBS-PCM) is one of the most practical techniques for achieving the high repetition rate of the high power laser. In this paper, we present the recent results about the beam combination laser, such as SBS reflectivity depending on the mode structure, the cross type isolator, and the phase-locking technique. For the phase-locking technique, especially, the self-phase-locking is proposed and its result is discussed.

Imploding indirect-drive double shell targets may provide an alternative, non-cryogenic path to ignition at the National Ignition Facility (NIF). Experiments are being pursued at OMEGA to understand the hydrodynamics of these implosions and the possibility of scaling it to the NIF design. We have used 40 beams from the OMEGA laser to directly drive the capsules, and we have used the remaining 20 beams to backlight the imploding shells from two different directions at multiple times. We will review the recent experiments to measure the hydrodynamics of the targets using two-view X-ray radiography of the capsules. We will present data on measured yields from the targets. We will present a measured time history of the hydrodynamics of the implosion. Experiments were pursued using direct drive in which the M-band effect (experienced in the indirect drive experiments) could be eliminated or controlled. It was learned in the direct drive experiments that the best performing capsules were those that had a thin outer layer of gold. This effectively causes M-band pre-heat effects giving implosion hydrodynamics and performance closer to the indirect drive case. We will review the methods used to radiograph the targets and the techniques used to extract useful information to compare with calculations. The effect of imperfections in the target construction will be shown to be minimal during the initial stage of implosion. The yields from the targets were observed to be uniformly low compared to indirect-drive.

The dynamics of fast laser-induced vacuum discharge, with a rather small value of amplitude of current (≤ 10 kA), as well as the voltage and energy of the capacitor bank (≤ 20 kV and 20 J, respectively), have been investigated. It has been experimentally demonstrated that the initiations conditions determined by the energy and duration of the laser radiation, fundamentally determine the dynamics of the discharge. Two types of space and time separated plasma instabilities are revealed. It was found that the first of instabilities occurs at the initial stage of the discharge and is caused by a pinch structure, which takes place in front of a cathode jet extending in vacuum. The second type of instabilities arises at the top or recession of the current and is accompanied by the generation of hard (energy ≥100 keV) bremsstrahlung X-ray radiation from the anode area. The excess energy of the hard components of radiation over the potential of the current source is associated with the effects of plasma-erosive breaking.

Electron ponderomotive acceleration in a vacuum by a short-pulsed laser of TEM (1, 0) + TEM (0, 1) mode is studied in this paper using a 3-dimensional (3D) particle simulation. It was found that the laser can trap electrons in transverse and accelerate them with the longitudinal ponderomotive force at the same time. Through this electron trapping and acceleration scheme of TEM (1, 0) + TEM (0, 1) mode laser, the electron bunch is confined well in transverse and compressed remarkably in longitudinal. Therefore, a high energy, high density, and low emittances electron bunch is generated. For example, the result shows that for a laser with intensity of a0 = eE0 /mωc = 10, the laser spot size of w0 = 15λ, and the laser pulse length of Lz = 10λ, the maximum energy gain reaches 301 MeV and the average energy 57.7 MeV. The electron bunch transverse radius is about 350λ and the longitudinal size about 20λ. The property of this accelerated bunch is improved compared with that generated by the laser of TEM (0, 0) mode.

This paper will present the nonlinearity and dispersion effects involved in propagation of optical solitons, which can be understood by using a numerical routine to solve the nonlinear Schrödinger equation (NLSE). Here, Mathematica v5© (Wolfram, 2003) is used to explore in depth several features of optical solitons formation and propagation. These numerical routines were implemented through the use of Mathematica v5© and the results give a very clear idea of this interesting and important practical phenomenon. It is hoped that this work will open up an important new approach to the cause, effect, and correction of interference from secondary radiation found in the uses of soliton waves in lasers and in optical fiber telecommunication. It is believed that these results will be of considerable use in any work or research in this field and in self-focusing properties of the soliton (Osman et al., 2004a, 2004b; Hora, 1991). In a previous paper on this topic (Beech & Osman, 2004), it was shown that solitons of NLSE radiate. This paper goes on from there to show that these radiations only occur in solitons derived from cubic, or odd-numbered higher orders of NLSE, and that there are no such radiations from solitons of quadratic, or even-numbered higher order of NLSE. It is anticipated that this will stimulate research into practical means to control or eliminate such radiations.

Very high plasma densities can be obtained at the end of the implosion phase in inertial fusion targets, particularly in the so-called fast-ignition scheme (Tabak et al., 1994; Mulser & Bauer, 2004), where a central hot spark is not needed at all. By properly tailoring the fuel compression stage, degenerate states can be reached (Azechi et al., 1991; Nakai et al., 1991; McCory, 1998). In that case, most of the relevant energy transfer mechanisms involving electrons are affected (Honrubia & Tikhonchuk, 2004; Bibi & Matte, 2004; Bibi et al., 2004). For instance, bremsstrahlung emission is highly suppressed (Eliezer et al., 2003). In fact, a low ignition-temperature regime appears at very high plasma densities, due to radiation leakage reduction (León et al., 2001). Stopping power and ion-electron coulomb collisions are also changed in this case, which are important mechanisms to trigger ignition by the incoming fast jet, and to launch the fusion wave from the igniting region into the colder, degenerate plasma. All these points are reviewed in this paper. Although degenerate states would not be easy to obtain by target implosion, they present a very interesting upper limit that deserves more attention in order to complete the understanding on the different domains for inertial confinement fusion.

Small water droplets (20 micron in diameter) have been exposed to intense (∼ 1019 W/cm2) laser pulses in order to study ultrashort (∼ 35 fs) laser pulse driven ion acceleration. Ion emission spectra registered simultaneously in forward and backward direction in respect to the incident laser beam carry similar integral ion energy but show different ion cutoff energies. With simple model estimations on basis of the confined and spherical geometry of the droplet-target, we inferred acceleration field strengths of about (0.7–2) MV/μm. Up to 9% of the incident laser energy is converted to kinetic energy of ions, which have been accelerated to energies above 100 keV and up to 1.5 MeV. A laser pedestal at an intensity of about 10−7 of the peak intensity at 1–2 ns in front of the pulse peak still limits the achievable cutoff energies of emitted protons from the droplet. The observed increase of cutoff energies with an enhanced temporal contrast of the laser pulse is elucidated within a simple acceleration model.

This paper presents an effect of relativistic mutual interaction of two laser beams of different frequencies on the growth of a laser ripple in laser produced plasmas. The nonlinearity due to relativistic mass variation depends not only on the intensity of one laser but also on the second laser. Therefore, one laser beam affects the dynamics of the second beam and hence a mutual nonlinear interaction (cross-focusing) takes place. The dynamical equations governing the laser intensity of two laser beams and the perturbation present on one laser beam (ripple) have been set up and a numerical solution has been presented for typical laser plasma parameters. It is found that a change in the intensity of the second laser beam can affect the growth of the laser ripple significantly. This study is important in plasma beat wave excitation and collective laser particle accelerators.

High energy heavy ions were generated in laser produced plasma at moderate laser energy, with a large focal spot size of 0.5 mm diameter. The laser beam was provided by the 10 GW GSI-NHELIX laser systems, and the ions were observed spectroscopically in status nascendi with high spatial and spectral resolution. Due to the focal geometry, plasma jet was formed, containing high energy heavy ions. The velocity distribution was measured via an observation of Doppler shifted characteristic transition lines. The observed energy of up to 3 MeV of F-ions deviates by an order of magnitude from the well-known Gitomer (Gitomer et al., 1986) scaling, and agrees with the higher energies of relativistic self focusing.

Long term research in low activation materials is being pursued in fusion programs and the assessment of allowable elements and/or impurities from safety and repository reasons are being studied at Instituto Fusión Nuclear (DENIM), using ACAB code, for national ignition facility (NIF) and inertial fusion energy (IFE) reactors. Uncertainties in nuclear data are being considered, and experiments for validation of modeling will be presented. Multiscale simulation of radiation damage is now starting to be compared with experiments, and results on the simplest material can be reported as a function of impurities, temperature, and dose. Molecular dynamics (MD) allows us to identify stress-strain curve of FeCr ferritic steels under irradiation, and macroscopic conclusions can be advanced using simple models. However, a neutron source of enough intensity and adequate energy spectrum is needed which will be very peculiar in the case of pulsed IFE, as we claimed in past years. Development of international fusion materials irradiation facility (IFMIF) will be commented and compared with solutions such as spallation, and others using ultra-intense lasers for obtaining required irradiation magnitudes. Research on radiation damage in SiC composite is being pursued at macroscopic level, but basic knowledge is scarce. A systematic identification of type of stable defects is being presented with a new tight binding MD technique. Our research on simulation of silica irradiation damage will also be presented. The role of tritium, when elemental tritium (HT) and titrated water (HTO) derive in organically bound tritium (OBT) will be explained. The deposition and absorption processes are now being considered in our calculations giving more precision and accuracy to our conclusions of dosimetry effects. The role of HT versus HTO and the importance of re-emission process will be remarked, together with the long-term role of OBT.

In this work, we first presents a review of the work that research teams have developed in collaboration in order to determine the optical properties of plasmas during the recent years, and showing the achievements reached. The second part of this paper is devoted to one of these improvements, which is to include reabsorption of the radiation in the calculations of dense optically thick plasmas in non-LTE conditions. Two models recently developed for this purpose are presented. The quantitative study was focused on aluminum plasmas, which was obtained recently at LULI experiments.

The study of heavy ion stopping dynamics using associated K-shell projectile and target radiation was the focus of the reported experiments. Ar, Ca, Ti, and Ni projectile ions with the initial energies of 5.9 and 11.4 MeV/u were slowed down in quartz and arogels. Characteristic radiation of projectiles and target atoms induced in close collisions was registered. The variation of the projectile ion line Doppler shift due to the ion deceleration measured along the ion beam trajectory was used to determine the ion velocity dynamics. The dependence of the ion velocity on the trajectory coordinate was measured over 70–90% of the ion beam path with a spatial resolution of 50–70 μm. The choice of SiO2 aerogel with low mean densities of 0.04–0.15 g/cm3 as a target material, made it possible to stretch the ion stopping range by more than 20–50 times in comparison with solid quartz. It allowed for resolving the dynamics of the ion stopping process. Experimentally, it has been proven that the fine porous nano-structure of aerogels does not affect the ion energy loss and charge state distribution. The strong increase of the ion stopping range in aerogels made it possible to resolve fast ion radiation dynamics. The analysis of the projectile Kα-satellites structure allows supposing that ions propagate in solid in highly exicted states. This can provide an experimental explanation for so called gas-solid effect.

Two-dimensional (2D) FLASH simulations were run with Spitzer-Härm conductivity on and off in an attempt to simulate a laser-produced blast wave. Dissociation, ionization, recombination, and radiative cooling were not included. An initial Gaussian temperature profile with T0 = 120 eV and spot radius r0 = 25 μm was used assuming 1 μm thickness of the CH disk is ablated into the background nitrogen gas. Evolution of the blast wave differs slightly between the cases of Spitzer-Härm on and off, and neither case matches well with experiment. Due to the high temperatures involved, a thermal wave should be expected such that the Spitzer-Härm conductivity on case is more likely. A simulation run with an initial temperature of ∼ 4 keV might match better with experiment.

Characteristics of two-element (PbMg) laser generated plasma ions were studied using a mass-spectrometer. It was found that increasing the fraction of Mg leads to widening of the energy spectra of Pb ions by more than a factor of two, while the intensity of Pb ions of all charge states does not depend on the Mg fraction. This effect is explained by the friction existing between light and heavy ions during their expansion away from the target.

The Vulcan Nd:glass laser at the Central Laser Facility (CLF) is a petawatt (1015 Watts) interaction facility, designed to deliver irradiance on target of 1021W.cm−2 for the UK and international user community. The facility came online to users in 2002 and considerable experience has been gained operating Vulcan in this mode. The facility delivers a wide-ranging experimental program in fundamental physics and advanced applications. This includes the interaction of ultrahigh intensity light with matter, fast ignition fusion research, photon induced nuclear reactions, electron and ion acceleration by light waves, and the exploration of the exotic world of plasma physics dominated by relativity. We report on the first year's operation of the facility and the highlights of the experimental campaigns.

We give on overview of recent advances in collisionally pumped optical field-ionization soft X-ray lasers developed at LOA. Saturated amplification has been achieved on the 5d-5p transition in Xe8+ at 41.8 nm, and on the 4d-4p transition in Kr8+ at 32.8 nm. We demonstrate a significant increase of the energy output from the Xe8+ laser driven within two types of wave-guide. Finally, we present results of a pioneering work aimed to set up and characterize the first true soft X-ray laser chain.

Laser technology developments, including construction of a 286-TW Ti:Sapphire laser with a focused intensity of 1021W/cm2, installation of the TIL, prototype of the SG-III, and operation of the SG-II laser are presented. Results of the experiments on hohlraum physics, indirect-drive implosion, Thomson scattering, EOS, and X-ray laser are briefly introduced. Simulations and a code package, LARED, for target physics are outlined.