In Russia, the Iskra-6 laser facility with pulse energy of up to 300 kJ and nanosecond pulse duration was being planned (Kirillov et al., 2000). The possibility of thermonuclear ignition with this laser energy was a goal of the theoretical investigation at RFNC-VNIITF. Results of one-dimensional (1D) and two-dimensional (2D) modeling of indirect-driven targets for ignition on the Iskra-6 laser facility are presented. Sensitivity of cryogenic single-shell and non-cryogenic double-shell targets to radiation flux non-uniformity and shells roughness are studied.

This new project relies on the capabilities collocated at Los Alamos in the Trident laser facility of long-pulse laser drive, for laser-plasma formation, and high-intensity short-pulse laser drive, for relativistic laser-matter interaction experiments. Specifically, we are working to understand quantitatively the physics that underlie the generation of laser-driven MeV/nucleon ion beams, in order to extend these capabilities over a range of ion species, to optimize beam generation, and to control those beams. Furthermore, we intend to study the interaction of these novel laser-driven ion beams with dense plasmas, which are relevant to important topics such as the fast-ignition method of inertial confinement fusion (ICF), weapons physics, and planetary physics. We are interested in irradiating metallic foils with the Trident short-pulse laser to generate medium to heavy ion beams (Z = 20–45) with high efficiency. At present, target-surface impurities seem to be the main obstacle to reliable and efficient acceleration of metallic ions in the foil substrate. In order to quantify the problem, measurements of surface impurities on typical metallic-foil laser targets were made. To eliminate these impurities, we resorted to novel target-treatment techniques such as Joule-heating and laser-ablation, using a long-pulse laser intensity of ∼ 1010 W/cm2. Our progress on this promising effort is presented in this paper, along with a summary of the overall project.

A two-dimensional (2D) multigroup radiation transfer hydrodynamics code LARED-R-1 is used to simulate a supersonic wave experiment performed earlier by the Livermore group. The main result is that, contrary to the conclusion of Back et al. (2000a), the average-atom opacity model is sufficient to explain the obtained experimental results, provided that an adequate description of the radiation transport was used. The simulation results from LARED-R-1 show the spectrum of radiation in foam with radius and length of several optical depths is not in Planckian distribution and the angular intensity distribution is anisotropic.

The energy transfer rate between the lattice and electrons in strongly nonequilibrium electron-phonon system of crystalline aluminum created by ultrashort femtosecond laser pulse is calculated in the frame of two-temperature model for a wide range of electron temperature. It is shown that the energy, transmitted from electrons to the lattice per unit volume of the crystal per unut time strongly increases when taking into account the umklapp processes in the electron-phonon scattering.

Due to their particular properties (low emittance, short duration, and large number density), the beams of multi-MeV protons generated during the interaction of ultraintense (I > 1019 W/cm2) short pulses with thin solid targets are suited for use as a particle probe in laser-plasma experiments. When traversing a sample, the proton density distribution is, in general, affected by collisional stopping, scattering and deflections via electromagnetic fields, and each of these effects can be used for diagnostic purposes. In particular, in the limit of very thin targets, the proton beams represent a valuable diagnostic tool for the detection of quasi-static electromagnetic fields. The proton imaging and deflectometry techniques employ these beams, in a point-projection imaging scheme, as an easily synchronizable diagnostic tool in laser- plasma interactions, with high temporal and spatial resolution. By providing diagnostic access to electro-magnetic field distributions in dense plasmas, this novel diagnostics opens up to investigation a whole new range of unexplored phenomena. Several transient processes were investigated employing this technique, via the detection of the associated electric fields. Examples provided in this paper include the detection of pressure-gradient electric field in extended plasmas, and the study of the electrostatic fields associated to the emission of MeV proton beams in high-intensity laser-foil interactions.

Stochastic instabilities are studied considering the motion of one particle in a very high intensity wave perturbed by one or two low intensity traveling waves. Resonances are identified and conditions for resonance overlap are studied. PIC code simulation results confirm the stochastic heating.This paper was presented at the 28th ECLIM conference in Rome, Italy.

High gain free electron laser devices, operating in the self amplified spontaneous emission regime, are under construction and was designed as the next generation of synchrotron radiation sources. In this paper we discuss the relevant physical aspects and derive simple relations for laser and higher order harmonic power, which can usefully be exploited in the preliminary design of these sources

Laser matter interaction in the regime of super-intense and ultra-short laser pulses is discovering common interests and goals for plasma and elementary particles physics. Among them, the electron laser wakefield acceleration and the X/γ tunable sources, based on the Thomson scattering (TS) of optical photons on accelerated electrons, represent the most challenging applications. The activity of the Intense Laser Irradiation Laboratory in this field will be presented.

Patterns of absorption and reflection of an ultrashort laser pulse by plasma with a solid-state density, which are realized in the mode of the normal skin effect, are studied. If the pulse power is so high to provide the electron heating during the time shorter than the reciprocal fundamental frequency, a nonlinear suppression of absorption takes place and the spectrum of the reflected radiation contains odd harmonics of the fundamental frequency.

Interactions of sub-nanosecond pulses of kJ-class iodine laser “PALS” with low-density foams and acceleration of Al foils by the pressure of the heated foam matter are investigated here, both experimentally and theoretically. X-ray streak camera is used for evaluation of the speed of energy transfer through the porous foam material. The shock-wave arrival on the rear side of the target is monitored by optical streak camera. Accelerated foil velocities, measured by three-frame optical interferometers, and shadowgraphs, reach up to 107 cm/s. The accelerated foil shape is smooth without any signature of small-scale structures present in the incident laser beam. Conversion efficiencies as high as 14% of the laser energy into the kinetic energy of Al foil are derived. Experimental results compare well with our two-dimensional hydrodynamics simulations and with an approximate analytical model.

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.

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.

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.

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.

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.

We present the current status-of-the-art in Stark broadening theory as a theoretical basis for diagnostics of low temperature plasmas in gas discharges, and of high temperature laser produced or z-pinch dense plasmas. The diagnostics abilities vary depending on the parameters of the gas discharges, or on the range of intensity, and duration of the laser or z-pinch pulses. In the case of high temperature plasmas, besides the conventional diagnostics based on the Stark broadening, the contemporary possibilities of UV and XUV interferometry for plasma density measurements and of tomography reconstruction of the macroscopic gradients of temperature and densities in laser produced plasmas are discussed.

The paper gives a review of investigations on generation of soft X-rays and EUV using a gas puff target irradiated with high-power laser pulses performed during last few years. In the studies a newly developed double-stream gas puff target approach was used. The gas puff targets were irradiated with various lasers, including Nd:glass, Kr:F, Nd:YAG, and iodine lasers. The aim of the studies was to develop efficient and debris-free laser plasma X-ray and EUV sources for applications in microscopy, lithography, micro- and nanotechnology.

We investigate intermediate unstable modes between two stream and filamentation instabilities. We detail the problem of the angle between the wave vector and its electric field and use an electromagnetic formalism allowing for any value for this angle. We display analytical results for 3 different models: cold beam-cold plasma, cold beam-hot plasma and cold relativistic beam-hot plasma. We demonstrate that plasma temperature prompts a critical angle for which waves are unstable at any k and show that for a relativistic beam, the most unstable waves are obtained for wave vectors which are neither normal nor perpendicular to the beam.

This paper reports on the status of the PHELIX petawatt laser which is built at the Gesellschaft fuer Schwerionenforschung (GSI) in close collaboration with the Lawrence Livermore National Laboratory (LLNL), and the Commissariat à l'Energie Atomique (CEA) in France. First experiments carried out with the chirped pulse amplification (CPA) front-end will also be briefly reviewed.

We investigated the optical properties of pure copper irradiated by a femtosecond laser pulse. Self-absorption of 50-fs laser pulses at 800 nm and 400 nm wavelengths (below and above the interband absorption threshold, respectively) is studied for peak laser intensities up to 1015 W/cm2. Theoretical description of laser interaction with copper target is developed, solving numerically the energy balance equations for electron and ion subsystems together with Maxwell equations for laser radiation field inside the target. The theory accounts for both intraband and interband absorption mechanisms. We treated in detail the changes in electron structure and distribution function with an increase in electron temperature, as well as the ensuing changes in thermodynamic properties, collision frequencies, optical and transport coefficients. Experimental work on self-absorption of femtosecond laser pulses in copper targets at 800 nm and 400 nm wavelengths is ongoing. Results for 800 nm wavelength are reported. Theory and experiment are in good agreement.