The results of a preliminary experiment on laser foam interaction performed at the ABC installation of the Associazione EURATOM-ENEA sulla Fusione are presented. Plastic foams with density of 5 - 20 mg/cm³ were irradiated with light produced from the neodymium laser of ABC (λ = 1.054 μm) and processed through a proper optical system to produce near field ISI smoothed radiation at ≈10¹³W/cm² on the target. The use of a smoothed beam was essential to detect in the plasma and in the accelerated dense phase evolving features related to the target foam structure without mixing with those of the irradiating beam. Structures in the plasma corona and in the dense phase were detected by optical shadography of foam slabs. In the same experiment time-dependent transmission of laser light through slabs of foams was measured by target imaging and masking on a photodiode (bandwidth of the system 5 GHz).

The new results obtained in experiments on the "Mishen" facility with laser-irradiated low-density porous media are presented and discussed. The variety of optical and X-ray diagnostic methods was used to characterize physical processes in laser-irradiated (λ = 1.054 μm, τ = 3 ns, I = 10¹³ - 10¹⁴ W/cm²) plane porous samples of different microstructure and chemical composition; an average density was varied in the range from 1 mg/cm³ to 20 mg/cm³. The features of laser light absorption and scattering as well as the efficiency of energy transport through porous layer to solid-density foil installed at the target rear-side were studied in dependence on the incidence angle of laser beam, average density, thickness and structure of irradiated porous layer. The plasma formation and energy transport processes are found to differ significantly in laser-irradiated low-density matter of different microstructure (chaotic fibrous structure agar, quasi-regular cellular polystyrene foam). The expansion of high-Z plasma was studied in experiments with porous layers deposited on the surface of plane high-Z targets. Desirable suppression of X-ray emitting plasma motion by porous material was obtained.

In the indirect scheme of ICF, a high-Z ablator is used as the inside wall material of the hohlraum cavity. This choice is made because a high-Z plasma is an efficient x-ray convertor, and it offers a high opacity to radiation conduction into the cavity wall. Recently it had been shown that a mixture of two or more high-Z elements can provide a higher opacity than that of any single materials used, and optimum composition was predicted from computer simulations. It is expected that such a wall will provide maximum conversion of absorbed laser energy into soft x-ray radiation. In this paper, we present a comparative experimental study of soft x-ray emission from copper-gold mix-Z planar targets of different atomic compositions irradiated at a laser intensity of ~10¹³ W/cm² (λ = 0.532μm). Spectral features of the soft x-ray radiation were recorded using a transmission grating spectrograph. Maximum enhancement in radiation intensity in the spectral region ~ 40 - 120 Å was observed for a mix-Z target of atomic composition of Cu 0.57 - Au 0.43. This is in broad agreement with theoretical results of opacity calculations performed for different atomic compositions using a screened hydrogenic average atom model.

A suite of experiments to measure the growth of turbulent mix in a compressible, convergent geometry has been performed on the Omega laser facility at LLE, Rochester NY. These employ a radiographically opaque marker layer to set the initial conditions at the unstable interface and to provide a diagnostic of the induced density gradients. The marker is sandwiched between a plastic ablator and a low-density polystyrene foam cylinder. The implosion is driven by uniform irradiation by 50 laser beams in an impulsive acceleration mode. The ablative drive launches a strong shock, causing the marker to become mixed into both the foam and the ablator. Compressible Richtmeyer Meshkov effects, modified by Bell-Plesset instability dominate the instability growth. The dependence on initial surface roughness is studied along with the time history of the evolution.

One proposed capsule design for the Laser Megajoule facility is analyzed to determine surface finish specifications required to achieve ignition and propagated burn. We estimate the sensitivity of this capsule to hydrodynamic instabilities by means of direct two-dimensional simulations. Configuring multimode perturbations located at the DT ice and ablator surfaces, the fusion yield is predicted.

Laser driven shock wave experiments were performed to study the equation of state (EOS) of Cu material using impedance-matching technique with Al as reference material. An Nd:YAG laser chain (2 Joule, 1.06 μm wavelength, 200 ps pulse FWHM) was used for generating shocks in the planar Al foils and Al-Cu layered targets. EOS of materials at shock pressure up to 11 Mbar is obtained with pressure enhancement by a factor of 1.67 at Al-Cu interface. Numerical simulations performed using one-dimensional radiation hydrodynamic code MULTI show close agreement with the experimental value of shock pressure enhancement. Simulation reveals the fact that 5 - 6 μm thickness of Al foil as a reference material is sufficient to prevent the x-ray preheating effect as well as to attain planar and steady shock wave propagation for a given laser beam used in the experiment. The experimental Hugoniot data points obtained are in excellent agreement with the existing standard SESAME data and with other reported experimental results.

We report on an extensive series of experiments using 2ω light on a variety of gaseous targets at the HELEN laser facility at AWE. The aims of the experiments were to investigate laser-plasma interactions and hot electron generation for 2ω light, and to test schemes for efficiently producing multi-keV X-rays. The experiments were diagnosed by an extensive suite of optical and x-ray instrumentation, including streaked SRS and SBS spectrographs, hard X-ray and Dante measurements. The targets used to data have been filled with C₅H₁₂, CO₂ and Kr. These three targets give very different backscatter, including almost no backscatter from the Kr targets, showing that plasma composition can also be used to minimize backscatter losses. These data also indicate that is possible to produce or quench hot electron production by varying the plasma composition, even near quarter critical density.

An experimental study of space-resolved x-ray emission from a laser produced magnesium plasma expanding in a helium gas background has been performed at different gas pressures up to 125 mbar. A strong enhancement in MgXI He-α resonance (1s^{2 1}S_o - 1s2p ¹P₁ at 9.17Å) and intercombination (1s^{2 1}S_o - 1s2p ³P₁ at 9.23Å) line emission is observed in the blast wave region extending upto ~6 mm from the target. Results of measurements of pressure dependence of peak x ray line intensity, onset distance, size of the emission region, and intensity ratio of the two lines are described and the role of background gas to explain the observed behavior is discussed. At optimum background pressure of about 40 mbar there is an order of magnitude increase in the x-ray line intensity compared to that for a gas pressure of few mbar. Charge exchange and three body recombination rates have also been analyzed for their relative contribution towards this intensity enhancement.

The pressure enhancement due to impedance-matching at the interface between the two-step layered targets has been well studied and established technique for EOS measurement of materials in laser driven shock wave experiments. A detailed numerical simulation study of shock wave propagation through Al standard material in laser driven shock wave experiments was performed using a 1-D radiation hydrodynamic code MULTI. The definitive role of mesh thickness was noticed. The experimental results of shock pressure enhancement in Al-Cu and Al-Au, layered targets corroborated with the numerical simulation results. Simulations were subsequently extended to plane-layered targets such as CH-Al, CH-Cu an CH-Au targets. It is shown that with proper tailoring of laser and target parameters, shock pressures in the range of up to 30 to 50 Mbar could be achieved with relatively moderate intensity lasers (I_L = 6 - 8x10¹³ W/cm²; Pulse FWHM 600 - 800 ps). The numerical simulations also enumerate appropriate conditions to maintain the steadiness of shock waves with minimal preheat effect.

In the present work a theoretical model of plasma absorption and emission is developed and applied to explanation of some experimentally observed spectra from laser-produced plasmas under conditions being of interest for the ICF as well. The targets for ICF contain the layers of various materials: Be, Al, Cu, SiO₂, agar (C₁₂H₁₈O₉)_n, and others. Of interest is the code, calculating the optical characteristics of plasma of a complicated chemical composition in a broad range of plasma conditions (density and temperature). This spectroscopic modeling has been performed by a collisional-radiative model DESNA for non-LTE mixtures involving detailed structure of excited levels of all charge states from a neutral atom to a fully ionized ion. In the paper we present some new results of theoretical investigation of x-ray emission in the conditions close to real experiments on interaction of short and powerful laser pulses with targets. The simulation and available experimental results are in good enough agreement for various target materials (C, Al, Cu).

The hydrodynamic-radiation codes are used for a simulation of mean Rosseland and Planck opacities from different models similar to Hartree-Fock model, average ion model, detailed configuration accounting model, and so on. At present the necessity in such a data is high especially for plasma of mixture of ions. In this work we present the results on a comparison of mean opacities calculated by means of various codes and models. The calculations were carried out for the local thermodynamic equilibrium (LTE) plasmas of various chemical elements and mixtures. The models under consideration are the DESNA model and the THERMOS, JIMENA (analytical opacity formula), and the LEDCOP codes. The main results and conclusions about applicability of each of the approaches based on the comparison are presented for LTE plasma on Be, C, Al, SiO₂. After verification, the results of the DESNA model calculations will be used to create the database on mean opacities in a broad range of plasma density and temperature for various materials, including the case of non-LTE plasma.

Results are presented for a theoretical model, known as the ion model (IM), recently elaborated to calculate the radiative opacity of hot dense plasma. The density-functional theory is used to obtain the general set of self-consistent field equations that describe the state of the whole ensemble of plasma atoms and ions. Theoretical features of the Hartree-Fock-Slater model (HFS), the detail configuration accounting (DCA) and the ion model (IM), are considered. The (IM) model is used for optimal selections of compound chemical compositions for laser and heavy ion target designs.

The results of experimental and theoretical investigations of craters originating in solid targets of different materials when powerful Nd:glass laser pulse irradiates the surface at flux densities in the range of 10¹⁰ - 10¹⁴ W/cm² are presented. The experimentally observed dependencies of crater depth and ablated mass on laser pulse energy and target material properties are analyzed employing the theory of shock wave initiation and propagation under the action of the plasma-producing laser beam. From the comparison of the theoretically deduced and experimentally observed dependencies, a simple formula is derived allowing to determine the pressures in the shock wave and in the plasma corona using the measurements for the crater depth and ablated mass.

To experimentally model laser-plasma interaction in low-density porous media, we have started irradiating plastic multifoil targets with a single 1.054 μm laser beam at approximately 10¹⁴ W/cm² at the "Mishen" facility. A first foil directly irradiated was thin enough to burn through and rapidly become underdense. Acceleration and expansion of the high-temperature plasma inward the target, its stagnation under impacts on successive foils, and reverse shock propagation into the plasma corona occur during the laser pulse. Hydrodynamics of plasma in multifoil targets was studied by analyzing the spectral shifts of backscattered laser light and its harmonics. The experimental data interpretation employs results of the one-dimensional hydrodynamic simulation.

Interactions of PALS iodine laser beam with low density porous targets and porous targets with Al foil attached to the rear side were studied using multi-frame interferometry and shadowgraphy. Electron density profiles at the front and the rear side of the targets were reconstructed from interferograms. Velocities of Al-foils accelerated by the pressure of the heated porous material were established from shadowgrams. A good symmetry and absence of local perturbations were observed both in the rear side plasmas of porous targets and in the shape of the accelerated Al-foils. Measured rear side velocities are in a good agreement with the presented theory of laser interactions with porous materials.

Results from PALS facility laser-massive Al target interaction experiments are reported. Main attention is devoted craters formation under the action of laser pulses of various energy (from 100 J up to 600 J), intensity (from 10¹³ W/cm² up to 10¹⁵ W/cm²), laser wavelength (0.438 μm and 1.315 μm), and focal beam radius (from 35 μm up to 600 μm). Crater replicas were made of wax and their depths and radii were subsequently obtained by microscopy measurements. Duration of the laser-pulse-initiated shock wave propagation into the targets was much longer than that of the laser pulse itself (400 ps). This was an important feature of the experimental arrangement. Theoretical model of the post-pulse crater formation by the shock wave propagating and decaying in solids after the end of the laser pulse is presented and applied for explanation of the results obtained in experiments.

United algorithm LATRANT for a simulation of a radiative gas flows in 2D cylindrical geometry has been developed on the basis of the gas-dynamic code ATLANT and the program for the radiation transport calculation LATRA. The developed program takes into account the radiation transport in the multi-group approximation and the gas dynamics within the framework of the improved Lagrangian method. Two modifications of LATRANT code for spherical and plane problems in r-z geometry respectively have been developed. A quasi-one-dimensional simulation of the heating and compression of a two-layer spherical target irradiated by isotropic X-rays has been carried out to demonstrate qualitative difference between LATRANT and three-temperature approximation results. Essentially 2D simulation of compression of the same target by the angular-nonhomogeneous radiation has revealed fuel preheating and radiative symmetrization of the inner shell compression, which are typical for the indirect compression schemes. Transition of infrared radiation to X-rays has been observed in 2D simulation of plain Al foil acceleration by Nd laser pulse.

Hot electrons may significantly influence interaction of ultra short laser pulses with solids. Accurate consideration of resonant absorption of laser energy and hot electrons generation at a critical surface was achieved through the developed physical and mathematical models. 2D ray tracing algorithm has been developed to simulate laser beam refraction and Bremsstrahlung absorption with allowance for non-linear influence of a strong electromagnetic field. Hot electrons transport was considered as a straight-line flows weakening by a friction force calculated in the approximation of the average state of ionization. Developed models were coupled with 2D Lagrangian gas dynamic code "ATLANT" that takes into account non-linear heat transport. The developed program has been applied to simulate irradiations of Al foils by picosecond laser double pulses. Hot electrons transport and heating resulted in thin foil explosions. The transition from exploding foil regime to the ablative one with foil thickening has been simulated and analyzed at various values of laser light intensity.

We have suggested a concept of laser-driven shock tube (LST) for generation of hypersonic shock waves (SW) in gases and compression waves in liquids. This novel laboratory technique might be applied to the studies of various fundamental hydrodynamic phenomena such as development of hydrodynamic instabilities at contact interfaces between different liquids and gases accelerated by shock waves, hypersonic gas flow around bodies, effects of strong shock wave refraction and cumulation in time scale of several microseconds and space scale of ten millimeters. These problems are of great importance in Inertial Confinement Fusion, comsology, astrophysics, and aerospace engineering. In this paper we present both numerical simulations and first experimental results to verify the laser-driven shock tube concept for studying of strong SW generation in the air.

The 2D codes "ATLANT-C" (Lagrangian coordiantes) and "NUTCY" (Euler coordinates) have been used for the modeling of experiments performed at laser installations "GARPUN" (KrF-laser with pulse energy about 100 J and duration of 100 ns) and "PICO" (Nd-laser with pulse energy of 30 J and duration of 3 ns). Both laser installations are located at Lebedev Physical Institute, Moscow, Russia.

We report on experiments conducted on the "Mishen" facility, in which thin burn-through and thick planar plastic foil targets were irradiated with a single 1.054 μm laser beam at intensities of ~5•10¹² - 10¹⁴ W/cm². Features of the stimulated Brillouin scattering along with the processes of resonance absorption, ion acoustic decay instability, and two- plasmon decay instability were studied. Interaction processes were identified from analysis of time behavior of backscattered light spectra at fundamental laser frequency, second and three-halves harmonics, as well as from transmitted light measurements. Experiments with obliquely irradiated targets of different types were also carried out and some interesting results were obtained. Comparison of the results with the published data is presented.

In inertial confinement fusion, pellet implosion efficiency can be severely limited by hydrodynamic instabilities. In particular, the ablation front instability -- ablative Rayleigh-Taylor instability -- plays a major role. Linear stability analyses of ablation fronts have been mostly performed under several assumptions: isobaricity, steadiness, continuous/discontinuous flows. In more general cases, such analyses inevitably resort to solving initial boundary value problems for linear perturbations. The physical model used here is that of ideal gas dynamics with nonlinear heat conduction. A general numerical approach for solving both one-dimensional flows and linear perturbations is briefly presented. Linear perturbation evolutions from initial external surface defects are investigated for a self-similar ablation flow of a semi-infinite slab, initiated from rest.

A consideration of turbulent mixing is especially important in the laser fusion problems where the intensities of shock waves and acceleration fields achieve great values and the arising instabilities lead to a considerable reduction of thermonuclear yield. A standard set of thermodynamic values is insufficient to describe a process of turbulent mixing because a classical set averaging takes no account of the coherent structures, which are essential for the process. However, there is supposed to be a certain "reasonable" number of parameters characterizing a further development of turbulent process, as evidenced by numerical calculations and experimental data. An attempt has been made to determine numerically the turbulent mixing steady-state formation at an example of two-dimensional Rayleigh-Taylor problems. In order to define such hidden characteristics one applied a mathematical apparatus of artificial intellect used effectively in fuzzy logic problems. The process states were coded by wavelet transform allowing one to consider spatially localized structures. The processes under study were determined by numerical calculations. As a result one obtained a steady-state representation of an RT-mixing process. The stable parameters are expressed through linear combinations of wavelet coefficients and Fourier transforms of the physical fields.

We study with ARWEN code a target design for ICF based on jet production. ARWEN is 2D Adaptive Mesh Refinement fluid dynamic and multigroup radiation transport. We are designing, by using also ARWEN, a target for laboratory simulation of astrophysical phenomena. We feature an experimental device to reproduce collisions of two shock waves, scaled to roughly represent cosmic supernova remnants. ANALOP code uses parametric potentials fitting to self-consistent potentials, it includes temperature and density effects by linearized Debye-Huckel and it treats excited configurations and H+He-like lines. Other is an average SHM using the parametric potentials above described. H-like emissivities and opacities have been simulated, using both, for Al and F plasmas with density 10²³ cm^-3 and temperatures higher than 200 eV. Advanced fusion cycles, as the aneutronic proton-boron 11 reaction, require very high ignition temperatures. Plasma conditions for a fusion-burning wave to propagate at such temperatures are rather extreme and complex, because of the overlapping effects of the main energy transport mechanisms. Calculations on the most appropriate ICF regimes for this purpose are presented. A new Monte Carlo procedure estimates effect of activation cross section uncertainties in the accuracy of inventory calculations, based on simultaneous random sampling of all the cross sections; it is implemented in activation code ACAB. We apply, with LLNL, to NIF gunite chamber shielding with reference pulsing operation. Preliminary results show that the 95 percentile of the distribution of the relative error of the contact dose rate can take values up to 1.2. Model is promising for uncertainty analysis of pulsed activation in IFE PP by using a continuous-pulsed model. Neutron intensities versus time after target emission are presented for IFE protections: LiPb/Flibe, including spectral effects. HT evaluation indicates that 90-98% of the total dose comes from ingestion of agriculture and meat, and the rest from inhalation by re-emission. A multiscale modeling (MM) study of pulse irradiation in Fe is presented up to microscopy; we give differences with continuous irradiation. Experimental validation of MM, using Fe⁺ in Fe, is being performed under VENUS II Spanish project with CIEMAT. Multiscale Modeling of SiC is reported; new defects energetic emerge using a new tight-binding molecular dynamics which has been proved in basic crystal parameters.

In experiments for the so-called Cone Focused Fast Ignition the imploded material was found contaminated by the cone high-Z material. In this paper the thermonuclear ignition thresholds for a fuel contaminated at atomic level were evaluated as function of the contaminant fraction. A short pulse of protons was used to start the ignition of a cylindrical assembly of compressed fuel uniformly contaminated at atomic level by gold. As a reference, a study for the ignition of a clean target at different proton energies was first performed and, after this, the ignition conditions for contaminated targets were found for a selected proton energy. Protons with proper energy can be used to mock-up deposition by fast electrons so that part of the study can be considered useful to predict the performances also for this energy vector.

Recent experiments at the HELEN laser at AWE have focused on investigations into the performance of a series of scaled NOVA halfraum targets. These were varied from scale 1 to scale 0.1, and used a single beam at 0.53 μm to irradiate the target. The aim of these experiments was to investigate performance limitations for higher temperature small hohlraums. Target diagnostics included time-resolved X-ray power measurements, full aperture measurements of stimulated Raman and Brillouin backscatter, and time-integrated soft and hard X-ray spectrographs. Analyses of the results from this campaign are presented with particular emphasis on the conditions present in the smallest scale targets, including comparison with calculated performance.

Review of recent results on direct ignition of ICF targets are presented. Main attention is focused on the second stage of direct ignition-heating of preliminary compressed thermonuclear fuel and burning wave initiation in it by the action of igniting driver pulse. There are discussed the main features of the direct ignition of ICF target by the initiating drivers of perspective types, such as fast electron beam of laser-produced plasma, light ion beam of laser produced plasma, heavy ion beam from accelerator, X-ray pulse and accelerated macroparticle.

Targets of the "Laser Greenhouse" (GH) type are very promising ones for direct laser compression. The key feature of this type of targets is the presence of a layer of low-density volume structured medium, which surrounds a thermonuclear cell and acts as the laser radiation absorber. Some methods to achieve highly symmetrical compression of these targets by small (e.g. two) number of laser beams (or beam clusters) have been presented earlier. Simulations of compression of targets for total laser pulse energy of 100 kJ and 2.1 MJ have proved, that this type of targets allows one to achieve combustion and effective burn. In the paper we introduce the results of 2D simulations of some processes, which are specific to this design of targets. The attention is paid to the problem of symmetry of compression. We also have performed calculations of neutron yield of the target designed for compression by two beams with full energy of 2.6 kJ, and series of 2D simulations to model some microscopic processes in the absorber. The experiments on compression of the targets at energy level of 2.6 kJ can be performed on a number of present laser installations.

The implosion of an indirectly driven optimized capsule for ICF is analyzed. We distinguish two media in the non-ablated capsule: the central hot spot and the cold shell, the boundary of the hot spot is defined such that this medium has no heat conduction losses, the features of each medium are described by mean quantities. The integral momentum conservation equation for volume of variable mass gives the rocket model for the acceleration phase, it is corrected to take into account the beginning of the acceleration. With approximations it gives the maximum implosion velocity. The entropy conservation is generalized for a non uniform medium of variable mass, it indicates what is the invariant quantity hidden in the hot spot during implosion and shows that the deceleration is approximately isobaric. The hot spot features and the implosion velocity in deceleration can be deduced from these results. The hot spot mass is obtained by integrating the heat conduction flux inside the hot spot. In the capsule parameters determining the ignition condition, the mass and the entropy of gas has to be included. All these results are compared with numerical simulations.

In all recently proposed schemes for laser-driven Fast Ignition (FI) of Inertial Confinement Fusion (ICF) targets, two key elements are the conversion of the energy of a Petawatt laser pulse into a beam of strongly relativistic electrons and its transport through a dense plasma or a solid target. The electron beam may either drive ignition directly or be exploited to acccelerate a proton beam which in turn is used to ignite the target. Both approaches to FI involve a number of physical processes that are challenging for theory and simulation. In this paper, theoretical and numerical investigations are presented concerning several fundamental issues of relevance to FI, including electron beam instabilities, electron transport in solid-density materials, and requirements for proton beam driven ignition.

Thermal x-ray radiation was generated and confined inside a spherical gold cavity of 1.2 mm diameter that was heated by a 50 J/1 ns laser pulse at 1.053 μm wavelength. The laser intensity on the inner surface of the cavity was ~5x10¹³ W/cm². The x-ray spectra recorded on high sensitivity x-ray film using a transmission grating spectrometer (TGS) positioned normal to the laser beam direction were analyzed to obtain the radiation temperature of the cavity. The unfolded x-ray spectra from the cavity have most of the emission between 15 - 60 Å with peak emission at 20 - 35 Å. The Planckian spectral fit to the x-ray spectra suggests a peak blackbody temperature of 90 eV inside the cavity.

By means of Monte-Carlo modeling of thermonuclear (TN) burn wave propagation in spherical laser deuterium-tritium targets criteria of fast ignition are elaborated and corresponding energy gain is evaluated. The critical ignitor parameters are calculated both for homogeneous and inhomogeneous targets with different parameters of main fuel. It is shown that in strong inhomogeneous target plasma the minimum values of required ignition energy could increase twice. Besides it is shown that critical values of ignitor dimension and energy are dependent on different distribution of energy between the electrons and ions of ignitor plasma. If all the additional thermal energy is coupled to ignitor electrons the value of corresponding ignition energy is 3 ÷ 4 times as many as in the case of equal initial temperature of ignitor ions and electrons. The overcritical burn efficiency and target gain is practically independent on ignition origin and may be evaluated with a good accuracy by the simple asymptotic expression.

This paper reviews the highlights of the high intensity laser-plasma experiments achieved with the six-beam and the 100 TW LULI laser facilities, as well as the progress of the LULI 2000 project. This covers fields of laser fusion, equations of state, hgih energy particle emission, atomic physics, X-ray production and laser developments.

The experiment of Badziak et al has shown that irradiation of copper by 1.5 ps laser pulses produced 50 times lower maximum ion energies than the 22 MeV expected after relativistic self focusing from laser pulses of about ns duration. This discrepancy was confirmed in the following reported experiments specifically designed for this clarification, where MeV Au⁺³⁰ maximum ion energies needed 400 times higher intensity with ps pulses than with 0.5 ns pulses. Comparing the theory for generating the fastest ions by relativistic self focusing and of the second fastest group by a quiver-collision model, we arrived at the conclusion that the mentioned ps-TW-generated ions are not following these usual theories but that a skin depth model with exclusion of relativistic self focusing explains the experiments. The essential importance is the suppression of the prepulse. We conclude how the experiment by Norreys et al. with the highest ever reported fusion gains may be increased to fusion reactor conditions if our results of prepulse control and suppression of relativistic self focusing would be applied following our skin layer interaction model. This extends the fast ignitor to the nonlinear-force block ignition without plasma precompression.

The paper presents a review of recent studies of plasmas produced in various experimental conditions performed mainly at the IPPLM and partially at the PALS Joint Research Laboratory ASCR in Prague in an international cooperation. These investigations were directed towards the clarification of the physical processes in such plasmas as well as at the optimization of sources of multi-charged ions for various applications. A 1-ps terawatt Nd:glass laser system (pulse energy up to 1 J, wavelength: 1053 nm, power density up to 10¹⁷ W/cm²) was employed for the experiments carried out at the IPPLM in Warsaw. Also, an option of this system operating with the 0.5 ns pulse (power density up to 10¹⁴ W/cm²) for comparative studies was used. In common experiments at the PALS JRL in Prague we used the PALS iodine laser system producing up to 1.2 kJ in a 0.4 ns pulse at 1315 nm wavelength or 0.25 kJ at 438 nm (third harmonic) wavelengths. The time-of-flight measuring systems namely: different ion collectors and an electrostatic ion energy analyzer were employed as main diagnostic methods. The properties of ion emission were investigated at various experimental conditions with the use of different massive and thin foil targets.

We report on multi-MeV ion beam generation from the interaction of a 10 TW, 400 fs, 1.053 μm laser focused onto thin foil targets at intensities ranging from 10¹⁷ to 10¹⁹ W/cm². Ion beam characteristics were studied by changing laser intensity, the preformed plasma scale-length and target material initial conductivity. We manipulated the proton beam divergence by using shaped targets. We observed nuclear transformation induced by high-energy protons and deuterons. A fully relativistic two-dimensional particle-in-cell simulation modeled energetic ion generation. These simulations identify the mechanism for the hot electron generation at the laser-plasma interface. Comparison with experiments sheds light on the dependence of ion-energy on preplasma scale length and solid density plasma thickness as well as relates ion energies for multi-species plasma.

Analysis and particle-in-cell (PIC) simulations of fast particles produced by a short laser pulse with duration of 40 fs and intensity ≥ 10¹⁸ W/cm² interacting with a foil target are performed. Initially, the plasma density distribution of the foil target has a smooth gradient with the scale-length of plasma density varying across it. The absorbed laser energy is transferred to fast electrons, which interact with the foil and are partially ejected from the foil surface. These electrons produce an electric field that causes an ion beam to be emitted from the foil. We analyze the different mechanisms of ion acceleration in the foil plasma and the influence of density gradient and other laser and plasma parameters on ion acceleration. The angular distributions of the ejected electrons and ions are calculated. The optimum laser-plasma parameters needed to achieve the most highly focused ion beam are analyzed.

Using our 3D PIC code VLPL (Virtual Laser-Plasma Laboratory) we study Laser-Wake Field Acceleration (LWFA) of electrons by laser pulses shorter than or comparable with the plasma wavelength. When driven into the highly non-linear wave breaking regime the plasma wave mutates to a solitary bubble that generates ultra-short dense bunches of electrons with quasi-monoenergetic energy spectra. The electron bunches may have density high enough to forward-scatter the tail of the laser pulse. The forward scattering results in blue shift of the laser pulse after interaction. The energetic electrons make betatron oscillations in transverse fields of the plasma wave and emit hard X- and γ-rays. We show that an extremely bright source of GeV γ-quanta can be built due to the combination of an external electron beam and the laser wake field. The GeV γ-source can be particularly used as an efficient plant for positron production.

The soft x-ray emission from He-like and H-like were obtained by using the double nozzle gas-puff (Nitrogen, and Oxygen) target irradiated by the laser which delivered a laser energy of 50 mJ in 400 ps pulse width. Efficient absorption of the incident laser energy into the double gas-puff target was demonstrated experimentally such as 15%, and 29% for Nitrogen and Oxygen, respectively. The sub keV x-ray emission from He-β(1s²-1s2p, 1s²-1s3p, and 1s²-1s4p) lines are observed around the 0.4 nm wavelength region by using the double nozzle Argon gas-puff target irradiated by a 5 J, 1 ns, 1 μm laser. Using the gas-puff target irradiated by a femto-second laser pulse, highly ionized ions of Cr-, Fe- and Ni-like Kr at the 5 - 20 nm wavelength region have been observed in a laser produced plasma. However, the intensity of the x-ray emissions from double nozzle gas-puff target are lower than that from the single nozzle gas-puff targets, using the Krypton gas. Using xenon gas, the intensity of the x-ray emissions from double nozzle gas-puff target is equivalent to that from the single nozzle target.

Significant progress has been made in recent years using lasers for electron acceleration to high energies in plasmas. The main idea of such laser-plasma schemes is based on an opportunity to use the lasers for generation a large amplitude regular plasma wave with strong longitudinal electric field and relativistic phase velocity, which is capable of acceleration injected electrons. The great interest to these accelerators is due to their ability to sustain extremely large acceleration gradients (<100 GeV/m) essentially exceeding the acceleration gradients of conventional radio-frequency linear accelerators (>100 MeV/m). At the first stage, the main attention was attracted to plasma beat wave accelerator scheme (PBWA) where two-frequency laser radiation was used to create a plasma wave. With development of chirped pulse amplification (CPA) and powerful laser systems, the new methods for excitation of large amplitude relativistic plasma waves appear as the laser wake-field accelerator (LWFA) and self-modulated laser wake-field accelerator (SM-LWFA). This report is intended to give a brief overview of up to date results obtained for different schemes of laser-plasma based accelerators. The problems and plans of future investigations are also discussed.

We have investigated a new mechanism for creation of relativistic electrons via the acceleration by the resonant field of laser excited surface plasma waves in sharp-edged overdense plasmas. This mechanism consists in a generalization to high-intensity laser fields of an effect recently observed in the context of short-pulse laser metal interaction. As it is well known, a p-polarized laser impinging onto a structured metal surface creates a plasma during the rise time of the laser pulse, which can reach temperatures of several hundreds of eV. If the pulse duration (<~ 100 fs) is such that the interaction of the electrons with the surface plasma wave occurs before the hydrodynamic expansion has time to smooth the plasma density sharp edge, the conditions for resonant excitation of surface plasma waves by the laser can be fulfilled. We show that in this case the strongly inhomogeneous enhanced electric field located near the plasma surface may accelerate the electrons toward the vacuum, the efficiency of this mechanism depending on the ratio R_L between two characteristic lengths: the extension length of the surface wave field in the vacuum and the typical distance covered by the particles in the high-frequency high-amplitude field. We find an optimum regime for R_L of the order of unity, in which case the electrons can be accelerated up to a momentum of the order of magnitude of the high-frequency momentum p_osc in the enhanced field of the surface plasma wave. The results of a 1D relativistic test-particle simulation modeling the interaction of the electrons with the plasma wave field are presented. In particular, we show that electron energies of some MeV may be reached for laser intensities of the order of 10¹⁸W/cm². The resulting electron energy distribution function is numerically calculated for the optimum case. The spectrum shows a well-defined peaked structure due to the dependence on the phase of the plasma wave field experienced by the accelerated electrons. This study suggests a novel possibility of high-current energetic pulsed electron sources.

The investigations of nonthermal processes in laser-produced plasmas are not yet complete, especially with regard to the ion acceleration in the plasma generated by high-energy short-wavelengths lasers. This contribution presents the results of studies of fast ion emission from plasma generated using a short wavelength (438 nm), high-energy (up to 250 J in 400 p5 pulse) iodine laser PALS at the Joint Research Laboratory PALS ASCR in Prague, Czech Republic. The properties of highly charged ion streams were investigated by ion diagnostic methods: ion collectors and solid state track detectors as well as a cylindrical electrostatic energy analyzer. Attention was paid to the determination of ion energy and comparison of the energies and abundance of different ion groups. The presented results shown the existence of highly charged ions with z <40 (measured z, =57 forTa) and with energies higher then 20 MeV in a far expansion zone. Ion current densities up to tens of mA/cm2 at a distance of 1 m from the target were obtained. On the basis of the ion diagnostic investigations the existence of nonthermal and nonlinear accelerating processes was demonstrated for the plasma produced by a high-energy short-wavelength laser pulse.

Dynamics of the interactions of atoms with intense electromagnetic fields is considered. The theory of ionization and excitation of atoms by the short laser pulses is developed on the basis of the close-coupling approach for solving the time-dependent Schrodinger equation. Studies of the interactions of atoms with intense electromagnetic fields require the use all the continuous states of the system, without discretization of the continuum. The systematic investigations have been done in the case of femtosecond laser pulses with linear and circular polarization, for the different vlaues of the laser frequency, intensity and duration times. Interactions of the intermediate discrete states with the continuum (bound-free transitions) are found to be very important for structures of the energy spectra of the ejected electrons. It is shown that these bound-free transitions give the larger contributions than the rescattering process (free-free transitions) at the medium energies of the ejected electrons. The resonance and interference structures in populations of the discrete and continuum atomic states are displayed as functions of the laser pulse parameters in the case of the H-atoms and H-like ions.

We report a spectroscopic study of x-ray line emission from a magnesium plasma produced by Nd:glass laser pulses of 30 ps (FWHM) duration at a laser intensity of ~ 3 x 10¹⁴ Wcm^-2. High-resolution x-ray line spectrum was recorded using a crystal spectrograph. Measurements of continuum radiation intensity were also performed for different x-ray filter cutoff energies. A peak electron temperature of ~ 2.4 keV derived from these measurements is in agreement with that calculated from an analytical model describing laser plasma heating in the short pulse regime. The intensity ratio of MgXII 1s-2p, λ = 8.42 Å and MgXI 1s²-1s2p, λ = 9.17 Å is observed to be much smaller than that calculated from the spectroscopic code RATION. Analytical estimates of ionization equilibrium time for different ionization states in the heated plasma as well as during its expansion using a simple hydrodynamic model can explain this behavior.

The photodissociation of H₂⁺ by an intense laser pulse is investigated by solving the close coupled equations without discretezation. The photodissociation spectra are calculated under the condition mimicking the experiment done by Sanding et al. and fairly good agreement obtained. The influence of the uncertainty in the relative phases of initial states is found to lead to somewhat of smoothing of the spectra depending on the laser intensity and pulse width. It is also found that Raman type transitions via intermediate dissociation continuum play an important role in determining photodissociation spectra. This effect leads to population increase of lower vibrational states and deforms spectral profile. The dissociation from the lower vibrational states due to bond softening cannot be good enough. The calculated results of the photodissociation spectra are presented in three-dimensional plot by introducing the field intensity as an extra axis. This is helpful for clearly understanding the dependence of photodissociation dynamics on the laser parameters.

Taking into account the Coulomb potential comes to a non-Keldysh mechanism of the ejection of photoelectrons from H-like atoms and ions. This new mechanism is responsible for a change of the ionization exponent in comparison with its value predicted by Keldysh's type theory. The analytic treatment of this new phenomenon is presented.

We consider a physical model of the interaction of high-power laser pulses with plasma created upon irradiation of condensed targets. The model is based on the equations of single-fluid, two-temperature hydrodynamics taking into account the ponderomotive force and the Maxwell equations for laser radiation at oblique incidence in the cases of s- and p-polarizations. The model takes into account the generation of fast electrons in the conditions of plasma resonance at the critical surface, and their transport with consideration for the friction force, caused by the ionization losses. For a number of experiments we have performed the numerical modeling of the laser picosecond pulse interaction with targets. We present the interpretation of the experiment on the basic harmonic shift depending on the pre-pulse energy. It has been shown that, if under the irradiation of a deuterated target the pre-pulse energy grows, the neutron yield of DD-reactions diminishes, since the produced plasma prevents the heating of the dense part of the target. It has been also shown that the growth of the pre-pulse energy can provoke, due to the induced scattering, the losses in the main pulse radiation. We give interpretation of the experimental data on the picosecond pulse absorption by plasma at the flux density of 10¹⁶-10¹⁹ W/cm².

1 MeV proton from thin Cu tape target with 5 μm thickness was observed in the region of laser intensity (α~1.5) and ultra short pulse range of 60 fs. Carbon ion acceleration was also observed and the maximum energy was higher than 0.4 MeV. The energy and charged states of proton and carbon were measured by a Thomson mass spectrometer with CR39. The maximum proton energy seems to depend more on the laser energy density I λ² τ_L [J μm²/cm²] than laser intensity I λ² [W μm²/cm²] in the short pulse region around 100 fs.

A mathematical model of clusters forming in gas jets is proposed. This model concerns with the representation of the clusters by the moments of the distribution function of the clusters with respect to the radius. This model uses the kinetic theory of phase transitions presented by Frenkel for the kinetic of the clusters formation. The numerical results obtained with the help of this model are compared with the direct experimental measurements based on Mach-Zehnder interferometry and Rayleigh scattering.

The phenomena of nonlinear bremsstrahlung absorption and generation of five first odd harmonics are investigated for a plasma photoionized in the Bethe regime of the suppression of the ionization barrier, in which case the velocity distribution of plasma electrons coincides with the distribution of atomic electrons. The partial nonlinear conductivities are obtained. A comparison is made between the features of the absorption and the effectiveness of harmonic generation in two different cases when atomic electrons before ionization are in the ns- or np-states. It was demonstrated that the nonlinear effective collision frequencies (NECF) have unique form in the limit of the high intensity of the pump field. On the other side NECF have the pump field dependencies near their maximum values which are different for the case of s-states and p-states. These dependencies are characterized by especial sealing functions, which give the dependencies on the pump field intensity, the values of the principal quantum number of the pre-excited states of atoms and harmonics numbers.

The control of coherence is a critical issue for the high-power lasers used in inertial confinement fusion (ICF). The level of coherence is an important parameter for the control of the light intensity distribution as well as the growth rate of parametric instabilities. Over the past few years, experimental and theoretical studies have evidenced the ability of an underdense plasma to reduce the spatial and temporal coherence of an intense laser beam prooagating through it. As any process affecting laser propagation, plasma-induced incoherence appears fundamental because it can impact on parametric instabilities. We present results obtained with the six-beam LULI laser facility, in the nanosecond regime, showing direct evidences of the reduction of spatial and temporal coherence of an initially RPP-smoothed laser beam after propagation through a preformed plasma. Plasma induced incoherence (PII) proceeds from several mechanisms which include self-focusing, filamentation and non-linear coupling between these mechanisms and forward stimulated Brillouin scattering (FSBS). Part of these experiments was dedicated to the understanding of the physical mechanisms involved in PII, as the break up of a single hot spot and the existence of ion acoustic waves having small wave vectors transverse to the interaction beam which are produced in the PII processes. The spatial and temporal characteristics of these waves give a unique access to the influence of PII on stimulated Brillouin and Raman scattering.

The generation of high-harmonics in laser-plasma interactions on the steep density gradients is discussed, especially by using short pulse UV laser radiation. Low intensity experiments with 5 • 10¹⁵W/cm² showed high harmonics in the VUV range and the efficiency could be optimized by modifying the density gradient. The disagreement among different experiments and the lack of a full theoretical understanding of the generation mechanism forced us to switch for higher intensities. The experimental arrangement for obtaining 5 • 10¹⁷W/cm² intensity with low-prepulse using a table-top system is shown. Preliminary results and future trends for high-harmonics generation with this method is given.

The oscillations of the gas dynamic and electrodynamics parameters of plasma generated under the action of a powerful UHF-modulated laser radiation are investigated theoretically when the characteristic laser radiation intensity modulation time is significantly less than the characteristic time of variation of the gas dynamic parameters of the plasma. It is demonstrated that the values of the parameters may be found using the averaging method and represented in the form of the sum of two parts, of which one part is the solution in the absence of modulation, and the other part describes small-scale oscillations about this solution.

CO₂ laser-produced plasma ion component parameters were studied experimentally and numerically for aluminum and lead targets at peak laser intensity of 4 x 10¹³ W cm^-2 and FWHM pulse duration of 15 ns. Angular dependences of ion number density, average velocity, and its spread were measured for different charge states by time-of-flight method. Ion charge state distribution shows high-charge and low-charge state groups. Ions in these groups have different average expansion velocity and longitudinal velocity spread. Angular distribution of high charge states is narrower than that of the low-charge state ion group, maximum yield of low charge states occurs at some angle from normal. For Al target the results show similar trends as for Pb target, but simulations have indicated that the effect of laser ponderomotive force is more pronounced in this case.

A treatment is given of harmonics generation resulting from nonlinear inverse bremsstrahlung in a plasma with an anisotropic bi-Maxwellian electron velocity distribution function. Inverse bremsstrahlung absorption of test electromagnetic wave is investigated as well.

Quasi-self-similar solutions to the stationary electron Fokker-Planck equation in diffusive approximation have been found in inhomogeneous plasma. These solutions describe reduction in the number of bulk electrons and formation of the suprathermal tail. The characteristics of the stationary electron distributions have been treated in terms of the collisionality parameter, the ratio of the electron stoping rage to the plasma gradient scale length. The dependencies of the electron distribution functions on density profile has been studied. Fokker-Plank simulations performed demonstrate good agreement with a theory.

Generation of relativistic electrons from the interaction of a laser pulse with a high density plasma foil, accompanied by an underdense preplasma in front of it, has been studied with 2D particle-in-cell (PIC) simulations for pulse duration comparable to a single-cycle and for single-wavelength spot size. The primary mechanism responsible for electron acceleration is identified. Simulations show that the energy of the accelerated electrons has a maximum versus the pulse-duration for relativistic laser intensities. The most effective electron acceleration takes place when the preplasma scale length is comparable to the pulse-duration. Electron distribution functions have been found from PIC simulations. Their tails are well approximated by Maxwellian distributions with a hot temperature in the MeV range.

The non-linear stage of stimulated Raman back-scattering is examined numerically in a collisionless non-relativistic laser plasma. The Euler-Vlasov method is applied in the simplest case of linearly polarized incident electromagnetic wave in 1-D geometry. The method of solution is a Fourier-Hermite expansion of the electron distribution function. The resulting ordinary differential equations are solved for the case corresponding to the interaction of the PALS laser beam with the plasma corona. The time evolution of the electron distribution function is visualized.

Within the context of inertial confinement fusion, experiments involving the "self-induced smoothing" of a laser beam propagating in an underdense semicollisional plasma are presented. These results, which reveal severe modifications of the focal spot intensity pattern via increased angular spreading and hot spot size reduction, are compared with three-dimensional simulations from the code PARAX.

A problem of scatterd radiation spectrum linewidth of stimulated Brillouin scattering (SBS) in multi-species plasma is studied. It is shown that the threshold and spectral composition of SBS can be varied by changing the concentration of species of the plasma. A possibility of existence of the scattered radiation spectrum with the frequency line width comparable to the ion-acoustic frequency is revealed.

We present some results of a recent experiment performed on LULI's nanosecond laser chain which puts light on the underlying mechanisms involved in plasma-induced incoherence. Following theoretical interpretation for this new-found phenomenon, we set-up a Thomson scattering diagnostic off ion acoustic waves having small k-vectors transverse to the interaction beam. Such waves would be the product of the interplay between non-linear processes undergone by an RPP-smoothed laser beam propagating through an under-dense plasma. We have observed ion acoustic waves with k-vectors ranging from 0.4k₀ to 0.6k₀ located near the plasma's summit and occurring at the top of the interaction laser pulse. Good correlation between Thomson scattering spectra and other PII signatures, namely the redshift of the transmitted light, when varying interaction conditions strongly supports our first assumptions pertaining to the ion waves' participation in PII.

The article reviews the progress in the development of discharge-pumped soft X-ray lasers. Especially the results of the last decade proved that discharge created plasmas in capillaries are sufficiently uniform to allow for soft x-ray amplification. Amplification conditions and population inversion mechanisms are briefly reviewed. Then the activities in individual fields are summarized with emphasis on the gas filled capillaries which obey electron-collisional excitation pumping. Namely these capillaries can work as an efficient, table-top, high average power soft X-ray lasers capable to produce millijoule-level laser pulses at a repetition rate of several Hz, with a corresponding spectral brightness. Finally, some of tested applications are also briefly mentioned.

Employing the crossed-beams technique, we have studied the interaction of fullerene ions both with electrons and He²⁺ ions. For fullerene ions C₆₀^q+ (q = 1,2,3), absolute cross sections have been measured for C₂-fragmentation at electron energies up to 1 keV. The cross sections for the loss of a C₂ molecule indicate the presence of two different mechanisms. For negatively-charged fullerene ions C_m^- (m = 60, 70, 84), absolute cross sections for multiple-ionization and fragmentation into product ions C_m-n^q+ (q = 1,2,3 and n = 0,2,3) have been measured in the same range of electron energies. A novel ionization mechanism is proposed. In a very first ion-ion crossed-beams experiment involving fullerene ions, we have studied the charge transfer in collisions between C₆₀⁺ ions and He²⁺ ions at keV energies. We have also calculated the total cross section for this reaction. Where the fullerene ion is described as an infinitely conducting hard sphere (ICS). The charge transfer S-matrix element was calculated as the electron transition coefficient over the time-dependent potential. For the calculation of the transition coefficients over a non-symmetric barrier, a new efficient method was developed.

K-shell emission spectra from laser-exploded aluminum foils and mylar foils with aluminum dots are recorded with a high spectral and spatial resolution using vertical-geometry Johann spectrometer. The experiments are modelled using cylindrical version of two-dimensional hydrocode "ATLANT." We describe our novel atomic physics post-processor "XEPAP" that is used here for the synthesis of the emission spectra. The predictions of the simulations are compared with the experimental spectra and the parameters of the emitting plasmas are deduced.

The reflectivity of Gallium films excited by femtosecond laser can be raised from ~55% to up to ~85% on a picosecond time-scale. Temporal behavior of the reflectivity exhibits three clearly distinguished stages: an initial 2 - 4 ps sharp rise, a relatively slow increase to a maximum value in a few 100 ps, and afterwards a long slope in ~ (0.1 - 1) μs to the original value. In this paper we present reflectivity measurements in a pump-probe scheme with one pump and two identical simultaneous femtosecond probes set at two different angles, which completely determines the real and imaginary parts of the dielectric function with time resolution ~ 200 fs. The analysis of the experimental data uncovered a number of new phenomena: (1) the energy density threshold to initiate phase transition is several times lower than the equilibrium enthalpy of melting; (2) the initial 2 - 4 ps rise of reflectivity relates to the transformation to a new phase in the absence of energy loss due to cooling. The second, slower stage (~100 ps) relates to a heat conduction dominated process; (3) the rate of the reflectivity change strongly increases with the increase of the pump laser intensity; (4) the volume fraction of the new phase reaches only 60% even with the deposited energy exceeds more than two times the equilibrium enthalpy of melting; (5) the electron-to-lattice coupling rate is a transient non-linear function of temperature that is drastically different from the equilibrium conditions. The results suggest a mechanism to control of the reflectivity switching, and thus the duty cycle of the reversible phase transition (crystal-metal-crystal), through an optimal combination of the laser parameters, target and substrate material. As a result, new all-optical switching devices with ps-range switching time could be designed utilizing the nonlinear dielectric properties of the non-equilibrium solid-state plasma.

All glass properties are dependent by their structure. It was established that hydrogen permeation, characterized by lgK_H as one of properties, is determined on the factor of glass network connectedness and the thermal expansion coefficient, which confirm the existing of free structure volume. Equations have been obtained for calculation of 1gK_H. They may be applied for predicting the changes in hydrogen permeability as a function of the indicated criterions.

The capillary experiment CAPEX was reconstructed to approach conditions suitable for creation of population inversion in Ne-like Ar. The reconstruction consisted in substitution of a ceramics capillary for former plastic one, in remarkable reduction of the pre-ionization current, and in change of Ar filling and pumping geometry. The soft X-ray spectroscopic measurements prior to and after this reconstruction are described. It is shown that the reconstruction resulted in appearance (under certain conditions) of the strong spectral line at the wavelength of laser transition (46.9 nm) that dominates the spectrum even at exposition 50 ns.

To measure the temperature and density of electronics in laser plasma accurately, two probe laser systems are built on XG-II laser facility. The one, called UV probe laser system, which can provide the UV laser pulse with duration of 30 ps by cascade Raman compressor after fourth harmonic conversion is used for density measurement of laser plasma. The other one, Thomson scattering system, which can provide the 4 ω laser pulse with energy of 3 - 5J, is now routinely operated for electronics temperature diagnostic in laser plasma. It is the first time that the density and temperature of laser plasma are measured directly by probe laser at the same shot.

We started a project to develop a very compact accelerator for cancer therapy. To reduce the size of the system, we adopted a laser plasma ion source using a compact ultra-high intensity laser. We have performed ion generation experiments in which the laser parameters were as follows: The wave length and the pulse duration were 800 nm and 50 fs, respectively. Peak power was 4 - 5TW. The laser pulse with normal incidence angle to the target was focused onto the target with 15 μm diameter giving power density of 3 - 4x10¹⁸W/cm². The thin foil metals (Ti, Al) and plastics (polypropylene, polyethylene) with the thicknesses of 4 - 100 μm were used for targets. We found that the angular distribution of ions with an energy of ~0.1 MeV had a significant peak in the backward and forward in respect to the laser incidence direction.

Instabilities of the discharge, as well as temporal and energetic characteristics of x-ray radiation a source based on the vacuum diode with laser-plasma cathode in a wide range of energies, power densities, duration of plasma forming laser pulse, have been experimentally studied. It has been observed that the characteristics of laser radiation significantly affect the dynamics of vacuum discharge and allow to control radiation processes at the early stages of its development. The minimum recorded duration of x-ray pulse (with photon number 10¹¹ per pulse) in titanium K-shells (~4.5 keV) was 10 ns in the case of generation of plasma cathode using laser radiation with the duration of 27 ps and intensity ~10¹³ W/cm². It has been established that in the regime of instability suppression and at the application of accelerating voltage (about 3 - 4 times the excitation threshold), the maximum value of contrast of characteristic radiation over Bremsstrahlung is achieved.

It is shown that heating of electrons due to the inverse bremsstrahlung absorption of high-power short-pulse laser radiation results in parametric generation of ion-acoustic waves. The range of wave numbers where the amplitude of the ion-acoustic oscillations increases by more than an order of magnitude is determined.

The PALS multi-user laser facility has been offering the beam time to the groups of both domestic and foreign rsearchers since September 2000. During the past two years of operation of its terawatt iodine laser system, a number of technical innovations and new diagnostic options were implemented, the most important of which are described in the paper. A brief survey of the current PALS research program is also given. Laser plasma sources of x-radiation and of highly stripped ions represent the two main lines followed. Recent highlights include the development and application of a highly coherent double-pass XUV laser based on Ne-like zinc. The reported studies of material response to the XUV pulses are mainly motivated by a potential use of the observed ablation phenomena e.g. in nanotechnology, while the x-ray contact microscopy permitted to image living biological objects with a resolution comparable to that of the electron microscopy. The PALS laser system is now in a routine operation, which opens the way to its new upgrades. The progress reached with the key ones -- application of elements of adaptive optics, replacement the original iodine oscillator by a solid-state based one, and, most important, implementation of the optical parametric chirped pulse amplification (OPCPA) technique -- is also reported.

In 2001 a primary start-up of one channel of the four-channel "Luch" facility, a module of 128-channel facility has been realized. The facility intend for inertial confinement fusion. This paper presents the main results of work on creation and start-up of front-end system (FES) of "Luch" facility. The pulse of radiation with the energy up to 3 J and regulated pulse shape 1 - 10 ns in a square (36 x 36 mm²) beam was obtained at the output of FES.

The experimental results of "Iskra-5" laser operation conversion at the second harmonic. (λ = 657.6 nm) are presented. The experiments were carried out with DKDP crystals of big aperture (size 32 x 33 x 2 cm). The scheme of one channel was upgraded for optimization of second harmonic generation. Maximum conversion efficiency has been achieved for primary laser intensity of 1 - 2 GW/cm². A second harmonic output of 500 J has been obtained at 60% of technical efficiency.

Gain measurements in x-ray lasers involves monitoring the intensity of lasing transition as a function of line focus length. Having a line focus of variable length with uniform intensity is important in these measurements. In addition, uniform line focusing of Gaussian laser beams has many other applications in material processing, pumping of dye lasers etc. In this paper, we describe a simple technique using a wedge to displace and overlap two halves of a Gaussian laser beam to obtain a uniform intensity line focus. Variation of the line length at a fixed intensity is facilitated by use of appropriate masks. X-ray emission pictures of a line focused laser produced plasma show the effectiveness of this geometry.

In the Laser MegaJoule indirect drive experiments, the time-averaged radiation asymmetry on a Deuterium-Tritium (DT) capsule must be minimized to achieve high-yield implosions. A two-dimensional model estimates the time-averaged effect of power imbalance, laser beam pointing and target fabrication errors on the final DT deformation, which is then submitted to an ignition threshold. As these errors will take random values from one LMJ shot to another, the robustness study aims at quantifying the probability of failing to reach ignition. Here, we focus on laser power imbalance. We distinguish two types of error sources in laser performance, according to whether they take long-time (more than the laser pulse duration) or short-time (less than the laser pulse duration) correlated values. Indeed, as the final DT deformation results from the whole laser pulse history, the failure probability depends on the error time-correlation. A 1D-time model of the laser beam power, from the front-end to the target, was developed to quantify the variations of the output power imbalance due to the source contributions. Taking into account this detailed time behavior, instead of modeling all errors as long-time correlated values, leads to cut the global effect of power imbalance on ignition probability by half.

The capsule targets for ignition experiments at the National Ignition Facility must meet very exacting requirements. Primary among them is an extremely high degree of symmetry at all length scales for the 2-mm-diameter 150-μm-walled capsule. At LLNL work is in progress to produce both polyimide and sputtered beryllium targets that meet these specifications. Both of these targets require a thin-walled spherical-shell plastic mandrel upon which the beryllium or polyimide ablator is deposited. In this paper we report on recent progress in developing NIF capsules that meet the demanding design requirements.

Targets containing foams have always been in demand in ICF and HDE experiments. These foams are usually quite different and highly specialized. These foams are at the edge of current foam knowledge with the combination of low density and small pore sizes are a challenge to all chemists. The science and property of these materials are still not fully understood and investigated. The low-density materials and the production methods of various types of foams are reviewed and the limitations of each discussed.

The present paper summarized recent activity of the target fabrication group at Institute of Laser Engineering (ILE), Osaka University. We focused on (1) organic photovoltaic materials to suppress the damage from laser-shine-through and (2) new emulsion technique to fabricate polyimide capsule. The following topics describes briefly, (3) organic feromagnetic materials for magnetic levitation of the target, (4) ultralow density foams of hydrocarbon whose density is ~2.0 mg/cc with micrometer-sized structures, and (5) new ultrathin (~nm) adhesion technique to provide laser-shock experiment targets.

This paper presents preparation of polystyrene-poly(vinyl alcohol) (PS-PVA) double-shell with micro-encapsulation method. In order to improve the gas-barrier property of the PVA shell, a mixture of 2wt% PVA solution and borax are used as matrix for PVA coating. The pH value of the matrix are kept less than 8 to prevent the PVA coating from formation of patch which arise from local gelation and ruin the uniformity of the PVA shell. The resultant PVA coating ranges from 2 μm to 15 μm with uniformity better than 95%.

In laser fusion experiments, for uniform irradiation, a stalk that supports a pellet affects uniformity. In our laboratory, we are studying non-contact suspension technique in the following four directions. First, we are introducing Magnetically Suspended Pellet (MSP) of a Ni coated Glass Micro Balloon (Ni-GMB) in high vacuum. Small external disturbances, however, cause it to vibrate horizontally. We have shown the effectiveness of active damping by use of optical forces. As another new method, we propose stabilization by rotation of Ni-GMB itself. Secondly, electric suspension system for a transparent GMB of laser fusion has been studied using RE-QTDQ (ring electrode quasi three dimensional quadrupole). Optical forces effect in electric suspension is experimentally confirmed. Thirdly, we are studying fundamentals of acoustic levitation. Lastly, a Pulsed Laser Deposition (PLD) enables us to have a uniform Ni coat over a laser fusion pellet. In heat-resister vacuum deposition method, we find gravitational effect of droplets and threshold distance of clean film. We have shown the pattern projection method is simple and effective to measure a PMB thickness.

The research results of an opportunity of radiation-stimulated diffusion use for laser fusion microtargets filling with heavy gases are given, which they can not be filled with by means of usual diffusion. The theoretical estimates of quantity and character of radiation damages, their distribution in the volume of an irradiated material are made. The calculations of glass microshells argon filling process in mode of vacancy and effusive mechanisms of wall permeability are carried out. The experiments on argon filling of glass microspheres are carried out by means of diffusion with irradiation of them with electrons, protons and neutrons. It is experimentally shown that the neutron irradiation of the glass microspheres placed in the chamber with argon in the reactor IBR-2 (JINR, Dubna) and their subsequent annealing has resulted in the argon penetration into microspheres.

Perdeuterated polystyrene (DPS) was synthesized by free radical polymer. DPS films with thickness 50 ~ 400 μm were prepared by casting. The influence of heat curing on the properties of DPS films were investigated by different scanning calorimeter (DSC), dynamical thermal mechanical analysis (DMA) and tensile strength measurement. It was approved that the heat curing process of films influenced the glass transition temperature, dynamical thermal mechanical properties and tensile strengths of the films.

The results of research of properties and preparation conditions of the plasmochemical SiO₂ films are submitted. These films coated various substrates (glass, metals, NaCl). Film deposition was carried out by decomposition of the tetraethoxycilane vapor by the electrical discharge with the frequency of about 18 kHz. The excessive products of decomposition were pumped out with maintenance of the tetraethoxycilane vapor and argon pressure of about 0.2 Torr. The study of element structure has shown that the film represents Si_xO_y with x ≈ 1 and y ≈ 2 and contains an impurity of organic inclusions. Density and index of refraction of a coating are close to these parameters for glass SiO₂. The form of the film surface is investigated depending on the coating conditions. Infrared spectra of absorption and Raman spectra are investigated. The results of attempts of the iodine in this film as an impurity are given. This method is applied for preparing of the covering with uniform thickness on glass microspheres used as targets in laser fusion experiments on the installation "Iskra-5."

The first experiment results on investigation of molecular composition kinetics in D-T mixture depending on temperature by means of Raman spectroscopy are given. The D-T mixture is contained within the glass microspheres used as laser thermonuclear fusion (LTF) targets. It is experimentally shown that the isotope molecules concentrations do not change with rapid temperature alteration from 4 - 77 K to room temperature. Two suppositions can explain the results: either the equilibrium concentration establishment time was less 5 minutes or molecule concentration is equal to the high temperature equilibrium concentration regardless of microspheres temperature.

The technique of argon determination in glass microspheres used in experiences on laser fusion is stated. The technique is based on registration of a spectrum of characteristic radiation of argon atoms, excited by β-radiation of tritium, contained in a target, or X-ray radiation of an external source for targets without tritium. The calculated dependencies of power of characteristic radiation on geometrical parameters of microspheres and results of measurement of various targets are submitted.

Earlier we have proposed and demonstrated a mechanism of formation of a smooth thermo stable glassy solid layer of hydrogen inside a microshell based on introduction of minor dopes into the fuel (so called minor dopes technique or MD-technique). This paper offers a more detailed overview and optimization of the method. The object under consideration is a microshell of ~1 mm dia filled with gaseous hydrogen H₂ and a minor dope of HD; density of H₂ is less than its critical density (30 kg/m³). It is found that for glassy structure formation it is necessary to maintain uniform dope distribution in the hydrogen volume during the layering process. The calculations have shown that this is achieved by (a) implementation of the drop condensation mode within the time period of t < 0.1 - 0.2 sec, and (b) solidification of the liquid phase within the time period of t < 10 sec. The results of calculations are confirmed by relevant experimental research work. Further model development involves research of specific features of formation of the glassy layer of D₂-fuel with minor dopes of HD or DT as well as analysis of the potential use of MD-technique for larger fuel quantities (IFE target).

Photo-nuclear reaction studies are introduced using photon sources developed at JAERI such as ultra high peak power laser expecting activation by intense high energy photons with wide energy spectrum, and laser-Compton scattering expecting controlled gamma ray emission for the cosmochronogical study, and photo fission reaction. Final target of these studies will be related to the emerging new method for the consmonuclear physics, up-conversion type induced gamma ray emission, and the controlled resonant fission into the short lived nuclei.