Results of an experimental study of a coaxial exciplex lamp pumped by glow discharge are presented. An average power of radiation in the wavelength region below 250 nm and as high as about 130 W has been achieved. Efficiency of the excilamp operation based on input power of 14% was demonstrated. The possibility of applications of this excilamp is discussed.

Using radial plasma acceleration in a laser beam, an alternative type of free electron laser has been developed by radial injection of electrons. Its properties have been elaborated for a laser amplifier of 400 μtm wavelength. To overcome the difficulties of this FEL, a basically new laser amplifier concept has been developed where a laser pulse is amplified by nearly lateral injection of solid particles (clusters, pellets etc.) whose kinetic energy (at appropriate adjustment and synchronisation) is converted into 80% optical energy of the laser pulse. The mechanism of energy transfer is the radial slowing down by nonlinear ponderomotive forces of the plasma made from the cluster reaching the beam axis, and the switching-off process of the beam with regard to the transient nonlinear force processes. It is an inversion of the plasma ejection with ponderomotive self-focussing. Apart from the unusually high efficiency, a relatively high gain is expected even for such small laser wavelengths as 10 nm. Furthermore, the difficult problem of modification of phase fronts and convergence (focussing, directing of X-ray beams) should be solved by the optical plasma properties at injection.

During the last few years, we have concentrated on developing plasma radiation sources (PRS) for the longer current rise time (up to 300 ns) of the direct-drive Decade Quad (DQ; Price et al., 1999). In particular, we have developed an argon gas-puff PRS that produces a high quality pinch with an ∼200-ns implosion time, twice the implosion time of typical z pinches. We have shown that large-diameter, solid-fill (i.e., the gas density is a smooth function of the radial distance rather than a discrete shell) gas puffs can achieve adequate heating and stability for long-implosion z pinches with good K-shell yield.

Strong ionization of the gas medium has significant effects in the process of medium-order harmonic generation. The combined effect of neutral atom depletion and defocusing of the pump beam due to the intensity-dependent density of free electrons, significantly modifies the conversion characteristics and efficiency. For moderate harmonic orders, the yield is optimized for well-defined values of the pump laser intensity that do not depend on the order or on the focusing geometry, but only on the ionization potential of the gas. In particular focusing conditions, the ionization-induced defocusing can effectively guide the pump beam along channels of optimum intensity, thus enhancing the overall conversion efficiency. We demonstrate that a very simple model is able to reproduce all our experimental results in a surprisingly good way.

Jets of laser–generated plasma represent a flexible and well-defined model environment for investigation of plasma interactions with solid surfaces (walls). The pilot experiments carried out on the iodine laser system (5–200 J, 0.44 µm, 0.25–0.3 ns, <1×1016 W/cm2) at the PALS Research Centre in Prague are reported. Modification of macroscopic characteristics of the Al plasma jets produced at laser-irradiated double-foil Al/Mg targets is studied by high-resolution, high-dispersion X-ray spectroscopy. The spatially variable, complex satellite structure observed in emission spectra of the Al Lyα group proves a formation of rather cold dense plasma at the laser-exploded Al foil, an occurrence of the hot plasma between both foils and subsequent thermalization, deceleration and trapping of Al ions in the colliding plasma close to the Mg foil surface. The spectra interpretation based on the collisional-radiative code is complemented by 1D and 2D hydrodynamic modeling of the plasma expansion and interaction of counter-propagating Al/Mg plasmas. The obtained results demonstrate a potential of high resolution X-ray diagnostics in investigation of the laser-produced plasma–wall interactions.

We have simulated the shock Hugoniot of copper and uranium based on the results of first principles electronic structure calculations. The room temperature isotherm has been obtained by evaluating the accurate ground state total energies at various compressions, and the thermal and electronic excitation contributions were obtained by adopting isotropic models using the results obtained by the band structure calculations. Our calculations ensure smooth consideration of pressure ionization effects as the relevant core states are treated in the semi-core form at the ambient pressure. The pressure variation of the electronic Grüneisen parameter was estimated for copper using the band structure results, which leads to good agreement of the simulated shock Hugoniot with the measured shock data. The simulation results obtained for U are also compared with the experimental data available in literature and with our own data.

Effect of intensity profile of the ablating laser on the dynamics of laser-blow-off (LBO) plume has been studied by fast imaging technique. This work emphasizes the geometrical aspect of the LBO plume, which is an important parameter for various applications. Visualization of the expanding plume reveals that geometrical shape and directionality (divergence) of the plume are highly dependent on the laser intensity profile. Present results demonstrate that the Gaussian profile laser produces a well-collimated, low divergence plasma plume as compared to the plume formed by a top-hat profile laser. The sequence of film removal processes is invoked to explain the role of energy density profile of the ablating laser in LBO mechanism.

A theoretical model for electrons in the conduction band intend to investigate the optical breakdown threshold in femtosecond laser pulse-fused silica interaction is presented. The model is derived from a rate equation that includes the avalanche and multi-photon ionization processes of Thornber and Keldysh, respectively, and also the three-body and exciton recombination mechanisms. In addition, the time evolution of electron mean energy is also considered through the energy balance equation. The mean energy acts as a trigger for the avalanche mechanism. The evolution of electron density profiles is calculated and discussed with respect to the ionization and recombination mechanisms. The results for the fluence threshold as a function of the pulse duration fall in good agreement with the experimental data reported in the literature.

The typical target structure of the inertial confinement fusion by using the ion beams as the energy driver, and its optimized parameters are shown in this paper. The phenomenon occurring at the fuel implosion in the target, from which the thermonuclear fusion output energy of 2·5 GJ is released, is analyzed, and the requirements for the driver beam are summarized.

Experiments conducted on the SOM facility at the Russian Federal Nuclear Center–VNIITF, concerning the turbulent mixing induced by the Rayleigh–Taylor instability in a three-layer system of immiscible liquids are described. The fluids are contained in a small tank 6.4 cm × 5.4 cm × 12 cm, which is accelerated vertically downward by a gas gun. The mixing layer evolution was imaged by seeding one of the fluids with particles and using a bidirectional light sheet method (refractive index matching was used to minimize measurement errors). Experiments were performed for two different accelerations (g = 350 g0 and g = 100 g0, where g0 = 980 cm/s2, and the acceleration decreases with distance traveled), and with aqueous solutions of glycerin and benzene (with density ratio 1.6). The lower, middle, and upper layers were a sodium hyposulfite–glycerin solution, a water–glycerin solution, and benzene, respectively. The glycerin solution was seeded with particles. The principal objective of the experiments was to obtain the distribution of fluid particle sizes arising from the mixing of the immiscible fluids.

Hundred picoseconds laser pulse with high energy and high peak power has broad application prospects such as inertial confinement fusion shock ignition. But it is hard to get effective amplification through MOPA or chirped pulse amplification method. Through simulated Brillouin scattering method, 100 picoseconds laser pulse can be amplified efficiently. To be able to meet the need of high energy and high-intensity laser pulse amplification, scalable two cell structure and four different FC series liquid were used to fulfill this experiment. The results indicate that the magnification of Stokes energy and efficiency of energy extraction are closely related to medium parameters and energy parameters. The minimum width of 340 ps Stokes pulse was amplified by 13.5 times in this experiment.

Hydrodynamic instabilities play an important role in the target compression for inertial confinement fusion (ICF). We present the analytical solution of a perturbed isentropic implosion. We compare the analytical solution to the results obtained with perturbation and bi-dimensional Lagrangian hydrodynamic codes. We also compare results from bi-dimensional code and perturbation code on an ICF like test case.

The plasma waves generated by resonant absorption of light in the vicinity of the critical density of laser-produced plasmas, are modelled by a non-linear Schrödinger equation with additional terms accounting for the presence of a source and the inhomogeneity of the medium.

We use an average lagrangian method to describe the behaviour of the solutions of this equation in the range of parameters where periodic soliton generation occurs. An iterating scheme describing the successive emission of solitons yields values for this range of parameters which are in reasonable agreement with those found from direct numerical simulations of the non-linear Schrödinger equation.

Experimental results obtained with “Kanal-2” facility under the study of powerful laser pulse interaction with the low density microstructure media are presented and discussed in this paper. Forward scattering, back scattering, and transmission of laser radiation by aerogel foil plasma have been investigated. The temporal, spectral, and energy characteristics of both the radiation scattering in the direction of heating radiation beam and the back scattering radiation were studied; the directional diagrams of forward and back scattering radiation were obtained for ω0 and 2ω0 frequencies. Analysis of intensity redistribution on the heating beam cross-section after passing through a polymer microstructure target was carried out.

An intense electron-beam accelerator, which consists of a primary storage capacitor system, a magnetic core Tesla transformer, Blumlein pulse forming line of water dielectric, and a field-emission diode, are constructed and described. The experimental results show that the output voltage of transformer is more than 740 kV, the rise time is about 5 µs, the diode voltage is about 596 kV, electron beam current is about 60 kA, the duration is about 100 ns, and the power is 36 GW when charging voltage is 40 kV. It was suitable to drive magnetically insulated transmission line oscillator. And it can be also used in materials surface modification. This accelerator is very compact and works stably and reliably.

The effects of coherently enhanced radiation reaction on the motion of subwavelength electron bunches in interaction with intense laser pulses are analyzed. The radiation reaction force behaves as a radiation pressure in the laser beam direction, combined with a viscous force in the perpendicular direction. Due to Coulomb expansion of the electron bunch, coherent radiation reaction takes effect only in the initial stage of the laser-bunch interaction while the bunch is still smaller than the wavelength. It is shown that this initial stage can have observable effects on the trajectory of the bunch. By scaling the system to larger bunch charges, the radiation reaction effects are strongly increased. On the basis of the usual equation of motion, this increase is shown to be such that radiation reaction may suppress the radial instability normally found in ponderomotive acceleration schemes, thereby enabling the full potential of laser-vacuum electron bunch acceleration to GeV energies. However, the applicability of the used equation of motion still needs to be validated experimentally, which becomes possible using the presented experimental scheme.

In this paper we determine the inelastic contribution to the energy losses by swift heavy ions in dense matter. At equilibrium, the charge transfer stopping is determined by a simple energy balance and the excitation stopping is determined by the photons emission. Using an average atom model, we determine the density influence on these inelastic stoppings.

Opacity calculations for targets used in inertial confinement fusion (ICF) needs sophisticated atomic physics models, assuming a large number of configurations and transitions to simulate the plasma. Depending on the degree of accuracy for calculations of targets for ICF, some hydrodynamic-radiation codes use multifrequency opacities or well mean opacities.

In this work, using a sophisticated atomic physics code for LTE opacity calculations, that provides well multifrequency opacities or mean opacities, useful analytical opacity formulas for several single elements used in ICF have been generated, giving both Rosseland and Planck mean opacities as a function of the plasma parameters.

This paper addresses the effect of target plasma electrons on the charge state of energetic ions, penetrating a target composed of bound as well as plasma electrons. Dynamic screening of the projectile Coulomb potential by the plasma electrons brings about a depression in the ionization energy of the ionic projectiles, as has been verified experimentally. This in turn makes the ionization cross-sections larger, while making the recombination cross-section smaller, thereby causing an increase in the ion charge state compared to the case of a gas target. The effect of the plasma environment, where the valence electrons are treated as plasma, is illustrated here for a 2 MeV carbon beam penetrating amorphous carbon targets of varying densities.

High-power pulsed lasers are used widely nowadays as shock generators. They settle as a complementary technique to the conventional shock generators by the high peak pressure and short duration shocks they deliver. They are used to investigate the feasibility of new industrial processes and to get information on the behavior of matter in specific conditions of extremely high strain rate. In this paper, some studies about typical applications of laser shocks are presented: surface densification of porous materials, spallation in ductile and brittle materials, α-ε phase change in iron, and an estimate of the relaxation time for this transition. Laser shock experiments provide additional data on the dynamic behavior of materials at the nanosecond time scale.