The paper is devoted to research and development of a novel experimental technique—liquid-filled laser-driven shock tube (LST) for modeling of Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) hydrodynamic instabilities development at the contact surface of two immiscible liquids under shock wave (SW) passage. 100-J, 100-ns KrF laser facility GARPUN has been used to irradiate some opaque liquids. A homogenizing focusing system combined multi-element prism raster and a lens to provide non-uniformity less than a few percents across a square 7 × 7-mm spot, laser intensities being varied in the range of q = 0.004–2 GW/cm2. Surface plasma blow-off produced a planar SW, which propagated into the liquid. SW amplitudes as high as 0.8 GPa weakly damping with increasing thickness were measured in dibutyl-phthalate (DBP), which volumetrically absorbed ultraviolet (UV) laser light. Nonlinear absorption coefficients and laser breakdown thresholds were measured for pure water and UV optical materials intended to confine plasma. Test bench experiments were performed to produce standing acoustic waves as initial perturbations at the interface between two immiscible liquids.

The aluminium side of two-layer Al-Plastic targets were irradiated with a long pulse (∼ 2.4 ns FWHM) 1.06-μm laser light at intensities up to 7 × 1013 W/cm2. The time history of the thermal emission of the confined rear surface of the aluminum was measured. Visible emission only occurs for a short time after the arrival of the laser-generated shock waves. Over the range of the measurements, the duration and the intensity of the emission reduce with increasing laser intensity. The experimental results are in good agreement with the results of a simple phenomenological model that assumes a linear temperature and density profile on the shock front. The values of shock velocity and maximum temperature and density that were used in the model were found using the hydrodynamic simulation code MEDUSA. From the model the shock width was measured for different conditions by matching the emission of the experiment and model. It is found that the time history of the emission is strongly sensitive to the ionization potential of the plastic that is assumed to change with density from ∼ 4 eV at zero pressure to zero at high densities. The technique provides a way to measure the pressure metallization of large band gap insulators.

Enhanced harmonic generation of second order based on exponential density ramp in plasma has been noticed. It is well known that self-focusing of pump laser induces a transverse intensity gradient, which gives rise to the plasma wave at the pump frequency. Highly intense Gaussian laser with exponential density ramp profile generates a second harmonic pulse in plasma. It is noticed that the amplitude of second-harmonic pulse varies periodically with the distance and reaches its peak value in the focal region. Further, it is found that exponential plasma density ramp is useful for stronger self-focusing, which lead to rise second harmonic generation (SHG). Wiggler magnetic field provides the additional angular momentum required for second harmonic photon and aids in growing of resonant process. One may clearly see that exponential plasma density ramp imparts a major role in enhancing the SHG in plasma. Further, the combined effect of exponential density ramp and wiggler magnetic field boosts the SHG in plasma.

We suggest an easily obtained laboratory configuration to observe jet and vortex flows for the Richtmyer–Meshkov (accelerated inhomogeneous flow) environment. A hemispherical bubble in air with density ratio of 5 is placed against an ideally reflecting wall and struck by a planar shock. This also models a spherical bubble struck symmetrically by two identical approaching shocks, that is, a “reshock” configuration. For all Mach numbers (M = 1.2, 1.5, and 2.0), our axisymmetric simulations show that the heavy hemispherical bubble expands axially away from the wall as a jet, and a weaker vortex ring moves radially along the wall. In addition, when M = 1.5, a ringlike vortex projectile (VP) of small diameter follows closely behind the reflected shock and is associated with its moving triple point. This VP contains an entrained shocklet and quadrupole structure of dilatation. Various methods are applied to quantify the emerging coherent structures.

Holographic methods developed to study the behavior of surfaces shocked by high power lasers are reported. Shock waves of the order of hundreds of kilobars are generated in Sn targets 50-μm thick, by a Nd:YAG laser system with a wavelength of 1.06 μm, a pulse duration of 7.5 ns FWHM, and irradiance in the range (1.0–2.6)·1013 W/cm2. Two configurations of off-axis holography were applied: holograms based on forward scattering, and holograms of both backward and forward scattering. The hologram is produced by scattering of a pulse, 6.7 ns (FWHM), of green laser light synchronized with the laser that generates the shock wave. Holograms of the topology of the rear surface of shocked Sn targets moving in vacuum and in air (at atmospheric pressure) are reported.

In review, general results obtained by Institute of Physics and Power Engineering (IPPE) during 1981–1992 are presented in the field of physics of nuclear-induced plasmas in the following directions: processes of primary ionization of different media by nuclear reaction products; function of electron distribution in nuclear-induced plasmas; processes of excitation and relaxation; track structure of nuclear-induced plasmas. Prospects of study progress are discussed with a view to improve the current concepts of physics of elementary processes occurring in nuclear-induced plasmas and obtain experimental and theoretical data on process constants needed to calculate the nuclear-pumped lasers.

Ponderomotive non-linearities arising by propagation of a linearly polarized laser beam through high-density quantum plasma are studied. The intense laser beam sets the plasma electrons in quiver motion and consequently ponderomotive non-linearity sets in leading to electron density perturbation inside the plasma. The interaction formalism has been built using the quantum hydrodynamic model. Laser beam traversing through high-density quantum plasma acquires an additional focusing tendency due to the perturbation induced by ponderomotive force in the plasma density. The ponderomotive force causes the beam to focus and the quantum effects contribute in focusing. The transverse magnetization of quantum plasma enhances the self-focusing and increase in magnetic field limits the spot size.

By the interaction of intense (1010 particles/500 ns) relativistic (∼300 MeV/amu) heavy ion beams with solid targets, large volumes (several cubic millimeters) of strongly coupled plasmas are produced at solid-state densities and temperatures of up to 1 eV, with relevance for equation-of-state (EOS) studies of matter at high energy density and heavy ion-beam-driven inertial confinement fusion (ICF). The time and space profile of the ion beams, focused by the plasma lens to diameters of a minimum of 0.5 mm in order to obtain specific energy depositions of up to about 4 kJ/g, were measured to calculate the energy deposition in the target. In the present work, the plasmas created by ion beam interaction with cryogenic gas crystals and metallic targets are studied, among other methods, by backlighting shadowgraphy and electrical conductivity measurements. The experiments are coupled with two-dimensional hydrodynamic simulations.

Oscillating two-stream instability (OTSI) of a high amplitude laser or a plasma wave is investigated in plasmas with strongly coupled ions. It is shown that in some parameter regime, the pressure of strongly coupled ions becomes negative, which leads to enhance the bunching of ion and concomitant destabilization of OTSI. Applications of these results to ion accelerator and inertial confinement fusion experiments are discussed.

We carried out a numerical analysis on the stability of targets designed to produce fusion energy gains close to 100 when irradiated with an appropriate heavy ion beam. To reach such performances, we found that a high-Z radiation shield was necessary to screen the DT fuel from the radiation coming from the surrounding hot material. As opacity of high-Z materials is only weakly density dependent, we considered targets with lead shields both at solid density and with a density equivalent to that of the contiguous external material. The behaviour of both kinds of targets has been studied by introducing a small spatial nonuniformity on the external surface of the lead shield. Targets with low-density shields have been tested with a beam intensity perturbation, too. Because density gradients are very sharp and ablation is practically absent, we have found these implosions to be Rayleigh-Taylor unstable. The evolution has been followed in the nonlinear regime because the full hydrodynamical-radiative model with a nonlinear heavy ion energy deposition and mesh correction was used.

The results of the development of the ITEP accelerator carbon ion injector based on a repetition-rate CO2 laser ion source are described. The improvement includes a modified pulsed HV-feeding generator for the discharge formation in the laser gas mixture. The advanced discharge module ensures essential increase of the laser active volume and specific electrical deposition energy. The comparative computer simulations of the discharge characteristics for the improved and the prototype lasers are applied. The design and the output spatial-temporal parameters of the free-running laser “Malish-M” are shown, so the significant increase of the laser power is reached. The spatial characteristics of the laser beam obtained with diffraction calculations are compared to measured radial distribution of the energy density. The target laser intensity and the different channels of the energy loss of the laser beam in the optical scheme are estimated. Finally, the output C4+ current trace of heavy ion injector as well as the injector scheme are shown.

Light ion beam inertial confinement fusion (ICF) is a concept in which intense beams of low atomic number ions would be used to drive ICF targets to ignition and gain. Here, results from numerical simulations are presented describing the operation of an indirect-drive light-ion ICF target designed for a commercial power plant application. The simulations indicate that the ICF target, consisting of an X-ray-driven capsule embedded in a spherical foam-filled hohlraum, will produce a fusion energy output of over 500 MJ when driven with lithium ion beams containing a total input energy of 8 MJ.

Collisionless shocks are key processes in astrophysics where the energy dissipation at the shock front is provided by collective plasma effects rather than particle collisions. While numerous simulations and laser-plasma experiments have shown they can result from the encounter of two plasma shells, a first principle theory of the shock formation is still lacking. In this respect, a series of 2D Particle-In-Cells simulations have been performed of two identical cold colliding pair plasmas. The simplicity of this system allows for an accurate analytical tracking of the physics. To start with, the Weibel-filamentation instability is triggered in the overlapping region, which generates a turbulent region after a saturation time τs. The incoming flow then piles-up in this region, building-up the shock density region according to some nonlinear processes, which will be the subject of future works. By evaluating the seed field giving rise to the instability, we derive an analytical expression for τs in good agreement with simulations. In view of the importance of the filamentation instability, we show a static magnetic field can cancel it if and only if it is perfectly aligned with the flow.

An advanced cone-nanolayer target with nanolayers on both inside and outside of the hollow-cone tip is proposed. Two-dimensional particle-in-cell simulations show that laser interaction with such cone-nanolayer targets can efficiently produce fast electron beams with manageable spotsize, and the beams can propagate for a relatively long distance in the vacuum beyond the cone tip.

We consider spontaneous thermalization of free photon field (in a vacuum) due to self-interaction, mediated by the virtual e−e+ field at ultra-high concentrations of the electromagnetic energy. That nonlinear, attractive, short-range interaction between photons triggers spontaneous evolution of the initial, low-frequency spectrum toward the maximum-entropy spectral distribution peaking in the gamma range of frequencies. Collimation and the total power of the photon beam (pulse) are hardly affected by the process of spontaneous thermalization. We estimate the threshold intensity that triggers spectral evolution of the photon field, the necessary power of the laser beam, the minimum size of the interaction region, parameters of the fully thermalized photon field, and discuss the near-threshold behavior of the electromagnetic field. Possible applications of thermalized photon beams are suggested, for example, they can serve as the pump field to attain gamma-lasing or facilitate ignition in the fusion pellet.

The spectral and amplitude-temporal parameters of HF (DF) lasers pumped by nonchain chemical reactions initiated by radially convergent or planar e-beams and self-sustained discharge were studied. Intrinsic efficiency of the HF lasers up to ∼10% was obtained for both excitation methods. It was shown that the high efficiency of an e-beam-initiated HF laser may be attained as a result of the simultaneous formation of atomic and molecular fluorine and of the participation of F2 in population inversion. A laser pulse has a complex profile caused by the successive generation of P-lines and the overlap during the radiation pulse of both the rotational lines of the same vibration band and of individual vibration bands. Experimental conditions providing high intrinsic efficiency of a discharge nonchain HF (DF) laser are determined. Intrinsic efficiency of HF and DF lasers up to ηin ∼ 10% and 7%, respectively, is obtained using excitation by inductive and LC generators in the SF6-H2 (D2) mixtures. High discharge uniformity obtained with the use of special shaped electrodes along with uniform UV preionization is a key parameter for improving the intrinsic efficiency of discharge HF (DF) lasers. It was found that in this excitation condition, output spectra of the HF laser significantly widen and cascade laser action on some rotational lines of the vibrational transitions of HF molecules ν(3–2) → ν(2–1) → ν(1–0) is observed. This can explain the high intrinsic efficiency obtained. Specific output of the discharge HF laser over 8 J/L (140 J/L×atm) and total laser efficiency ηt ∼ 4.5% were achieved. For the discharge DF laser, specific output and total efficiency were as high as 6.5 J/L and 3.2%, respectively.

The excitation of large-amplitude plasma waves by intense few-cycle laser pulses in thin overdense plasma layers is studied using one-dimensional particle-in-cell simulation. P-polarized pulses generate relativistic electron pulses (jets) at the irradiated surface that penetrate the layer and then oscillate back and forth due to reflection by self-generated space charge fields building up in front of the surfaces. Counterpropagating plasmons of large amplitude are excited and start to emit radiation at 2ωp and other harmonics of the plasma frequency. The analogy to type III solar radio emission that is driven by electron bursts from deeper layers of the solar corona is pointed out; it highlights the present topic as another example of laboratory astrophysics with lasers.

A novel approach of beam cleanup based on stimulated Brillouin scattering with a large core fiber is proposed to improve the laser beam quality. The fusion splice scheme from a single-mode fiber to a very large core fiber (105 µm) is first employed in stimulated Brillouin scattering to steadily excite the fundamental mode of the Stokes beam. As a result, the output beam achieves a measured M2 value of around 1.3 meanwhile the pump conversion efficiency is up to 90%, which is the best in the reports of stimulated Brillouin scattering cleanup to our knowledge.

The Multiphase Buoyancy-Drag model recently formulated in Balakrishnan & Menon, Laser and Particle Beams, 2011 is applied to investigate the (1) rise of dusty gas Rayleigh-Taylor bubbles into a pure gas and (2) fall of pure gas Rayleigh-Taylor spikes into a region of particles. It is demonstrated that for these two scenarios, the bubble or spike amplitude oscillates about the dusty gas/pure gas interface. The ratio of the bubble or spike amplitudes on the pure gas side to the dusty gas side, asymptotes to a constant that depends only on the initial Atwood number, A, the multiphase Atwood number, Am, and the initial wavelength of the perturbation, λo. For the same Am, the ratio decreases with A for oscillating bubbles, and vice versa for oscillating spikes.

A magnetically insulated diode with an active anode source has been developed which produces a high-quality intense ion beam. The anode plasma of annular shape is produced independently of the main diode power pulse by the inductive breakdown of a radially expanding gas cloud supplied by a fast puff valve and nozzle configuration. The diode was developed on a 1010-W pulsed power generator that typically produces 150-kV, l-μs pulses. Prompt ion beam turn-on was attained in this diode when an adequate delay between pulsing the plasma source and delivering the diode power pulse was chosen. The neutral atom density in the diode accelerating gap was sufficiently low that the presence of the neutrals did not limit the beam pulse duration. When the puff valve was filled with H2 gas, a pure proton beam was produced, within the 20% uncertainty of the measurement technique. Proton beam pulses longer than 1 μs and current densities higher than 100 A/cm2 at 70–150 keV were generated.