The hydrodynamics of the flow formation due to the interaction of a shock wave with two-dimensional density perturbations is experimentally investigated on the Iskra-5 laser facility. Shadow images of a jet arising as a result of the impact of a shock wave (formed by a soft X-ray pulse from a target-illuminator) on a flat aluminium target with a blind cylindrical cavity are recorded in experiments with point-like X-ray backlighting having a photon energy of ~4.5 keV. The sizes and mass of the jet ejected from the aluminium cavity by this shock wave are estimated. The experimental data are compared with the results of numerical simulation of the jet formation and dynamics according to the two-dimensional MID-ND2D code.

In this paper, studies of gas-dynamic flows in samples of various materials loaded with an X-ray flux in “Illuminator”-type targets on Iskra-5 laser facility of the ILFI VNIIEF are presented. The obtained results on the velocity of shock waves in the sample under the study are compared with model calculations to match the gas-dynamic parameters to their calculated estimates.

We set forth the data of experimental investigation of X-ray spectral absorption coefficients in the 1.1-1.6 keV photon energy range for Al and Ge specimens bulk heated by soft X-ray radiation. Two experimental techniques are described: with the use of one facility channel and the heating of specimens by the X-ray radiation from a plane burnthrough target, as well as with the use of four channels and the heating by the radiation from two cylindrical targets with internal input of laser radiation. The X-ray radiation absorption coefficients were studied by way of transmission absorption spectroscopy using backlighting X-ray radiation from a point source. The results of investigation of X-ray spectral absorption coefficients on the 1s-2p transitions in Al atoms and the 2p-3d transitions in Ge atoms are presented.

Results are presented from the development of a method for measuring plasma temperature in indirect (X-ray) drive targets by recording the shock wave velocity in the Iskra-5 facility. The samples under investigation were irradiated by X-rays in a converter box, and the shock wave velocity was determined from the time at which the wave reached the back surface of the sample and the surface began to emit visible radiation. This emission, in turn, was detected by a streak camera. The results of experiments on the interaction of X radiation with a hot dense plasma, as well as the accompanying gas-dynamic processes in aluminum samples, are analyzed both theoretically and numerically. In experiments with Al and Pb samples, the shock wave velocity was measured to vary in the range U = 8–35 km/s, and the range of variation of the temperature of the box walls was measured to be T e = 140–170 eV.

Results in some directions of the target technology for research on high energy density and laser fusion at the Russian Federal Nuclear Centre-All-Russia Research Institute of Experimental Physics for the last three years are presented. The results of development of optical and X-ray methods of characterization and manufacturing techniques of targets for studying the equation-of-state at high pressures and the condensed rare gas targets for the influence of pulse-repeated laser irradiation are given.

Powerful iodine ISKRA-5 laser facility was upgraded and now operates on the second harmonic. Experiments were performed to measure the x-ray spectral opacity of dense plasma of different materials. Sample of material under study was fabricated as a thin plate with the 0.1-0.15 mu m thickness and was heated by the soft x-rays generated by irradiation of a thin film gold converter by one beam of the ISKRA-5 laser facility. Typical laser intensity on the converter was (1-5)(.)10(13) W/cm(2) and laser pulse duration was 0.5-0.6 ns. The effective temperature of sample under experimental conditions didn't exceed 30-40 eV. The sample was tampered by similar to 1 mu m plastic layers on both sides to avoid its rarefaction during heating and to obtain a quasistationary layer of a dense plasma prepared to be probed by a backlighter. The backlighter was aluminum or dysprosium film irradiated by another beam of the ISKRA-5 laser facility with an intensity of 10(14)-10(11) W/cm(2). Probe x-rays were registered by a Bragg spectrometer with spatial resolution. Comparison between experimental data and simulations is discussed.

Results are presented from experimental and theoretical studies of a glowing plasma object emerging behind a shock front that propagates through the background gas at a pressure of p 0 = 6 torr after laser irradiation of a hollow spherical target. The results of calculations are compared to the experimental results obtained in the MKV-4 device (a component of the Iskra-5 facility).

The spatiotemporal smoothing of the intensity distribution of a focused laser beam was investigated on the Iskra-4 laser setup using a dynamic plasma phase plate produced by vaporisation of a special target placed at the beginning of the caustic of the focused beam. It is shown that the transmittance of the plasma target in the 1013— 2 × 1014 W cm-2 intensity range is no less than 70% — 80%. The introduction of the dynamic plasma phase plate lowered the relative fluctuations of the spatial intensity distribution from 100% to ~10%. The characteristic time of the intensity distribution variation in the focal plane is 0.4 ps.

The experiments to study the indirect drive targets' dynamics in a highly symmetrical X-radiation field were performed on the ISKRA-5 facility. This paper covered the results of experiments with the targets in the form of a Cu spherical hohlraum, the internal surface of which is coated with Au, with six holes for laser radiation input. In the center of the aforementioned hohlraum, a glass capsule filled with D–T gas was placed. In several experiments, the central capsule was coated with an ablator made of plastic with a different thickness. This allowed us to perform a series of experiments in which the different compression degree of D–T fuel was achieved. The analyses of experimental results revealed good agreement between the latter and the spherically symmetrical hydrodynamic calculations.

Measurements of spectral and energy X-ray characteristics of almost transparent Fe plasma produced by laser radiation inside the inverted-corona targets have been made at ISKRA-5 facility. The targets were spherical plastics cavities with 2-mm diameter and 4.6-μm thickness covered from inside with Fe layer 0.25-μm thickness. X-ray spectrum, X-ray total energy, and the energy of a HeαFe resonance line have been measured. Experimental data and calculation results are collated.

The first experiments to study the shell's controlled asymmetry of capsule with DT-fuel in a highly symmetrical X-ray field, which is obtained inside a spherical hohlraum, were implemented. The asymmetry results from the coating of one hemisphere with the additional layer of material. The main goal of the experiment was to define the value of the capsule asymmetry, allowing us to experimentally obtain the neutron yield, which would be very different from the yield obtained in the experiment with the spherically symmetrical shell having the same mass as the asymmetrical one. It was shown that the shell asymmetry of ∼50% leads to the ∼(2–4) times reduction of the neutron yield as compared with the symmetrical shell. 2D calculations of the asymmetric capsule compression, using the MIMOZA-ND code, were conducted. The calculations demonstrated that the compression of targets, when exploding pusher regime occurs has a complicated character. The computational neutron yield, and the delay of the neutron generation time are in good agreement with the experimental data.

The experiments measuring the density of DT mixture compressed in indirect drive targets (X-ray targets) were conducted on the ISKRA-5 facility. The density was determined from the line broadening of H- and He-like Ar doped in DT-gas as a diagnostic substance. A series of three experiments with the X-ray targets having different shell thickness of capsule filled with DT + Ar mixture were carried out. In two of the three experiments, radiation spectra of Ar were recorded and the density of compressed gas was determined. The analysis of the experimental results for the X-ray target with a 280-μm diameter and a 7 μm wall thickness revealed that the density of the compressed gas may be estimated as ∼1 g/cm3.

Two shells with the diameter of 0.8–0.9 mm and a wall thickness of ≅1 μm were produced at the Lebedev Physics Institute for the experiments conducted at the ISKRA-5 facility. The results of two experiments with the aforementioned shells conducted at the ISKRA-5 facility with the use of an indirect-drive set up. In one of the experiments, the diameter of the golden hohlraum was D = 2 mm while in the other it was D = 4 mm. In these experiments it was observed to be ≅4 times the difference of the average laser intensity on the hohlraum surface. The results of computational analysis of the experiments are also presented here.

Experiments designed to investigate the effect of a controlled large-scale asymmetry of a shell containing deuterium-tritium fuel on the shell compression and neutron production under indirect (x-ray) action are performed on the Iskra-5 laser fusion device. The uniformity of the x radiation near the target is not worse than 3%, and the shell asymmetry is varied from 30 to 100%. The observed decrease of the experimental neutron yield as compared with experiments using symmetric targets is in satisfactory agreement with two-dimensional calculations.

The first experiments measuring the density of a compressed deuterium and tritium mixture in microtargets of indirect irradiation (x-ray targets) were performed at the Iskra-5 facility. The density was determined according to the broadening of the lines of hydrogen-and helium-like argon added to the DT gas as a diagnostics material. A series of three experiments was performed with x-ray targets in which the central capsule filled with a DT + Ar mixture over a range of shell thicknesses. In two of the experiments, argon emission spectra were recorded and the density of the compressed gas was determined. For a microtarget approximately 280 μ m in diameter with a wall approximately 7 μ m thick, an analysis of the experimental results yielded an estimated density in the compressed gas of ∼1 g/cm 3 . Gas-dynamic calculations using the SNDA (spectral nonequilibrium diffusion with absorption) program show that argon emission takes place just after reaching maximum temperature, but much sooner than maximum compression. The results of a calculation for an experiment with low relative Ar concentration are in overall agreement with the experimental data. Additional investigations are needed to interpret experiments at a relatively high concentration.

Experiments have been carried out using the Iskra-5 facility in order to study the behavior of x-ray targets in response to a highly symmetric x-ray field. Results are presented of experiments using targets in the form of a spherical copper hohlraum coated with gold on the inside, with six laser entrance holes and a glass microtarget filled with DT gas located at the center. In some experiments the central capsule was coated with a plastic ablator layer of varying thickness. An analysis of the experimental results showed that on the whole, they are satisfactorily described by spherically symmetric gasdynamic calculations.

Experiments on the indirect (x-ray) irradiation of high-aspect-ratio capsules (with a diameter-to-thickness ratio ≈900) filled with DT gas are performed on the Iskra-5 laser facility. It is shown that all the characteristics measured (neutron yield, ion temperature, shell implosion time, etc.) are faithfully reproduced in calculations based on the one-dimensional SNDA (spectral nonequilibrium diffusion of absorption) program for nonequilibrium radiation gas dynamics. The calculations provide an explanation for the experimentally detected generation of a smaller number of neutrons in an experiment with a higher measured value for the ion temperature of DT gas.

The results of the first experiments devised to investigate the mixing of thin layers of Al and Au during the laser acceleration of flat three-layer targets of Si (5 μ m), Al (2 μ m), and Au (0.05–0.26 μ m) by radiation converted to the second harmonic from the Iskra-4 iodine laser with an intensity of 4×10 13 −7×10 13 W/cm 2 ( τ 0.5 ∼1 ns), which acts on the Si side of the target. A method for detecting the occurrence of mixing is developed. It is established that under the experimental conditions the thickness of the mixing region is at least ∼0.15 μ m. The results of a theoretical analysis of the evolution of the disturbances leading to mixing are presented.

The main effort of the ICF target fabrication group is support of the experiments performed on the ''ISKRA-4'' and ''ISKRA-5'' laser systems. The main types of targets used in these experiments are direct drive, inverted corona, and indirect drive. A direct drive target is a glass spherical container coated with a metal or polymeric film and filled with a D-T mixture and some diagnostic gas.(1,2) The inverted corona target is a spherical shell with holes for introducing laser radiation. The inside surface of the shell is coated with a compound containing heavy hydrogen isotopes.(3,4) The indirect drive target is assembled from a spherical shell with holes for introducing laser radiation and a direct drive target placed in the shell center. The inside surface of the shell is coated with high-Z material(5) (Fig. 1).For production of direct drive targets, manufacturing techniques have been developed for both hollow glass and polystyrene microspheres. Hollow glass microspheres are fabricated by free-fall of liquid glass drops or dry gel in a 4 meter vertical kiln.(6) These methods allow us to manufacture glass microspheres with diameters from 50 mu m to 1 mm, wall thicknesses from 0.5 to 10 mu m, and aspect ratios (radius/wall) from 20 to 500. The microspheres have a thickness inhomogeneity less than 5% and non-sphericity less than 1%. Polystyrene microspheres are fabricated from polystyrene particles with a blowing agent in a similar vertical kiln. Polystyrene microspheres are fabricated with diameter up to 800 mu m and wall thicknesses from 1 to 10 mu m.