We report on the results of experiments performed on the Iskra-5 laser facility for studying the effect of the polydeuteroethylene (CD 2 ) n working layer thickness on the operation parameter of an inverted-corona target. In all experiments of this series, the neutron yield at a level of 10 7 –3 × 10 8 DD neutrons per shot was detected for the total laser radiation energy supplied to the target by 12 second-harmonic beams in the range of 1.6–2.2 kJ. Using the neutron time-of-flight technique, we have detected an increase in the ion temperature from approximately 6.4 to 14 keV upon a decrease in the (CD 2 ) n layer thickness from 1 to 0.1 μm.

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.

The results of the field experiments of HTO washout with rainfall in the vicinity of the HT and HTO emission source are presented. The objective of the current study was to obtain the direct experimental data on the impact of raindrops characteristics (rate and spectrum of the drops) on HTO washout from the atmosphere. The results can be applied in for the development and validation of various models of washout.

The results of field experiments, involving HTO scavenging from the atmosphere by precipitation in the vicinity of HT and HTO emission sources, are presented. The experiments were aimed at obtaining direct experimental data on atmospheric HTO scavenging for a variety of rain characteristics (rain intensity and drop spectra).The most reliable are the calculations of the rate of wash-out with precipitation with the use of the method of integration of the constant exchange for a spectrum of drops. The results of such calculations are in good agreement with the experimental data and can serve as a basis for the generalized parameterization dependences. It is shown that the exact calculation can be replaced by a simpler formula using the mean-value theorem.For the known approximations of the spectra of the rain drops, formulas were obtained to give parameterization dependence of the rate of wash-out A on the intensity of precipitation p. This approach can be used for rapid assessment, as well as to determine parameters of wash-out of gases with precipitation in the numerical complexes, which are used for the calculation of the transfer and removal of impurities from the atmosphere. (c) 2012 Elsevier Ltd. All rights reserved.

An investigation is made of the dynamics and visible-range luminosity of the plasma cloud produced behind the front of a shock wave in air at a pressure of 1 Torr. The shock wave was produced on introducing the radiation of the twelve-channel Iskra-5 laser facility with a total energy of ∼2300 J into a hollow spherical plastic target of mass ∼10-4 g. Experimental data are compared with simulations.

A train of a few tens of high-power subnanosecond laser pulses with a repetition period of 10 ns is generated in the Iskra-5 facility. The laser pulse train has an energy of up to 300 J and contains up to 40 pulses (by the 0.15 intensity level), the single pulse duration in the train being ∼0.5 ns. The results of experiments on conversion of a train of laser pulses to a train of X-ray pulses are presented. Upon irradiation of a tungsten target, a train of X-ray pulses is generated with the shape of an envelope in the spectral band from 0.18 to 0.28 keV similar to that of the envelope of the laser pulse train. The duration of a single X-ray pulse in the train is equal to that of a single laser pulse.

The results of investigation of two plasma clouds interaction appearing at the laser irradiation of two different targets in background gas atmosphere on the MKV-4 facility of the "Iskra-5" has been described. The experimental data are compared with the results of the theoretical simulation.

Results are presented from studies of the interaction of two plasma clouds produced from two different-type laser targets in an ambient gas in the MKV-4 stand of the Iskra-5 facility. The experimental data are compared with the results of numerical simulations.

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.

The twelve-channel 'Iskra-5' iodine laser facility was updated to enable investigations in the regime of high-power two-pulse target irradiation, when the second pulse is delayed by a time of up to 10 μs relative to the first one and possesses an energy equal to or comparable with the energy of the first pulse.

The conversion of the 'Iskra-5' iodine laser to the regime of fusion target irradiation by second harmonic radiation at 657.5 nm is reported. The laser upgrading enabled obtaining from 12 channels a total second-harmonic energy yield of 2.5 kJ, which corresponds to an output power of 5 TW. The conversion efficiency was equal to ∼50% in experiments with DKDP crystals with an aperture of 35 cm. A series of 12-channel experiments was conducted involving second-harmonic irradiation of microtargets.

The experimental results of "Iskra-5" laser operation conversion at the second harmonic. (lambda = 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/cm(2). A second harmonic output of 500 J has been obtained at 60% of technical efficiency.

Experimental research of various conditions for effective conversion of "Iskra-5" iodine laser radiation to the second harmonic (lambda = 657.5 nm) were carried out. The influence of intensity, depolarization, divergence of main harmonic, optical quality of big aperture (size 32 x 33 cm) DKDP crystals, which are used for conversion and also angular error of their adjustment, was investigated. It was shown that the most essential factors, decreasing the conversion efficiency under Type II phase-matching condition are depolarization and small-scale noise of main harmonic radiation.

There are presented in the research results of HTO washout and the model of HTO atmosphere concentration in the vicinity of a long-term HT and HTO emission source. The site of the scavenging experiments was around a 30 m emission source. The sampling arcs were chosen at 150-300 m from the base of the source to minimize dry deposition on the precipitation collectors. To study dependence of scavenging of tritium on raindrops characteristics, an optical device was constructed and used to measure the distribution of the drop radii and velocities during the period of experiment.The washout model, used for assessments, takes into account dispersion, deposition and re-emission. The model of HTO wet deposition is taken into account kinetics of HTO exchange between vapor and liquid phase with parameters such as rain drop spectra, rain intensity, condensation-evaporation on drop's interface. Gauss type formulae for permanent emission source is used to calculate HTO atmospheric concentration. Meteorological data are used as input parameters for modeling.

Quasi-rectangular pulse of (tau) approximately equals 0.5 - 0.7 nsec duration has been shaped at `Iskra-5' output using the method of time splitting of initial light pulse followed by composition of its part with the necessary delay (strengthened in a tract). Numerical modeling of such pulse train in a forced tract shows pulse shape change in an area of wave overlapping due to a phase climb.

A proper description of the fibre fragmentation test becomes more and more important because of the continual development of new types of fibres, an example being the oxide composite fibres tested in the present work. An attempt at a strict formulation of the problem involved in the description of the fibre fragmentation test is presented. It takes into account a distortion of fibre strength distribution function caused by the fibre breakage process occurring under increasing external load. The fibre strength distribution function is determined by a distribution function of defects on a fibre as well as the distribution function of the defect strength. The formulation of the problem considered results in a system of differential equations which is solved assuming some simplifications. The solution leads to a choice of a particular set of statistical fibre strength characteristics. The procedure is applied to oxide composite fibres developed for a high temperature use.

The first experiments have been carried out on the hot plasma produced during indirect illumination of microballoons containing a gaseous DT mixture at the Iskra-5 laser installation. The integrated yield of DT neutrons reached 6 X 10(9) per pulse.