We report the results of numerical analysis of radiation dynamics (laser absorption and X-ray generation) by using SND-LIRA code in a combined box used in the X-ray opacity measurements on the 'Iskra-5' facility (laser radiation wavelength, lambda = 0.66 mu m; laser pulse duration, tau(0.5) approximate to 0.6 ns; and energy, 900 J). Combined boxes used in these experiments comprised three sections: two illuminators delivering laser radiation and a central diagnostic section with a test sample. We have proposed a scheme for step-by-step calculation of the heating dynamics of the sample under study in a three-section hohlraum. Two designs of a combined box, which differ in the ways the laser radiation is injected, are discussed. It is shown that the axial injection of the beams results in intense secondary laser irradiation of the illuminator edge which leads to its partial disruption and penetration of laser radiation into the central diagnostic section. In this case the sample under study is exposed to additional uncontrolled action of scattered laser radiation. Such an undesirable action may be avoided by using the lateral injection of the beams through four holes on the lateral side of the illuminators. For the latter case we have calculated the heating dynamics for the sample and found an optimal time delay for an X-ray probe pulse.

The dynamics of laser and X-ray radiation fields in experiments with cylindrical converter boxes (illuminators), which had earlier been carried out on the Iskra-5 laser facility (the second harmonic of iodine laser radiation, lambda = 0.66 mu m) was investigated in a sector approximation using the SND-LIRA numerical technique. In these experiments, the X-ray radiation temperature in the box was determined by measuring the velocity of the shock wave generated in the sample under investigation, which was located at the end of the cylindrical illuminator. Through simulations were made using the SND-LIRA code, which took into account the absorption of laser driver radiation at the box walls, the production of quasithermal radiation, as well as the formation and propagation of the shock wave in the sample under investigation. An analysis of the experiments permits determining the electron thermal flux limiter f: for f = 0.03 it is possible to match the experimental scaling data for X-ray in-box radiation temperature to the data of our simulations. The shock velocities obtained from the simulations are also consistent with experimental data. In particular, in the experiment with six laser beams (and a laser energy E-L = 1380 J introduced into the box) the velocity of the shock front (determined from the position of a laser mark) after passage through a 50-mu m thick base aluminium layer was equal to 35 +/- 1.6 km s(-1), and in simulations to 36 km s(-1). In the experiment with four laser beams (for E-L = 850 J) the shock velocity (measured from the difference of transit times through the base aluminium layer and an additional thin aluminium platelet) was equal to 30 +/- 3.6 km s(-1), and in simulations to 30 km s(-1).

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.

The dynamics of laser and X-ray radiation fields in experiments with spherical boxes was numerically investigated in a sector approximation using the SND-LIRA numerical code. The experiments were performed on the Iskra-5 laser facility at a wavelength λ=0.657 μm (the second harmonic of iodine laser radiation). The characteristics of X-ray generation were investigated with the inner surface of a converter box coated with different-Z materials (Au, Cu, Mg). With lowering Z, the laser energy absorption coefficient ka decreases and there occurs a lowering of the effective X-ray radiation temperature. Our calculations reveal a strong dependence of the results on the electron free-streaming flux limitation f. In particular, on lowering f from 0.1 to 0.03 for a conventional box with a gold coating, the coefficient ka decreases from 0.83 to 0.5 and the peak X-ray radiation temperature drops from 170 to 150eV. In these calculations, the rms nonuniformity of the X-ray irradiation of a capsule with thermonuclear fuel amounted to 1%—3%.

Gas release from the ZrO 2 -Y 2 O 3 ceramics used for the seeded growth of diamond single crystals in a temperature range from 100 to 700°C and a pressure of 10 −4 Pa is investigated. It is experimentally found that the air content in the pores of ceramic elements of the container is 0.086 sccm 3 /g. The coefficient of the gas release and diffusivity are determined; this allows one to determine the degassing time for which the gas fraction from the sample attains a definite value from the starting amount. It is revealed that vacuum annealing at a temperature no lower than 700°C and P = 10 −4 Pa provides a decrease in the content of the adsorbed gas on the parts of the reaction cell by an order of magnitude.

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.

The results of spectral calculations of the dynamics of laser radiation absorption and X-ray generation in a spherical box converter are presented for experiments on inertial fusion performed in the 1990s on the Iskra-5 facility. Numerical simulations were carried out taking into account the actual configuration of 12 laser beams and six apertures for introducing laser radiation. Calculations were performed in the sector approximation in which the inner surface of the box is divided into a certain number of regions or sectors. The movement of matter and radiation transport in each sector were calculated by using the one-dimensional spectral nonequilibrium dynamics program. Spectral calculations showed a strong inhomogeneity of irradiation of a capsule in the M-band region (2.7–2.9 keV). It is shown that the spectrum-averaged root-mean-square inhomogeneity of the X-ray energy flux on the capsule (during the time of its compression) is about 2.5% for laser beams of the same energy and is about 3% if the characteristic energy misbalance between the beams is taken into account.

The interaction of plasma clouds generated during laser irradiation of a spherical target in a background gas with a magnetic field was studied on the MKV-4 test bench of the Iskra-5 facility. The dynamics of the plasma cloud expansion in a 300- to 500-Oe magnetic field was investigated using magnetic and probe diagnostics. The results obtained are compared with calculations by different models of laser plasma diffusion in a magnetic field.

Results are presented from studies of the spectral characteristics of a glowing plasma object that forms behind a shock wave propagating in a background gas at a pressure of 1 Torr after laser irradiation of a spherical organic target in the MKV-4 device (a component of the Iskra-5 facility). The experimental data are compared to the results of calculations.

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).

3-Methyl-1,4-pentazadienes (pentazenes) were proposed as highly efficient photoinitiators of vinyl polymerization. The efficiency of pentazene initiation correlates with the quantum yield of their photolysis. The kinetics of polymerization of a number of vinyl monomers in solution in the presence of pentazenes was studied, and numerical modeling of the process was performed. In terms of kinetics, photoinitiated polymerization includes two steps: the first step is characterized by a much higher rate, whereas the rate of the second step remains virtually unchanged. Steady movement of the polymerization front along the direction of solution radiation was observed at the second step.

Novel organic azides were prepared, viz., derivatives of xanthone and fluorane (formulas I and II), and their photolysis initiated by radiation (lambda = 365 nm) was studied in ethanol and dimethylformamide (DMF) solutions in terms of IR and UV spectra (Scheme A, Figs. 1-4). A 15% methyl methacylate (MMA) solution in DMF was photopolymerized in the presence of the azides, benzoin and xanthone, and also in the bulk (to eliminate solvent effects) at 30 +/-1 degreesC in an argon atmosphere. The kinetics of the reaction was followed by dilatometry: The rate of polymerization of MMA photoinitiated with xanthone and fluorane azides was found to be higher than that run in the presence of xanthone and lower than that run in the presence of benzoin (Table 1, Fig. 5). Incorporation of a second azide group into the carbonyl photoinitiator (xanthone) resulted ill higher reaction rates as compared with the rate observed in the presence of the monoazides. Discontinuation of irradiation was followed by the "dark" polymerization effect. The process was first accelerated and then decelerated. With xanthone or benzoin, no such effect was found to occur. The energy of activation of the "dark" polymerization with 2-azidoxanthone was estimated at 43 kJ/mol over 22-42 degreesC. The durable effect of the "dark" polymerization and its temperature dependence were also observed in the bulk polymerization (Fig. 12). The aromatic azides containing no carbonyl group (e.g, azidobenzene, p,p,p ' -diazidobiyphenyl, p,p ' -diazidodiphenylmethane) failed to initiate photopolymerization under the present experimental conditions.

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