[en] 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.

[en] Results are presented from experimental studies of the glow dynamics of a plasma jet generated during the irradiation of a plane aluminum target by an iodine laser pulse with the wavelength 1.315 μm. The laser pulse energy was 330–480 J, the pulse duration was 0.5 ns, and the focal spot diameter was 3 mm, the laser intensity on the target surface being ∼10¹³ W/cm². The jet expanded across an external magnetic field with the strength ∼1 kOe. The residual air pressure in the vacuum chamber was ∼10⁻⁵ Torr. The spatiotemporal behavior of the jet glow was investigated using a nine-frame camera in two mutually perpendicular directions (along and across the magnetic field). The results of measurements indicate azimuthal asymmetry of the jet expansion.

[en] We set forth the data of experiments involving direct microtarget irradiation by the 12 second-harmonic beams (λ = 0.66 μm) of iodine laser radiation carried out on the Iskra-5 facility. For microtargets we employed glass shells ∼500 μm in diameter with ∼1-μm thick walls, which were filled with a DT mixture at a pressure p_DT ∼ 3-4 atm. In one of these experiments, a tomographic image of the microtarget was recorded from the images obtained using pinhole cameras, which were arranged along seven different directions. The pinhole images were acquired in the X-ray radiation with photon energies above 1.5 keV. The procedure used for reconstructing the volume luminosity of the microtarget is described. An analysis of the tomographic image suggests that the compressed microtarget domain possesses a complex asymmetric shape; 20-30 μm sized structural elements being clearly visible. The resultant data set allowed us to estimate the initial nonuniformity of microtarget surface irradiation by the laser radiation. The rms nonuniformity of microtarget irradiance was estimated at ∼60 %. (interaction of laser radiation with targets)

[en] A neodymium-glass diode-pumped amplifier with a zigzag laser beam propagation through the active medium was elaborated; the amplifier is intended for operation in a repetitively pulsed laser. An amplifier unit with an aperture of 20 × 25 mm and a ∼40-cm long active medium was put to a test. The energy of pump radiation amounts to 140 J at a wavelength of 806 nm for a pump duration of 550 μs. The energy parameters of the amplifier were experimentally determined: the small-signal gain per pass ∼3.2, the linear gain ∼0.031 cm^-1 with a nonuniformity of its distribution over the aperture within 15%, the stored energy of 0.16 - 0.21 J cm^-3. The wavefront distortions in the zigzag laser-beam propagation through the active element of the amplifier did not exceed 0.4λ (λ = 0.63 μm is the probing radiation wavelength).

[en] Since 30 years already, the All-Russia Institute of Experimental Physics (VNIIEF) is engaged in investigations on the problem of inertial confinement fusion. The high-power laser facilities 'Iskra 5' (Kirillov G A et al 1990 Laser Particle Beams 8 827-31) and 'Luch' (Sukharev S A 3rd Int. Conf. on Solid State Lasers for Application to Inertial Confinement Fusion ed W H Lowdermilk Proc. SPIE 3492 12-24) were created and are operating now in the framework of this programme. The main lines of the work at these facilities are the investigation of the physics of thermonuclear targets and the development of laser technologies. This work resulted in the development of a project of the new generation facility 'Iskra-6'. This report presents the main results of these works carried out at Russian Federal Nuclear Center - VNIIEF in the period 1991-2002

[en] 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.

[en] 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. (lasers)

[en] We report on the results of experiments performed on the Iskra-5 laser facility for studying the effect of the polydeuteroethylene (CD₂)_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 10⁷–3 × 10⁸ 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 (CD₂)_n layer thickness from 1 to 0.1 μm.

[en] The compression conditions are analyzed and the capsules are discussed for the energy of ∼2 kJ and pulse duration of ∼0.5 ns at the second harmonic of an iodine laser (λ = 0.66 μm) under irradiation by a small number of beams at Iskra V facility (the facility has 12 beams, which are focused in a certain way onto the capsule). The authors consider different capsules filled with DT gas: the glass capsules (the inner radius is 260 μm; the thickness, 1.2-1.3 μm; the aspect ratio A = 200) experimentally examined with Iskra V; the capsules made of polystyrene (R = 140-170 μm; δ = 5-10 μm; A = 14-34), and the capsules made of polystyrene and covered by a foam absorber (R = 140-170 μm; δ = 5-10 μm; A = 14-34, foam absorber δ = 150 μm) - 'Laser Greenhouse'

[en] 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. (laser plasma)