This paper presents the optical layout and composition of a system for automatically adjusting the multipass power module of a next-generation laser apparatus. An adjustment technique based on near-field and far-field markers is described. A control program under the Astra Linux operating system is described for the automatic-adjustment system.

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.

This paper describes the optical layout of a test stand for developing the automatic adjustment system of a neodymium-laser channel. Samples of the laser diodes used on the test stand are investigated. A marker grid based on laser diodes has been developed. A version of the placement of the markers is selected. An automatic adjustment algorithm based on the marker grid is presented. Special software-the Control Program-is described. (C) 2017 Optical Society of America.

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.

This paper describes a method and a precision optical sensor for remotely determining the coordinates of the center of a spherical interaction chamber (the target chamber) 10 m in diameter to within +/- 20 mu m when the target of a multichannel laser installation intended for studies in high-temperature plasma physics is being automatically adjusted. (C) 2014 Optical Society of America.

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.

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 x 25 mm and a similar to 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 mu s. The energy parameters of the amplifier were experimentally determined: the small-signal gain per pass similar to 3.2, the linear gain similar to 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 0.4 lambda (lambda = 0.63 mu m is the probing radiation wavelength).

A module of an automatic adjustment system has been developed and studied, consisting of a scaled segment of the main four-pass amplifier of the Iskra-6 128-beam laser apparatus. The adjustment methods are based on the use of small light markers, centered with the stops of the elements. The adjustment algorithm, the image-processing methods, and the adjustment accuracy and rate have been experimentally investigated. A software package has been developed for modeling radiation propagation through the optical system and the automatic adjustment of the system, and a comparison has been made with experiment. The results serve as a basis for further development of the system for automatically adjusting the laser apparatus. (C) 2006 Optical Society of America.

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.

The research on studying and development of iodine lasers for experiments in the field of ICF, conducted in RFNC-VNIIEF, were resulted in the creation of 120 TWt 12-channel pulse iodine laser facility "Iskra-5". Wavelength of radiation is lambda=1.315 mum. "Iskra-5" installation is designed on the scheme of parallel amplification of pulse, generated by front-end system, in 12 identical amplifying channels. Front-end system includes four main parts: master oscillator (MO), two cascades of preliminary amplification (PA1, PA2) and final amplifier (A0). Radiation from front-end system after A0 passes through the splitting system to the input of amplifying channels. Topics of report are short description of "Iskra-5" front-end system and analysis of its parameters during previous five years of facility operation. Modernization of master oscillator is reported also. This modernization includes changing of electro-optical mode-locker on acousto-optically mode-locker made from crystalline quartz. Using of crystalline quartz allowed to get 100% depth of modulation on the wavelength of iodine laser radiation under control power about 10 Wt. The analysis of results revealed that using of acousto-optical modulator significantly stabilizes the parameters of front-end system radiation pulse.

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.

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.