Methods for estimating the precipitate thickness on the surface of cooled optical elements in vacuum with contamination sources

We describe a simple method for estimating contamination (thickness and growth rate of precipitate layers) on the surfaces of elements of an optical system operating in vacuum. Experimental results of physical simulation of contamination of on-board optical elements of a spacecraft orbiting with its own external atmosphere are reported and compared with calculated values. The results of this research can be used in cryostatting of optical elements in the residual atmosphere of a vacuum chamber.     

Measurement of the dynamics of the compression of high aspect-ratio shell targets in the “Delfin-1” installation

With the help of a specific diagnostic system designed for the “DELFIN-1” installation we have measured implosion velocities ? 250 km/s, which are record values for experiments on compression at sufficiently high hydrodynamic efficiency of ablative shell targets. An empirical scaling is shown to agree well with the measured compression velocities.     

Regeneration and renovation in queues

Regenerative events for different queueing models are considered. The aim of this paper is to construct these events for continuous-time processes if they are given for the corresponding discrete-time model. The construction uses so-called renovative events revealing the property of the state at timen of the discrete-time model to be independent (in an algebraic sense) of the states referring to epochs not later thann −L (whereL is some constant) given that there are some restrictions on the “governing sequence”. Different types of multi-server and multi-phase queues are considered.     

The general approach to mode-locking mechanism analysis for CW solid-state lasers with a nonlinear Fabry-Pérot interferometer

The effective mode locking of a CW solid-state laser with a nonlinear Fabry-Pérot interferometer with a period matched to that of the main cavity period (mode locking by additional cavity, or coupled-cavity mode locking) is considered. The main features of the ultra-short pulse generation obtained on the basis of numerical simulations in the framework of the fluctuation model are interpreted using an analysis of nonlinear reflectivity of the interferometer. A correlation between parameter ranges for effective mode locking and self-consistent solutions of the system describing the CW ultra-short pulse generation allows one to explain a discrete range character. A new mode-locking regime has been described and the influence of interferometer bistability on the mode-locking efficiency has been evaluated.     

Shell-target laser-plasma images in the light of intrinsic and backlit X radiation

Results are presented of calculation of x-ray plasma images of glass shell targets with diagnostic additives Na, K, and Ca in the light of the intrinsic radiation of the resonance lines of H and He ions with Z_n = 8, ii, 14, and 20, and also in the light of cw radiation in the wavelength range = 1-300 Å. The calculation results are compared with laser-plasma images obtained in experiments with the Del'fin-l thermonuclear facility. The temperature and density of the plasma, the rate of corona expansion, the target mass ablation rate, and the hydrodynamic coefficient of laser-energy transfer into kinetic energy of the ablating shell are determined. The plasma images obtained by backlighting the shell target with an auxiliary x-ray source are analyzed with account taken of the radiation refraction. The required energy, temporal, and spectral characteristics of the auxiliary source are determined.Laser-Plasma Laboratory, Lebedev Physics Institute. Translated from Preprint No. 70 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1989.     

The “Del'fin” high-power laser facility for heating spherical thermonuclear targets

The Del'fin H twelve-channel laser facility for high-temperature heating of thermonuclear targets in a spherical geometry is described. It consists of a neodymium driver laser with maximum energy ~10 kJ, pulse duration 10^-10–10^-9 sec, andbeam divergence ~5·10^–4 rad, a vacuum chamber in which the laser radiation interacts with the plasma, and the devices for the diagnostics of the laser and plasma parameters. The Del'fin focusing system, which ensures a high degree of symmetry of the spherical irradiation of the target at a maximum flux density on its surface ~10¹⁵ W/cm², is described. The problem of realizing the maximum ability of heating spherical thermonuclear targets by radiation from high-power laser systems is considered.Translated from Trudy Ordena Lenina Fizicheskogo Instituta im. P.N. Lebedeva, Vol. 103, pp. 3–51, 1978.     

Estimation of the role of side reactions in the simulation of complexometric titration

A mathematical model was selected to describe the titration of metal ions with an arbitrary reagent in the presence of masking agents. The model takes into account the stepwise character of the complexation reaction and side reactions of protonation, hydrolysis and masking. The computed titration curves were in good agreement with the data of potentiometric titration. The corresponding program was used to optimize the titration conditions, to select promising titrants (other than complexones), and to predict systematic errors due to the shift of the titration jump in the presence of masking agents. Because of the last-named effect, the results of analysis may be underestimated several times     

Modification of the physicomechanical properties of metallic materials by formation of nanoscale intermetallic phases under ion implantation

The fundamental and technological aspects of application of nanosized intermetallic compounds as implanted layers have been considered. The existing theoretical and experimental data on the effect of ion implantation on the structural state and physicomechanical properties of surface layers of metals (nickel and titanium) have been analyzed. The common features and differences in the phase composition and distribution of the phases formed by implantation over the alloyed metal layers are demonstrated.     

Specific features of generation of the quasi-Schrödinger soliton in the CW mode-locked solid-state laser with a semiconductor saturable absorber

The mechanism of mode-locking in the cw solid-state laser with the saturable semiconductor switch caused by the formation of the quasi-Schrödinger soliton is investigated on the basis of the self-consistent laser field theory. The possible regimes of the quasi-soliton destabilization are studied: the sharp transition from the femtosecond to picosecond generation (“the picosecond collapse”), the self-oscillation instability, as well as the breakdown of the pulsed generation. The existence of multistable states and hysteresis phenomena upon the variation in the group-velocity dispersion and the pump power are shown.     

Effect of Stimulated Raman Scattering on Spectral Characteristics of Ultranarrow Pulses in a Mode-Locked Solid-State Laser

On the basis of numerical modeling, it is shown that the effect of the higher-order group-velocity dispersion is unable to account for the noticeable Stokes displacement of the generation spectrum in a LiSGaF laser with mode-locking due to self-focusing. The results of calculations indicate the determining influence of stimulated Raman scattering on the spectral characteristics of femtosecond pulses.