Effect of flow conditions on the amplification and generation of pulsed gasdynamic lasers in N2O and CO2

The weak signal amplification is studied in jets involving N₂O-N₂He, N₂O-N₂ and CO₂-CO-N₂-He mixtures with installations combining a shock-tube and slit-throat (1.5×40 and 2.5×70 mm²) or two-dimensional wedge (=15°, A/A _* = 15) nozzles. The relationships between amplification and gasdynamic characteristics are elucidated.     

Optimization and limiting characteristics of CO2 lasers

It is shown that the limiting characteristics of CO₂ lasers are determined mainly by two parameters: the specific power of the electric discharge, referred to the square of the active medium pressure, and the product of the pumping time and the gas pressure. An investigation is made of the dependence of the efficiency and the radiation pulse shape over a wide range of the parameters. For the first time it is noted that the energy from the lower laser level can be given to the upper vibrational states of the symmetric and deformed modes, which allows high radiation density, ～0.2 J/cm³ · atm, to be achieved, as is shown by calculation. Because of energy redistribution in the asymmetric mode the limiting gain coefficient in C₀₂ lasers is ～0.12 cm^?1.     

Population inversion and radiation density in a Q-switched CO2 laser

The mechanism of lasing in a steady-state CO₂ laser has been investigated in [1–3]. In this paper we present a numerical analysis of the processes which occur in a CO₂ laser when the resonator is rapidly Q-switched. It is shown that the transition of the laser into the state with a new Q has an oscillatory form.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 18–23, November–December, 1972.We wish to thank R. I. Soloukhin for his interest and help.     

Fracture of long and short notched columns

Studies were conducted on machined-notched and fatigue-cracked columns of various lengths subjected simultaneously to axial compression and bending. Different failure criteria were examined for columns under such loading. Three methods are used to analyze the failure data. Results obtained for the aluminum columns investigated indicate that the energy required to initiate crack propagation may be stated approximately as an exponential function of crack length, and that stress-intensity factors calculated for the limiting case, where ρ→0 and, using Neuber's expressions for maximum stress, appear to form a basis for a valid fracture-toughness analysis.     

Choice of turbulence model for calculating gas dynamic CO2 lasers with selective thermal excitation

Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 163–168, Septebmar–October, 1990.     

Thermohydrodynamics of continuous-wave CO2 lasers with a closed cycle of the flow

The problem of pressure losses upon gas motion along a closed circuit containing channels in which heat is supplied to and removed from the gas is studied. The object where the pressure losses are studied is a CO₂ laser with a crossflow. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, 630090 Novosibirsk. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 1, pp. 3–13, January–February, 2000.     

Effect of laser radiation on the vibrational distribution of CO2

In connection with progress in the field of CO₂ lasers, questions of the vibrational kinetics of molecules of CO₂ have been discussed in many communications. In a majority of cases of practical importance, the distribution of CO₂ is due to processes of vibrational exchange (V-V) on which is based the well-known thermodynamic model [1]. In other cases, the V-V exchange does not determine the vibrational distribution, since the perturbation is small; therefore, it is found sufficient to consider a small number of levels of CO₂ (usually three), whose populations satisfy the linear equations of the balance [2]. There is the possibility of conditions where the vibrations are strongly excited and, at the same time, V-V processes are insignificant (a very small CO₂ impurity in the inert gas, with a high degree of ionization). Then the number of equations becomes large. The present article discusses one such case: the excitation of a steady-state vibrational distribution in a glow discharge by laser radiation, whose solution is rather graphic.     

A shock-tube study of the formation of stagnation parameters in N2O gas dynamic lasers

The main regularities of the formation of conditions behind the reflected shock wave in a shock tube in presence of chemical reactions are studied. The dependence of the parameters of supersonic flows on the conditions at the nozzle inlet is discussed.     

Effect of dissipation on the interaction between long and short waves in bubbly liquids

The interaction of long and short waves in a rarefied monodisperse mixture of a weakly compressible viscous liquid and gas bubbles is considered. For taking the dissipation effects into account an effective-viscosity scheme is used. Four cases of dissipation are distinguished, namely, strong, medium, weak, and very weak dissipation. In the cases of moderate, weak, and very weak dissipation the equations of resonance and non-resonance wave interaction are derived using the multiscale method. The effect of "degeneration" of the interaction is detected in certain of the models constructed. In the case of "degeneration" a class of new models of the dissipative resonance interaction is constructed and investigated numerically. Ufa. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 126–138, July–August, 2000.     

Nonequilibrium radiation from the CO2 band (1 B 2 —X 1σ g /+ ) in shock-heated flows

The processes of population and decay of the optically active state CO₂(¹ B ₂) behind shock waves and in supersonic jets are investigated. It is shown that the vibrational distribution function of the electronically excited state¹ B ₂ is determined by the full energy of the colliding particles CO and O and, at temperatures above 3000 K, the branch of dissociation with the electronically excited O(¹ D) atoms is essential.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.