Theory of the acoustic instability and behavior of the phase velocity of acoustic waves in a weakly ionized plasma

Torosyan, O. S.; Mkrtchyan, A. R.

doi:10.1134/1.1568145

Cited by 3 publications

(7 citation statements)

References 10 publications

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“…The dispersion equation for acoustic waves is derived and numerically analyzed to find that the amplification of sound waves in weakly ionized plasma cannot be explained using the concept of energy transfer between electrons and neutrals in elastic collisions, and that it is the energy transfer due to inelastic collisions that is more important. This inference supports the correctness of the results of [11,12]. Fairly detailed numerical analysis of dispersion equation and comparison with experimental data results enable one to identify the concrete conditions necessary for the amplification of sound waves in weakly ionized gas-discharge plasma.…”

Section: Introductionsupporting

confidence: 83%

“…As was mentioned above, it was further demonstrated in [11,12] that a high energy contribution to neutral gas is a necessary but insufficient condition for the emergence of acoustic instability, because the gas is heated strongly in the case of a high energy contribution, and the heating prevents the amplification of sound. For demonstration of the foregoing, Figs 4,5,6), it causes an increase in β.…”

Section: Discussion Of the Resultsmentioning

confidence: 87%

“…Another, more effective mechanism must exist for the transfer of energy from electrons to neutral gas. The energy received by electrons from an external field (Joule heating) J 2 /σ (J is the current density, and σ is the electrical conductivity of plasma) is fairly high at commonly employed currents I ≈ 30-100 mA and tube radius R 0 ≈ 0.01--0.03 m, and, as is demonstrated in [11,12], electronatom and atom-atom inelastic collisions are capable of more effectively transferring the thermal energy of electrons to neutral gas. Therefore, one can state with assurance that the mechanism suggested by Ingard et al [1][2][3][4][5] is incapable of explaining the experimental results in the amplification of sound waves in weakly ionized atomic gas-discharge plasma.…”

Section: Discussion Of the Resultsmentioning

confidence: 96%

“…It was further demonstrated that, in the case of inelastic collisions, neutrals may receive a much higher energy from electrons than in the case of elastic collisions at values of plasma parameters at which the sound wave amplification was recorded experimentally. However, in this case as well no acoustic instability may arise [11,12], because the gas will be heated significantly; this precludes the amplification of sound waves. Note that the main concept of the theory of sound wave amplification developed in [1][2][3][4][5] is based on the fact that the energy transfer between electrons and neutrals in weakly ionized plasma occurs mainly owing to electron-atom elastic collisions.…”

Section: Introductionmentioning

confidence: 99%

“…An attempt was made recently [11,12] at investigating the effect of nonuniform (over the plasma column cross section) distribution of gas temperature on the propagation of a sound wave in atomic gas-discharge plasma. It was demonstrated that the nonuniformity of the temperature field cannot cause the sound amplification either, because the energy transfer from electrons to colder neutrals by means of elastic collisions is too low and cannot cause an acoustic instability.…”

Section: Introductionmentioning

confidence: 99%

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Acoustic Instability in Inhomogeneous Gas-Discharge Plasma

2005

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The possibility of amplification of acoustic waves in inhomogeneous atomic dc gas-discharge plasma (positive column of glow discharge) is investigated theoretically. This amplification is caused by the transfer of thermal energy from electrons to colder electron gas under conditions of elastic electron-atom collisions. It is demonstrated that the inclusion of nonuniform distribution of equilibrium temperature, neutral gas concentration, and electron concentration over the plasma column cross section, similar to the case of uniform distribution, cannot result in acoustic instability and, consequently, in the interpretation of the experimental results in sound amplification in weakly ionized plasma. The dispersion equation for sound waves in inhomogeneous glow-discharge plasma is derived and numerically analyzed in detail. Comparison of the theoretical and experimental results enables one to identify the reasons for their discrepancy and to actually reveal the basic principles essential for constructing a theory which will make it possible to quantitatively and adequately describe the experimental data on the amplification of sound in weakly ionized atomic plasma.

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Section: Introductionsupporting

confidence: 83%

Section: Discussion Of the Resultsmentioning

confidence: 87%

Section: Discussion Of the Resultsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Acoustic Instability in Inhomogeneous Gas-Discharge Plasma

2005

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Vortices in a gas-discharge plasma

Aramyan¹,

Galechyan²

2007

Phys.-Usp.

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The article discusses a mnvenion identity through which the series expansion of the Green's function periaining to the scalar Helmholk equation can be readily mnvened into a series expanded Green's dyadic. This expansion finds a simple application in the electromagnetic radiation theory leading to eleciric multipole and magnetic multipole terms of the vector potential and the resulting E and B fields. The dyadic is also used to obtain a series expansion of the magnetostatic vector potential. Finally, the role played by localized longitudinal and localized transverse currents in the generation of the electromagnetic field is brieEy examined, leading to the conclusion that a localized longitudinal current is self-screening. That k, it does not produce any electromagnetic fieid outside the domain of its distribution.

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Control of Co2 Laser Power by Acoustic Fields

Abrahamyan¹,

Chilingaryan²

2019

REFFIT

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The present study investigates the optimization of the operation of the CO2 laser in the acoustoplasma mode (i.e., dependence of the laser radiation power on the composition of the working mixture, pressure, value of the direct component of the discharge current, frequency, and modulation depth). A three-dimensional dependence on the frequency and modulation depth of the discharge current is experimentally obtained for the normalized efficiency of the conversion of the electric power supplied to the discharge tube into laser power. The maximum gain when transition to the acoustoplasma mode exceeds 2.5 times. The optimum depth of the discharge current modulation is 0.5–0.7. The laser radiation power modulation caused by the discharge current modulation is measured. Laser power is not modulated at modulation frequencies of current >1 kHz. Meanwhile, at current modulation frequencies <0.5 kHz, the modulation depth of the laser radiation power nonlinearly depends on the modulation depth of the discharge current and has a threshold character. The modulation depth of the laser radiation power is associated with the creation of an acoustoplasma and not simply with the discharge current modulation.

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Theory of the acoustic instability and behavior of the phase velocity of acoustic waves in a weakly ionized plasma

Cited by 3 publications

References 10 publications

Acoustic Instability in Inhomogeneous Gas-Discharge Plasma

Acoustic Instability in Inhomogeneous Gas-Discharge Plasma

Vortices in a gas-discharge plasma

Control of Co2 Laser Power by Acoustic Fields

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