Glow discharge in a gas flow

Велихов, Евгений Павлович; Голубев, В. С.; Pashkin, S. V.

doi:10.1070/pu1982v025n05abeh004552

Cited by 60 publications

(79 citation statements)

References 2 publications

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“…For a specific energy input ∼ 10 3 kJ/kg, based on an approximation of the complex geometric structure of the temperature field in the discharge zone, ∼ 300 kJ/kg is contributed to the translational and rotational degrees of freedom and the electron states, ∼ 600 kJ/kg to the vibrational degrees of freedom, and ∼ 100 kJ/kg to dissociation. These data are in agreement with the values obtained in gas-discharge lasers [1].…”

Section: Resultssupporting

confidence: 92%

“…The absence of appreciable perturbations from a fairly powerful discharge (N ≈ 50-70 kW) appears to be attributable to the fact that the discharge energy is mainly imparted to the internal degrees of freedom. Later, this was confirmed by experiments carried out by other authors [1].…”

Section: Resultssupporting

confidence: 67%

“…The probability of dissociation by electron impact is one-two orders of magnitude higher than the probability of dissociative adhesion or ionization and the O 2 and N 2 dissociation energy is large as compared with the mean electron energy [1]. Therefore, breakdown of O 2 and N 2 molecules mainly takes place via several excited states.…”

Section: Resultsmentioning

confidence: 99%

“…In this case no features of the passage of current in the flow in the presence of strong gas inhomogeneities were considered since they did not correspond to the problem formulated, namely, obtaining a homogeneous gas-discharge plasma. An extensive literature devoted to both the technological and the physico-kinetic aspects has been published on the basis of these studies [1].…”

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confidence: 99%

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Investigation of the structure of a strong electric discharge in a high-velocity air flow

Alfyorov¹

2004

Fluid Dyn

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 67%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Investigation of the structure of a strong electric discharge in a high-velocity air flow

Alfyorov¹

2004

Fluid Dyn

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“…These are filaments through thermal insiabiliiies [2], striations through aflachmenl ins2abiliiies [3] as well as an electrical breakdown in the space charge layers at high electrical field strengths [4].…”

Section: 2 Sources Of Instabilitiesmentioning

confidence: 99%

<title>Spatially resolved measurements in CO2 laser active media</title>

et al. 1995

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Industry has growing interest in lasers with high output power of high beam quality. Therefore, laser developers have to coflcentrate their efforts on the optimization of every component involved in the beam generation, e. g. the rf-power incoupling and the gas flow generation.At present CO2 lasers of very high output power are developed by increasing the dimensions of the whole system. Inevitably, a more or less pronounced reduction of beam quality and efficiency will occur, if scaling laws are not considered. In order to reach the goal of a well designed system with high performance data the knowledge of homogeneity and stability of the discharge as a function of the various parameters involved is essential. The evolution of filaments for example increases with the rf-input power. This filamentation, however, is a complex mechanism that also depends on gas temperature, gas turbulence and contamination as well as on the excitation frequency of rf-discharges. In this work, diagnostic methods for determining the degree of filamentation are presented. The results achieved are used to determine the frequency-dependency and scaling laws of rf-excited CO2 discharges.The range of parameters favourable for a stable discharge is generally not the same compared to the parameters yielding high values of small signal gain and saturation intensity. The optimal discharge geometry (length and diameter) depends on various quantities. The values for mass flow and of rf-input power are given by the gas circulating system and the rf-generator. The maximum rf-input power density depends on the limit of stable operation, which itself is a function of gas pressure and velocity and various other parameters. Taking into account the gain saturation of the medium, the optimal gas pressure itself depends on the input power. Measurement data of small signal gain and saturation intensity spatially resolved parallel to the gas flow direction as well as electro-optical efficency will be given. Based on these measurements, scaling laws are derived and will be presented.The range of rf-input power into the discharge (i. e. the input power density) is limited by the emergence of filaments. It is known, that these instabilities should be avoided because they lead to a reduction of the laser output power as well as of beam quality. For this reason, the elaboration of relations independent of the geometrical size of the discharge tube in combination with similar relations for maximum gain resp. excitation efficiency would provide a powerful means for the assessment and the comparison of different discharges and for the scalability of gas lasers.A necessary prerequisite for a maximum level of stable discharge operation is a homogeneous discharge. For this reason, an appropriate electrode shaping is necessary in order to provide a homogeneous incoupling of rf-power. A stable discharge is defined to be one without any appearance of filamentation. Hence, if the input power density is raised, the limit of stable discharge operation is reached if at leas...

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Paul¹

1994

Laser in Der Materialbearbeitung

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Glow discharge in a gas flow

Cited by 60 publications

References 2 publications

Investigation of the structure of a strong electric discharge in a high-velocity air flow

Investigation of the structure of a strong electric discharge in a high-velocity air flow

<title>Spatially resolved measurements in CO2 laser active media</title>

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