Modeling of Plasma-Chemical Reactions in Gas Mixture of CO2 lasers. II. Theoretical Model and its Verification

In the paper we have modelled plasma-chemical reactions in the CO₂ low pressure, DC excited lasers. A good agreement of theoretical and experimental results has been achieved. It has been proved that neglect of reactions with electronic excited species or heterogeneous recombination leads to almost 50% overestimation of CO₂ equilibrium conversion. The relation of CO₂ equilibrium conversion to the reduced field E/N, pressure and current density depends on discharge conditions and mainly on the role played in discharge by ambipolar diffusion. This role decreases with an increase of the discharge diameter and of the mixture convection velocity. The CO₂ equilibrium conversion increases with growth of E/N and j and with decrease of pressure for discharges in small, sealed-off laser systems. The CO₂ equilibrium conversion is not always a monotone function of p in large, convection cooled lasers. It does not depend so much on E/N as the electron temperature alone if conversions in different mixtures are compared.     

Quenching Effect of Microwave to DC Glow Discharge in Gas Lasers

Ｑｕｅｎｃｈｉｎｇ　Ｅｆｆｅｃｔ　ｏｆ　Ｍｉｃｒｏｗａｖｅ　ｔｏ　ＤＣ　Ｇｌｏｗ　Ｄｉｓｃｈａｒｇｅ　ｉｎ　Ｇａｓ　ＬａｓｅｒｓＱｕｅｎｃｈｉｎｇＥｆｆｅｃｔｏｆＭｉｃｒｏｗａｖｅｔｏＤＣＧｌｏｗＤｉｓｃｈａｒｇｅｉｎＧａｓＬａｓｅｒｓ￥ＷＡＮＧＹｕ...     

Spectroscopic Study of CO2 Decomposition in Sealed‐off CO2 Lasers

The CO₂ decomposition in a DC glow discharge in a sealed‐off CO₂ laser mixture (6% CO₂ : 20% N₂ : 74% He) in the pressure range 2 ‐ 22 Torr is investigated. Both the time evolution and the steady‐state CO₂ decomposition are studied by means of time resolved optical emission spectroscopy. A decrease of the time to reach steady‐state values of particles concentrations in the discharge system with decreasing pressure and increasing discharge current is observed. The degree of CO₂ decomposition rapidly decreases with increasing pressure and exhibits only a small increase with increasing discharge current. This behaviour can be explained by the variations of the reduced electrica field strength E/N and of the electron density. Also the influence of the balast volume is discussed in this work.     

Atmospheric Pressure DC Glow Discharge in Semiconductor Gas Discharge Electronic Devices

The stabilization of dc glow discharges in a dc plasma is studied experimentally in air and neon media functions of pressure $p$, interelectrode distances $d$, and diameter $D$ of the cathode areas in the semiconductor gas discharge electronic devices (SGDED) with GaAs cathode. Comparision of current and discharge light emission (DLE) from SGDED are used for the determination of the stabilization under low- and atmospheric-pressure glow microdischarge conditions. It is found that uniform DLE can be generated in Ne up to atmosphere pressure different from the case in air under specific conditions. Apart from the homegeneous results, nonhomogeneous current–voltage characteristic forms are also observed for some parameter sets. The experimental results reveal different discharge behaviors in both gas media at atmospheric pressure.      

Spectroscopic Investigation of the Separation of A Glow Discharge in an Argon-neon Mixture

The passage of a steady state electric current in a mixture of binary gases between apair of metal electrodes has been found to result in an enrichment of the minority constituent gas near the cathode and the majority gas in the vicinity of the anode (1–7). The study of the separation of the mixture of binary gases under the influence of a discharge current is important for practical applications in gas lasers and for obtaining very pure gas samples. Although extensive studies have been reported in various gas mixtures it seems relatively few have been made in argonneon^(2,3,5) and these were restricted to either low gas pressures or low discharge currents. In the present contri-bution a preliminary study of the cataphoresis separation is reported in a low proportion of argon in neon using spectro-scopic techniques.     

Characteristics of a Glow Discharge in a Krypton/Elegas/Air Mixture

The longitudinal glow discharge in the Kr/SF₆/air mixture at a pressure of P = 0.7–6.0 kPa has been investigated. The electric characteristics and plasma radiation in the spectral region 150–340 nm are studied. The optimization of the radiation brightness (power) at = 249 nm in the KrF(B–X) mixture and in the nitrogen bands is carried out depending on the workingmedium composition and current magnitude. It is shown that a d.c. discharge in the Kr/SF₆/(N₂:O₂) mixture can be used in the multiwave UV–VUV radiation source on a system of the KrF and N₂ molecular bands.     

Investigation of Eco-Friendly Gas Mixture for Gas Discharge Particle Detectors

Physics of Atomic Nuclei - The first results of studying the Ar/CO2/HFO1234ze eco-friendly gas mixture for gas discharge detectors are presented. The work is performed using a prototype multiwire...     

Multifrequency Diagnostics of a Vibrationally Equilibrium CO2-Containing Gas Mixture

We present a technique which makes it possible to simultaneously determine the temperature T and the partial pressure of carbon dioxide in a vibrationally equilibrium gas mixture at atmospheric pressure by using the experimentally measured spectral distribution of the absorption factor at the oscillation lines of a tunable CO₂ laser. The technique developed can be employed for monitoring both the energy efficiency and the ecological purity of the processes of combustion of large amounts of hydrocarbon fuels accompanied by release to the atmosphere of combustion products containing carbon dioxide.     

Kinetics of the Excited States of Helium in an Atmospheric-Pressure Glow Discharge in a Helium-Nitrogen Mixture

Using an atomic-absorption spectral analysis technique, we determined the concentrations of helium atoms in states 2¹S, 2¹P, 2³S, and 2³P in an atmospheric-pressure glow discharge in helium (99.98%) and in a mixture of helium with nitrogen (99.5%He+0.5%N₂). It is shown that the population of the lower excited levels of helium atoms (n = 2) in its mixture with nitrogen is almost an order of magnitude smaller than in the case of a discharge in helium. The maximum of the concentration of excited atoms in a discharge both in helium and in its mixture with nitrogen is in the cathode region at a distance of about 0.1 mm from the cathode. The reaction of quenching of excited helium atoms by nitrogen molecules is responsible for the sharp decrease in the concentration of He(n = 2) on addition of nitrogen into helium. Presented at the 5th Symposium on Physics and Diagnostics of Laboratory and Astrophysical Plasmas, Belarus, Serbia and Montenegro, Minsk, Belarus, September 20–23, 2004; 12th International Congress on Plasma Physics, October 25–29, 2004, Nice, France. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 530–537, July–August, 2005.     

Decomposition of NO2 in Oxygen-free NO2: N2 Gas Mixture by Back-Corona Generated Plasma

The back-corona discharge has been successfully applied as a plasma source for decomposition of NO₂ in the oxygen-free gas mixture of N₂:NO₂. The paper reports a first attempt to use back-corona discharge for noxious gas conversion. The preliminary results of laboratory experiments in a needle-to-plate reactor show that the De-NO_x processes in back-corona discharge are similar to the dc streamer corona discharges generated in the same geometry. Both types of discharges convert NO₂ to nitrogen, oxygen and also to N₂O and NO. However, back-corona discharge produces less NO, and is more efficient energetically in NO_x decomposition than the dc streamer corona discharge.     

Plasma-Chemical Decomposition of Hydrocarbons on the Basis of the Micro-Arc Discharge with Disc Electrodes Rotating in the Bulk of Raw Materials

Russian Physics Journal - An innovative plasma-chemical hydrocarbon processing reactor has been developed. It is based on the interaction of nonequilibrium gas-discharge plasma with hydrocarbons in...     

用于激励高功率气体激光的自持体放电技术

通过两种放电等离子体形成的模型，研究了自持体放电的形成过程，介绍了能量注入激光介质的特点，并以不稳定模型解释了体放电收缩过程。分析了各阶段放电对激光输出特性的影响，并给出了较好的放电实验参数。     

Passage of a Plane Shock Wave through the Region of a Glow Gas Discharge

Technical Physics - The interaction of a plane shock wave (M = 5) with an ionized plasma region formed before the arrival of a shock wave by a low-current glow gas discharge is considered...     

一类气体辉光放电条件下的X射线发射与冷核聚变

本文主要依据在辉光放电条件下Ｄ／金属系统的ｘ射线发射和中子、γ射线产生的实验结果说明冷核聚变的存在,并介绍了电荷－电子偶模型的解,说明Ｄ￣＋～Ｄ束缚态的存在．束缚能Ｅ（Ｄ￣＋～Ｄ）＝１４ｋｅＶ．在假设核力作用尺度Ｒ＿０＝０．５×１０￣（－１３）（ｃｍ）时,Ｘ射线的发射几率是核聚变几率的３．５×１０￣５倍．指出第一周期的气体（Ｈ、Ｈｅ及它们的同位素）及它们的混合物在辉光放电条件下均有可能发射ｘ射线．有的进一步发生核聚变． Existance of cold nuclear fusion was explained based on experiment results in glow discharge process in D/metal system in which X--ray, neutron and y--ray were measured. The model of charge--dipole for solution of Schrodinger equation was introduced.There was some bound state with energy about 14 keV in (D+,D) system.As length of nuclear force was about 0. 5× 10-13 (cm), the rate of X--ray emission was about 3. 7× 104 times of rate of neutron emission. This paper...     

Diagnostics of a Vibrationally Equilibrium CO2-Containing Gas Mixture at Atmospheric Pressure

A technique is presented for determining the partial pressure and temperature of carbon dioxide in a vibrationally equilibrium gas mixture at atmospheric pressure from experimentally recorded spectra of the absorption coefficient of the lasing lines of a tunable CO₂laser.     

Negative Ions in a Glow Discharge of Tetrafluoromethane

The Langmuir — probe measurements in a CF₄ — glow discharge reveal a large number of negative ions (10¹⁰ cm^?3) in the plasma between the planar C-electrodes. Under special conditions the density of them exceeds the electron density at several orders of magnitude and sustains a quasi — electron free plasma. The ratio depends on the residence time of the molecular gas in the discharge reactor. It is due to dissociative electron attachment to highly molecular gas components arising from the plasmachemical conversion of CF₄. F^? and CF₃^? are the most important negative ions.     

Strong-Field-Induced N_2~+ Air Lasing in Nitrogen Glow Discharge Plasma

We investigate N_2~+ air lasing at 391 nm,induced by strong laser fields in a nitrogen glow discharge plasma.We generate forward N_2~+ air lasing on the B~2Σ_u~+(v'=0)-X~2Σ_g~+(v"=0) transition at 391 nm by irradiating an intense 35-fs,800-nm laser in a pure nitrogen gas,finding that the 391-nm lasing quenches when the nitrogen gas is electrically discharged.In contrast,the 391-nm fluorescence measured from the side of the laser beam is strongly enhanced,demonstrating that this discharge promotes the population in the B~2Σ_u~+(v'=0) state.By comparing the lasing and fluorescence spectra of the nitrogen gas obtained in the discharged and laser-induced plasma,we show that the quenching of N_2~+ lasing is caused by the efficient suppression of population inversion between the B~2Σ_u~+ and X~2Σ_g~+ states of N_2~+,in which a much higher population occurs in the X~2Σ_g~+ state in the discharge plasma.Our results clarify the important role of population inversion in generating N_2~+ air lasing,and also indicate the potential for the enhancement of N_2~+ lasing via further manipulation of the population in the X~2Σ_g~+ state in the discharged medium.     

UV Radiation Source Based on the Plasma of a Glow Discharge in a Mixture of Helium with Water Vapors

The results on the optical characteristics of the glow–discharge plasma in an He/H₂O mixture are presented. It has been established that it is a source of UV radiation in the region 306–315 nm (_max = 309.6 nm). Radiation lines of the atoms of hydrogen (H 486.1 nm and H 656.3 nm) and helium (491.1, 501.1, 587.6, and 667.8 nm) were recorded in the visible region of the spectrum; they can be used as diagnostic lines in measuring the parameters of this plasma (n _e, T _e) by the method of emission spectroscopy. The intensity of the UV bands and of the spectral lines HI and HeI have been optimized depending on the partial pressure of helium and the discharge current. The results obtained are of interest for the development of an ecologically pure source of UV radiation on the basis of chemiluminescence of water vapors in a longitudinal glow discharge.     

Atomic Emission Spectrometry of Microsamples in a Glow Discharge

A glow discharge system for atomic emission spectrometry is evaluated for physical and analytical characteristics. Lead (as the nitrate) is the model element used for these studies. The sputtering characteristics of several electrode designs are studied with the best system tried resulting in total sample vaporization in less than 1 s. Discharge currents up to 200 mA at a discharge voltage of 1200 V and a pressure of 2 torr are found to give the best results. The detection limit for lead is 0.9 ng and the linear dynamic range of response is greater than 2 orders of magnitude. Sodium chloride at a 100-fold excess amount causes a 50% decrease in the signal level.     

用发射光谱法测量氮气直流辉光放电的转动温度

本文报道了氮气气压分别为10和20Pa时，对直流辉光放电的发射光谱进行测量和分析的结果。选择的研究对象为N2放电中形成的N2^ B^2∑u^ →X^2∑g^ 跃迁的Δv=v′-v″=0谱带系中v′=0→v″=0谱带的R支。在阴极背面辉光区、阴极鞘层区、正柱区以及阳极辉光区中分别选择一点进行了转动分辨的发射光谱的测量。利用自己编写的光谱拟合程序，获得了相应的实验条件下N2^ 的转动温度，给出了转动温度随放电电压的变化趋势，其结果可以用直流放电的帕邢定律得到很好的解释。在10和20Pa气压下，放电的阴极鞘层区、正柱区、阳极辉光区中的转动温度都随放电电压呈现出了不同的变化趋势，甚至是完全相反的变化趋势。我们认为这是由于气压不同时，放电状态不同所致：气压为10Pa时的放电是正常辉光放电，而气压为时20Pa的放电为反常辉光放电。