Electrical characteristics of pulsed glow discharges

The i-v characteristics, energy partitioning, and time evolution of the discharge current and reduced field (E/N) for a nitrogen discharge are simulated using a self-consistent calculation of the electron energy distribution function and the vibrational level populations. The model includes diffusion losses and takes account of the external circuit parameters. The results discussed are for pressures of 1-100 torr, discharge currents in the range of 10^-3-5.0 A, and a reduced field (E/N) in the range of 150-250 Td. For a typical discharge in a tube of 2-cm diam. and a current of a few amperes, the results show that the energy stored in the vibrational manifold saturates a few milliseconds after the initiation of the discharge     

Modulation instability in pulsed surface-wave sustained discharges

Experimental results showing development of modulation instability and tendency to soliton formation in pulsed gas discharges sustained by surface waves are presented. The measurements are performed in argon discharges at gas pressure 13-1.3·10³ Pa sustained by pulsed microwave power at 2.45 GHz, The changes along the discharge length of the shape of the pulses of the total light emission, which is an indication for the plasma density, and of the wave electric field creating the discharge, are registrated. The cases when the modulation instability arises from the level of fluctuations in the plasma and when it is forced by the applied signal producing the discharge are demonstrated. The obtained results are discussed in terms of weak nonlinearity superimposed on the mechanism of strong ionization nonlinearity responsible for the discharge creation itself. A separation of a solitary-like wave front the leading edge of the pulse is also reported as an experimental result     

重复频率脉冲大气放电中氮气的振动温度

氮气分子的振动自由度在大气放电低温等离子体中会被高度激发。从振动能级的简谐振子模型和Boltzmann分布近似出发,研究重复频率脉冲放电中振动温度的变化行为。结果表明,决定重频条件下振动温度的主要过程是电子碰撞振动激发和振动-平动弛豫,而在振动能级高度激发的情形下其与氧原子的化学反应也会产生影响。对于振动激发过程,通过跃迁反比相似率推导出的特征弛豫时间与动理学模型符合较好。在振动-平动弛豫中占主导贡献的为干燥大气中的氧原子或潮湿大气中的水分子。当氧原子数密度为1014 cm-3时,若初始振动温度在5000 K,在化学反应过程中振动能量的特征弛豫时间在0.1~1 s量级。     

脉冲放电产生螺旋流注的等离子体特性研究

通过脉冲放电方式产生三维螺旋形的等离子体放电通道,在高速摄像机拍摄下观察到放电通道中的发光电离体以流注形式沿螺旋轨迹快速传播.建立电磁模型解释螺旋放电的形成机制,对造成对称性破缺及影响其手性性质的极向电场进行分析.研究表明,螺旋放电产生的放电通道存在两种不同的手性特征,而脉冲重复频率等放电参数及边界条件对螺旋流注的传播特性存在影响.脉冲电源驱动的电磁场在介质管内所形成的波模是极向电场形成的一个重要来源,当极向电场与轴向电场强度相近时则形成螺旋流注放电.     

Radiation of pulsed and glow discharges in CCl4

The radiation of a pulsed-periodic discharge in CCl₄ has been investigated. Its spectrum is found to differ considerably from the spectrum of the glow discharge. It is found that ‖60% of the energy from the 215–650 nm region falls in the UV spectrum. Moscow Physicotechnical Institute, 9, Institutskii Per., Dolgoprudnyi, 141701, Moscow Region, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 2, pp. 302–305, March–April, 1998.     

气体脉冲放电等离子体阻抗的参量研究

在纯净氦气条件下，对高频纵向脉冲放电的等离子体动态阻抗进行了实验研究.测量了放电等离子体阻抗随放电电压、频率以及气体压强之间的变化关系，表明等离子体阻抗随频率和电压的增加而下降，随气压的升高而增大.定性分析了这些宏观参量与等离子体阻抗变化之间的关系，拟合出等离子体阻抗随电压、频率、气压变化的经验公式，并对数值模拟与实验结果进行了比较研究. 关键词： 等离子体阻抗 气体脉冲放电     

High-pressure pulsed avalanche discharges: formulas for requiredpreionization density and rate for homogeneity

The requirements on preionization for the formation of spatially homogeneous pulsed avalanche discharges are examined. We derive two formulas which apply in the case of a slowly rising electric field, one which gives the required preionization density at breakdown, and one which gives the required preionization rate. These quantities are expressed as functions of the electrochemical properties of the gas, the neutral density, and the electric field rise time. We also treat the statistical effect that the electrons tend to form groups, in contrast to being randomly distributed in space, during the prebreakdown phase. This process is found to increase the required preionization rate significantly, typically by a factor of five for a discharge at atmospheric pressure     

Experimental investigation of pulsed electron-beam-controlled carbon monoxide lasers

Experimental facilities and tests are described for the investigations of the energy, temporal, and spectral characteristics of the emission of pulsed high-pressure CO lasers excited by the electron-beam-controlled discharge method, with emission energy up to 400 J and efficiency up to 35%, and with an excitation volume of 5 liters. The dependences of the output parameters of such lasers on the excitation power and duration, as well as on the composition and density of the working gas mixturej are investigated. It is shown that the results of numerical calculations of the parameters of pulsed electron-beam CO lasers agree qualitatively with the experimental data. The greatest discrepancies are observed for a laser with an uncooled gas mixture and for a pure carbon monoxide laser.Translated from Trudy Ordena Lenina Fizicheskogo Instituta in. P. N. Lebedeva Akademii Nauk SSSR, Vol. 116, pp. 54–97, 1980.     

Use of average value of Langmuir probe characteristic for characterization of pulsed discharges

Based on numerical calculations a new method has been developed, which enables plasma analysis from the average value of the Langmuir probe current measured in pulsed discharge. The application of this method for characterization of a planar reactor used for plasma enhanced chemical vapor deposition of TiN and (TiAl)N hard coatings is described as an example. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A rapid-scan device for the determination of spectral line profiles in pulsed discharges

The results of a time-of-flight experiment are presented, in which the total cross-sections for 2–400 eV positrons on H₂, D₂, N₂, and CO were measured.     

A rapid-scan device for the determination of spectral line profiles in pulsed discharges

The results of a time-of-flight experiment are presented, in which the total cross-sections for 2–400 eV positrons on H₂, D₂, N₂, and CO were measured. Paper F7 presented at 3rd Internat'l. Conf. Positron Annihilation. Otaniemi, Finland (August 1973).     

Frequency tunable single-line pulsed first-overtone carbon monoxide laser

Tunable single-line first-overtone (FO) CO lasing on wavelengths from 2.7 up to 4.2 μm corresponding to overtone vibrational transitions from 13→11 up to 38→36 on 413 ro-vibrational lines was experimentally obtained. A parametric study of energetic and spectral characteristics of the single-line FO CO laser was carried out. Energy distribution over ro-vibrational lines was measured. The maximum specific output energy (SOE) came up to 3 J/l Amagat, with single-line output efficiency being up to 0.6%. For the first time, a multi-quantum theoretical model was used to describe the tunable single-line FO CO laser. This multi-quantum approach demonstrated better agreement between theoretical calculations and observed experimental data for laser output as a function of vibrational quantum numbers.     

Time-resolved Fourier transform infrared spectroscopy: Application to pulsed discharges

Time-resolved Fourier transform spectroscopy (TR-FTS) is reviewed, with emphasis on synchronous FTS using continuously scanning interferometers. By using a high-resolution Bruker IFS 120 HR, a TR-FTS method has been developed with the help of a microcontroller SX, where a maximum of 64 time-resolved data are recorded with a preset time interval in a single scan of the interferometer. The time resolution is 1 μs, limited by the response time of the detector system used. This method has been applied to a pulsed discharge in an Ar and H₂ mixture to observe time profiles of ArH⁺ and ArH emission spectra. Electronic transitions of He₂ have been observed in the infrared region with this method, and from the time profiles, He₂ in Rydberg states with higher energy than the b³Π state is found to be produced efficiently in afterglow plasma. Fifteen bands in the 2300-8000 cm⁻¹ region have been assigned by using previously reported data from the optical region. A new band from the 5f state has been assigned for the first time through the 5f-4d band in the 2600 cm⁻¹ region.     

Features of the development of pulsed microwave discharges in various gases in a quasioptical beam

Photographs of pulsed microwave discharges initiated by a metallic sphere placed at the focus of a quasioptical electromagnetic beam with linear polarization of the field in air, sulfur hexafluoride, hydrogen, and helium under a pressure of several hundred Torr are presented. The common and distinctive features of the discharges in these gases are noted. Zh. Tekh. Fiz. 68, 33–36 (April 1998)