Resonance radiation in the cold cathode region of a glow discharge in argon

The imprisonment of resonance radiation in the cold cathode region of a glow discharge in argon is calculated. It is shown that the number of resonance photons reaching the cathode surface is substantially smaller than the number of positive ions.     

Surface condition and electron emission from cold cathodes in vacuum and in noble gas glow discharge

An optogalvanic method is used to measure photoemission coefficient γ_ph in a gas discharge exposed to the resonant radiation of helium atoms. The range of working current j/P _He ² (j is the current density, and P _He is the gas pressure) extends from 2 to 1000 μA/(cm² Torr), and field strength E/N at the cathode varies from 0.45 to 13 kTd. Up to j/P _He ² = 10 μA/(cm²Torr²), photoemission coefficient γ_ph grows and then tends toward saturation at a level of γ_ph = 0.30 ± 0.01. Under the no-discharge conditions, γ_ph = 0.35 ± 0.05. It is concluded that the emissivity of cold cathodes in a gas discharge is governed by adsorption of the working gas on the cathode surface and its implantation into the cathode. With allowance for this factor, the contribution of photoemission to the discharge current is reconsidered. It is shown that, for cathodes with diameter d _c ? l _c (l _c is the length of the cathode layer), a normal or weakly abnormal glow discharge in noble gases is largely of a photoelectron character. In light noble gases, the photoelectron character of the discharge persists even for a strongly abnormal discharge. The energy dependences of coefficients γ of kinetic and potential emission in helium are calculated with allowance for implantation of helium atoms into the cathode and compared with published data. The influence of particle implantation on γ in a vacuum is estimated.     

Spherical striations in a glow discharge

The stratification of a volume glow discharge is observed experimentally. Spherically symmetric stationary striations are detected. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 11, 679–682 (10 December 1997)     

The excitation of spectral lines in the cold cathode region of a glow discharge in argon

Calculations on the excitation of spectral lines emitted by the cathode fall and the negative glow regions of a glow discharge in argon have been performed using space-dependent electron velocity distributions allowing for electron impact excitation and ionization of atoms.     

Plasma-dust structures in He-Ar DC glow discharge

The gas mixture discharge has a number of features which can appear in experiments with dusty plasma. For example, in the case of a significant difference in atomic masses of ions and atoms, strong anisotropy of the distribution function over ion velocities takes place, which in turn can cause a significant change in properties of dust structures. In this work, experiments on the study of the dust structures in the gas discharge of a mixture of light and heavy gases, i.e., helium and argon, are analyzed. The results of numerical simulation of ion and electron drift in the mixture of these gases and dust particle charging processes are presented.     

Electron collision rates in oxygen glow discharge

The calculations of the distribution function of electrons and the collisional rates were carried out on the basis of a numerical solution of the Boltzmann equation for a weakly ionized discharge in O₂ rangingE/N from 5 Td to 200 Td. The distribution function, Townsend ionization and dissociative attachment coefficients calculated were found to be in good agreement with experiments. A comparison of the results on the collisional rates with the values available in the literature was performed as well.     

�����н�����-�����ѹ�Թ�ŵ�

空气中的大气压辉光放电通常因放电易过渡到火花状态而难以产生。在静态大气压空气针-板等离子体发生器中，采用阻容耦合负反馈方法控制等离子体放电发展过程，成功地抑制了辉光放电向火花放电的过渡，产生了稳定的交流辉光放电。研究了电压、电极间距等参数变化对放电的影响。     

Numerical analysis of glow discharge in oxygen

Computational analysis of the positive column in a dc oxygen glow discharge was performed. Considering the discharge plasma as a mixture of electrons, positive molecular ions, negative atomic ions, metastable molecules O ₂ ^* (a¹_g), atoms and molecules particle balance equations were solved. As a result the particle concentrations in a dependence on discharge parameters were obtained and the mechanism of the discharge was discussed.     

Ordered dust structures in glow discharge plasmas

Ordering of dust grains suspended in glow discharge plasmas into quasi-steady liquid-or crystallike structures in an external field is considered. The self-consistent electric field generated by free electrons, ions, and dust grains is found. An estimate is obtained for the confining potential required to hold dust grains in the direction perpendicular to the discharge axis. It is shown that the potential energy of interaction between ordered dust particles has the form characteristic of ionic crystals. Critical parameters are estimated for a liquidlike dust structure. The correlation function calculated for a dusty plasma by using this approach is compared with a measured one.     

Ordered dust structures in a glow discharge

Highly ordered three-dimensional dust structures are created in a striated glow discharge, and their horizontal cross-sectional images are analyzed. Calculated correlation functions, local correlation parameters, and corresponding approximations are used to classify the state of a structure according to the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) two-dimensional melting theory and a phenomenological approach. An orientational map based on an orientational parameter is proposed to expose domains in a cross section of a structure. It is shown that a plasma crystal is a polycrystal consisting of hexagonal domains (crystallites). Thermophoretic forces are used to create corners of various angles in the perimeter of the structure. Transition between hexagonal and square cell shapes is observed.     

Hollow cathode glow discharge in long tubes

An analysis is made of some burning characteristics of a hollow-cathode glow discharge with a long tube (L≫D) used as the cathode. It is shown that, as in the case L∼D, the main factor imposing a lower limit on the range of operating voltages is the drift of fast electrons through the aperture in the cavity. Assuming that the electrons move along the cavity as a result of diffusion, it was possible to calculate the critical pressure at which the discharge can no longer burn and to determine the optimum ratio L/D for which the discharge can be sustained at the lowest voltage. The calculations showed satisfactory agreement with the experiment. Zh. Tekh. Fiz. 69, 36–39 (June 1999)     

Subprocesses accompanying nitriding in a glow discharge

Nitriding in a glow discharge is analyzed at the level of its components. A basically new (as compared to the classical) scheme of the process is proposed taking into account the most significant subprocesses.     

Spectroscopic study of a glow discharge in krypton

The concentrations of excited atoms at the 4p⁵5s and 4p⁵5p levels of Kr I are determined by the reabsorption and emission methods. The absolute values off for ten Kr I lines in the infrared region of the spectrum are determined from the known value off ₈₈₁₂ and from measured relative values of the oscillator strengths. Processes leading to the formation and decay of excited states of krypton atoms are discussed.In conclusion, the authors wish to thank Professor A. N. Tekuchev for valuable comments, and also Yu. P. Grigorov, T. F. Dubtsov, L. V. Zaitsev, and V. S. Korchunov for assisting with the experiments.     

Laser induced excitation transfer in helium glow discharge

Some experimental results on the temporal decay of the fluorescence induced by a resonant laser pulse excitation focused onto a helium gas discharge are presented. In particular, excitation transfer between singlet-singlet and singlet- triplet sub-levels has been studied when 2¹ S → 3¹ P and 2¹ P → 4¹ D transitions of He I are optically pumped.     

Mixed-mode oscillations and chaos in a glow discharge

We present results from numerical simulations on mixed-mode oscillations and chaos excited in a glow discharge, where a model of one-dimensional fluid equations coupled with an external circuit is used. Long duration of high ion and electron densities and fast recharge of a capacitor after a breakdown contribute to the generation of mixed-mode oscillations. The chaotic behavior is characterized by a one-dimensional multibranched map.     

Emission by nitrogen in a high-pressure glow discharge

Relative intensities are reported for the emission spectrum of N₂ in a glow discharge. The bands of the first and second positive systems were studied at pressures between 10 and 100 mm Hg. Pressure reduces the intensity of the first system more rapidly than that of the second: this may be due to quenching of the B³II state.