Formation of macroparticle charge in a classical Coulomb plasma

An expression is derived for the average macroparticle charge and the electron temperature in a heated dense gas. Pis’ma Zh. Tekh. Fiz. 25, 52–55 (January 12, 1999)     

Formation of conical structures during the growth of nanofibers in a glow discharge plasma

A theoretical model of the growth of conical carbon structures, when employing the “vapor-liquid-solid body” mechanism in a glow discharge plasma, is suggested. It is shown that the radius of a catalytic nanoparticle influences the cone apex angle. Translated from Inzhenerno-FizicheskiiZhurnal, Vol.81, No. 6, pp. 1094–1096, November–December, 2008.     

射频容性放电Ar等离子体离子能量分布和角度分布

通过MC模型对射频容性Ar等离子体中离子入射的能量及其分布特性进行了模拟计算,结果表明,放电压力低时,高能量离子分布较多,且在高能区域分布曲线呈双峰形式,离子入射的角度较小;放电压力高时,低能量离子分布较多,能量分布曲线偏向于低能量区域,且高能峰消失,离子入射角度增大;放电电压升高,离子能量分布曲线向高能区域移动,能峰之间的距离变长,角度分布曲线向小角度区域移动;随着自偏压升高,入射离子的能量增大,能量分布曲线向高能量区域移动,能峰间距变化不大,离子入射角度减小。法拉第离子能量分析器的测试结果表明,低放电压力时,离子能量较高且在高能区域呈双峰形式,高放电压力时,离子能量较低且能量分布高能峰消失。     

Localization of an rf capacitive discharge in a long strip line

The self-consistent problem of a an intermediate-pressure rf capacitive discharge in a long strip line is analyzed with allowance for heating of the gas. Steady-state distributions of the discharge parameters along the line are derived. It is shown that the discharge burns in certain regions, whose lengths and locations depend on the amplitude of the applied voltage. Pis’ma Zh. Tekh. Fiz. 23, 64–70 (January 26, 1997)     

Dynamics of dusty plasma structures in modulated RF discharge

Parametric excitation of the resonance oscillations of dust particles in a near-electrode layer of an RF discharge with low-frequency-modulated amplitude of the discharge voltage gas been studied. Depending on the modulation depth, both the dynamic stabilization of particles (leading to a change in the structure of dusty medium) and the parametric resonance in a certain band of excitation frequencies are possible. A model for the observed phenomenon is proposed. It is shown that the excitation of oscillations of dust particles has a threshold character.     

Effects of ethylene on NO conversion and product distributions in an rf discharge reactor

In the previous study, high concentration of NO in N(2)/O(2) mixtures could be converted mainly into N(2) via a radio-frequency discharge approach at a low pressure (4 kPa). To enhance the efficiency of NO removal, C(2)H(4) was added to elevate significantly the NO conversion in this study. The results showed that at inlet C(2)H(4)/NO molar ratio of 1 and 120 W in the C(2)H(4)/NO (1%)/O(2) (6%)/N(2) mixtures, the NO conversion reached 93.7% with a C(2)H(4) conversion of 100%, to much higher than without C(2)H(4) condition (NO conversion=77.6%). Moreover, as high as 99.8% of the fraction of total N atoms converted from NO into N(2) was achieved. In addition, the relationship between the major active species observed in the optical emission spectra at different inlet C(2)H(4) concentration and the important reactions for NO removal and N(2) formation were discussed.     

Electronic energy spectrum of the sheath of an asymmetric low-pressure capacitive rf discharge

The high-energy part of the electron energy spectrum of the plasma of an asymmetric capacitive low-pressure rf discharge in air associated with electron beams near the electrodes is studied experimentally. It is found that the energy distributions obtained under different conditions contain a beam peak, both quasimonoenergetic and substantially broadened in energy. It is established on the basis of quantitative estimates that the substantial damping of the electron beam is due to the excitation of collisionally dissipative and collisionless beam-plasma instabilities. Pis’ma Zh. Tekh. Fiz. 25, 32–39 (October 12, 1999)     

Self-consistent model of a low-pressure rf capacitive discharge

A simple self-consistent model of a low-pressure rf capacitive discharge is formulated. Effects associated with stochastic heating of the electrons and the nonlocal nature of the electric field are taken into account. The relations obtained can be used for a qualitative analysis of the main features of these low-pressure discharges. The results of the numerical calculations show good agreement with available experimental data. Pis’ma Zh. Tekh. Fiz. 23, 39–45 (January 12, 1997)     

Periodic plasma structures in nanosecond discharge with a slit cathode

The spatial structure of optical emission from a transverse nanosecond pulsed electric discharge with a hollow (slit) cathode has been experimentally studied. A regular periodic plasma structure has been observed during nanosecond pulsed discharge in helium at medium pressures. Conditions of the plasma structure formation with respect to the discharge voltage and current are determined. It is shown that the observed plasma structure differs from the known types of striations.     

Ion energy cost in a combined inductive-capacitive rf discharge

Experimental measurements were made of the ion energy cost η as a function of the parameters of a combined rf inductive-capacitive discharge at low pressures (p<10⁻² Torr). It was established that η does not depend on the power supplied, it has a minimum as a function of pressure, and also decreases when an rf potential is applied to the electrodes. The results can be used to find the optimum parameters in terms of energy efficiency of ion formation and may be useful for refining the theoretical models of a combined rf inductive-capacitive discharge. Pis’ma Zh. Tekh. Fiz. 24, 33–39 (November 26, 1998)     

Formation of a cathode plasma jet in a laser-induced vacuum discharge

The process of formation of micropinch structures in the plasma of a vacuum discharge initiated by a laser pulse on the cathode is studied. It is demonstrated that the micropinch formation takes place mainly in the substance evaporated by the laser pulse upon the discharge initiation. The size of the hot region of the plasma jet and the distance from the cathode to the micropinch increase with increasing laser pulse energy.     

Oxygen implantation and diffusion in pure titanium by an rf inductively coupled plasma

The superficial oxidation of pure titanium, 9 mm diameter, 5 mm thick disc samples by implantation and diffusion from inductively coupled plasmas is reported. Such rf plasmas were generated in a 15 l cylindrical Pyrex-like glass chamber containing pure circulating oxygen. A quarter wavelength solenoidal antenna capable of transmitting 500 W at 13.54 MHz was externally wound around the chamber and connected to an rf generator capable of up to 1200 W through an automatic matching network. The oxidation process was carried out for 6 h periods while varying the gas pressure between 1 × 10² and 5 × 10^?1 Pa and the sample bias up to ?3000 V DC. It was found that the sample temperature was a function both of the plasma density and the bias voltage. Without bias, the plasma heated the sample up to ～200 °C, and with maximal bias voltage, the substrate was heated to 680 °C. At the latter temperature, the presence of the rutile phase was particularly evident in X-ray diffraction patterns. According to EDX data, the average oxygen to titanium ratio rose, from ～0.06 for an untreated reference sample, to a ～1.7 value for samples treated up to 680 °C.     

Evolution of rf instability in a steady-state plasma accelerator

For the first time experimental data are obtained which indicate a stable relation between the microwave radiation intensity of a steady-state plasma accelerator and the rate of bulk erosion of the accelerating channel walls. The frequency range of the electromagnetic radiation corresponds to the excitation of a specific beam instability of the plasma flux at the edge of the accelerating channel, caused, in the opinion of the authors, by electron emission from the eroded part of the dielectric walls. Pis’ma Zh. Tekh. Fiz. 23, 37–41 (May 26, 1997)     

The growth of amorphous and graphitic carbon layers under ion bombardment in an rf plasma

Methods of preparing C-films from energetic C-ions and from ion impact bombardment of hydrocarbon species are reviewed. It is shown that amorphous C-deposits resulting from impact damage can have dielectric properties and be exceptionally hard. The rf plasma technique used to grow a-C-films on a negatively biased target is described and the effects of temperature rise on structural change is followed using differential scanning calomimetry. The as-grown films contain absorbed hydrogen which produces compressive stress and is released to form gas bubbles at 400°C.     

Formation of fractal carbon structures in barrier-discharge plasma under atmospheric pressure

Conditions in which fractal carbon structures are formed in barrier-discharge plasma under atmospheric pressure to obtain submicrometer carbon particles have been studied.     

Doping of rf plasma deposited diamond-like carbon films

Rf plasma deposited diamond-like carbon (DLC) films have been doped n-type with the addition of nitrogen as a feed gas to a magnetically confined rf plasma. Controlled amounts of nitrogen are added to the CH₄/He plasma and the films are characterised. The electronic properties together with the microstructure of the deposited films are examined. Activation energy studies show the Fermi level can be moved from 0.5 eV away from the valence band for the undoped DLC films, through a maximum activation energy of 0.9 eV corresponding to the midgap and to 0.45 eV away from the conduction band with maximum N incorporation. The optical band gap first increases, indicative of a reduction in the band-edge tail states, and then tends to a steady value of ˜2 eV. Activation energy studies together with the optical band gap data are used to analyse the density of states for the deposited films. The preferential doping configuration of the atomic nitrogen and the importance of the π-π* states for electronic conduction for DLC:N films is discussed in the light of the findings.     

Microwave and rf excitation of a discharge in sulfur vapor with added neon

An experimental investigation was made of the transient emission of a discharge excited by microwave radiation in mixtures of sulfur and rare gases. Several typical spectral types of emission were identified which alternate over time. Pis’ma Zh. Tekh. Fiz. 25, 27–33 (July 12, 1999)     

Metal-insulator cathode in an rf electron gun

The possibility of using metal-insulator cathodes in rf guns of 10 cm linear resonant electron accelerators has been studied experimentally for the first time. Results of calculations and the development of a prototype cathode are described. Results of an experimental investigation of the operating regimes of an rf gun are presented. The gun delivered a beam having a particle energy greater than 300 keV, a pulse length of 40–50 ns, and a pulsed current of 3.5–4.5 A. Pis’ma Zh. Tekh. Fiz. 24, 36–39 (October 12, 1998)