Three-body recombination of electrons and ions in the presence of two-level atoms

The distribution function of bound electrons and the recombination rate of electrons and ions in the presence of two-level atoms is considered within a diffusion model. Two cases are considered: (a) it is assumed in accordance with traditional theories that relaxation occurs as a result of binary collisions; (b) it is assumed that the anomalous drift previously discovered on the basis of a first-principles simulation takes place. It is shown that the distribution of bound electrons obtained on the basis of the theory of binary Coulomb collisions is not consistent with the results of a numerical many-particle dynamics simulation, while a kinetic model which utilizes the theory of anomalous drift is consistent with the simulation results. Zh. Tekh. Fiz. 68, 15–19 (January 1998)     

Drift mobility correlation in a simple cubic lattice

A Monte Carlo method is described for the calculation of the drift mobility of interacting ions on a simple cubic lattice in an electric field. This formalism provides a useful operational model for electromigration in interstitial solid solutions. The results, which show a correlation in the drift of the ions, can be interpreted either in terms of a deviation from the Nernst-Einstein relation in the sense of vacancy wind effects or as an intrinsic correlation effect in the diffusion coefficient of the charge carriers. It is also shown that the usual tracer correlation factor can be calculated upon subtracting the square of the average drifts from the average squared displacements.     

Light-induced drift of ions in a magnetic field

The effect of a magnetic field on the ion drift in a weakly ionized gas under the combined action of the light-induced drift and light pressure is studied theoretically. It is shown that, under the action of light, a component of ion drift velocity transverse to the direction of propagation of radiation may appear in a weakly ionized gas upon the application of an external magnetic field. It is shown that the Lorentz force acting on ions in the magnetic field radically changes the dependence of the ion drift velocity on the radiation frequency detuning. It is predicted that the ion drift velocity component along the direction of radiation must reverse its sign upon an increase in the magnetic field and an anomalous light-induced drift may be observed.     

Collective acceleration of xenon ions in a plasma-anode vircator

The collective acceleration of xenon ions in a plasma-anode vircator is studied. It is shown that the energy of accelerated ions may reach 900 MeV. The image of a bremsstrahlung source on the target suggests effective transport of relativistic electrons in the drift channel.     

Nonlinear development of the dust acoustic instability in acollisional dusty plasma

We study the nonlinear behavior of the low-frequency dust acoustic instability in a collisional dusty plasma by means of particle simulations. The instability arises due to the streaming of plasma ions and neutrals relative to charged dust grains. According to linear theory, the presence of collisions between the plasma ions and a neutral gas background reduces the growth rate of the instability. Nonlinearly, however, the presence of drifting neutrals maintains the initial relative drift between plasma and dust ions until the unstable waves grow to large amplitude and collisions due to wave-particle interactions exceed the neutral collisions. As a result, stronger nonlinear effects, as manifested by enhanced fluctuations, larger amounts of plasma and dust heating, and a temporary reduction of the relative drift velocity, can occur in the presence of collisions     

On the thermodynamics of phase transitions in metal hydrides

Metal hydrides are solutions of hydrogen in a metal, where phase transitions may occur depending on temperature, pressure etc. We apply Le Chatelier’s principle of thermodynamics to a particular phase transition in TiH _x , which can approximately be described as a second-order phase transition. We show that the fluctuations of the order parameter correspond to fluctuations both of the density of H⁺ ions and of the distance between adjacent H⁺ ions. Moreover, as the system approaches the transition and the correlation radius increases, we show -with the help of statistical mechanics-that the statistical weight of modes involving a large number of H⁺ ions (‘collective modes’) increases sharply, in spite of the fact that the Boltzmann factor of each collective mode is exponentially small. As a result, the interaction of the H⁺ ions with collective modes makes a tiny suprathermal fraction of the H⁺ population appear. Our results hold for similar transitions in metal deuterides, too. A violation of an -insofar undisputed-upper bound on hydrogen loading follows.     

Effect of Surface Potentials on Interaction between Ions and Surfaces

It is shown by studying the scattering of helium and neon ions with hyperthermal energies on the surfaces of semiconductors that the crystal surfaces reflect some incident ions by means of pairwise interaction and some ions with no loss of energy. Reflection without loss of energy is also assumed to occur due to pairwise interaction between ions and surface atoms bound to underlying atoms by a rigid interaction potential.     

高场不对称波形离子迁移谱谱图峰分析方法研究

从离子运动轨迹入手,引入损耗高度,建立了高场不对称波形离子迁移谱(FAIMS)的谱图峰模型. 该模型将流场分布、离子迁移管结构、分离电压以及补偿电压等FAIMS关键参数与FAIMS谱图峰形、峰高、半高宽联系起来,得到了清晰的量化关系,与实验数据符合较好.     

On the ion drift in gas mixtures

The features of the velocity distribution function of ions during their drift in a mixture of different gases are analyzed. Examples of drift of heavy ions in light gas, a mixture of two gases with equal concentrations, and drift of light ions in heavy gas are considered. It was shown that the transition to discharge in mixtures of different gases allows the formation of an ion flux with characteristics unattainable for discharge in single-component gas under typical conditions under which experiments with dust structures in plasma are performed.     

Geodesic mode spectrum modified by the energetic particles in tokamak plasmas

Effect of a minor concentration of the energetic particles on GAM spectrum in a tokamak is analyzed by drift kinetic theory taking into the account the electron current and diamagnetic drift. A novel method of Jacobi functions is applied to solve the drift kinetic equation for the energetic bounce particles in the limit of high bounce frequency in comparison with the GAM frequency. Using the Q-asymptotic of Jacobi function, it is shown that the energetic minority ions can form the continuum minimum/maximum at the NB or ICR power deposition maximum where the geodesic eigenmode may be excited. In this case, the electron current modeled by shifted Maxwell distribution overcomes the ion Landau damping threshold thus resulting in the GAM instability.     

Linear and Nonlinear Coupling of Electrostatic Drift and Acoustic Perturbations in a Nonuniform Bi-Ion Plasma with Non-Maxwellian Electrons

Linear and nonlinear coupling of drift and ion acoustic waves are studied in a nonuniform magnetized plasma comprising of Oxygen and Hydrogen ions with nonthermal distribution of electrons. It has been observed that different ratios of ion number densities and kappa and Cairns distributed electrons significantly modify the linear dispersion characteristics of coupled drift-ion acoustic waves. In the nonlinear regime, KdV (for pure drift waves) and KP (for coupled drift-ion acoustic waves) like equations have been derived to study the nonlinear evolution of drift solitary waves in one and two dimensions. The dependence of drift solitary structures on different ratios of ion number densities and nonthermal distribution of electrons has also been explored in detail. It has been found that the ratio of the diamagnetic drift velocity to the velocity of the nonlinear structure determines the existence regimes for the drift solitary waves. The present investigation may be beneficial to understand the formation of solitons in the ionospheric F-region.     

The transport of slow ions in gases: Experiment, theory, and applications

This review is concerned with the two most important transport phenomena in involving slow ions in gases, namely their drift and diffusion in an externally applied electric field. The energy range of interest extends from thermal values at low temperatures up to about 10 eV. The transport phenomena are first discussed in physical terms, and experimental techniques for measuring ionic drift velocities and diffusion coefficients are then described. Brief coverage is given to ionic transport theory up to the time of Wannier's landmark contributions in 1951–1952; later theoretical developments are treated in more detail. Special emphasis is placed on aspects of modern theory that permit the determination of interaction potentials and collision frequencies for momentum transfer from experimental transport data. The review ends with a discussion of several applications of transport data to ionospheric problems.     

Dust Sheared Flow Driven Instability of Dust Drift Waves in a Nonuniform Magnetoplasma

We investigate instability of dust drift waves in a nonuniform dusty magnetoplasma containing transverse sheared plasma flow that is produced by a nonuniform electric field. By using Boltzmann distributed electrons and ions, Poisson’s equation, as well as the dust continuity equation with perpendicular guiding center dust drift speed, we derive an eigenvalue equation, which strongly depends on the profiles of dust sheared flow and dust density gradient. The eigenvalue equation is analytically solved to obtain expressions for the growth rate and threshold of a convective instability arising from resonant interactions between the dust drift waves and sheared flows. The result may be relevant to the understanding of short wavelength (in comparison with the ion gyroradius) electrostatic fluctuations in magnetized plasmas of Saturn rings and in cometary tails. PACS numbers: 52.27.Lw; 52.35.Fp     

Experimental study of the influence of the processes in the ion-beam drift space on beam current measurements

A method is proposed for separate measurements of the current produced by slow charge-exchange ions and that produced by the ions generated due to gas ionization by the beam ions and fast secondary electrons in the beam drift space. The method is based on an analysis of the current distribution over the electrodes of a modified Faraday cup with nonequipotential electrodes and allows one to determine the coefficient of ion-induced electron emission from the ion collector and the charge-exchange cross section of the accelerated ions. The method has been employed to measure the current of an argon ion beam with an ion energy from a few electronvolts to several tens of kiloelectronvolts and to study the processes in the beam drift space at pressures of 0.03–0.15 Pa.     

Poloidal rotation of main ions in the CT-6B tokamak

The poloidal rotation velocity of neutral hydrogen atoms is measured using the Doppler shift of the Hα spectral line emitted in the CT-6B tokamak. The poloidal rotation of hydrogen atoms is generated through the collisions and charge-exchanges with main ions (protons). Therefore, the rotation direction of main ions can be deduced from that of neutral hydrogen atoms. The experimental results show that the main ions rotate in the electron diamagnetic drift direction, the same as the impurity ions, in the plasma core. The neutral hydrogen atoms rotate also in the electron diamagnetic drift direction in the edge region of the plasma. However, the rotation direction of main ions in the edge region cannot be judged from the experimental result due to the long mean free path of hydrogen atoms in the edge region. An inward diffusion flux of hydrogen atoms toward the torus inside with a velocity of the same order of magnitude as their poloidal rotation is also observed.     

Diagnostics of an H− ion beam by light emission from the drift chamber

The possibility of diagnosing an ion beam by light emission from the drift chamber is demonstrated using a 2-MeV H⁻ ion beam as an example. For a local gas puffing and negligible beam losses, spatial characteristics of the beam and the time behavior of the current pulse were monitored and the falling of a small number of ions onto the vacuum-chamber wall was recorded. A profilometer for recording the emission from individual layers of the observed region is described.     

New physical methods of organic compound identification using a surface ionization drift spectrometer

A new material for an ion thermoemitter is developed that provides efficient selective ionization of nitrogen-, sulfur-, phosphorus-, and arsenic-based organics and stability of ionization parameters. A new design of a drift spectrometer that allows for drift spectrometry analysis of unneutralized ion beams is suggested. It is shown that a drift spectrometer of such a design makes it possible to simultaneously determine a number of physicochemical characteristics of organic molecules (such as a complete set of drift mobility parameters for ions, activation energy of organic molecule ionization, and activation energy of organic molecule desorption from the test sample carrier), which is equivalent to significant improvement of the instrument’s effective resolution.     

CT-6B托卡马克等离子体角向转动的光谱测量

利用高分辨光谱测量系统，根据杂质离子谱线ＯⅡ４６４.２ｎｍ，ＣⅢ４６４.７ｎｍ和氢Ｈα谱线的多普勒位移，测量了ＣＴ-６Ｂ托卡马克等离子体角向转动速度的径向分布．结果表明：杂质离子的角向转动速度的方向在等离子体内部为电子逆磁漂移方向，其线速度在小半径约９ｃｍ处达到极大值３.５ｋｍ／ｓ；在接近孔阑ｒ＝１０ｃｍ处，反转为离子逆磁漂移方向．由此导出等离子体内部的径向电场向里，其最大值为１８Ｖ／ｃｍ．中性氢原子只存在其方向为电子逆磁漂移方向的角向转动分量，其数值较杂质离子谱线所得结果要低．最后对所得的结果作了初步的讨论 关键词：     

Ti扩散铌酸锂光波导特性的热固定技术

在Ti扩散铌酸锂光波导中,因光致折变效应而导致光波导特性漂移.在光波相干性的导波光学器件中,光致折变效应的影响尤为严重.本文报道了稳定光致折变效应的热固定技术实验结果;并提出在光波导特性的热固定过程中,不是H~+离子起主导作用这一看法.