Electromagnetic Forces on Plasma Particles in the Presence of Resonant and Nonresonant Plasma Turbulence

Nonlinear forces on plasma particles in the presence of a test nonresonant wave and resonant plasma wave turbulence are calculated. The important feature of the considered nonlinear effect is that the forces due to the nonresonant test wave act on the plasma particles in the absence of linear and nonlinear resonances between the wave and the particles. Although in a closed plasma-wave system the process is balanced by the quasilinear interaction between the plasma resonant turbulence and plasma particles (leading to nonstationarity and inhomogeneity of the system), in open systems the effect can be significant.     

The Influence of Particles Interaction in Low-Temperature Plasma on its Composition and Optical Properties

A model theory of the influence of particles interaction in plasma on its composition and optical properties is developed. The interaction of charged particles in plasma reduces the ionization energy of atoms and ions. The action of internal microfields in plasma on atoms and ions reduces the statistical weight of electron levels which affects the populations of excited states. The latter effect leads to an effective cutoff of partition functions and determines the behaviour of optical properties of plasma (of absorption coefficient and emissivity) at increased number densities of charged particles. The formulas are obtained for calculation of the continuous and discrete spectrum in plasma taking into account the particles interaction. A non-monotonic dependence of optical plasma density upon number density of charged particles is quantitatively explained. A satisfactory agreement is obtained with a large number of experimental data some of which were considered to be contradictory. The method developed can be used for calculations in the field of atomic spectroscopy and low-temperature plasma physics including increased densities of charged particles. The use of the formulas obtained in plasma diagnostics will enable one to avoid considerable errors.     

The stationary confinement of plasma by a magnetic field at anisotropic pressure

The method of moments of the Boltzmann-Vlasov equation is used to derive relations between the macroscopic quantities of high-temperature plasma (i.e. the density of particles, the mass velocity and the generally anisotropic tensor of the kinetic pressure of particles) and the static electromagnetic field by which the plasma is stationarily confined. The well-known relation between the isotropic pressure of particles and the pressure of the magnetic field is then obtained from this as a special case. Plane geometric configuration of the plasma boundary and negligible collision interaction of the particles are assumed. The results are verified on a simple kinetic model of plasma with known trajectories of the particles.     

Sizing of particles levitating in a glow discharge dusty plasma

The dust particle size distribution in a volume glow discharge dusty plasma is studied. Polydisperse quartz particles are used as a dust component. It is found that a dusty plasma forms in a glow discharge not only in a dust trap but also near the wall at the bottom of the discharge chamber. Dust objects in the latter region are large: they contain up to 30000 particles. The size of particles levitating in discharge striations is three times larger than that of particles levitating near the wall. The idea of using the glow discharge dusty plasma for particle-size fractionation of polydisperse powder is put forward.     

Nanoparticle Tracking Analysis of Polymer Nanoparticles in Blood Plasma

A successful drug delivery system must overcome complex biological barriers. For particles injected into the blood, one of the first and most critical barriers pertains to blood stability to circulate through the human body. To effectively design drug delivery vehicles, interactions between the particles and blood, as well as the aggregation behavior, must be understood. This work presents a method to analyze particle size and aggregation in blood plasma using a commercially available nanoparticle tracking analysis (NTA) system. As a model system, fluorescently labeled polystyrene nanoparticles are incubated in goat blood plasma and analyzed using NTA. The particles incubated in plasma are found to have a protein corona that is larger than what has been observed by dynamic light scattering (DLS) in diluted plasma. Particles that are decorated with a PEG layer are also found to have large protein coronas in undiluted plasma. Because NTA is based on a unique visualization method, large multicomponent aggregates could be observed and quantified in a manner not feasible with other techniques. PEGylation of the particles is found to decrease the multicomponent aggregation from 1000 ± 200 particles for unmodified to 200 ± 30 particles for 1K PEGylated per 1 × 10⁵ total particles.     

Conditions for laser-induced plasma to effectively remove nano-particles on silicon surfaces

Particles can be removed from a silicon surface by means of irradiation and a laser plasma shock wave.The particles and silicon are heated by the irradiation and they will expand differently due to their different expansion coefficients,making the particles easier to be removed.Laser plasma can ionize and even vaporize particles more significantly than an incident laser and,therefore,it can remove the particles more efficiently.The laser plasma shock wave plays a dominant role in removing particles,which is attributed to its strong burst force.The pressure of the laser plasma shock wave is determined by the laser pulse energy and the gap between the focus of laser and substrate surface.In order to obtain the working conditions for particle removal,the removal mechanism,as well as the temporal and spatial characteristics of velocity,propagation distance and pressure of shock wave have been researched.On the basis of our results,the conditions for nano-particle removal are achieved.     

Self-sustained oscillations in a plasma-wall system with strongly inhomogeneous diffusion of charged particles

A simple system with a hydrogen plasma confined by a magnetic field parallel to the bounding material wall is considered. The charged particles diffuse out of the plasma, recombine on the wall and return into the plasma volume as neutrals, which are ionized by electrons. It is demonstrated that macroscopic self-sustained oscillations are an intrinsic feature of such a system if the diffusion coefficient of charged particles is strongly inhomogeneous in the plasma.     

Effect of a dust component on the rates of elementary processes in low-temperature plasmas

Elementary processes in dusty, beam-driven plasma discharges are studied experimentally and theoretically for the first time. A theoretical model is constructed for a beam-driven plasma containing macroscopic particles. The effect of macroscopic particles on the electron energy distribution function is estimated assuming a Coulomb field for the particles. The resulting rate of electron-ion recombination on the macroscopic particles is compared with the electron loss constant calculated from the electron energy distribution function with an electron absorption constant in the orbital-motion approximation. This approximation, which is valid in the collisionless case, is found to work satisfactorily beyond its range of applicability. The distributions of the charged particles and electric fields created by macroscopic particles in a helium plasma are determined. The experimental data demonstrate the importance of secondary emission by high-energy electrons. Zh. éksp. Teor. Fiz. 115, 2020–2036 (June 1999)     

Features of film growth during plasma anodizing of Al 2024/SiC metal matrix composite

Plasma anodizing is a novel promising process to fabricate corrosion-resistant protective films on metal matrix composites. The corrosion-resistant films were prepared by plasma anodizing on SiC reinforced aluminum matrix composite. The morphology and microstructure of films were analyzed by scanning electron microscopy. Specifically, the morphology of residual SiC reinforcement particles in the film was observed. It is found that the most SiC reinforcement particles have been molten to become silicon oxide, but a few tiny SiC particles still remain in the film close to the composite/film interface. This interface is irregular due to the hindering effect of SiC particles on the film growth. Morphology and distribution of residual SiC particles in film provide direct evidence to identify the local melt occurs in the interior of plasma anodizing film even near the composite/film interface. A model of film growth by plasma anodizing on metal matrix composites was proposed.     

Free energy of nonideal two-component thermal plasma

The free energy of nonideal two-component thermal plasma is calculated using the Poisson-Boltzmann equation. The possibility of the existence of a metastable state is shown for a component of heavy multicharged particles with particle charge values bounded from below and plasma temperature values bounded from above. The component of oppositely-charged light singly-charged particles and plasma generally do not feature the metastable state.     

Highly nonideal classical thermal plasmas: Experimental study of ordered macroparticle structures

The formation of spatially ordered CeO₂ particle structures in a thermal plasma at atmospheric pressure and temperatures of 1700–2200 K is studied. The spatial structure of the particles in the plasma is analyzed using laser time-of-flight counting of individual particles. Probe and optical diagnostics are used to determine the parameters of the thermal plasma. The CeO₂ particles were positively charged (about 10³ electronic charges). The resulting Coulomb interaction parameter for the particles is γ _p>120, which corresponds to a highly nonideal plasma. Zh. éksp. Teor. Fiz. 111, 467–477 (February 1997)     

Simulation of generation of ultradisperse particles upon irradiation of metals by a high-power electron beam

A model of formation of ultradisperse particles in the plasma torch emerging during evaporation of a metal target by a high-power electron beam is described. A model of heterogeneous media is proposed for describing the plasma torch dynamics taking into account heat conduction, heat transfer and friction between components, relaxation of components to equilibrium, condensation, and evaporation and coagulation of drops as a result of their collisions. Numerical simulation of the generation of ultradisperse particles in the plasma torch formed during irradiation of a metal target by a powerful electron beam is performed. The size distribution of ultradisperse particles is obtained for various regimes of irradiation and cooling.     

等离子体对含硼两相流扩散燃烧特性的影响

为排除来流空气对含硼燃气的掺混效应, 研究等离子体对含硼富燃料推进剂在补燃室二次燃烧过程的影响, 建立了含硼两相流平行进气扩散燃烧物理模型. 利用高速摄影仪拍摄了含硼燃气在补燃室二次燃烧的火焰图像, 分析了该物理模型的扩散燃烧特性和硼颗粒的二次点火距离. 采用硼颗粒的King点火模型、有限速度/涡耗散模型、颗粒轨道模型和RNG k-ε模型以及等离子体模型, 模拟了一定条件下等离子体对含硼两相流扩散燃烧过程的影响. 结果表明, 依据含硼燃气二次燃烧图像得到的硼颗粒二次点火距离, 与数值模拟结果基本一致, 保证了该物理模型和计算方法的可靠性. 含硼两相流经过等离子体区域后, 硼颗粒在运动轨迹上颗粒温度明显增加, 颗粒直径明显减小, B₂O₃的质量分数分布区域明显扩增, 70%的硼颗粒在到达补燃室2/3尺寸前燃烧效率已达到100%, 硼颗粒充分燃烧释放出更多热量导致中心流线区域温度增加近1/2, 可见等离子体可以明显强化含硼两相流的燃烧过程, 提高硼颗粒的燃烧效率.     

Measurement of temperature of a dusty plasma from its configuration

A new concept called “configurational temperature” is introduced in the context of dusty plasma, where the temperature of the dust particles submerged in the plasma can be measured directly from the positional information of the individual dust particles and the interaction potential between the dust grains. This method does not require the velocity information of individual particles, which is a key parameter to measure the dust temperature in the conventional method. The technique is initially tested using two-dimensional (2D) OpenMP parallel molecular dynamics and Monte Carlo simulation and then compared with the temperature evaluated from experimental data. The experiment have been carried out in the Dusty Plasma Experimental (DPEx) device, where a 2D stationary plasma crystal of melamine formaldehyde particles is formed in the cathode sheath of a DC glow discharge argon plasma. The kinetic temperature of the dust is calculated using the standard particle image velocimetry technique at different pressures. An extended simulation result for the three-dimensional case is also presented, which can be employed for the temperature measurement of a three-dimensional dust crystal in laboratory devices.     

球形及柱形磁化等离子体靶中α粒子能量沉积率分析

基于单粒子理论模型及积分算法,编写了单粒子轨道数值模拟程序———ALFA,分析了柱形和球形两种边界位形磁化等离子体靶中非热α粒子通过库仑碰撞对D-T等离子体加热的能量沉积率。在均匀背景磁场及相同的D-T等离子体密度、温度条件下,柱形边界中非热α粒子能量沉积率比球形边界更高。在相同等离子体温度及密度条件下,α粒子的能量沉积率随磁场的增大而增大,但计算结果表明,磁场的有效作用区域存在明显的上下限值,当等离子体内磁场小于下限阈值时,磁场增加对α粒子能量沉积率的提高贡献不大,而且当等离子体内磁场超过上限阈值后,磁场再增加对提高α粒子能量沉积率的作用也不明显。对不同几何尺寸的磁化等离子体靶,磁场有效作用区域的上下限值不同,靶尺寸越大,相应的上下限阈值越小。提高等离子体密度,可增加α粒子能量沉积率,也能降低磁场有效作用区域的上下限阈值。     

Heating of Powders in the Fire Ball of an Induction Plasma

A theoretical model has been developed for the calculation of the trajectories and temperature histories of particles injected in the fire-ball of an inductively coupled plasma. Calculations were made for alumina particles of different diameters ranging between 10 and 250 ?m. The particles were injected through a water cooled probe upstream of the fire-ball. The results shows that the internal plasma recirculation in the coil region is responsable for the bouncing of the particles on the fire-ball. Particles of the order of 10 ?m and smaler are entrained in the fire-ball by the inward radial flow caused by the electromagnetic pumping, and are subsequently completely evaporated. Larger particles, depending on their initial position and velocity of injection, could by-pass the plasma fire-ball, and in some cases, end up deposited on the wall of the plasma confining tube. Particles with diameters larger than 100 ?m were found to pass straight through the fire-ball when injected close to the center line of the torch.     

Effect of dust particles on the properties of low-temperature plasmas

Parameters of a low-temperature plasma containing dust particles are calculated numerically with the help of a self-consistent solution of the balance equation for production and recombination of electrons and ions, combined with the molecular dynamics method for direct simulation of processes in the vicinity of macroparticles. The relation between the charges of macroparticles and the neutral gas pressure, as well as the dependence of the low-temperature plasma parameters on the volume concentration of dust particles, is analyzed. It is shown that the plasma characteristics and composition may change noticeably relative to the case unperturbed by dust even for comparatively low concentration of dust particles.     

Scaling Law for Ablation of a Hydrogen Pellet in a Plasma

A scaling law is derived which gives the rate of ablation of a frozen hydrogen pellet immersed in a plasma without the presence of a magnetic field or space charge. Plasma particles penetrate the ablating gas-plasma cloud to the evaporating pellet surface and deliver power to the cloud to drive its expansion. The evaporation rate is determined by a "self-regulating" mechanism. The ablation time is shown to be proportional to a5/3?o-2/3?o-1/3 where a is the pellet radius, ?o is the effective penetration depth of the incident particle into solid hydrogen and ?o is the power flux density of the incident particles. It is found that for ablation in a thermonuclear plasma, the alpha particles significantly affect the ablation rate. For thermonuclear plasma electrons and alpha particles, the energy required to ablate one molecule is shown to be of the order of 10 eV or less. The scaling law is applied to presently available experimental results, and reasonable agreement is found.     

Metastable states of dust plasma

The free energy of three-component dust plasma has been calculated analytically based on the spherical model of an elementary electroneutral volume. It has been shown that metastable states of dust particles, ions, and simultaneously all plasma particles can exist for finite interparticle distances. These states can be attained due to spatial correlation of electrons, while some states can be attained due to the correlation of ions. A large charge of dust particles, high electron temperature, and a small fraction of the charge of the electrons compared to the total absolute charge of the plasma particles are important conditions for the existence of metastable states. A possible connection between the existence of metastable states of particles in the plasma and their agglomeration has been analyzed.