The Effect of the Charge Fluctuation of Dust Particles onn Ion—acoustic wave Excited Through Ionization Instability

The effect of the charge fluctuation of dust particles on ion acoustic wave(IAW) excited through ionization instability was investigated.The hydrodynamic equations and linear time-dependent perturbation theory served as the starting point of theory,by which the dispersion relatioin and growth rate of the IAW were given.By comparing the results with the case of constant dust charges,it was found that the charge fluctuation of dust particles reduces the instability of the wave mode.     

The Excitation of the Low-Frequency Electromagnetic Wave in Dusty Plasma with Vortex Flows

The Excitation of Alfven wave in dusty plasma with vortex flows is investigated. The coupled equations for density and electromagnetic potential of dusty plasma with vortex-flow were obtained. The stability and amplitude behavior were studied both analytically and numerically. Using a non-modal method, it was found that the presence of dust can suppress the growth of the instability which can also be affected by the vortex eccentricity.     

Effect of polarization force on the Jeans instability in collisional dusty plasmas

The Jeans instability in collisional dusty plasmas has been analytically investigated by considering the polarization force effect.Instabilities due to dust-neutral and ion-neutral drags can occur in electrostatic waves of collisional dusty plasmas with self-gravitating particles.In this study,the effect of gravitational force on heavy dust particles is considered in tandem with both the polarization and electrostatic forces.The theoretical framework has been developed and the dispersion relation and instability growth rate have been derived,assuming the plane wave approximation.The derived instability growth rate shows that,in collisional dusty plasmas,the Jeans instability strongly depends on the magnitude of the polarization force.     

The Effects of Inhomogeneity and Adiabatic Dusty Charge Fluctuation on Solitary Waves

Using the perturbation method, the modified variable coefficient Kadomtsev-Petviashvili (MKP) equation governing nonlinear dust acoustic solitary waves is for the first time derived with the combined effects of adiabatic dust charge fluctuation and higher-order transverse perturbation in inhomogeneous dusty plasmas due to the spatial gradients of dust charge and plasma densities. The MKP equation is reduced to the standard Kadomtsev-Petviashvili (KP) equation. The numerical results show that inhomogeneity has strong influence on the nonlinear properties of dust acoustic solitary waves.     

Dusty Sheaths in Magnetized Plasmas

Parameters of self-consistent magnetized dusty sheaths are investigated using computer simulations of a temporal evolution of one-dimensional slab plasma with dust particles. The evolution is caused by a collection of electrons and ions by both a wall (electrode) and dust particles, which are initially immersed into plasma and distributed in front of the electrode. Obtained results show the existence of oscillations of a self-consistent potential in magnetized dusty sheaths including boundary potentials. Dust particles weaken magnetized sheaths and create additional sheaths close to a boundary of dust particles. The magnetic field does not influence on the dust particle charge.     

Dynamics of Dust in a Plasma Sheath with Magnetic Field

Dynamics of dust in a plasma sheath with a magnetic field was investigated using a single particle model. The result shows that the radius, initial position, initial velocity of the dust particles and the magnetic field do effect their movement and equilibrium position in the plasma sheath. Generally, the dust particles with the same size, whatever original velocity and position they have, will locate at the same position in the end under the net actions of electrostatic, gravitational, neutral collisional, and Lorentz forces. But the dust particles will not locate in the plasma sheath if their radius is beyond a certain value.     

Simulation of DC glow discharge plasma with free-moving dust particles in the radial direction

A self-consistent fluid model is developed to investigate the radial distributions of dusty plasma parameters in a DC glow discharge, in which the extended fluid approach of plasma particles and the transport equations of dust particles are coupled. The electrical interaction between charged dust particles is considered in the model. The time evolution of radial distributions of dust density, plasma density, the radial component of electric field and the forces acting on dust particles when dust...     

Controlling fine particles in flue gas from lead-zinc smelting by plasma technology

With the aim of controlling the problem of fine particles in the flue gas of lead-zinc smelting, a low-temperature plasma-electrocoagulation and electric bag composite dedusting experimental platform was designed by combining electrocoagulation and electric bag composite dust removal technology based on the research of low-temperature plasma technology. Firstly, the properties of fine particles in flue gas from lead-zinc smelting were analyzed, and the effects of input voltage, filter wind speed, dust concentration, and pulse-jet ash-cleaning cycle on the dust collection efficiency of the integrated device were studied. Then, the energy efficiency of the integrated technology was analyzed, and the control mechanism of the fine particles was revealed. The experimental results show that the integrated technology of low-temperature plasma-electrocoagulation and electric bag composite dust removal achieves a fine particle removal efficiency of more than 99.99% and the energy consumption per unit mass of the dust is only 0.008 k W·h/g. The integrated technology has broad application prospects and farreaching practical significance for the lead-zinc smelting industry to achieve ultra-low emission targets for flue gas and achieve energy-saving and emission reduction effects.     

Characterization of dust collected in EAST after 2019 campaign

Dust presented in experimental advanced superconducting tokamak(EAST) with mixed plasmafacing materials has been collected and characterized for the first time. Dust at different positions in the vessel was collected by vacuum cleaner after the first experimental campaign in 2019. The shape, composition, and size of dust particles have been analyzed using different methods. About80% of the total number of dust particles have size between 20 and 80 μm, and most of dust particles are spherical, while schistose shape, columnar and irregular shape were also found.With the help of energy-dispersive x-ray spectroscopy different elements of dust have been identified, which is generally consistent with the different plasma-facing components in EAST.Both x-ray fluorescence and inductively coupled plasma emission spectrometer are complementary methods for measuring the dust composition quantitatively. It was found that the major components of dust were lithium dust in the form of lithium carbonate and lithium hydroxide, which is due to the routine lithium wall conditioning during EAST operation.     

Propagation characteristics of microwaves in dusty plasmas with multi-collisions

In this study, we consider three main collisions in dusty plasmas and investigate the effects of dust grains on the propagation of electromagnetic(EM) waves through uniform, unmagnetized and weakly ionized dusty plasma. The Drude model is improved to describe the dielectric property of dusty plasmas, which accounts for collisions including electron–molecule, electron–ion, and electron–dust particles. Based on the improved Drude model, the propagation characteristics of microwaves in dusty plasmas have been numerically calculated and studied.The results show that the propagation characteristics of microwaves through dusty plasmas are different from those through normal plasmas. The effects of dust density and size are mainly studied. Numerical results indicate that the momentum transfer between electrons and dust grains makes more energy loss. The dust density and dust size have a similar influence on EM wave propagation, resulting in less transmission and more absorption.     

Suppression of a spontaneous dust density wave by modulation of ion streaming

Synchronization of a self-excited dust density wave has been experimentally investigated in a strongly coupled dusty plasma. A dust density wave of frequency ~78 Hz is spontaneously generated from the dust void boundary due to the ion streaming instability. The electric field in the dust void region is measured, and the electric field force and ion drag force on the dust particles at the void boundary are estimated to explain the mechanism of spontaneous dust density wave excitation. Synchronization occurring through the suppression mechanism is observed by modulating the ion streaming by applying an external sinusoidal signal to the dust void. At sufficiently high modulation amplitude, the onset of period-doubling bifurcation is observed. Fast Fourier transform spectral analysis is done using time-series data obtained from high-speed video imaging. The van der Pol equation with a force term is used to correlate the observed suppression phenomena.     

Dust Charging and Dynamics in Tokamaks

Fundamental characteristics of charging of a dust particle and its dynamics in SOL/divertor plasma in tokamaks are studied. According to the OML (orbit motion limited) theory, the charging process is extremely faster, with a charging time of nanoseconds, than the dynamics process of the dust particle in SOL/divertor plasma, with a characteristic time of milliseconds, which means that the local charge state can be taken as the equilibrium charge state. It was clarified that the equilibrium charge Zd,eq can be determined in the form of Zd,eq / Rd Te, which is a function of both the normalized relative speed of plasma ion flow with respect to the velocity of the dust particle and the plasma temperature ratio. After the investigation of dominant forces acting on dust particles, the friction forces due to the plasma ion absorption and ion Coulomb scattering are found of the same order for the case of low relative speed. The critical radius of a dust particle, for which the gravity is larger than the friction forces due to plasma ions, is obtained.     

Calculation of Electrical Potential and Dust Particle Charge in a Double Dusty Plasma Device

Dusty plasma consists of macroscopic particles of nanometer to micrometer size immersed in a gaseous plasma environment. It can be observed by introducing a flow of molecular impurity in a double plasma device. The impurity particles will be charged quickly, while keeping relatively in low temperature. The particles typically attain several hundred or thousand elementary charges due to the inflow of plasma electron and ions. The dust particles potential and electrical charge in plasma with two ions at different temperatures is calculated. Electrical charge of dust particles is self consistently determined by local plasma electron and ion currents. It is found out that the dust particle potential is strongly affected by the mass and temperature difference of plasma ions.     

Experimental study on two-phase flow instability of natural circulation under rolling motion condition

Two-phase flow instability of natural circulation under a rolling motion condition is experimentally studied. The experimental results show the rolling motion induces a fluid flow fluctuation. At the trough point of the flow fluctuation, rolling motion can cause the early occurrence of natural circulation two-phase flow instability, and this case is defined as trough-type flow oscillation. The system stability decreases with increasing rolling amplitude and effect of rolling frequency is nonlinear. The complex overlap effect of trough-type flow oscillation and density wave oscillation can enhance the system coolant fluctuation; this case is defined as complex flow oscillation. Complex flow oscillation may be divided into two types: regular and irregular complex flow oscillations. Irregular complex flow oscillation is a transition type from trough-type flow oscillation to regular complex flow oscillation. Under the same thermal hydraulic conditions, the marginal stability boundary (MSB) of regular complex flow oscillation is similar to that of density wave oscillation without rolling motion, and the influences of rolling parameters on the MSB are slight.     

基于脉动比预处理FFT的密度波不稳定性边界研究

两相流不稳定性试验的数据会包含一定程度的噪声信号。在判断两相流不稳定边界时,传统的基于流量脉动量幅值的方法具有局限性。本文研究了一种基于脉动比预处理的快速傅里叶变换(FFT)方法,通过捕捉密度波不稳定发生时频域上的特征信号来确定稳定边界,并对两组不同工况的试验数据进行分析。试验结果表明,本文方法具有较好的准确性。     

Dust Acoustic Shock Waves with Non-Thermal and Vortex-Like Ions in Dusty Plasma

A rigorous investigation is presented on the propagation characteristics of non-linear dust acoustic(DA)waves in an unmagnetized dusty plasma system containing non-thermal and vortex-like ions and Maxwellian electrons under the effect of a fluctuating charged dust fluid.The three-dimensional(3D)Burgers'equation and a new form of a lower degree modified 3D Burgers'equation with their analytical solutions are derived to study the features of shock waves in such plasmas.The effect of the population of non-thermal ions,the vortex-like ion parameter as well as the temperature ratios of ions and electrons on the evolution of shock waves in the presence of dust charge fluctuation is presented.This theoretical investigation might be effectively utilized to unveil the nature of many astrophysical plasma environments(Saturn's spokes etc.)where such plasmas are reported to have existed.     

Thermo-hydraulic instability of boiling natural circulation loop induced by flashing (analytical consideration)

An analytical study is presented on the thermo-hydraulic stability of a boiling natural circulation loop with a chimney at low pressure start-up. The effect of flashing induced by the pressure drop in the channel and the chimney due to gravity head on the instability is considered. A method to analyze linear stability is developed, in which a drift-flux model is used. The analytical result of a stability map agrees very well with the experimental one obtained in a previous report. Instability does not occur when the heater power is too low to generate voids in the chimney and only natural circulation of single phase can be induced. Instability tends to occur when boiling occurs only near the chimney exit due to flashing. This instability phenomenon has some similarities with density wave oscillation, such as the phase difference of temperature between the boiling region and non-boiling region, and the oscillation period which is near to the time required for fluid to pass through the chimney. However, there are also some differences from density wave oscillation, such as the boiling region is very short, and pressure fluctuation can affect void fraction fluctuation.