Dust Particle Density Research Articles

Observation of self-excited oscillations in DC glow discharge dusty plasma

We present a detailed experimental study of discharge current oscillations in a planar cathode plasma with poly dispersed alumina dust particles. Our experimental measurements suggest that surface density of dust particles play an important role together with cathode spots, in deciding self excited oscillating regime or stable dust cloud regime. Experiments conducted with dust particles density below the critical limit shows self excited oscillations. Operating above the critical limit, a dust cloud levitated in the sheath region was observed.

Exploring the dynamics of the heavy magnetized dusty plasma in laboratory experiments and solar wind interaction with lunar terminator: Theoretical predictions into the role of polarization force

This study is motivated by the lack of research that connects the dynamics of space dusty plasma (DP) with the existing experimental findings and the role of the magnetic field in the case of massive DP. For that purpose, we presented a theoretical interpretation of the dynamics of strongly (experimental) and weakly (space) magnetized DP, including the influence of the polarization force (PF). We used the multifluid model to describe the dynamics of dust particles while the hot plasma of electrons and ions is described by the Boltzmann distribution. We derived the dispersion relation to investigate the behavior of the compressive dust-acoustic waves (DAWs). To get a full picture of the mechanism of dust particles, we used the reductive perturbation technique to obtain the periodic solution for the Zakharov–Kuznetsov equation (ZK), which is coincidental with the observed wave profiles. In the case of the experimental application, we observed that the non-propagating instability starts at a small value of the polarization parameter (R), which is 0.02. Therefore, for values of R less than 0.02, the linear analysis revealed that increasing the value of the polarization parameter is not significant in distinguishing the growth rates. Moreover, we noted that both R and the applied magnetic field enhance the strength of the wave electric field. Interestingly, calculating the value of the electric field required to levitate the dust particles that are subject to a high magnetic field agrees with our theoretical findings. The current model has also been applied to DP observed in the lunar terminator. Our results reveal no role for the PF in the lunar terminator. The analysis conducted using the New Hampshire Dispersion Relation Solver (NHDS) confirms the dominance of electrostatic modes in response to the solar wind interaction with the lunar terminator. Moreover, at certain values of plasma parameters such as the temperature of solar wind electrons and ions and the density of dust particles and solar wind electrons, there is a cutoff in the fluid dispersion curve corresponding to certain values of the normalized wavenumber. Such electrostatic profiles could contribute to the observed glow in the horizontal direction of the lunar terminator.

Experimental study of discharge current oscillations with dust particles

We present a detailed experimental study of discharge current oscillations in a planar cathode plasma with poly-dispersed alumina dust particles. The dominant frequency of oscillation depends on the discharge voltage, operating pressure, and amount of dust particles placed on the cathode. The power-law variation in the dominant frequency with different external operating parameters is presented. Experimental observations suggest that the dominant mechanism behind the generation of these oscillations is the cathode spot injection of sub-micron-sized dust particles. The cathode spots also aid in the generation of fine dust particles. The threshold limit on dust particle density dispersed on the cathode suggests that below the threshold limit, the fine particles depleting the electrons play an important role and lead to the generation of self-excited oscillations. Operating above the threshold limit, a stable dust cloud was observed together with the suppression of self-excited oscillations.

Complex shock structure in multi-species dusty plasma with nonextensive electrons and two-temperature nonthermal ions

A theoretical investigation has been made to explore the behavior of nonplanar (cylindrical and spherical) electrostatic shock waves in a dusty plasma system that consists of arbitarily charged dust particles, negatively charged heavy ions following Cairn’s distribution, positively charged ions with two different temperatures, and nonextensive electrons. The reductive perturbation technique is used to derive a modified Burgers equation analytically. Analytical analysis shows that the characteristics of the nonplanar shock waves, including their polarity, amplitude, width, and phase speed, undergo significant alterations due to factors such as the charges on dust particles, the number density of particles, the temperatures of heavy and light ions, nonextensive electron behavior, and dust kinematic viscosity. Furthermore, this study found shock structures with either a positive or negative potential, depending on the critical value of the proportion of ions to the density of dust particles. The findings maybe useful in understanding the characteristics of shock waves both in space plasma environments and laboratory plasmas.

Heat transfer analysis of magnetohydrodynamics peristaltic fluid with inhomogeneous solid particles and variable thermal conductivity through curved passageway

PurposeThe particle distribution in a fluid is mostly not homogeneous. The inhomogeneous dispersion of solid particles affects the velocity profile as well as the heat transfer of fluid. This study aims to highlight the effects of varying density of particles in a fluid. The fluid flows through a wavy curved passage under an applied magnetic field. Heat transfer is discussed with variable thermal conductivity.Design/methodology/approachThe mathematical model of the problem consists of coupled differential equations, simplified using stream functions. The results of the time flow rate for fluid and solid granules have been derived numerically.FindingsThe fluid and dust particle velocity profiles are being presented graphically to analyze the effects of density of solid particles, magnetohydrodynamics, curvature and slip parameters. Heat transfer analysis is also performed for magnetic parameter, density of dust particles, variable thermal conductivity, slip parameter and curvature. As the number of particles in the fluid increases, heat conduction becomes slow through the fluid. Increase in temperature distribution is noticed as variable thermal conductivity parameter grows. The discussion of variable thermal conductivity is of great concern as many biological treatments and optimization of thermal energy storage system’s performance require precise measurement of a heat transfer fluid’s thermal conductivity.Originality/valueThis study of heat transfer with inhomogeneous distribution of the particles in a fluid has not yet been reported.

Design of Environmental Detector System (EDS) application through industrial and vocational collaboration

Politeknik Negeri Medan (POLMED) as a vocational institution and PT Berkat Solusi Teknik as a partner have the same responsibility to solve problems that exist in society. Problems in society related to pollution from industrial waste. This is due to many complaints from the public, NGO, and other organizations regarding environmental damage due to production and economic activities. Based on the problems above, this study is needed to detect and monitor environmental parameters such as CO2 level, lighting, noise, temperature, humidity, and measurement data that can be accessed and displayed in real-time via the internet. The implementation method is strengthening work organization, making EDS prototype brackets, design of an environmental detector system (EDS) prototype, prototype testing, MBKM internship, international conferences, monitoring and coordinating with partner, internal monitoring, and evaluation I and II, and preparation of final report. We innovate in the selection of components and the technology used. This collaboration is a symbiotic mutualism between POLMED and industry. The results are in average values, namely the density of dust particles is 1.418 µg/m3. Temperature 36.60oC. Humidity 53.82%RH. Light intensity 10,615 lux. These values above are still normal condition, and there is no pollution in campus. Especially for temperature and humidity. This condition above on the threshold.

Numerical simulation of dual-layer granular bed filtration based on particle collision rebound effect

This article established a dual-layer granular bed filtration model based on the dust collision rebound effect and investigated the influence of dust properties and filtration air velocity on the collision rebound effect and grade efficiencies of the filter layers. The results indicated that the characteristics of dust particle size, density, and effective Young's modulus had a significant impact on the critical adhesion velocity and collision rebound effect. Large dust particle size, density, and small effective Young's modulus resulted in a larger collision rebound effect. The collision rebound effect led to a decrease in grade efficiencies of each filter layer and the dual-layer granular bed with an increase in filtration velocity. To reveal the impact of the collision rebound effect on the movement of dust in the filter material layer, the trajectory and velocity changes of dust in the granule layer were simulated and calculated. The results show that the collision rebound effect caused the dust to repeatedly collide and rebound within the granular bed, penetrating deeper into the granular bed and increasing dust escape.

Attenuation characteristics analysis of the THz circularly polarized waves in inhomogeneous fully ionized dusty plasma using FPL model

When the hypersonic vehicle is flying, the plasma in the area near the stagnation point of the front end of the vehicle can be approximately seen as the fully ionized dusty plasma. Due to the existence of dust particles, dusty plasma affects the communication quality of the hypersonic vehicle. In this paper, the general Boltzmann equation applicable to dusty plasmas containing electrons and the Fokker–Planck–Landau collision model are combined to derive a general formula for the electron distribution function of fully ionized dusty plasmas. Considering the contribution of the collision effect and charging effect to the dispersion relationship of fully ionized dusty plasma, the dielectric constant of fully ionized dusty plasma under an external magnetic field is solved. The Wentzel–Kramers–Brillouin method is used to calculate the attenuation coefficient (α) of the THz wave in fully ionized dusty plasma, and the influence of the external magnetic field strength and other dusty plasma parameters on the attenuation characteristics of the THz circularly polarized wave is analyzed. The research results show that the α of the THz left-hand circularly polarized wave decreases with the increase in the external magnetic field strength, while the α of the THz right-hand circularly polarized wave increases. In addition, increasing the dust particle radius, dust particle density, and electron density in a certain frequency range can increase the α of the THz circularly polarized waves. These research results provide theoretical guidance for the exploration of the interaction mechanism between the THz waves and fully ionized dusty plasma.

Investigation of the Rayleigh–Taylor instability in charged fluids

The present study shows that the Rayleigh–Taylor (RT) instability and its growth rate are strongly dependent on the charge-mass ratio of charged particles in a charged fluid. A higher charge-mass ratio of the charged fluid appears to result in a stronger effect of the magnetic field to suppress the RT instability. We study the RT instabilities for both dusty plasma (small charge-mass ratio of charged particles) and ion-electron plasma (large charge-mass ratio of charged particles). It is found that the impact of the external magnetic field to suppress the RT instability for ion-electron plasma is much greater than that for dusty plasma. It is also shown that, for a dusty plasma, in addition to region parameters such as the external magnetic field, region length, its gradient, as well as dust particle parameters such as number density, mass, and charge of dust particles, the growth rate of the RT instability in a dusty plasma also depends on parameters of both electrons and ions such as the number densities and temperatures of both electrons and ions.

Propagation Characteristics of Terahertz Waves in Magnetized Dusty Plasma

The propagation characteristics, including reflectivity, transmissivity, and absorptivity, of terahertz (THz) waves in magnetized dusty plasmas sheath are investigated theoretically by the analytic method. Both the right-and left-hand circularly polarized (RCP and LCP) waves are considered. The calculation results illustrate that external magnetic field, plasma slab thickness, electron collision frequency, dust particles, and electron relaxation rate can affect the propagation characteristics of THz waves in plasmas. When dust particles are absent, a strong external magnetic field will cause the transmissivity of RCP waves to produce a transmissivity valley at the lower frequency band. Due to the action of external magnetic field and dust particles, a transmissivity peak appears at the lower frequency band for RCP waves. Increasing the density or radius of dust particles can cause an increase in transmissivity peak. For LCP waves, the transmissivity increases monotonously as the frequency of THz wave increases, whether the dust particles exist or not. These simulation results may provide a significant theoretical basis for solving the problem of “blackout.”

Temporal afterglow between two pulses of repetitively pulsed argon-acetylene plasma: measuring electron and negatively charged species densities

The temporal afterglow between two pulses of a repetitively pulsed radio-frequency driven low-pressure argon-acetylene plasma is experimentally explored using laser-induced photodetachment combined with microwave cavity resonance spectroscopy. The densities of electrons and negatively charged species, i.e. anions and dust particles, are measured temporally resolved until 1.9 s in the temporal plasma afterglow. Two different plasma-on times are adjusted to investigate the dynamics of anions and dust particles in the afterglow phase. The measurements show that while electrons decay rapidly within the first few milliseconds of the afterglow phase, the negatively charged species reside much longer in the plasma after the plasma is switched off. The electron density decay is measured to be faster for a longer plasma-on time. This effect is attributed to an enhanced recombination rate due to a higher dust particle density and/or size. The density of negatively charged species decays within two different timescales. The first 20 milliseconds of the afterglow is marked with a rapid decay in the negatively charged species density, in contrast with their slow density decay in the second time scale. Moreover, a residual of the negatively charged species densities is detected as long as 1.9 s after extinguishing the plasma.

Generation of an obliquely propagating shear alfven wave in dusty plasma by an ion beam

AbstractIon beam‐dusty plasma interaction leads to significant changes in the dispersion relation of shear Alfven wave depending on the beam, dust grain, and plasma parameters. Hydrogen ion beam particles interact with the shear Alfven wave via cyclotron interaction when they counter‐propagate with the wave and they can also interact with the co‐propagating wave via Cerenkov interaction. The interaction causes beam as well as plasma density fluctuations and gives rise to perpendicular currents. We have analytically obtained the dispersion relation and the growth/damping rate expressions for obliquely propagating shear Alfven waves in dusty plasma. The effect of beam velocity, magnetic field, wave number, dust particle density, and dust charge fluctuations are discussed. It is shown that both the wave frequency and the maximum growth rate decrease with an increase in beam velocity and the variations are different for parallel and perpendicular wave numbers. The dust particles enhance the frequency and maximum growth rate while the dust charge fluctuations induce damping. The results are in good agreement with the experimental observations.

Dusty plasmas above the sunlit surface of Mercury

Above the sunlit surface of Mercury, the properties and formation of dusty plasmas are investigated. It is demonstrated that the dusty plasmas are formed for subsolar angles exceeding approximately 76° due to photoelectric and electrostatic processes. As a result, the dusty plasmas are present in the polar regions of Mercury, characterized by latitudes of about 70° and above. The formation of dusty plasmas is also possible for lower latitudes, but only where the surface profile allows it. Plasmas above the sunlit surface of Mercury consist, in particular, of photoelectrons, electrons, and ions of the solar wind, and also charged dust particles. The distribution functions of photoelectrons near the surface of Mercury, as well as the altitude dependences of the number densities of dust particles, their charges and sizes, as well as electric fields, are obtained. The calculations are carried out which correspond to the position of Mercury at aphelion and perihelion of its orbit for the situations of dusty plasma location in the vicinity of magnetic poles of Mercury and in other regions. It is shown that there are qualitative differences between the dusty plasma systems of Mercury and the Moon related to the fact that Mercury has a magnetosphere and Mercury's orbit is one of the most eccentric of all planetary orbits in the Solar System. The effects of magnetic fields can slightly influence the dust particle transport and, correspondingly, the expansion of the region of the existence of dusty plasmas above the surface of Mercury due to the effect of dust particle transport is not so significant as at the Moon. Furthermore, due to the presence of Mercury's magnetosphere, the solar wind is important for the formation of dusty plasmas at Mercury only in the vicinity of the regions of the magnetic poles. In other regions of Mercury, in contrast to the situation at the Moon, the solar wind does not influence significantly the dusty plasma properties. The dusty plasma parameters are different in the cases of aphelion and perihelion of the orbit of Mercury.

Dust acoustic wave properties in varying discharge volumes

Properties of self-excited dust acoustic waves under the influence of active compression of the dust particle system were experimentally studied in the laboratory and under microgravity conditions (parabolic flight). Ground based laboratory experiments clearly show that wave properties can be manipulated by changing the discharge volume, its aspect ratio, and thus the dust particle density. Complementary experiments under microgravity conditions, performed to exclude the effects of gravity inflicted sedimentation and anisotropic behavior, were less conclusive due to residual fluctuations in the planes acceleration indicating the need for a better microgravity environment. A theoretical model, using plasma parameters obtained from particle-in-cell simulations as input, supports the experimental findings. It shows that the waves can be described as a new observation of the dust acoustic mode, which demonstrates their generic character.

Scattering characteristics of non-uniform dusty plasma targets based on Fokker-Planck-Landau collision model

Dusty plasma is a multi-particle system of dust particles suspended in plasma, which is generally composed of free electrons, ions, and dust particles. It is widely found in natural space and aerospace equipment, such as the Earth’s ionosphere, rocket tail flame, and sheath of the hypersonic vehicle. The dust particles will interact with free electrons and ions in the plasma so that the dust particles are charged. They also significantly change the characteristics of dusty plasma, showing some phenomena different from those in ordinary plasma, such as dust acoustic solitary waves and dust void. Electromagnetic (EM) waves will interact with dusty plasma, which results in the attenuation of EM wave signal and the change of phase and other serious effects, and the phenomenon of “blackout” appears. This is very unfavorable for the guidance and control system of the vehicle. The generation of “blackout” is related to the dynamics of dusty plasma and the analysis and research of EM characteristics, so studying the scattering characteristics of dusty plasma is of great significance. First, starting from the Boltzmann equation, the iterative expression of finite-difference time-domain under the Fokker-Planck-Landau (FPL) collision model of fully ionized non-uniform dusty plasma is derived. The expression of the conductivity of the fully ionized dusty plasma under the FPL collision model is obtained by combining the collision effect and charging effect of the dusty plasma. By using the <i>Z</i>-transform finite-difference time-domain method, the radar cross section (RCS) of the dusty plasma coated metal blunt cone in two dimensions is calculated. The effects of dust particle density, dust particle radius, ratio of electron density to dust particle density, dust particle charging frequency, and EM wave incident angle on the scattering characteristics of the mental blunt cone are analyzed. The results show that the Debye shielding effect is weakened and RCS is increased with the increase of the radius of dust particles in the fully ionized non-uniform dusty plasma. In addition, it is affected by the collision effect and charging effect of dusty plasma, which will have a great influence on the RCS of the target. These results provide a theoretical basis for studying the EM waves scattering problem of fully ionized non-uniform dusty plasma and the communication problems in near space.

Application of the scattering matrix method for investigating the propagation characteristics of terahertz waves in magnetized dusty plasma

A scattering matrix method is applied to investigate propagation characteristics of oblique incident terahertz waves into magnetized dusty plasmas. The numerical results agree well with those given by the Wenzell–Kramer–Brillouin method. Three different electron density distributions are taken into account, and both the right- and left-hand circularly polarized (RCP and LCP) waves are analyzed. Transmission properties of terahertz (THz) waves with different physical parameters, such as external magnetic, dust particle density, and dust particle radius, are discussed systematically. There exists a transmissivity peak at the lower-frequency band for RCP waves when an external magnetic field is presented. The value of the peak nearly keeps invariant, and its location moves toward the higher-frequency direction if the magnetic field enhances. Increasing the dust particle density or radius can make the value of a transmissivity peak larger. The transmissivity of higher-frequency RCP THz waves decreases if the external magnetic field increases. However, for LCP waves, there is no transmissivity peak. It increases monotonously as the frequency of a THz wave increases. Different from the RCP waves, enhancing the external magnetic field is better for the LCP waves to penetrate the dusty plasma. Our results may provide some theoretical basis for alleviating the problem of “blackout.”

Improved dusty gas cleaning in open-cast automobile transport

Service life extension of internal combustion engines is an urgent task for open-cast automobile transport. Dust contamination of oil and constructive elements of the internal combustion engine accelerates its wear and tear, resulting in breakage. The authors developed a separation device with sections of double-T elements as a replacement for the first stage cleaning device in open-cast automobile transport. Numerical results show that the proposed separation device provides gas cleaning with high efficiency from fine, medium, and coarse solid particles. The use of this device improved the overall efficiency of gas cleaning and extended the service life of the fine filter, which has a positive effect on the internal combustion engine. Studies have shown that the separation device has an average efficiency of 81.2% with the following parameters: dust particle size 5–20 μm, dust particle density 1000–7000 kg/m3, inlet gas velocity 3–15 m/s.

Transmission and reflection of a solitary wave in two-dimensional dusty plasma due to an interface

The reflection and transmission of an incident solitary wave with an arbitrary propagation direction due to an interface are investigated in the present paper. It is found that the propagation direction of the transmitted solitary wave depends on not only the propagation direction of the incident solitary wave, but also on the system parameters such as the masses, the number densities of dust particles in two different regions. Dependence of the transmission angle on the plasma parameters and incident angle are given analytically. Moreover, the number and amplitude of transmitted solitary waves and reflected solitary waves are also given when there is only one exact incident solitary wave. Our result has potential application, for example, we can devise an appropriate experiment to measure the differences of the masses and number densities of dust particles between two different regions by using our present results. Furthermore, we can also measure the electric charge of a dust particle by devising an appropriate experiment by using our results.

An Efficient Automatic Water Sprinkler Design for Operate in Dust Environment

The dust density within the environment must be continuously monitored in open cast mines. Water sprinklers are used to suppress the dust in mining field. Water sprinklers capacity used are of 28,000 and 70,000 L. These conventional water sprinklers comprise of 4 kinds of sprinkling thus the operator must choose and actuate any 1 type of sprinkling which is appropriate to suppress the dust. The traditional water sprinkler is worked physically by the operator that is operator turns on the type of sprinkling dependent on the dust seen by him. This technique does not completely suppress the dust and it’s not accurate. Furthermore, water is squandered if the dust density is according to the directions given by central pollution control board. Supportive to the above background, it is necessarily essential to actualize the water sprinkling system automatically which measures the dust density contained in mine atmosphere and likewise module will consequently actuate the sprinkling so as to suppress the dust in the environment. This technology is compatible to inbuild display for continuous monitoring of dust concentration also the system has both auto/manual operation. At the point when the dust concentration crosses the admissible value automatically system will activate solenoid driver to start out the sprinkling activity. Therefore, the designed dust monitor module is employed to implement an automatic system, utilizing advanced technology to monitor the density of fine dust particles in the mining environment & accordingly the sprinkling operation is actuated with minimal human intervention.

Specificities of the Nonlocal EDF Formation in a Dusty Plasma With the Different Spatial Distribution of the Microparticle Density

The formation of a nonlocal electron distribution function (EDF) in an argon dusty plasma of a dc glow discharge has been studied in a wide range of microparticle densities and their different spatial distributions inside a dusty cloud have also been explored. It is shown that the spatial profile of charges and the ambipolar potential can vary greatly, both with a change in the absolute values of the density of dust particles and the type of their spatial distribution. In turn, changes in the profiles of the ambipolar potential lead to strong differences in the nonlocal EDF at different points of the tube radius. This is most clearly seen at high densities of dust particles when nonmonotonic profiles of the potential distribution and reversal of the sign of the ambipolar field are formed. In this extreme case, great changes in the nonlocal EDF are observed not only at the discharge periphery but also inside the dust cloud.