Search

The interest in the use of atmospheric-pressure plasma jets (APPJs) is constantly growing. APPJs offer various ranges for applications, such as wound healing, cancer treatment, and dental care. The complex plasma chemistry plays an important role in each of these fields but is often poorly understood. In this paper, the production of atomic oxygen in a radio frequency helium–oxygen plasma is investigated by means of a numerical simulation. A 1-D discharge of an atmospheric-pressure plasma jet is created with the plasma module of COMSOL Multiphysics, using a set of 25 reactions. Many 1-D simulations usually cannot estimate the power deposition in a correct way because of suspected arising losses, such as radiation and inefficiencies of the external circuit. In order to match the experimental power deposition of 13 W, high voltages (855 V) are required in the model. Such high voltages cause changes in the plasma characteristics like a switch in the glow mode. The impact of the voltage on the plasma is investigated by the comparison of a low-voltage (325 V) simulation, which matches the experimental oxygen production, and a high-voltage (855 V) simulation, which matches the experimental power deposition. Outcomes of this paper further support the idea that the power deposition measured in experiments is higher than the actual power deposition coupled to the plasma. [ABSTRACT FROM AUTHOR]

We have studied the two-electron pseudodot (TEPD) system immersed in plasma environments under the influence of a monochromatic linearly polarized laser field. The four different sets, constituted by the potential parameters, of the more general exponential cosine screened Coulomb potential are used to characterize the Debye and quantum plasma environments. The time dependent in the Schrödinger equation arising from the laser field is interchanged to the potential energy term from the kinetic energy term through the dipole approximation and the Kramers–Henneberger transformation. Then, the laser-dressed potential that denotes the effects of the laser radiation field is constituted by using the Ehlotzky approximation. In that case, as the analytical solution is impossible just now due to the complicated form of the Schrödinger equation, the numerical solution is carried out via the asymptotic iteration method. In this paper, the pseudodot system is considered because the quantum dots are very similar to atomic systems, and the pseudoharmonic potential is successful in explaining the atomistic structures. However, it is an important motivation for us that, as well as the importance of the laser–plasma interactions, the laser field is a considerable exciter for radiating, which exhibits remarkable confinement effects. Since, as well as the screening effects exhibited by plasmas on atomic systems, and their significant results, the plasma is a significant experimental argument in manufacturing and modification of the quantum dots, the plasma effects are taken into consideration in this paper. Within these motivations, all parameters that operate on the energies of TEPD system with the laser effect in plasmas are analyzed in detail, and the corresponding results are discussed thoroughly. [ABSTRACT FROM AUTHOR]

This paper embodies the results of experimental studies of a dielectric barrier discharge low-temperature nonequilibrium plasma reactor that runs in air and nitrogen at atmospheric-pressure conceived for surface treatment applications. A homemade reactor, of typical plane-to-plane geometry with the dielectric covering the upper electrode which is stressed by a high voltage (40 kV, 3–20 kHz) is used. Electrical signals (current and voltage), optical emission spectroscopy records, and total light emission measured by photomultiplier have been analyzed and used to distinguish different plasma regimes which are studied for the treatment of a lignocellulosic material (sugarcane bagasse). In the filamentary discharge regime, the gas temperature of few tens of degree Celsius above the ambient one was determined, the electronic temperature of some electronvolts and electron density in the range of 1012–1013 cm−3 were estimated. Plasma treated pellets of sugarcane bagasse were analyzed by diffuse reflectance infrared Fourier transform spectrometry and the relative results obtained under filamentary discharge regime have shown significant degradation of the lignin macromolecule. It has been shown important modifications on the lignocellulosic material, namely, the plasma attacks drastically the lignin bonds. Strong modification of lignin was observed near wavenumber of 3400 cm−1, due to stretching vibrations of OH, and for the band 1114 cm−1 which is related to C=C and C=O stretching. Severe decrease of the band intensity 1596 cm−1, which due to C=C stretching and C=O, is also a result of the treatments done in this paper. [ABSTRACT FROM AUTHOR]

In this paper, the capacitances of the two-stage bushing that is installed in the 1-MV test bed for neutral beam injectors in the future fusion reactors are calculated by modeling the bushing in a 3-D electrostatic code. One of the modeling results is the stored energy in the bushing, which corresponds to 1/2 CV2. After evaluating the bushing capacitance, a MATLAB/Simulink model is presented to model the possible breakdown in the bushing and between the electrodes in the 1-MV test bed. When a breakdown occurs between anode and cathode, an overcurrent is drawing that can cause damage in the electrode surfaces while an overvoltage takes place when the breakdown happens between the bushing stages. Such damage has been observed experimentally in the past. This paper also presents some of the possible protection against the breakdown in the 1-MV test bed to dissipate the stored energy in order to protect the electrode surfaces and the bushing. The suggested protections presented in this paper are damping resistors, surge arrester individually, and both of them. Also, a coil can be added to the DR either in series or in parallel. [ABSTRACT FROM AUTHOR]

The past measurements of the plasma density and potential profiles near the exit of the keeper electrode in a hollow cathode device suggested that turbulent ion acoustic fluctuations and ionization instability in the cathode plume significantly increased the energy of the ions that flow from this region. The lifetime of keeper electrode is limited by sputtering or ion bombardment of the Molybdenum surface exposed to the discharge plasma. Increases in the cathode gas flow reduce the amplitude of the fluctuations and the number and energy of the energetic ions, which decreases the erosion rate of the keeper electrodes. However, as the cathode gas flow is raised for a given discharge current, the performance of a 5-kW Annular-Geometry Ion Engine (AGI-Engine) declines. There is a strong relationship between the performance and the lifetime of the ion thruster. To validate whether the 20-A hollow cathode satisfied China’s communication satellite platform’s application requirement for North-South station keeping, this paper analyzed the effect of the cathode gas flow on the performance and the lifetime of the AGI-Engine. Different from the previous methods, this paper first tracked the movement of energetic ions generated in the plume of the hollow cathode, predicted erosion rates, found where they hit the keeper electrode, and then determined the amount of material that they sputtered. A review of past experimental results was presented first. Next, based on the existing experimental data, theoretical analysis and numerical calculations were performed to determine the optimum gas flow range and the performance curve of the 20-A hollow cathode. The results showed that the primary erosion mechanism of the keeper electrode was caused by impact from Charge Exchange Xenon (CEX) ions, which caused the cathode orifice to be widened and attenuated over time. However, heavy double xenon ($\text{X}_{\text{e}}^{++}$) ions, which struck the keeper electrode more severely than CEX ions, were the most crucial factor that limited the lifetime of the 20-A hollow cathode due to their high energy and large mass. [ABSTRACT FROM AUTHOR]

Linear and nonlinear properties of obliquely propagating waves are studied in a degenerate dense cold magnetoplasma, comprising of Thomas–Fermi distributed electrons and ions as well as non-degenerate negatively charged dust particulates. By using the plane wave approximation, a linear dispersion relation for the dust-cyclotron (DC) and dust-acoustic (DA) waves is derived and analyzed numerically. For fully nonlinear waves, a Sagdeev pseudopotential theory is employed to derive an energy-balance equation and the soliton existence domain depending upon the dust concentration $(h)$ , obliqueness $(L_{z})$ , and Mach number $(M)$. Numerical analysis reveals that the parameter $h$ enhances the domain for allowed Mach numbers, i.e., $M_{1} < M < M_{2}$ and therefore favoring the solitary excitations, where $M_{1}$ and $M_{2}$ are the lower and upper Mach numbers, respectively. In addition, the dust concentration significantly reduces the amplitude and the profile sharpness of the solitary pulses. Similarly, variations in the obliqueness parameter and the Mach numbers modify the wave characteristics. This paper is important for understanding the nonlinear properties of electrostatic excitations in degenerate dusty magnetoplasma, relevant to white dwarfs (WDs), namely $GD56,\,\,GD29-38,\,\,GD362$ , and $WD2115-560$ , being termed as the DUSTY DAZ WDs. [ABSTRACT FROM AUTHOR]

The front plates and embedded particle sensor shells that are part of the electric field instrument (EFI) on the Swarm satellites have recently been used as planar Langmuir probes, as an additional diagnostic tool to infer environment parameters. The interpretation of measured currents in terms of the plasma density or incoming flow speed, however, requires a knowledge of the front plate effective cross section $A_{\textrm {eff}}$. Measurements made under various space plasma conditions have led to the conclusion that this cross section is generally larger than the known geometrical cross section $A_{\textrm {geo}}$. Interpretations of measurements have thus been made using fixed relative enhancements of $A_{\textrm {geo}}$ ranging from 8% to 17%. In this paper, results from kinetic simulations are presented, from which the effective cross section can be determined over a range of plasma parameters. These are used to shed light on the physical mechanisms responsible for this enhancement and construct an empirical fit to the relative enhancement $\delta $ , where $A_{\textrm {eff}} = A_{\textrm {geo}}(1 + \delta)$ , and, in turn, enable improvements in the accuracy of inferred plasma parameters. [ABSTRACT FROM AUTHOR]

Data from the Magnetospheric Multiscale (MMS) mission, in particular, the spacecraft potential measured with and without the ion beams of the active spacecraft potential control (ASPOC) instruments, plasma electron moments, and the electric field, have been employed for an improved determination of plasma density based on spacecraft potential. The known technique to derive plasma density from spacecraft potential sees the spacecraft behaving as a plasma probe which adopts a potential at which the ambient plasma current and one of photoelectrons produced at the surface and leaving into space are in equilibrium. Thus, the potential is a function of the plasma current, and plasma density can be determined using measurements or assumptions on plasma temperature. This method is especially useful during periods when the plasma instruments are not in operation or when spacecraft potential data have significantly higher time resolution than particle detectors. However, the applicable current–voltage characteristic of the spacecraft has to be known with high accuracy, particularly when the potential is actively controlled and shows only minor residual variations. This paper demonstrates recent refinements of the density determination coming from: 1) the reduction of artifacts in the potential data due to the geometry of the spinning spacecraft and due to effects of the ambient electric field on the potential measurements and 2) a calibration of the plasma current to the spacecraft surfaces which is only possible by comparison with the variable currents from the ion beams of ASPOC. The results are discussed, and plasma densities determined by this method are shown in comparison with measurements by the Fast Plasma Instrument (FPI) for some intervals of the MMS mission. [ABSTRACT FROM AUTHOR]

The effective control of magnetohydrodynamic instabilities in fusion experiments by means of actively controlled coils calls for challenging dynamic requirements to the relevant power supply (PS) systems. The first part of this paper gives an overview on typical requirements and technological solutions adopted in some present fusion experiments. Then, the advantages of SiC devices with respect to the Si ones are described in this paper, including lower switching losses, higher switching speed, higher operating junction temperature, and higher voltage capability. As an application example, this paper reports on the case of the PS system for resistive wall mode control in the JT-60SA satellite tokamak, where analyses showed the difficulty of satisfying the demanding requirements in terms of high current bandwidth (3 kHz) and short latency ( <50~\mu \texts ) with a simple H-bridge topology adopting standard IGBT. On the contrary, the use of Si–SiC IGBT with the same topology can allow meeting the specifications, as demonstrated by the development and test of such a power amplifier, rated for $300~A_{{\mathrm{pk}}}$ and 240 V. [ABSTRACT FROM AUTHOR]

Modeling the dynamics of charged dust particles, confined in a glass box placed on the lower electrode of a Gaseous Electronics Conference cell, requires that the interactions between the charged dust, plasma, and boundaries need to be accounted for in a self-consistent manner. The charged lower electrode affects the plasma conditions throughout the glass box, altering the electron and ion densities and temperatures within the plasma sheath. These plasma characteristics determine the charge collected on the walls of the surrounding glass box, the electric potential within the glass box, the dust charge, and ultimately the dynamics of the dust. This paper describes the steps taken to build a simple model of the relationship between the plasma conditions and the potential within the box as well as the expected dust charge near the center of the box. The calculated potential and dust charge are used to construct acceleration maps for the dust, which are compared to experimentally measured acceleration of the dust within the box. [ABSTRACT FROM AUTHOR]

This paper presents the numerical simulation results of characteristics and efficiency of separation of uranium ion fluxes and its fission products in the process of the plasma separation. The movement of beams of heavy (238 u) and light (160 u) single-charged ions in vacuum and in helium buffer plasma has been investigated at a pressure of 10 mtorr, magnetic fields 0.8–1.2 kG and electrical potentials up to 1 kV. The interaction between the ion beams and their interaction with the buffer plasma has been taken into account. The numerical simulation of plasma has been conducted in a drift–diffusion approximation. It has been shown that the presence of buffer plasma in the area of ion fluxes and occurring compensation of their space charge can greatly improve the separation efficiency compared to the separation of ion fluxes in vacuum. [ABSTRACT FROM AUTHOR]

This paper outlines the requirements for a source of buffer plasma, which is necessary for elaboration of plasma separation method of substances and following foundations development of plasma reprocessing technology of spent nuclear fuel and radioactive waste. Such source is implemented on the basis of a helicon discharge, allowing plasma generation in a cylindrical volume with characteristic dimensions on the order of 1 m and bounded by metal walls. At plasma-forming gas (argon) pressure of 1 mTorr, radial profiles of density $n_{e}$ and temperature $T_{e}$ of electrons were obtained for various magnetic field magnitudes (0–200 G) and RF power (up to 6 kW) using double probe and optical methods. The typical value of $T_{e}$ amounted to eV units and $n_{e}$ was about 1012 cm−3. [ABSTRACT FROM AUTHOR]

The influence of the electric parameters, applied voltage, and pulse repetition rate on the energy efficiency for hydroxyl radical production from pulsed discharge inside of a bubble is investigated in this paper, as a possible application for waste water treatment. To evaluate the energy efficiency, indigo carmine, a common dye, is used as a chemical probe of hydroxyl radicals. Argon is injected into water through a vertically positioned glass tube, into which high-voltage wire electrode is placed to generate plasmas at low applied voltage. The energy efficiency increases with the decreasing pulse repetition rate and output voltage with the same indigo carmine concentration. The results show that the energy efficiency for the hydroxyl radical production increases with the decreasing amount of energy input into the solution per unit time because of the decrease in the recombination reaction of the hydroxyl radicals in the solution. The impedance between the electrodes decreases with the increasing output voltage, which increases the ohmic losses in the solution but does not contribute to the production of hydroxyl radicals. [ABSTRACT FROM AUTHOR]

In this paper, the experimental results of the behavior of an X-pinch plasma conducted in a small capacitive generator of low impedance and inductance are reported. The generator produces currents of the order of 120 kA in times about 500 ns, when a charging voltage of 24 kV, and wires as load are used. W, Al, and Cu X-pinches of different diameters were tested. The experimental observations show a similar global dynamic to those observed in experiments of higher current and shorter quarter period, with an intense emission of energetics X-rays (>5 keV) generated by plasma dynamics in the cross point of wires. The fast plasma dynamic is evidenced from the strong change of frequency in the current-derivative signal, which is correlated with the X-ray signals observed from the radiation detectors. From the time-integrated pinhole images and time-integrated aperture images, filtered with different aluminum foils of different thicknesses, an estimated X-ray source size of $70~\pm ~20~\mu \text{m}$ with energies above 7 keV is obtained. [ABSTRACT FROM AUTHOR]

This paper is related to the study of the formation conditions and dynamics of self-sustained plasma-beam discharge at high energy density in the plasma of multiply ionized atoms. The efficiency of energy input into the discharge is shown by using a high-current pulsed plasma diode of low pressure. Based on the original calculation method, the dynamics of active voltage and active power inputted into the discharge are given. In such a system, the level of inputted active power can reach the value of 100 MW at the initial stored energy of 140 J. It is pointed out that the main mechanism of energy input into the discharge is a double electric layer of the space charge that is formed in the discharge gap. The intense electron beam accelerates in the double layer and heats the plasma to a high temperature in a short period of time. By controlling the arrangement of double-layer formation, one can input the energy locally into a certain discharge region. The distinctive features of the double-layer formation near the high-voltage electrode with a limited working surface for the even and odd half periods of the discharge current are indicated. The distribution of space potential in the discharge gap confirms that the double-layer formation is the result of not only the current instability but also the discharge transition to a new form of the self-sustained electric discharge in gas environment. [ABSTRACT FROM AUTHOR]

It is observed that nanosecond pulsed electric field induces extracellular calcium inflow, which suggests great potential in manipulating cell functions. In this paper, a mathematical model of calcium transmembrane transport is set up to make a systematic research of calcium transport through voltage-gated calcium channels (VGCCs) in response to electrical pulses. The particle-in-cell simulation method is employed to simulate the transport process and obtain calcium concentration at any time. The simulation results show that nanosecond electric pulse can activate low VGCCs during the radiation period. Besides, the results reveal the nonlinear relation of the increment in intracellular calcium concentration caused by activation of VGCCs to pulse widths and field intensities. The numerical simulations lay the foundation for quantitative manipulation of intracellular calcium concentration via nanosecond electric pulses. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of ionization waves’ (IWs’) propagation in a nanosecond-pulse dielectric barrier discharge at atmospheric pressure in air. The effect of the rise time and pulse duration on IW propagation is studied by an intensified charge-coupled device, and the mechanism of the discharge propagation is analyzed. The experimental results show that the discharge produced in the rise time of the applied voltage develops in a structure of discontinuous sphere, while the discharge produced in the falling time exhibits a continuous form due to the effect of space charge. Furthermore, the rise time of the applied voltage has a significant influence on the velocity of IWs, and the maximal velocity of IWs rapidly decreases from 0.08 to 0.008 mm/ns when the rise time of the applied voltage increases from 50 to 300 ns. However, the pulse width has almost no influence on the velocity of IWs. The electric field distortion caused by both the propagation of IWs and the accumulation of surface charges is responsible for the formation and propagation of IWs. [ABSTRACT FROM AUTHOR]

This paper presents a self-consistent model of plasma polarization around an isolated micrometer-sized dust particle being under the action of an external electric field. It describes ion focusing and wake formation for dust particles with different radii and external electric fields. It is shown that despite the formation of wake, plasma maintains a quasi-neutral condition around a negatively charged dust particle, and the volume charge formed as a result screens the dust particle completely. It is also shown that in the external electric field, the dipole moment of the part of the ion nearest to the dust particle is proportional to the dust particle charge. As the external electric field increases and reaches some threshold value, a positive peak appears in plasma potential downstream of the dust particle. It then increases linearly and shows a broad maximum. [ABSTRACT FROM AUTHOR]

This paper examined the extent of the dependence of the interrupting capability on the shape of the contact system in a molded case circuit breaker (MCCB). Thus, a simple analysis method was suggested for estimating the interrupting capability and used to investigate the magnetic flux density distribution in a contact system caused by a short-circuit current. However, the MCCB produced by a joint-research company turned out to have the poor interrupting capability and a low magnetic flux density distribution for driving arc plasma between two contacts in the contact system. To build up additional interrupting capability without making many changes, a new arc runner was devised to prevent arc plasma from returning to its original position in the contact system. The arc voltage characteristics were tested with a simplified synthetic testing facility using an LC resonant circuit. The result showed that the new MCCB had a much higher arc voltage than the existing MCCB. This implies that investigating the arc voltage is fairly comparable to predicting the arc plasma extinction and the interrupting capability. [ABSTRACT FROM AUTHOR]

This paper presents the analysis of cylindrical electron beam and beam-impact-generated plasma using particle-in-cell simulation code VSim 6.2 at different operating conditions. The transient plasma parameters, such as, beam density, charge neutralization factor, space charge potential, ionization time, beam compression, and plasma electron temperature, have been estimated and analyzed for a 40-keV, 10-100-A electron beam propagating in argon gas-filled drift space at different operating pressures. These parameters are difficult to be measured experimentally. The evaluated charge-neutralizing factor has been found dynamic in space and time, which is maximum at the beam envelope. The voltage profile of space charge potential required for effective electron beam propagation approaches zero due to formation of the plasma in the order of ionization time. The estimated average plasma electron temperature has been found to be less than ~1 eV, which is less damaging for interaction structure of the plasma-assisted microwave sources. It has been observed that an optimum pressure limit needs to be maintained inside the drift space to prevent the loss of electron beam due to instabilities resulting in excessive collisions with the drift space walls. [ABSTRACT FROM AUTHOR]

The capillary-based pulsed plasma thruster (PPT) has high-energy transfer efficiency, which provides potential to improve traditional PPT performance. In this paper, the discharge characteristics of a capillary-based PPT have been investigated. First, the typical process of voltage and current waveform is recognized. It is featured with a fast voltage drop (~25 ns) and a consequent damped sine wave oscillation discharge. Then based on the circuit analysis, the equivalent plasma resistance has been calculated. The current waveform is well fit with a linearly increasing resistance model. The influence of charging voltage has also been studied. The deposited energy increases while the transfer efficiency decreases with the increasing applied voltage. The cavity dimension has effects on the equivalent circuit parameters. The results show that longer cavity and smaller diameter lead to more deposited energy and higher transfer efficiency. The influence of voltage and capillary dimension on the mass shot characteristic has been discussed. Finally, the estimated impulse bit has been calculated and the impulse bit characteristics have been discussed. These results can contribute to the further optimization of PPT. [ABSTRACT FROM PUBLISHER]

This paper is focused on investigation of the electrical, hydrodynamic, and acoustic parameters of underwater plasma discharges, stabilized with thin copper wires. The experimental current and acoustic waveforms have been obtained using different combinations of the circuit capacitance, charging voltage, and wire length. The resistances of plasma discharges have been calculated for all combinations of electrical and topological parameters, based on the constant resistance approach. Phenomenological scaling relationships that link the plasma resistance and the total energy delivered to the plasma, the period of discharge cavity oscillation and the peak magnitude of the acoustic impulse have been obtained. These relationships can be used in optimization of the acoustic output from the wire-guided discharges for different practical applications. [ABSTRACT FROM PUBLISHER]

We present numerical simulations of the Solar Orbiter spacecraft (SC)/plasma interaction performed with the SC–plasma interaction system software. Solar orbiter, to be launched in 2019, is dedicated to observe the sun and the solar wind. The SC will be equipped with both in situ and remote sensing instruments and will approach the sun as close as 0.28 AU. The whole SC will be subjected to an intense electromagnetic radiation flux (ten times that at the earth) leading to specific thermal and SC–plasma interactions issues. This paper investigates plasma interaction effects with two instruments: the radio and plasma waves and the electron analyzer system. [ABSTRACT FROM PUBLISHER]

This paper reports the experimental results from the appearance of three discharge modes in a special geometry as a function of applied negative voltage pulses. The geometry is a four-gap pseudospark one with a gap distance of 4 mm, a metallic hollow cathode, and an anode. The applied pulsed voltage Up varies from −20 to −80 kV. The pulse shape is a rectangular one with a pulsewidth of 50 ns and a rise time of 4 ns. There is no breakdown at Up < 27 kV, and at Up > 27 kV, a pseudospark discharge starts, which transforms at Up > 45 kV into a surface discharge. The working gas is dry air at a constant pressure of 13 Pa. Using these parameters, electric field simulations of the triple point junctions are conducted and time-integrated pictures of the different discharge modes are presented. When the gas pressure is increased from 13 to 35 Pa, the voltage range of the pseudospark discharge mode grows from 13 to 65 kV. [ABSTRACT FROM PUBLISHER]

NASA’s magnetospheric multiscale (MMS) mission was successfully launched in March 2015. The scientific objectives of MMS are to explore and understand fundamental plasma physics processes in the earth’s magnetosphere: magnetic reconnection, particle acceleration, and turbulence. The region of scientific interest of MMS is in a tenuous plasma environment where the positive spacecraft potential may reach an equilibrium as high as several tens of volts. The active spacecraft potential control (ASPOC) instrument neutralizes the spacecraft potential by releasing the positive charge produced by indium ion emitters. While the method has successfully been applied to other spacecraft such as Cluster and Double Star, new developments in the design of the emitters and the electronics are enabling lower spacecraft potentials and higher reliability compared to previous missions. In this paper, we report the initial results from the tests of the ASPOC performance during the commissioning phase and discuss the different effects on the particle and field instruments observed at different plasma environments in the magnetosphere. [ABSTRACT FROM PUBLISHER]

This paper first presents a short review of the recent experiments performed on large test fixtures, whose aim was to evaluate the flashover (FO) propagation during an electrostatic discharge. Then, the model of plasma bubble expansion is presented and compared with the results collected during the review. We will show that the model can represent qualitatively and quantitatively most of the results. The parameters of the model are mainly the ion velocity and the backscattered electron emission yield. The other experimental parameters influencing the FO propagation will be discussed. [ABSTRACT FROM PUBLISHER]

New instrumentation might aid new ventures in space. Grappling missions are now being considered for geosynchronous Earth orbit. If spacecraft are at differing floating potentials, arcing during grappling might prove a hazard. In this paper, a device that might warn of arc-inducing conditions is described. The device is of a class of instruments that have been flown on many missions: curved plate electrostatic charged particle energy analyzers. However, the sensor is of a novel configuration that might enable the determination of very low absolute spacecraft floating potentials. Since very few spectra of the sort that the instrument would collect in space are available, estimates of its performance are necessarily uncertain. It is possible that such an instrument would prove useful on grappling missions. [ABSTRACT FROM PUBLISHER]

This paper describes the results analysis obtained during the experimental campaign conducted in the frame of the ESA EMAGS3 project “Flash-over (FO) evaluation on large solar panels.” A numerical model has been developed in order to better understand the characteristics of the so-called FO phenomenon. The experimental results, presented in detail in a companion paper, are analyzed in correlation with the present FO model. A basic model based on the assumption of a plasma bubble expansion in vacuum has been developed to model the FO propagation. The model holds on a two-dimensional Cartesian mesh representing the surface of the solar panel. On this mesh, the electrical potential evolution and the current collection are computed supposing that the bubble velocity is constant, the current extracted from the plasma bubble is space-charge limited, the secondary emission is the only source of electrons from the cover-glasses and its potential evolution is only due to the current collection. The inputs of the model are the potential topology before the ESD, the ESD triggering position, and the solar array characteristics (dimensions and cover-glasses capacitance). The outputs of the model are the time evolution of the total FO current, the potential map, and the current collection map on the solar array. The results comparison between the model and the experiments shows a very good agreement in the cases where the potential topology before the ESD is well known. It is especially true when using IPG by plasma because the potential profile is relatively uniform. In that case the comparison with numerical results is concluding. In the case of IPG by electron guns, the potential map before the ESD is relatively hard to obtain. In this case, the agreement between the model and the experimental result is obtained only for a limited number of cases. The detailed comparison between model results and experimental data is shown and analyzed in this paper. It appears clearly that the plasma bubble extends at the acoustic velocity of the ions generated at the cathode spot level. As a result, ESDs generated on solar cells junction or interconnects do not have the same dynamics. [ABSTRACT FROM PUBLISHER]

In this paper, a dual-electrode gas switch triggered by ejected plasma is proposed to ensure the switch to be triggered reliably under extremely low switching coefficient. The switch has the configuration of dual electrodes, in one of which a microincentive chamber is embedded to develop ejected plasma into the switch gap, leading to the breakdown of the switch. Both the features of ejected plasma and the triggering discharge characteristics of the switch are studied with different types of gas, gas pressures, voltage polarities, gap distances, triggering pulse energies, and so on. The results show that the switch can be triggered reliably in a much wide working voltage range, as the minimum switching coefficient is low to 9% with the delay time of about 10 \mu \texts . With the decrease of gas pressure and the increase of triggering pulse energy, the height of ejected plasma increases while the delay time of the switch reduces. The polarities of charging voltage and triggering voltage both have obvious influence on the delay time of the switch, and the effect of the former is greater. Under the same gas pressure and triggering pulse energy, the delay time in SF6 is much bigger than that in N2. [ABSTRACT FROM PUBLISHER]

The three-electrode plasma reactor for the treatment of polluted gases combines a dielectric-barrier discharge with a remote third electrode, designed to enhance streamer propagation in a relatively large region. In this paper, experimental studies of the electrical magnitudes of the discharge for different electrode bias voltage configurations are presented. Also, the Laplacian electric field distribution in the interelectrode gap is calculated for each configuration. The degradation efficiency of NO in an N2 atmosphere for the different configurations is also reported. It is found that the discharge is generated only for that electrode bias configuration for which the external electric field promotes the streamer propagation across the electrode gap. Also, for a triggered discharge, the reactor efficiency for the removal of NO changes with the different electrode bias configurations. This result can be explained in terms of the electric field intensity. The configuration with higher external electric field improves the number of streamers propagating in the interelectrode gap so that more reactive species generated in the streamers are effectively entrained in the gas flow to be treated. [ABSTRACT FROM AUTHOR]

This paper contains results of numerical and experimental investigation of glow discharge plasma created in a chamber of a new-type large-volume coaxial gridded hollow cathode. The discharge is created in argon at 25 Pa by applying time-varying power with frequency 20 kHz on electrodes. A 2-D model of the discharge was built using COMSOL Multiphysics. Self-consistent description of the discharge was obtained using the extended fluid approach, which couples continuity equations for charged particles and electron energy balance with Poisson’s equation for electric potential. Electron transport coefficients and rates of electron-impact reactions were calculated using the electron energy distribution function. The spatial and radial distributions of plasma potential ( Vp ), electron density ( ne ), and electron temperature ( Te ) were obtained. It is shown that the plasma inside the chamber is similar to the negative glow of a dc glow discharge. Comparison of numerical results with the Langmuir probe measurements of electron density and electron temperature is presented and showed a good agreement. [ABSTRACT FROM AUTHOR]

In this paper, the well-known Hulthén potential is used for describing the plasma screening effect on a hydrogen atom embedded in weakly coupled plasma. As the radial Schrödinger equation with Hulthén potential gives analytical solutions, the energy levels and wave functions are obtained in a closed form. Structural properties such as dipole polarizability, transition probability, and oscillator strength are calculated easily using the corresponding analytical formulas. Moreover, the analytic solutions of the Hulthén potential enable us to obtain many other observables reliably. Asymptotic iteration method solutions of the Hulthén potential for different screening parameters are considered to calculate the transition energies, oscillator strength, and transition probability values for a few dipole allowed states of hydrogen atom embedded in weakly coupled plasma. Use of the Hulthén potential to determine the screening effects on hydrogen atom embedded in weakly coupled plasma would be useful for modeling Debye plasma in investigations of the atomic structure and collisions in the plasma physics field. [ABSTRACT FROM AUTHOR]

There has been a significant interest in many technical applications and natural phenomena concerning two-phase mixture discharges (TPMDs). Few studies have focused on the influences of different macroparticles on TPMDs. The dielectric constant is usually considered to be the only factor affecting the discharges, but in this paper, 21 kinds of different dielectric materials were used to investigate the effects on TPMDs. By the experimental results, this paper reveals the effects of macroparticle sizes, and the dielectric constant has little influence. When the diameter of TPMs is less than about 0.01 mm, the percentage of the selection of TPMs is always smaller than 50%, the discharge path selects the air but TPM, and the breakdown voltage is higher than that in air. However, when the diameter is greater than about 0.1 mm, the conclusion is opposite. When the diameter is in the range of 0.01–0.1 mm, the TPMDs have a polarity effect. The dipole-enhanced approximation model is applied to explain the experimental phenomena. It is very important in TPMDs that the macroparticle dielectric constant, the saturation charge, and the adsorption/desorption process on the material, except the effects of TPMDs, are highly correlated with the macroparticle sizes. [ABSTRACT FROM AUTHOR]

Aggregates immersed in a plasma or radiative environment will have charge distributed over their extended surface. Previous studies have modeled the aggregate charge using the monopole and dipole terms of a multipole expansion, with results indicating that the dipole–dipole interactions play an important role in increasing the aggregation rate and altering the morphology of the resultant aggregates. This paper examines the effect that the inclusion of the quadrupole terms has on the dynamics of aggregates interacting with each other and the confining electric fields in laboratory experiments. The results are compared with modeling aggregates as a collection of point charges located at the center of each spherical monomer comprising the aggregate. [ABSTRACT FROM PUBLISHER]

This paper presents an overview of some of the most enjoyable low-temperature plasma experiments I have carried out with my students over the course of my career. It begins with the connection between solitons and the Schrödinger equation, and continues with the discovery of cylindrical solitons. From moving structures, we progress to stable ones: sheaths and double layers. How can we measure double-layer potentials? This question leads to the development of emissive probe techniques. From there, we move on to the Bohm criterion and the first measurements of the full plasma potential variations of sheaths and presheaths in a single-species plasma, and later in two-ion-species plasmas. Finally, our recent measurements of double layers and presheaths in uniform helicon plasma are presented. [ABSTRACT FROM PUBLISHER]

In this paper, research studies on the breakdown progresses of multigap pseudospark discharge under nanosecond pulsed voltages are reported. The experimental results show great differences from dc voltages. The discharge mechanism of the pseudospark under nanosecond pulsed voltages has been successfully explained by the fast electron ionization effect. In each gap, collision ionizations caused by the fast electron start step by step, and development progresses are almost the same and approximately simultaneous until the main gap breaks down. [ABSTRACT FROM PUBLISHER]

Surface dielectric barrier discharge (SDBD), used as the plasma actuator for airflow control at atmospheric pressure, has been widely concerned over the past decades. In this work, four different electrode configurations, i.e., copper mesh, thin wire, blade, and aluminum foil, are chosen as exposed electrodes for the SDBD plasma actuator. The different effects of the four structures on the airflow acceleration behavior are experimentally investigated through the discharge current, surface potential distribution, ionic wind velocity, and mean thrust production. The result shows that the actuator with the copper mesh exposed electrode can generate the maximal induced force, while the actuator with the aluminum foil exposed electrode can generate the minimal induced force. This difference, as analyzed, is mainly due to the distinct discharge characteristics, i.e., different discharge asymmetry and surface potential, caused by the specifically designed exposed electrode configurations. This paper illustrates that the actuator with low surface potential has preferable mechanical performance. [ABSTRACT FROM PUBLISHER]

With the benefits of the high chemical selectivity and low energy cost, atmospheric rotating gliding arc (RGA) plasma is considered as a promising method in various industrial applications. In this paper, rapeseed oil is first proposed as the raw material to produce high-valued chemical products by RGA plasma. The influences of operating conditions (applied voltage, oil flow rate, and gas flow rate) on RGA discharge with rapeseed oil are focused, in terms of the basic physical properties ( $V$ – $I$ characteristics and discharge visualization) investigated using electrical diagnostics and high-speed photography. Blank experiments are conducted by supplying only pure N2 gas. The visual images presented complex arc dynamic behavior in N2 discharge, with the phenomenon of arc contact spot leap, spatial curl arc, and cracked. Intense purple light emission was observed by adding 3-mL/min oil droplets with four distinguished reaction stages. According to the electrical results, average current and power of arc increased with increasing applied voltage, while the average voltage indicated opposite variation tendency in different feedstocks. The augment of rapeseed oil flow rate decreased the average voltage and power, whereas raised the average current value in contrast. [ABSTRACT FROM PUBLISHER]

The speed plasma propagates across a charged solar panel after a primary arc is one of the most important, yet poorly known, quantities in determining Electrostatic Discharge (ESD) currents for spacecraft arcing events. A review of the literature over the last two decades reveals that measured propagation velocity varies by as much as an order of magnitude. To overcome this deficiency, a round-robin set of tests was initiated with partners from industry, academia, NASA and the U.S. Air Force. This paper will provide the most recent results from the Air Force Research Laboratory testing conducted at the Spacecraft Charging and Instrument Calibration Laboratory. [ABSTRACT FROM PUBLISHER]

A recent proposed technique for geostationary debris mitigation is the electrostatic tractor. The tug vehicle approaches a debris object to within 20 m and emits a focused electron beam onto it. This results in a negative charge on the debris and a positive charge on the tug vehicle. Used in conjunction with low thrust, the electrostatic force is used to tow a debris object into a disposal orbit. In this paper, the impacts of geomagnetic storm activity on the charging of tug and debris are considered. The influence of electrons emitted from the debris (photoelectrons and secondary electrons) on tug charging is also considered. Both of these phenomena yield improved electrostatic tractor performance. The simultaneous emission of an electron and ion beam by the tug is also considered to improve tractor performance and enable charge transfer for scenarios where it fails when only an electron beam is used. The theoretical maximum electrostatic force that is possible with simultaneous emission is computed, and the results indicate that emitting both an electron and ion beam enables smaller tug vehicles to tow larger objects that could not otherwise be towed with only an electron beam. [ABSTRACT FROM PUBLISHER]

This paper presents a fully kinetic particle-in-cell simulation of collisionless mesothermal plasma expansion with a focus on the macroscopic electron properties. The results show that the electron thermal properties are anisotropic and nonuniform. In the beam core region, the electrons are thermalized due to interactions between the trapped electrons and the potential well between the beam exit and the beam front. The electron expansion inside the beam is equilibrium and significant cooling occurs associated with the expansion. Immediately out of the beam boundary, the electrons undergo an isothermal expansion. In the outer expansion region, the electrons transition into a nonequilibrium expansion and again exhibit significant cooling. We find that the commonly used assumption of Boltzmann electron simplification is not valid for modeling electrons in mesothermal plasma expansion. An analysis of the electron temperature and density correlation along each individual ion streamlines suggests that simplified models for electron dynamics may be constructed using multiple polytropic laws in different plume regions. [ABSTRACT FROM PUBLISHER]

The basic structure and work mechanism of laser-triggered vacuum switch (LTVS) are introduced briefly in this paper, and the processes of primary plasma production and expansion are analyzed as well. A series of experiments has been carried out with different gap voltages, laser wavelengths, laser energies, polarity configuration modes, switch structures, focal lengths, and laser waveforms. The switch structure is modified to improve the heavy-current capability of the switch, and the gap distance is increased to improve the voltage capacity. The special design of the trigger structure can reduce the dependence on the laser energy of the switch and the time delay. A new laser waveform of LTVS multiple wave crests could further decrease the laser energy, and it is the research basis of laser trigger miniaturization and its application in the LTVS. [ABSTRACT FROM PUBLISHER]

A heated emissive probe is a smart diagnostic tool for acquisition of the plasma potential in the discharge and in the plume of a Hall thruster. However, measurements of high-frequency oscillations of the potential require a specific electrical circuit with a low $RC$ time constant. We developed and tested an emissive probe system with a cutoff frequency of 1 MHz. Details about the low-pass filter design as well as first experimental outcomes obtained in the plume of a 200 W permanent magnet Hall thruster are given in this paper. [ABSTRACT FROM PUBLISHER]

The Hall effect thruster is an electric propulsion device for space applications that efficiently reduces the propellant mass requirements on a spacecraft in comparison with chemical rockets. To date, the Hall effect thruster technology relies on the thermionic cathodes that consume up to 10% of the total propellant used in the system to neutralize the ion beam of the thruster; however, such propellant usage does not contribute to thrust generation. An array of thin-film, carbon nanotube field emitters that emit electrons through field emission can potentially neutralize the ion beam without consuming any propellant. This paper examines the effects of 40 min exposure of carbon nanotube field emitter arrays to the plasma environment in the exit plane of a Hall effect thruster. The physical structures that enable field emission appear largely unaffected by placement in the plasma as well as operation in the plasma. This indicates that a refined design of this carbon nanotube field emitter array may potentially provide an alternative to the thermionic cathode used on contemporary Hall effect thrusters and verifies that no fundamental incompatibilities exist between these two technologies. [ABSTRACT FROM PUBLISHER]

We report the performance of an A6 relativistic magnetron with single-stepped cavities output. Particle-in-cell simulation shows the electronic efficiency of an A6 relativistic magnetron with an anode block made of six single-stepped cavities can be up to 78% with an output power of one gigawatt for an applied voltage of 400 kV. When the A6 relativistic magnetron with axial extraction using six single-stepped cavities is applied with a voltage of \(V \sim 400~{\rm kV}\pm 50\) kV the electronic efficiency can be as high as 60%, while the output power can be as high as 1 GW. And, when a 10-ns voltage pulse of 400 kV is applied on this magnetrons with diffraction output using single-stepped cavities, the output power pulse can be as high 1.2 GW. The results in this paper will provide a reference for choosing a cavity that is easily manufactured, so that a physical experiment is more feasible. [ABSTRACT FROM PUBLISHER]

This paper demonstrates for the first time the use of microplasma to perform AND, OR, and XOR logic operations. The logic circuits are implemented similar to diode-resistor logic. Output voltages are in the range of \(5-40\) V and can be modified by varying the load resistor. The active area of the microplasma device is just \(50~\mu \) m \(\times 5~\mu \) m. The small interelectrode gap kept breakdown voltage to \(\sim 250\) V when operated in He gas at atmospheric pressure. The use of plasma as a source of free carriers is also demonstrated, with free carriers available up to 500- \(\mu \) m away from plasma. [ABSTRACT FROM PUBLISHER]

In this paper, an experimental investigation of pseudospark discharge behaviors was conducted under nanosecond pulsed voltages using a flexible discharge chamber. The breakdown voltages of the pseudospark discharge gap were measured for a wide range of gas pressures, anode-cathode gap distances, and cathode aperture diameters to find the match of gap distance and cathode aperture diameter at a certain gas pressure with the nanosecond pulsed voltage. According to the experimental results, an empirical relationship was obtained. The roles of the parameters in the empirical relationship during the discharge were analyzed. The breakdown characteristics were also consistent with the Paschen’s law in the pseudospark under nanosecond pulsed voltages, when the gap distance was replaced by the effective gap distance. In the end, a possible reason was put forward to explain the difference between the empirical relationships obtained under dc voltages and nanosecond pulsed voltages. [ABSTRACT FROM PUBLISHER]

In this paper, a device for accurate electrical measurements for nanosecond repetitive pulsed discharges (NRPDs) is presented. The experimental setup developed is based on an interelectrode system integrated in a transverse electromagnetic cell. This setup allows synchronizing the voltage and current measurements with a 4-GHz frequency bandwidth, corresponding to 250-ps pulse duration. A coaxial-shaped sharp metallic needle serves as a probe for current measurements. The needle probe is also the point electrode of a point-to-plane system used to generate discharges. The experimental setup was used to electrically characterize NRP corona and diffuse discharges, in negative polarity. Discharge current pulses with rise times less than 1 ns and amplitudes up to 120 mA were measured. The energy deposited by discharges was also determined. [ABSTRACT FROM PUBLISHER]

When a satellite leaves earth's atmosphere, the satellite potential floats negatively with respect to the surrounding plasma environment. Once the satellite surface consisting of different materials is charged and depending upon the dielectric constant of various materials, a potential difference develops between the surface of insulators and that of conductors, and under favorable conditions it exceeds the threshold value, which finally results in an electrostatic discharge (ESD). The potential difference arises on the solar panels when satellite bus voltage is increased to meet the present demand of the transponders. The resultant ESD may trigger a secondary arc, which can destroy the solar panel circuit and severely damage the substrate. Therefore, there is a need to test the performance of these solar arrays in a ground simulation facility. Recently, based on the collaborative research work in France, USA, and Japan, international standards for space solar panels have been finalized. This ISO document [ISO-11221] specifies qualification and characterization test methods to simulate plasma interaction and electrostatic discharges on solar array panels in the space. A linear circuit model has been jointly developed by Facilitation Center for Industrial Plasma Technologies, Institute for Plasma Research and ISAC, Indian Space Research Organization. This model explains the primary arc in low Earth orbit like plasma environment and geo-synchronous Earth orbit like electron irradiation environment. This paper discusses about the automated ISO test facility developed for detection and analysis of arc on the solar coupon. From the initial test results it has been confirmed that there is a gradual increase in surface potential on the solar coupon. The velocity of arc is measured based upon the neutralization currents in the adjacent solar cell strings. Damage caused by permanently sustained arc on solar coupon's surface is also studied. [ABSTRACT FROM PUBLISHER]

A numerical model for the inductively coupled plasma in radio frequency (RF) ion thruster discharge chamber is developed to evaluate the plasma parameters for a 2-D axisymetric domain. The spatial distributions of various plasma parameters are obtained. The ion thruster performance is evaluated by calculating the discharge loss per ion for different deposited RF power values. The geometry of RIT-15LP is applied as the thruster configuration and the results are shown to have the same tendency as presented in the literature. The results of this paper proved that above a certain RF power deposition into the discharge chamber, there is a tradeoff between the thrust obtained from the ion engine and the discharge loss per ion. [ABSTRACT FROM AUTHOR]