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This paper reports on the behavior of red and black ink from a historical printed book, subjected to a plasma discharge treatment, applied for the decontamination and cleaning of naturally aged paper. As some preliminary experiments using high-frequency (HF) plasma showed a slight fading of red ink, the study was focused on the comparison of HF cold plasma and afterglow plasma treatments in order to get conclusive information on the effect of plasma active species on the red ink. Energy Dispersive X-ray Scanning Electron Microscopy SEM-EDX and Attenuated Total Reflection Fourier-Transform Infrared Spectroscopy FTIR-ATR analyses were used for the identification of inks and binder, while the impact of plasma on inks was assessed by SEM analysis and color determinations. The experiments have been performed on an especially designed modular equipment, allowing the samples to be subjected alternately to HF cold plasma or afterglow plasma treatment. The study proved that direct HF plasma could result in a more important deterioration at treatment duration exceeding 5 min, while in afterglow plasma, this discoloration is not observable. The color fading is imputable to the corrosion of pigment crystallites produced by direct plasma discharge. [ABSTRACT FROM AUTHOR]

A low-cost and simple-arranged paper-based microplasma array device made by tape and Xerox paper was presented. Uniform array of discharge can be sustained in Ar, He, and ambient air atmosphere. Stable discharge can be sustained for at least 55 min when plasma is ignited in Ar ambient, based on the examination of time-resolved optical emission spectra. Throughout the conditions investigated, the power consumed by the device was well below 0.3 W. We also demonstrated that stable and uniform discharge can be generated when the device was bent to a radius of curvature of 2.5 mm. [ABSTRACT FROM PUBLISHER]

The 16th version of the Latin American Workshop on Plasma Physics (LAWPP 2017) took place at the main campus of the Universidad Nacional Autónoma de México, Mexico City, Mexico, on September 4, 2017—September 8, 2017, organized by the Sociedad Mexicana de Física Division of Plasma Physics. This was the third time LAWPP was held in Mexico, following those in 1992 and 2005. The main mission of this series of meetings is to promote plasma physics in the region, providing a proper forum, as well as collaborations between scientists within Latin America, and broadly across the world. However, while it is a regional event in nature, it fulfilled its objective of bringing in an important international undertone. Furthermore, a wide range of topics were covered, in the fields of space and astrophysical plasmas, controlled nuclear fusion, laser-produced plasmas, dense magnetized plasmas, and industrial and environmental applications of plasmas. [ABSTRACT FROM AUTHOR]

The IEEE International Conference on Plasma Science (ICOPS) is an annual meeting of the plasma physics community known for the broad range of topics addressed as well as for its varied international locations. The 42nd ICOPS was held in Belek, Antalya, Turkey, on May 24–28, 2015. It was the first time that ICOPS was held in Turkey and the region. The General Chair of ICOPS 2015 was Prof. Lütfi Öksüz from Suleyman Demirel University (Isparta, Turkey), the Technical Program Chair was Dr. Christine Coverdale from Sandia National Laboratories (Albuquerque, NM, USA), and the conference Liaison was Prof. Edl Schamiloglu from the University of New Mexico (Albuquerque, NM, USA). As is traditional, the conference consists of all plasma science topics including 7 technical sessions and 35 subsessions. There were almost 400 registrants at ICOPS 2015, and over 500 abstracts are included in the conference. This ICOPS 2015 meeting especially attracted attendance from the Middle East, China, and Russia. [ABSTRACT FROM PUBLISHER]

Welcome to the 27th Symposium On Fusion Engineering (SOFE) Special Edition of the IEEE Transactions on Plasma Science (TPS). [ABSTRACT FROM AUTHOR]

The paper aims at assessing morphological and chemical changes on the surface of the cellulose-based materials, such as paper, induced by high frequency (HF) plasma discharge. The topic is discussed using capacitive coupled plasma discharge at 1.2 MHz, performed in Ar/O2 mixtures, on objects made up of natural polymers, such as lignocellulosic fibers. The preliminary findings indicate the possibility of using HF cold plasma discharge for obtaining the modified properties of the cellulose-based surfaces. Simultaneously, this treatment is well suited for cleaning and decontamination purposes. The improved wettability of the cellulose-based materials after surface activation in low pressure HF Ar/O2 plasma is favorable for a subsequent deposition of protective coating formulas specific in the conservation practices. [ABSTRACT FROM PUBLISHER]

The 2013 IEEE Pulsed Power and Plasma Science Conference (PPPS 2013) was held at the Hyatt Regency in San Francisco, CA, USA in June 2013. The PPPS 2013 combined the 19th IEEE Pulsed Power Conference (PPC) and the 40th IEEE International Conference on Plasma Science (ICOPS). This conference marks the third combined IEEE PPPS meeting, following the very successful PPPS 2001 in Las Vegas, NV, USA, and the PPPS 2007 in Albuquerque, NM, USA. The most recent ICOPS was held in 2012 in Edinburg, Scotland, and the most recent PPC was held in 2011 in Chicago, IL, USA. [ABSTRACT FROM PUBLISHER]

This paper presents the results of mathematical simulation of processes in argon-hydrogen inductively coupled plasma/radio frequency induction plasma torch for plasma chemical reactions. This first part starts a series of papers for simulation and study of plasma properties for a variety of gases and mixtures, which could be used for a number of prospective technologies. The results of mathematical simulation allow further research on the mechanisms of chemical reactions in argon-hydrogen plasma to increase effectiveness of obtaining the target product. [ABSTRACT FROM AUTHOR]

This paper proposes unconventional control techniques for a portable power supply consisting of electric double-layer capacitors (EDLCs), a dc–dc converter, and a low-impedance load such a plasma load. Between the EDLCs and the plasma load consuming high power, a dc–dc converter is required to control the output voltage from the rapidly decreasing voltage of EDLCs. In addition, the dc–dc converter should maintain a set point by responding to arcs occurred in plasma process. This paper proposed hybrid analog and digital controls for a nonideal boost converter which was setup by theoretical analysis. The proposed system is verified with experiment and simulation. As a result, the proposed control method can maintain the constant output voltage longer than a traditional analog pulsewidth modulation control. [ABSTRACT FROM AUTHOR]

This paper presents the development and description of research aimed at investigation of nanosecond surface microdischarge plasma effect on biomaterials. The technique is based on application of a simple discharge device. The device is assembled on a standard microscope slide from inexpensive materials. An optical microscope equipped with a digital camera is used for visualization of the studied samples and microdischarges. Many images of the microdischarges on the biological objects are presented in this paper. Spatial resolution of the images allows studying the discharges along the cellular structure of the tissue. [ABSTRACT FROM PUBLISHER]

The 41st IEEE International Conference on Plasma Science (ICOPS14) and the 20th IEEE International Conference on High-Power Particle Beams (Beams14) combined for the first time in 2014 as the IEEE ICOPS/Beams meeting. This scientific meeting took place from May 25 to May 29, 2014, in Washington, DC, at the historical Marriott Wardman Park hotel in Northwest DC. Participation included a broad range of scientific attendance, with a total of 566 researchers from 36 countries, with scientists from China, Russia, and Japan making the largest contribution to the international contingent. [ABSTRACT FROM PUBLISHER]

This paper presents the results of studies of dust formations in a radio frequency (RF) discharge plasma. In particular, the behavior of dust clouds in various types of traps was investigated. The experiments were carried out in argon plasma with the following discharge parameters: gas pressure of 0.02–0.6 Torr and discharge power of 1–50 W. Two types of the ring were used as a trap—“closed” and “nonclosed.” It was found that by changing the discharge parameters and using a different type of trap, it is possible to control the capture region of dust formations, and therefore, manipulate the extraction of dust particles by mass (size, in the case of monodispersity of particles). It has been observed that at a lower gas pressure the dust cloud is less affected by the traps; moreover, the wider the edge opening of “nonclosed” ring trap, the more efficient the process of extracting dust particles. The results of this paper can be useful for practical application in the processes of separation and extraction of dust particles from a plasma crystal, the study of particle interactions, and the manipulation of individual particles, etc. [ABSTRACT FROM AUTHOR]

This paper presents a simulation study of the dynamics of dust grains around a small asteroid. Plasma-asteroid interactions and asteroid charging are obtained from fully kinetic particle-in-cell simulations. Dust transport simulation takes into account the electrostatic force, solar radiation pressure, and the gravitational force. Both the result derived from laboratory measurements of regolith surface charging and the single dust charging model are considered for dust charging. For the small asteroid considered in this paper, we find that dust transport is mostly determined by the competition between the electrostatic force and the solar pressure and dust distribution is sensitive to both dust charging and dust grain size. For dust grains in the tens of micrometer size range, the solar radiation pressure dominates dust transport at small dust charge-to-mass ratio, whereas the electrostatic force dictates dust transport at large dust charge-to-mass ratio. [ABSTRACT FROM AUTHOR]

As part of the ongoing China Fusion Engineering Test Reactor (CFETR) studies, this work focused on the study of the electromagnetic (EM) loads distribution on inboard (IB) and outboard (OB) blanket vertical segments. In this paper, a major central disruption scenario with a 36-ms linear current quench was performed in the ANSYS finite element software. EM forces and moments, both on the single module and the complete blanket segment, were calculated for the updated helium-cooled ceramic breeder (HCCB) blanket. Furthermore, the effect of EM loads with respect to poloidal segmentations on the back plate (BP) was studied. Results show that the EM forces and moments in the IB blanket barely changed, but in the OB blanket, great changes occurred. With poloidal segmentations increasing, EM forces loads on the BP will be reduced. This paper may provide important data to support subsequent optimization of the BP of CFETR and could also be a technical reference for other fusion organizations. [ABSTRACT FROM AUTHOR]

Iron nanopowders (Fe-NPs) were extracted and downsized by evaporating the iron powders in an atmospheric microwave plasma flame. The microwave plasma, which was generated by a mixture of nitrogen and argon swirl gases, evaporated the iron powders, immediately downsizing them to Fe-NPs. Subsequently, the Fe-NPs samples were collected by using bar magnets inside the collecting chamber. The Fe-NPs were analyzed by X-ray diffraction, Raman spectroscopy, optical emission spectroscopy, and a scanning electron microscopy. The Fe-NPs consisted of only iron phase and no Fe2O3 or Fe3O4 phases were formed during synthesis. The average sizes of the raw iron powders and the Fe-NPs were approximately $20~\mu \text{m}$ and 20 nm, respectively. The proposed method is simple and easily scalable. Thus, it is suitable for the mass production of Fe-NPs, overcoming the limitations of other catalyst-based synthesis methods. This paper provides a potential method for large-scale production of metal nanopowders which have potential applications in various fields owing to their unique properties at the nanoscale. [ABSTRACT FROM AUTHOR]

This paper clearly demonstrates the structure of Experimental Advanced Superconducting Tokamak (EAST) power supply system and analyzes principles of the finite-state machine (FSM) elaborately. Depending on the characteristics of EAST power supply system and the requirements of it, this paper chooses the real-time Linux as system platform and experimental physics and industrial control system (EPICS) as development tool to design a control system of the EAST poloidal field power system supply. This paper utilizes a temporal logic control based on the FSM in order to regulate the operation process of real-time sequence logic control of 12 sets of power controllers. This design is evaluated and tested, and it completely meets the real-time requirement of the poloidal field power supply (PFPS) control system. Several experiments have proved that this design definitely meets the real-time sequence logic control requirement of the PFPS control system in the complex situations under magnetic fields. [ABSTRACT FROM AUTHOR]

This paper is focused on using plasma as element of a frequency selective surface (FSS). FSSs have been used for filtering electromagnetic waves for many years. Conventional FSSs use metal patch pattern as periodic element. This paper takes the plasma tube as a substitution for metal patch. The 3-D finite-difference time-domain method with periodic boundary condition is utilized to simulate the interaction of incident wave and plasma FSS. Numerical calculation results in that electron number density of plasma can dominate the resonance frequency obviously. The resonance frequency increases as the increasing of electron number density of plasma to the limit of that of perfectly electric conductor. Thus, the FSS can be designed to be tunable by changing the ionized electron number density. Both of the noncollision and collisional plasma model are introduced to study the FSS characteristics. The numerical calculation results show that the collision frequency only influences the reflectivity while has no effect on the resonant frequency. The resonant frequency and transmitted power ratio can be tuned by assigning the plasma’s electron number density and collision frequency. Thus, plasma elements offer the possibility of improved shielding effect along with reconfigurability. Plasma FSS can also be made transparent by tuning the plasma off which makes the use of FSS more versatile. [ABSTRACT FROM AUTHOR]

Basic kinetic process of plasmas is studied by a first principle based N-body simulation. By confirming Coulomb collisional relaxation process, this paper is extended to investigate the dynamics of Debye shielding. Some of the key numerical techniques are discussed, including how to avoid singularities at the near encounter of two charged particles. Electron distribution function in Debye shielding is revealed, which deviates from conventional Maxwellian distribution function. [ABSTRACT FROM AUTHOR]

The values of the propagation constants of electromagnetic (EM) waves through the plasma using as the example of a homogeneous plasma layer for different electron distribution functions (EDFs) are the subject of this paper. The Maxwellian, Druyvesteyn, Pipe-line, and Bi-Maxwellian distribution functions were considered in this paper. Using values of the complex dielectric permittivity obtained from using different EDFs, the results for corresponding reflection, transmission, and absorption coefficients can be significantly different. The EDFs sometimes can have a considerable effect on the dielectric properties of plasma. Hence, comparing the results obtained, it is helpful to analyze the interaction between EM waves and plasma and provide a theoretical basis for the experiments. [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]

Linearly polarized spectral emission is induced by non-Maxwellian electrons with anisotropic velocity distributions through collisional processes with ions in plasmas. X-ray line polarization is a viable diagnostic tool for the study of these electrons, which has been tested in controlled settings, e.g., the electron beam ion trap, but due to strong depolarization effects, has been relatively unexplored in laboratory-produced high-energy-density plasmas. This paper explores the X-ray line polarization for the study of Ne-like molybdenum X-pinch plasmas. Previous polarization studies have focused mostly on K-shell spectral lines, whereas the current paper expands on these studies by investigating L-shell line polarization. The X-pinch is favorable due to its high-density plasma formation, high radiation yield, fixed hotspot location, and reliable electron beam production. L-shell X-ray line polarization and spectral emission of Mo X-pinches were investigated through dual $\alpha $ -quartz ($2d=6.687$ Å) crystal spectropolarimetry with axial and radial spatial resolution. In particular, line polarization is evaluated through a comparative analysis of relative line intensities observed over a range of Ne-like Mo transitions simultaneously recorded with two spectrometers with different sensitivity to polarization. An appreciable degree of X-ray line polarization (up to 15%) is observed in the Ne-like Mo plasmas and analyzed using depolarization effects. These results are the first polarization measurements in high-Z pulsed power plasmas. [ABSTRACT FROM AUTHOR]

This paper presents the results of the experiment with an overmassed wire-array $Z$ -pinch load that is powered by a current pulse (amplitude ~4.3 MA and rise time $\sim 0.9~\mu \text{s}$) from a multidisk magnetocumulative generator. Interesting feature of the experimentally recorded soft X-ray (SXR) pulse is short (~10 ns) duration at a microsecond current rise time with total energy of several hundreds of kilojoules. Obtained results are the evidence of high-quality implosion of the current-carrying plasma. The 2-D magnetohydrodynamic code FLUX-rz was used for the numerical simulation and analysis of the obtained results. The calculations indicated that only ~30% of the initial load mass took part in the SXR generation. The main peculiarities of the overmassed $Z$ -pinch implosion are discussed in this paper. [ABSTRACT FROM AUTHOR]

This paper describes an investigation of plasma influence on the germination rate of brown mustard seeds (Brassica juncea L.). It was found that five pulses of a nanosecond microspark have a suppressing action increasing the time of the seeds germination by 5 h; the plasma influence and UV-radiation of the nanosecond surface discharge with the frequency of 1 Hz for the course of 15 min being at a distance of 25 mm from the surface of the seed have a stimulating action on it reducing the germination time by 3 h; a combined treatment using the discharges of both types showed that germination rate may look as two-pulse mode. Repeated experiments confirmed this conclusion. Visual observation of the seeds after the UV-radiation and plasma treatment revealed cracks on the seed coats. The cracks significantly increase moisture penetration into the coat. [ABSTRACT FROM PUBLISHER]

Atmospheric corona discharge plasmas are the most common diversely occurrence in the electric power system. In this paper, four elementary processes occurred in corona discharge are taken into account, including elastic collision, excitation, attachment, and ionization. As one of the most important parameters in corona characteristics analysis, the effective Townsend ionization coefficient is completely calculated by the Boltzmann equation under the consideration of humidity. This paper also derives the electron energy distribution function (EEDF) in water vapor and dry air, respectively. With reference to previous researches and the existing literature, comparisons and validations on ionization and attachment coefficient are conducted. Besides, the effects of humidity, pressure, and temperature on the effective ionization coefficient are also discussed in this paper. It is concluded that humidity can enhance both ionization and attachment. The results show that the ionization coefficient in this paper is well consistent with traditional ones, while there are variations for attachment coefficient. In normal condition, the effective ionization coefficient varies slightly with humidity, but it increases significantly with a decreased pressure or an increased temperature, which cause the change in critical electric field correspondingly. [ABSTRACT FROM PUBLISHER]

This paper presents a shutdown dose rate (SDR) calculation to estimate a newly developed preliminary concept of the equatorial port model for the Korean fusion demonstration reactor (K-DEMO). The equatorial port model was designed to provide effective radiation shielding abilities adopting the port shielding block and labyrinth structure, which was integrated into the modified K-DEMO neutronic analysis model by the Monte Carlo automatic modeling system. A rigorous two-step method was applied to couple transport (MCNP) and activation (FISPACT) codes according to three steps of calculation procedures. The results of neutron flux and decay gamma transport calculation for the equatorial port area have been indicated in this paper. The SDR calculation result near the equatorial port area reveals that a dose level in the equatorial port interspace was below $100~\mu $ Sv/h after 12 days of the shutdown. Shielding blocks and two labyrinth structures prove that they effectively attenuate neutrons on the current concept of the equatorial port model. [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]

The pseudospectral analytical time-domain (PSATD) particle-in-cell algorithm solves the vacuum Maxwell's equations exactly, has no Courant time-step limit (as conventionally defined), and offers substantial flexibility in plasma and particle beam simulations. It is, however, not free of the usual numerical instabilities, including the numerical Cherenkov instability, when applied to relativistic beam simulations. This paper presents several approaches that, when combined with digital filtering, almost completely eliminate the numerical Cherenkov instability. This paper also investigates the numerical stability of the PSATD algorithm at low beam energies, drawing in many cases on the pioneering work of Prof. Ned Birdsall, in whose memory this paper is dedicated. [ABSTRACT FROM PUBLISHER]

According to Internationa Thermonuclear Experimental Reactor (ITER) integration procurement arrangements, the installment of diagnostics in a port should not increase the shutdown dose rate (SDDR) in the port interspace area by no more than \sim50~\muSv/h above the baseline, assuming another 50 \muSv/h is attributed to contribution from the port structure and other ITER in-vessel components, such that the upper SDDR limit of 100 \muSv/h is not exceeded 10^6~s after shutdown. It was found that placing the initial design of the motional stark effect (MSE) and the charge exchange recombination spectroscopy (CXRS) in the equatorial port #3 resulted in an increase in the SDDR that far exceeded the limit. When we follow the optimization process discussed in this paper, substantial reduction in the port interspace SDDR was achieved. The results of this paper show that even when we combine the optimized CXRS and MSE diagnostics with a third glow discharge diagnostic, the excess of the SDDR over the baseline value did not exceed the allowed upper limit. This paper is based on utilizing the 3-D CAD-based ATTILA code for assessing the SDDR. [ABSTRACT FROM PUBLISHER]

The microwave plasma torch (MPT) is an attractive plasma source in both industry and scientific research because of its advantages in electrodeless operation ability, high energy efficiency, and flexibility under different operational conditions. However, relatively few numerical studies have been carried out for the MPT fed by a rectangular waveguide in two or even three dimensions. Therefore, this paper presents a 2-D, axisymmetric, and stationary fluid models to characterize the MPT, with an emphasis on the mechanism of the surface wave formation and the sustentation of the plasma column. Nine partial differential equations are included in this research, coupling microwave radiation, heat transfer, plasma bulk flow, and transport of different species with each other. The obtained results reveal how the traveling surface wave occurs and elucidate the consequent influence of the surface wave formation. Furthermore, this paper demonstrates the extension of the plasma column length and the propagation of the surface wave with an increase in the total plasma-absorbed microwave power. The dependence of the plasma column length on the plasma-absorbed microwave power is found to be motivated by the surface wave propagation. The limitations of the model and the difficulties in its numerical implementation are also discussed in the paper. [ABSTRACT FROM PUBLISHER]

Risk of arcing in space plasma environment on satellite solar panel has always been an issue of major concern in the aerospace community. The outcome of round robin tests performed in various laboratories has resulted in finalization of the guidelines for the ground test of satellite solar panel coupons (SSPCs). This is documented as ISO-11221 standards. Authenticity of arc plasma flashover (FO) parameters are still under debate. Some experimental findings that support the perimeter theory of arc FO on geostationary (GEO) satellites are discussed in this paper. It has been observed that characteristics of an the arc are dependent on its location on the solar coupon, bias charge (charge due to bias voltage and external capacitance), and the total charge dissipated during the arc discharge. It is also observed that the duration between the two consecutive arcs is directly proportional to the dissipated charge or energy of the latter arc. A combined dielectric consisting of solar cell, adhesive, Kapton, and Carbon Fiber Reinforced Polymer sheet holds charge during irradiation by the electron gun. This resembles surface FO capacitance. Arc energy is governed by the combined effects of a surface flashover capacitor (C-sf) and an external capacitor. It is observed that if intermittent arc duration is sufficiently longer than the gradual accumulation of charge on the SSPC, body may lead to a major arc. This would increase the probability of secondary arcs when the sustained arc environment is experienced by the satellite. To understand primary arcs on dielectrics, an artificial triple junction is prepared and exposed under adverse GEO-like space conditions. Various signatures identified from the arc current and arc neutralization current waveforms specify the behavior of these arcs at different locations on the coupon surface. In this paper, current waveforms of arcs captured on different types of solar panel coupons and their significance are studied. Information about arc energy, arc velocity, and neutralization velocity are extracted from the measured waveforms. [ABSTRACT FROM PUBLISHER]

This paper considers thermal neutralized charge electron flux moving through immovable static ion background. A 2-D dispersion equation is derived. The equation describes linear waves of space charge (WSC) in the flux. In the result of the dispersion equation analysis, we proved the existence of the backward and sideward WSCs. Maps on the plane $\{{k_{x}; k_{y}} \}$ were calculated and plotted for two values of the electrons drift velocity. The lines on those maps correspond to the direct, sideward, and backward WSCs. Areas of obtuse and acute drift angles are marked out. [ABSTRACT FROM AUTHOR]

In this paper, we report a qualitative model of operation and energy release in pulsed dielectric barrier discharges (DBDs). We demonstrate that pulsed DBDs operate according to the “maximum power principle” and explain the relevant physical processes. Compared to experimental data, the proposed model allows an accurate estimation of the discharge pulse energy as a function of dielectric properties, electrode size, and pulse parameters (shape and voltage amplitude). [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]

In nuclear fusion reactors, unipolar arcing is a longstanding plasma surface interaction issue. In this paper, short summaries of morphology changes by helium plasma irradiation under fusion relevant conditions and ignition of arcing on the He irradiated surfaces are given. Helium plasma irradiation leads to surface morphology changes, and arcing can be ignited on the surface in response to pulsed heat load accompanied by plasma instabilities. Then, we focused on arcing ignited on large-scale fiberform nanostructures (LFNs) formed with deposition of metallic particles together with helium-ion irradiation. Dusts release from the arc spot and the amount of material erosion are discussed based on the experiments. [ABSTRACT FROM AUTHOR]

NorSat-1 was launched on July 14, 2017 as a satellite carrying, among other instruments, the multineedle Langmuir probe (m-NLP), an instrument which, on NorSat-1, is capable of measuring the ionospheric plasma electron density with the high sampling frequency of 1000 Hz. The m-NLP instrument operates by analyzing the current–voltage diagram resulting from the measurements from each individual probe. In principle, the m-NLP operation methodology should be insensitive to spacecraft charging. However, this is not always the case. In this paper, we present an overview of the instrument response to passes into and out of eclipse. When the satellite exits eclipse, we observe a collapse in the collected probe currents. This acute drop is unaccounted for by the theoretical operation of the instrument. We present a statistical analysis of the phenomenon based on several months of NorSat-1 data, and we suggest a plausible reason for the observed drop in the current, namely, spacecraft charging, by solar cell arrays upon eclipse exit. We briefly discuss how satellite orientation and plasma wake affect the current drop. With this paper, we address Langmuir probe current susceptibility to spacecraft potential. [ABSTRACT FROM AUTHOR]

This paper is devoted to the further development of a numerical model for the simulation of high-current vacuum arcs (HCVA) with cathode attachment in the form of multiple cathode spots. The model allows one to simulate different modes of HCVA and the transition between them. It is shown that the secondary plasma, arising from the anodic sputtering and nonadherence of the incident ions, affects the constriction of the plasma and the transition between the HCVA modes. [ABSTRACT FROM AUTHOR]

Equilibrium reconstruction is an important basic work for the design and operation of a multipole Galatea magnetic trap device, and it is also a fundamental theoretical work for plasma equilibrium control. Based on the static equilibrium model of the multipole Galatea magnetic trap, an equilibrium reconstruction scheme based on solving the Grad–Shafranov equilibrium equation is proposed. In the proposed scheme, a plasma current density distribution model is established, and the combination of the Green function and the finite difference method is investigated to realize the fast solution to the Grad–Shafranov equilibrium equation. At the same time, the least-squares fitting method is employed, along with the magnetic probe measurement data, which realizes correction and iteration of the parameters of the plasma current density distribution model. Through simulation, the magnetic field distribution, plasma current density distribution, and plasma pressure distribution of multipole Galatea magnetic trap can be obtained, which confirms the effectiveness of the equilibrium reconstruction when compares with other experimental results. At the end of this paper, the influence of the magnetic field produced by the solenoid coil on the equilibrium configuration of plasma is studied. [ABSTRACT FROM AUTHOR]

Laser electron accelerators utilize a bubble regime of nonlinear plasma waves driven as laser wakefields that, from theoretical considerations, require a matched laser spot size incident on plasma. A strongly mismatched regime of nonlinear laser–plasma acceleration in the bubble regime, favored by experiments, is introduced and modeled for optimization of laser-to-particle energy efficiency with application to the recently proposed laser positron accelerator. Strong mismatch, in contrast with the matched condition, arises from the incident laser spot size being much larger than that needed for equilibration of the laser ponderomotive and electron-ion charge-separation forces in the nonlinearly driven density structure of a plasma bubble. This is shown to be favorable for optimization of large self-injected electron charge and ultralow transverse emittance without precluding beam spectral shaping. It is shown that there are prominent signatures of the mismatched regime, strong optical-shock excitation, and bubble elongation, which are validated using multidimensional particle-in-cell simulations. This paper thus uncovers a generalized regime that apart from being used in many laser–plasma acceleration experiments also opens a novel pathway for a wide range of future applications. [ABSTRACT FROM AUTHOR]

In this paper, the design and implementation of a plasma antenna array using Yagi–Uda reflectors with beamforming is discussed. The structure consists of the circular array of plasma tubes enclosed a unipolar L-band monopole antenna. Beamforming is possible using stimulated plasma tubes. The combination of the above structure with plasma excitation controller provides smart beamforming and uses of the Yagi–Uda structure increases gain compared to previous models. An experimental model in the L-band is fabricated that shows a good agreement between simulated and measured results. [ABSTRACT FROM AUTHOR]

Many terrestrial and astrophysical plasmas encompass very large dynamical ranges in space and time, which are not accessible by direct numerical simulations. Thus, idealized subvolumes are often used to study small-scale effects including the dynamics of magnetized turbulence. A significant aspect of magnetized turbulence is the transfer of energy from large to small scales, in part through the operation of a turbulent cascade. In this paper, we present a new shell-to-shell energy transfer analysis framework for understanding energy transfer within magnetized turbulence and in particular, through the cascade. We demonstrate the viability of this framework through application to a series of isothermal subsonic and supersonic simulations of compressible magnetized turbulence and utilize results from this analysis to establish a nonlinear benchmark for compressible magnetized turbulence in the subsonic regime. We further study how the autocorrelation time of the driving and its normalization systematically change properties of compressible magnetized turbulence. For example, we find that $\delta $ -in-time forcing with a constant energy injection leads to a steeper slope in kinetic energy spectrum and less efficient small-scale dynamo action. We examine how these results can impact a range of diagnostics relevant for a range of terrestrial and astrophysical applications. [ABSTRACT FROM AUTHOR]

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]

Radiation particles and rays will be produced during each nuclear fusion plasma discharge, especially neutrons which will be largely emitted out with high intensity and energy under the neutral beam injection (NBI) discharge mode. To well obtain the neutron dose rates during the nuclear fusion plasma discharge, 3He-based neutron detector is adopted in this paper, and to fully obtain the neutron dose rates in the Experimental Advanced Superconducting Tokamak (EAST) hall, three neutron detectors have been set at three selected monitoring sites with a long distance to the monitoring personal computer (PC), and the monitoring system, based on the RS-485 differential communication mode, was designed and setup. Along with each nuclear fusion plasma discharge, the neutron radiation field should appear as a pulsed radiation field. Based on the neutron dose rates, saved by the monitoring system, the neutron radiation dose rates were studied during one NBI-based nuclear fusion plasma discharge. Finally, the Gaussian function model of neutron dose rates during one nuclear fusion plasma discharge was obtained and presented. [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 is devoted to the design, implementation, and test of a low cost, modular, and reliable pulsed high-voltage (HV) converter (dc chopper). The distinct characteristics of the present prototype refer to: adjustable voltage amplitude up to 7 kV, amplitude drop less than 4‰ for $2 \times 10$ A output peak current at 5 kHz, adjustable pulse frequency up to 5 kHz, adjustable duty cycle between 1% and 10%, rising/falling time around 100 ns, and jitter about 10 ns. In principle, 1-kV modules based on a fast MOSFET each are combined in series to form a completely modular push–pull switch configuration. Contrary to sophisticated optical fiber-based insulation techniques, the driving low-voltage stage of the power supply is magnetically coupled to the HV stage. The low-voltage stage defines and schedules the HV pulses by means of a microcontroller. The 7 kV is equally distributed along MOSFETs due to balancing networks of passive components. Zener diodes in parallel with MOSFETs provide sufficient protection against overvoltages. The power supply has been successfully tested on dielectric-barrier discharge-based plasmas which have nowadays continuous technological interest. [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]

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]

Gas flow plays an important role in determining the discharge properties in microwave plasma torches sustained by the propagating surface wave. This paper aims to investigate the gas flow effects on the plasma column length, the surface wave propagation, and the heavy species temperature in a surface wave plasma torch operated at atmospheric pressure. The steady-state discharges of pure argon gas at atmospheric pressure under different gas inflow rates in the plasma torch are characterized by an improved 2-D axisymmetric fluid model. The obtained results demonstrate that increasing the gas inflow rate is able to decrease the surface wave propagation distance, accelerating the contraction of the plasma column length. The discharge instability is found to be motivated by the disappearance of the sustaining surface wave at high gas inflow rates. Besides, a temperature drop of about 64 °C is observed at the temperature-maximum point of the glass tube with an increase in the gas inflow rate from 1 to $16\,\,\text {L}\cdot \text {min}^{-1}$. Therefore, for the surface wave plasma torch operated with only the axial gas flow, increasing the gas inflow rate cannot solve the glass overheating problem. [ABSTRACT FROM AUTHOR]

The increased usage of diesel fuel of late has led the researchers to pay more attention toward abatement of increased emission of oxides of nitrogen (NOx) in the engine exhaust. The focus is, therefore, lies in providing a technique that is economical, feasible, and long lasting. The combination of electric discharge plasma with adsorbent/catalyst derived out of solid waste can be one such possible technique. In this paper, waste foundry sand from foundry industry and red mud or bauxite residue from aluminum industry have been used. Diesel engine exhaust under dry condition was exposed to an oxidizing discharge plasma environment. The plasma-treated exhaust was subjected to either adsorption over waste foundry sand or catalysis over red mud. Studies were carried out in the laboratory environment with 20% loading of diesel generator. The oxidizing plasma environment was either with direct plasma or with indirect plasma in which case ozone injection into the exhaust was accomplished. The ozone-adsorbent cascading system has resulted in about 87% NOx reduction in the dry exhaust case. The effect of O3:NO ratio was discussed from the point of NO/NO2. [ABSTRACT FROM AUTHOR]

This paper describes an investigation of effect of high-power UV-radiation plasma, generated by electric discharges, on germination rate of Altaic flax seeds (Linum altaicum). It was found that UV-radiation scarifies flax seeds by means of cracks formation in the seeds’ coat. The cracks shorten moisture penetration time to a seed bud thus twice increasing the germination rate. It is found that the germination rate function has the three-stage character; the velocity-growth function has the view of three pulses, which separates the seeds into three subgroups. Division of the group into subgroups is stipulated by the probabilistic nature of the cracks formation. The number of subgroups is equal to the number of layers +1. We calculated average times of natural moisture penetration through the flax seed coat layers: $T_{s} =11.8$ h through the spermoderm and $T_{e} =17.7$ h through the endosperm. It is possible that scarification of the flax seed coats can shorten the germination time for these times. We also noted that some seeds could die due to the effect of high-power UV radiation. So, it is necessary to find more sparing regimes of the seeds UV irradiation. [ABSTRACT FROM AUTHOR]

This paper demonstrates the improved simulation of a Z-pinch experiment with 2-D magnetohydrodynamic code FLUX-rz developed in RFNC-VNIIEF. A Z-pinch load was nested wire array powered by a helical magnetocumulative generator with the current pulse $I_{\max } \approx 4.2$ MA and effective rise time $\tau \approx 400$ ns. Validation of X-ray spectral measurements carried out with scintillation detector filters pointed out a necessity to take into consideration both the scintillator “dead” layer and oxide films on the aluminum filter surface. [ABSTRACT FROM AUTHOR]