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Cold atmospheric-pressure plasma is used widely for treating material surfaces and can be considered for modifying insulation paper (IP) to improve its surface performance. However, the mechanism for interaction between reactive oxygen species (ROS), which are the dominant components of such plasma, and IP is important for setting experimental parameter values but is difficult to observe experimentally. In this paper, reactive force field molecular simulation technology is used to study the mechanism for interaction between ROS (O atoms, OH radicals, and H2O2 molecules) and cellulose, which is the main component of IP. The results show that the ROS can abstract H atoms, and the H2O2 molecules can also abstract hydroxyl groups from a cellulose chain, resulting in changes to the cellulose chain structure, such as reductions of the hydroxyl groups and pyran rings and formations of aldehyde and vinyl groups. The three types of ROS exhibit different reactivities when reacting with the cellulose chain, and the difficulty of breaking different bonds therein also differs, which influences how the chemical groups change the cellulose chain. This study provides basic insight into the mechanism for interaction between ROS and IP at the atomic level as well as offering some guidance for practical experiments. [ABSTRACT FROM AUTHOR]

The tutorials also covered the field of plasma physics and introduced some new topics and technologies to plasma physicists that connect to our research. The presentations included four invited review talks, 98 invited talks, four tutorials, and four presentations from this year's prize and award recipients. The 64th Annual Meeting of the APS Division of Plasma Physics (DPP) was held October 17-21, 2022 in Spokane, Washington at the Spokane Convention Center. [Extracted from the article]

Plasmas 28, 053505 (2021).10.1063/5.0045947 12 J. Moreno, A. Khodaee, D. Okerstrom, M. P. Bradley, and L. Couëdel, " Time-resolved evolution of plasma parameters in a plasma immersion ion implantation source", Phys. However, there is still a lack of understanding of the plasma parameters in the complex mixture gas (radical/ion species, electron/ion energy distributions, temperature, etc.) and plasma physics (electron heating dynamics, electron kinetics, wave-particle interaction, dust plasma characteristics, etc.). The "Plasma Physics and Science in Current and Next Generation Semiconductor Process" Special Topic in I Physics of Plasmas i consists of articles on research presented at The 8th International Conference on Microelectronics and Plasma Technology (ICMAP), which was held in Hwaseong, South Korea, January 17-20, 2021.[1] The "Plasma Physics and Science in Current and Next Generation Semiconductor Process" Special Topic is devoted to understanding such plasma source, plasma parameters, plasma-surface interaction, and processing results in semiconductor process and its related fields, and to bring new insight from theory and experiment for the next generation of plasma process techniques. [Extracted from the article]

10.1063/5.0061234.1 [ABSTRACT FROM AUTHOR]

In a recent Comment, Chang et al. [Phys. Plasmas 29, 114703 (2022)] have studied the electron dynamics for an electron accelerating in a tightly focused Gaussian laser pulse with the higher order correction terms, and it is found that the initial position of the electron is the reason why the electron is pushed to the −z axis at the end. In this Reply, the electron dynamics and its nonlinear Thomson backscattering in a tightly focused Gaussian laser pulse with the higher order correction terms are presented, and it is found that the result is consistent with the lowest order approximation case in our paper [Hong et al., Phys. Plasmas 29, 043102 (2022)]. Meanwhile, it is also found that when the longitudinal deceleration effect of the ponderomotive force on the electron introduced by the falling part of the tightly focused laser pulse is greater than the longitudinal acceleration effect of the rising part, the electron that is initially stationary will be slightly pushed to the −z axis at the end, which can well explain the "return" phenomenon of the electron in the longitudinal direction both in our paper and in the Comment. [ABSTRACT FROM AUTHOR]

BAAE gap represented by the analytic expression, Eq. (9) of Ref. [5], and the Alfvén wave to slow mode coupling analytic dependence obtained in the CKPN paper for the plasma equilibrium at m / n =1.75, =(C s / V A)2= /2=2.5×10-3. Essentially, the only possibly new result reported in the CKPN paper is the claim that they have discovered a new mode for the MHD continuum, which includes, due to finite beta, a coupling of the Alfvén to the acoustic wave. [5] and [8], which show that the modified Alfvén branch, given in Eq. (84a) of Ref. [8], with clear Alfvén velocity dependence, and is opposite to acoustic interpretation of CKPN paper Fig. [Extracted from the article]

This Special Issue consists of articles on research presented in the Second International Conference on Data-Driven Plasma Science (ICDDPS-2), which was held in Marseille, France, May 13-17, 2019.[1] The ICDDPS-2 follows the initiative launched in 2018 by Sadruddin Benkadda, Deborah O'Connell, and Satoshi Hamaguchi to establish a regular international conference series that gathers a wide spectrum of plasma scientists interested in emerging data-driven methods applied to various topics in plasma science, including plasma-based future medical therapeutics such as cancer treatment, plasma sterilization, sophisticated materials synthesis, and coatings, advanced plasma processing for the manufacturing of next-generation semiconductor devices, and plasma-based clean energy technologies such as thermonuclear fusion and other non-fossil energy sources. Embracing data-driven discovery in plasma science will enable a new era of research and development in plasma science and technology. This conference series aims to stimulate dialog and collaboration among researchers from the wide disciplines of plasma and data sciences. [Extracted from the article]

This paper highlights the most important results achieved at the spherical tokamak Globus-M2 with a high magnetic field. This paper also covers the most important topics of fusion research: thermal energy confinement in regimes with neutral beam injection, toroidal Alfvén eigenmode and correspondent fast ions confinement issues, L-H transition, turbulence suppression and edge-localized modes' behavior, experimental and theoretical study of regimes with nitrogen seeding that allow to significantly reduce thermal loads on the divertor plates, and experiments and simulations of lower hybrid current drive. The research results provide the basis for the next step toward a fusion neutron source—the development of the Globus-3 spherical tokamak. [ABSTRACT FROM AUTHOR]

Two recent papers, P. H. Yoon and G. Choe, Phys. Plasmas 28, 082306 (2021) and Yoon et al., Phys. Plasmas 29, 112303 (2022), utilized in the derivation of the kinetic equation for the intensity of turbulent fluctuations the assumption that the wave spectra are isotropic, that is, the ensemble-averaged magnetic field tensorial fluctuation intensity is given by the isotropic diagonal form, ⟨ δ B i δ B j ⟩ k = ⟨ δ B 2 ⟩ k δ i j . However, it is more appropriate to describe the incompressible magnetohydrodynamic turbulence involving shear Alfvénic waves by modeling the turbulence spectrum as being anisotropic. That is, the tensorial fluctuation intensity should be different in diagonal elements across and along the direction of the wave vector, ⟨ δ B i δ B j ⟩ k = 1 2 ⟨ δ B ⊥ 2 ⟩ k (δ i j − k i k j / k 2) + ⟨ δ B ∥ 2 ⟩ k (k i k j / k 2). In the present paper, we thus reformulate the weak magnetohydrodynamic turbulence theory under the assumption of anisotropy and work out the form of nonlinear wave kinetic equation. [ABSTRACT FROM AUTHOR]

During the flight of hypersonic vehicle, air will be decomposed and ionized due to the "friction" under ultra-high speed, thus forming a plasma layer. Because the plasma has the ability to absorb and reflect electromagnetic waves, the "black barrier" phenomenon is formed. In addition, when the hypersonic vehicle passes through the atmosphere, the surface temperature rises sharply due to aerodynamic heating, and the surface material undergoes a series of complex changes to form ablation. In this paper, the finite volume method and the laminar finite rate model are used to study the flow field velocity, pressure distribution, flow field temperature, and spatial distribution of each component of the aircraft at different Mach numbers, angles of attack, and heights. In the flow field of supersonic aircraft, N and O are mainly concentrated in the tail of the aircraft, NO is mainly concentrated in the head of the aircraft, and N2 and O2 are full of the whole space. Because of the accumulation of NO+ and O2+ in the tail of the aircraft, the charge accumulation is formed, which will further interfere with the electromagnetic wave signal. The mass fraction of N and O increases with the increase in Mach numbers, while the mass fraction of O2 decreases with the increase in Mach numbers. Different angles of attack will affect the asymmetry of the shock wave of the aircraft. In this paper, the evolution mechanism and distribution characteristics of aircraft plasma are revealed, which lay a theoretical foundation for solving the problem of black barrier and ablation. [ABSTRACT FROM AUTHOR]

This paper concerns the correlation of hard x-ray and neutron signals, which were recorded with scintillation detectors oriented in the axial and radial directions, in a comparison with interferometric and extreme-ultraviolet radiation frames, as recorded within the plasma focus (PF)-1000 facility operated with a deuterium filling. The considered signals showed two different phases. In the initial phase, the fusion neutrons are mainly produced by deuterons moving dominantly downstream during the disruption of a pinch constriction (lasting tens nanoseconds). In the later phase (usually after about 100 ns), the fusion neutron emission reaches its maximum in the radial directions. This emission (lasting 100–200 ns) is caused by the fast deuterons moving in both the downstream and radial directions. It correlates usually with a decay of dense plasma structures in remnants of the expanding pinch column. This can be explained by a decay of internal magnetic fields. The neutron signal is usually composed of several sub-pulses of different energies. It was deduced that the primary deuterons producing the observed fusion neutrons undergo a regular and repeated temporal, directional, and energy evolution. [ABSTRACT FROM AUTHOR]

The aim of this paper is to explore the possibility of simultaneously characterizing instabilities in vacuum arc thrusters on a broadband frequency range (kHz–GHz) in situ, meaning in a conventionally used vacuum chamber where vacuum arc thrusters are usually operated. We show in this paper that, despite the reverberant nature of the vacuum metallic chamber, useful information is extracted over a large frequency range from the measurements done with an antenna in this environment. This leads to the first characterization of the self-emission of a vacuum arc thruster in the GHz frequency range. [ABSTRACT FROM AUTHOR]

A novel design methodology based on a current-tunable magnetic focusing system that can flexibly switch between Brillouin and immersive flow focusing modes is presented in this paper. Such a magnetic system, which comprises cascaded solenoid coils and pole pieces, could be used in beam optics systems of vacuum tubes, particle accelerators, and free-electron lasers. Although the profile of this magnetic system is not brand new, the novel way proposed in this paper to establish and manipulate such a system to fit versatile purposes has never been reported in the literature to the best of the authors' knowledge. The specific structure of the magnetic system should be optimized, starting from the immersive flow focusing mode together with the electron gun design, which will be determined on successful optimization. According to our analysis, such systems could be transformed into the Brillouin bunching mode by simply adjusting the coil currents without modifying the hardware. To verify such an approach, single-beam and multi-beam optical systems are demonstrated in this paper. Moreover, the beam radius in such systems could also be conveniently adjusted via a similar technique. [ABSTRACT FROM AUTHOR]

This paper presents a novel coupling of a kinetic description of neutrals with a fluid description of a fusion plasma. The code, plasma interacting super-atoms and molecules (PISAM), employs a grid-free Cartesian geometry and a direct simulation Monte Carlo approach to solve the kinetic equations of deuterium atoms and molecules. The grid-free geometry and the parallel nature of the neutral dynamics, in the absence of neutral–neutral interactions, allow for an unlimited and work-efficient parallelization of PISAM that always ensures a balanced workload. The highly optimized Python implementation obtains good performance while securing easy accessibility to new users. The coupling of PISAM with the edge turbulence model HESEL is outlined with emphasis on the technical aspects of coupling Message Passing Interface-parallelized Python and C++ codes. Furthermore, the paper presents and analyzes simulation results from running the coupled HESEL-PISAM model. These results demonstrate the impact of radial neutral transport and plasma–neutral dynamics perpendicular to the magnetic field. Specifically, they illustrate how the inward flow of neutral kinetic energy and the inhibition of radial electric shear, resulting from poloidal momentum transfer between atoms and ions, can affect the energy containment time. By comparing the results of the HESEL-PISAM model with those obtained from coupling HESEL with a diffusive-fluid-neutral model, the capabilities of diffusion models in predicting neutral transport in the plasma edge and scrape-off layer are elucidated. [ABSTRACT FROM AUTHOR]

The plasma weak turbulence theory is a perturbative nonlinear theory, which has been proven to be quite valid in a number of applications. However, the standard weak turbulence theory found in the literature is fully developed for highly idealized unmagnetized plasmas. As many plasmas found in nature and laboratory are immersed in a background static magnetic field, it is necessary to extend the existing discussions to include the effects of ambient magnetic field. Such a task is quite formidable, however, which has prevented fundamental and significant progresses in the subject matter. The central difficulty lies in the formulation of the complete nonlinear response functions for magnetized plasmas. The present paper derives the nonlinear susceptibilities for weakly turbulent magnetized plasmas up to the third order nonlinearity, but in doing so, a substantial reduction in mathematical complexity is achieved by the use of Bessel function addition theorem (or sum rule). The present paper also constructs the weak turbulence wave kinetic equation in a formal sense. For the sake of simplicity, however, the present paper assumes the electrostatic interaction among plasma particles. Fully electromagnetic generalization is a subject of a subsequent paper. [ABSTRACT FROM AUTHOR]

Abstract-dynamic plasma sheath can severely interfere with the communication of hypersonic vehicles during atmospheric reentry. Theoretical and experimental results show that low-frequency (LF) electromagnetic (EM) waves could penetrate the plasma sheath, building a feasible method to solve the "radio blackout" problem. This paper discovers that the propagation of LF EM waves in plasmas is still influenced by parasitic modulation effects. Compared to microwave frequencies, the impact of parasitic modulation effects on signal modulation patterns is more distinct for LF EM waves. In contrast to the microwave frequency range, where the rotation direction of QPSK signal constellation points changes with the ratio of plasma frequency to electromagnetic wave frequency, in the LF range, the constellation points undergo limited clockwise rotation. This phenomenon can be attributed to the unique magnetic field propagation mechanism of LF EM waves in dynamic plasmas. This paper analyzes the mechanism of this specific parasitic modulation effect and discovers a sinusoidal transformation relationship between amplitude attenuation and phase shift. Meanwhile, the experimental and simulation results proved that the time-varying plasma could cause the parasitic modulation effect of LF EM wave, resulting in a limited clockwise rotation of orthogonal phase-shift keying constellation points, which is consistent with the theoretical analysis. [ABSTRACT FROM AUTHOR]

In a direct drive laser fusion, nonlocal transport of the more energetic electrons can have at least two potentially important effects. First, the most energetic electrons, furthest out on the tail of the distribution function can cause preheat of the fuel deep inside the target. Second, nearby the nonlocal deposition of less energetic electrons can spread out the ablation layer, possibly having a stabilizing effect on the Rayleigh Taylor instability. This sequence of two papers treats two different methods of modeling nonlocal transport. For about 20 years, these phenomena have been treated with a Krook model for the electron collisions. However, different versions have given different results, especially as regards preheat. Our first paper attempts to analyze the various reasons for discrepancies, correct errors, and derives a variety of simple formula to evaluate preheat. The second paper offers, for the first time, a steady state, nonlocal method of using the Fokker Planck equation to evaluate the nonlocal transport and deposition of energetic electrons deposited by some mechanism, at some particular point in the plasma. Regarding ablation surface broadening, the two models are not very different; but regarding preheat, the Fokker Planck model gives orders of magnitude less. This is a very optimistic result for the direct drive laser fusion. [ABSTRACT FROM AUTHOR]

The finite volume time domain (FVTD) method is proposed to accurately calculate the electromagnetic (EM) scattering of hypersonic vehicles coated with non-uniform plasma sheath. The plasma sheath in the actual flight environment is accurately established by solving the Navier–Stokes equations and combining appropriate thermochemical models. The radar cross section (RCS) of metal and uniform medium coated metal targets calculated by FVTD are in good agreement with those simulated by the software FEKO (MoM) and the Mie series. The calculated RCS of the vehicle under the reentry condition is consistent with the flight test data, too. The calculated electron number density distribution is consistent with the flight experiment results. The body fitted structure EM grid is adopted. The EM grid independence of the target coated with plasma sheath is studied. Then, the scattering and plasma EM parameters of the vehicle during the actual reentry are studied. The reentry altitude is from 78 to 55 km, and the reentry velocity is from 6406 to 6350 m/s. With the reentry altitude decreasing, the plasma angular frequency and collision frequency increased gradually. The scattering of different incident conditions and different wall catalytic conditions is analyzed in depth. This paper provides a valuable reference for vehicles' detection, recognition, and stealth during reentry flights. [ABSTRACT FROM AUTHOR]

The inter-electrode state of the transverse magnetic field contact during the current-zero period is determined by the evolution of the arcing process. It has an important effect on whether the vacuum switch can be successfully broken. In this paper, a series of contacts were subjected to arcing and fixed gap distance experiments. The results show that a special inter-electrode phenomenon (glow flow) appears during the current-zero period when the current exceeds the threshold for the transition from diffused to constricted state of the vacuum arc. The mechanism behind the formation of this phenomenon was elucidated through an analysis of multiple sets of experimental results. It is found that the inter-electrode phenomenon arises from the disruption of the equilibrium process between the pressure from the arc column plasma and the anode vapor flux on the near-anode side at the current-zero. The copper vapor falls and is ionized by collisions with heat-emitting electrons. The experimental results and theoretical analysis also show that this phenomenon has a time interval with the reignition phenomenon. When this phenomenon is intense to a certain degree, the reignition will occur with high probability. The observation and theoretical analysis results of this paper are relatively consistent with the research results of other scholars, which can help to improve the vacuum arc characteristics and interrupting mechanism. This can provide a basis for improving the arc extinction performance of the vacuum switch. [ABSTRACT FROM AUTHOR]

This paper analyzes the two-dimensional motion of a charged particle in constant mutually perpendicular electric and magnetic fields. The magnetic field is assumed to be uniform, and the electric field components are assumed to be linear functions of the Cartesian coordinates. Under these assumptions, the equations of particle motion can be solved analytically. This solution is used to study the stability of particle motion and to assess the accuracy of the guiding center approximation in the presence of electric field gradients. It is well known that if the gradient of a one-dimensional electric field is sufficiently large, the motion of the charged particles becomes unstable and the particles are effectively energized by the electric field. This paper, however, demonstrates that the instability threshold depends on the spatial derivatives of both electric field components and is, under certain conditions, very sensitive to both. The analytical solution is averaged over the gyroperiod to derive simple expressions for the drift speed and the position of the gyrocenter, which explicitly account for the electric field gradient. The results of this averaging are used to develop equations for tracing the particle gyrocenter location, which incorporate the effects of non-uniformity of the electric field. These equations are shown to be noticeably more accurate than those based on the standard E × B drift velocity, which is exact only for uniform electric and magnetic fields. Simple expressions for the local errors in the E × B drift velocity are also derived, which arise from the electric field gradients. [ABSTRACT FROM AUTHOR]

Ion fast ignition (IFI) is one of the proposed options for inertial fusion in which the ignition of nuclear fuel is initiated by an intense ion beam. In this paper, the properties of a laser-accelerated heavy ion beam are investigated for the possible use of such a beam as a fuel igniter in the IFI scenario. Using a two-dimensional particle-in-cell code, detailed studies of laser-driven heavy ion acceleration were carried out to determine the possibility of improving the properties of the heavy ion beam relevant for IFI by the appropriate selection of certain laser and target parameters. In simulations, a 1-ps laser with an energy of 150–250 kJ irradiated targets with a variety of atomic mass numbers, areal densities, thicknesses, and densities. For each of the sets of laser and target parameters considered in the paper, the parameters of the heavy ion beam relevant for IFI were determined and discussed. It was found that for realistic laser driver parameters, the IFI requirements are best met by ion beams with moderate ion mass numbers (A ∼ 50–100), such as the beam of Cu ions. It was shown that by optimizing the laser focal spot, as well as by properly matching the energy and power of the laser to the target areal mass density, it is possible to significantly improve the properties of the heavy ion beam relevant for IFI and, in particular, bring a many-fold increase in the intensity, fluence, and energy of the beam. [ABSTRACT FROM AUTHOR]

Hall thrusters are known to exhibit a large variety of instabilities. Their physical mechanisms have been identified at low (kHz) and intermediate (MHz) frequencies, even though they are still not fully understood. Furthermore, electromagnetic radiations generated by Hall thrusters, named "self-emission" of the thruster, have been measured from kHz to MHz as expected from the identified instabilities, but also at higher frequencies. The origin of the high frequency (GHz) self-emission remains for now unknown. Assessing this self-emission, that is important for understanding the physics of Hall thrusters as well as for electromagnetic compatibility issues with the spacecraft, is challenging. Another aspect that makes the understanding of the physics of Hall thrusters complex comes from the eventual coupling between instabilities, which has been recently suggested and observed. The aim of this paper is to explore the possibility of characterizing simultaneously instabilities in Hall thrusters on a broadband frequency range (from kHz to GHz) in situ, meaning in a conventionally used vacuum chamber where Hall thrusters are usually operated. We show in this paper that, despite the reverberant nature of the vacuum metallic chamber, useful information is extracted at low and intermediate frequencies and even at high frequency from the measurements done with an antenna in this environment. [ABSTRACT FROM AUTHOR]

This document serves as a preface to a special topic collection in the journal "Physics of Plasmas" that focuses on the study of relativistic plasma in supercritical fields. The collection includes papers from a mini-conference held at the 2022 meeting of the American Physical Society Division of Plasma Physics. The objective of the mini-conference was to bring together researchers from different physics communities to address the physics of matter in extreme astrophysical objects and high-power laser systems. The papers in the collection cover topics such as electron-positron pair production, extreme astrophysics, radiation reaction, and vacuum physics. The mini-conference aimed to facilitate knowledge exchange and inspire future research in this emerging field of plasma physics. The authors of this document, Alec G. R. Thomas and Stepan S. Bulanov, declare that they have no conflicts of interest to disclose and were supported by the U.S. Department of Energy Office of Science Offices of High Energy Physics and Fusion Energy Sciences. [Extracted from the article]

Adiabatic heating of solar wind electrons at the Earth's bow shock and its foreshock region produces transversely anisotropic hot electrons that, in turn, generate intense high-frequency whistler-mode waves. These waves are often detected by spacecraft as narrow-band, electromagnetic emissions in the frequency range of [0.1, 0.5] of the local electron gyrofrequency. Resonant interactions between these waves and electrons may cause electron acceleration and pitch-angle scattering, which can be important for creating the electron population that seeds shock drift acceleration. The high intensity and coherence of the observed whistler-mode waves prohibit the use of quasi-linear theory to describe their interaction with electrons. In this paper, we aim to develop a new theoretical approach to describe this interaction, which incorporates nonlinear resonant interactions, gradients of the background density and magnetic field, and the fine structure of the waveforms that usually consist of short, intense wave-packet trains. This is the first of two accompanying papers. It outlines a probabilistic approach to describe the wave–particle interaction. We demonstrate how the wave-packet size affects electron nonlinear resonance at the bow shock and foreshock regions, and how to evaluate electron distribution dynamics in such a system that is frequented by short, intense whistler-mode wave-packets. In the Paper II, this probabilistic approach is merged with a mapping technique, which allows us to model systems containing short and long wave-packets. [ABSTRACT FROM AUTHOR]

Electron resonant scattering by high-frequency electromagnetic whistler-mode waves has been proposed as a mechanism for solar wind electron scattering and pre-acceleration to energies that enable them to participate in shock drift acceleration around the Earth's bow shock. However, observed whistler-mode waves are often sufficiently intense to resonate with electrons nonlinearly, which prohibits the application of quasi-linear diffusion theory. This is the second of two accompanying papers devoted to developing a new theoretical approach for quantifying the electron distribution evolution subject to multiple resonant interactions with intense whistler-mode wave-packets. In the first paper, we described a probabilistic approach, applicable to systems with short wave-packets. For such systems, nonlinear resonant effects can be treated by diffusion theory, but with diffusion rates different from those of quasi-linear diffusion. In this paper, we generalize this approach by merging it with a mapping technique. This technique can be used to model the electron distribution evolution in the presence of significantly non-diffusive resonant scattering by intense long wave-packets. We verify our technique by comparing its predictions with results from a numerical integration approach. [ABSTRACT FROM AUTHOR]

Due to vacuum interrupter's excellent interruption performance, an increasing number of on-load tap-changers (OLTCs) have chosen it as a load changeover switch in recent years. The stability of the arcing process is crucial for the interruption since the vacuum interrupter in OLTC must break current frequently with the requirement of long electrical life. In this paper, experiments on butt contacts and axial magnetic field (AMF) contacts applied in OLTC were carried out in a demountable vacuum chamber, and the arcing process was investigated by a high-speed camera. Investigations were conducted on the effects of opening speed, opening phase, current amplitude, and AMF on arc characteristics, e.g., arc expansion and arc voltage. The experiment findings demonstrated that expansion and instability of arc increased with higher opening speed, number of cathode spots moving to the inclined surface decreased with shorter arcing time, and that cathode spots' propensity to form group cathode spots increased with higher current. AMF lessened the impact of high opening speed and high current on the arcing process. The investigation carried out in this paper helps to better understand the characteristics of arc evolution and the influence of some key factors, which may serve as a guide for improving the design and vacuum arc control of vacuum OLTCs. [ABSTRACT FROM AUTHOR]

The paper [R.T. Sandberg and A. G. R. Thomas, Phys. Rev. Lett. 130, 085001 (2023)] proposed a scheme to generate ultrashort, high energy pulses of XUV photons through dephasingless photon acceleration in a beam-driven plasma wakefield. An ultrashort laser pulse is placed in the plasma wake behind a relativistic electron bunch so that it experiences a density gradient and therefore shifts up in frequency. Using a tapered density profile provides phase-matching between the driver and witness pulses. In this paper, we study via particle-in-cell simulation the limits, practical realization, and 3D considerations for beam-driven photon acceleration using the tapered plasma density profile. We study increased efficiency by the use of a chirped drive pulse, establishing the necessity of the density profile shape we derived as opposed to a simple linear ramp, but also demonstrating that a piecewise representation of the profile—as could be experimentally achieved by a series of gas cells—is adequate for achieving phase matching. Scalings to even higher frequency shifts are given. [ABSTRACT FROM AUTHOR]

A new solid state plasma reconfigurable dipole based on surface PiN diodes is presented for high-integration communications in this paper. The proposed antenna consists of several solid state plasma diode elements, which use the microwave characteristics of solid state plasma to realize the radiation and reception of electromagnetic waves. The plasma diode is designed and fabricated on a silicon-on-insulator wafer, and its size is 50 × 100 μm2. Measured results show that the plasma region appeared to be metal-like (carrier concentration is exceeding 1018 cm−3) when a forward bias is applied, and its steady-state current can reach 0.02 A. Based on these results, a high-integration reconfigurable dipole is designed with two working states at 2.21 and 3.01 GHz, and the overall dimensions of this dipole are 40 × 40 mm2. Other radiation performances are also discussed in this paper, which lay a good foundation for further studies. [ABSTRACT FROM AUTHOR]

A plasma sheath will be generated around the hypersonic vehicle during reentry, and a large number of electrons in the plasma sheath will seriously affect the communication between the vehicle and the ground station. In order to reduce the electron number density of the hypersonic vehicle plasma sheath, a method of using pulsed discharge active actuation to regulate the plasma sheath is proposed. Based on the air dissociation and ionization model including 11 components and 32 chemical reactions, the reduction effect of pulsed discharge actuation on the electron density of plasma sheath is studied by numerical simulation. A first test is performed in which the pulsed discharge is compared with the plasma jets' experimental data. Then, a second test compared the plasma flow field around the RAMC-II vehicle with the flight test and NASA data. In these two tests, the simulation results are basically consistent with the experimental results. Finally, the effect of pulsed discharge with different energy density on the plasma sheath electron density is studied. The numerical results show that the interaction between the high-pressure aerodynamic actuation generated by the actuator and the plasma sheath produces an obvious shock wave, which blocks electrons from flowing downstream, reduces the velocity and pressure of the flow field behind the shock wave, and, finally, makes the electron density downstream of the actuator attenuate significantly, with the maximum attenuation amplitude of about 35%. Compared with the traditional method, the method proposed in this paper requires less space, load, and source power and has certain engineering feasibility. [ABSTRACT FROM AUTHOR]

In recent years, the interaction of electromagnetic waves (EM) with plasma sources under argon and helium discharges has been extensively studied due to its potential applications in plasma stealth. However, nitrogen, as a more economical discharge gas, has been ignored in terms of its absorption of EM waves and stealth effect. In this work, a numerical calculation model combining two-dimensional capacitively coupled plasma (CCP) fluid model and EM wave model was developed to investigate the plasma uniformity degree and broadband microwave absorption effects in helium and nitrogen CCP. It is concluded that the two-dimensional model in this paper has more accurate and reasonable through comparison with the one-dimensional and experimental results in helium CCP. Nitrogen CCP shows better broadband absorption effects than that of helium, and helium plasma has better uniformity than nitrogen under the same discharge parameters. But the uniformity degree of nitrogen plasma is not much different from that of helium under the same electron density, which means that nitrogen can significantly improve its broadband wave absorption properties to some extent without loss of uniformity degree. Based on the above conclusions, the absorption characteristics of nitrogen CCP under different radio frequency (RF) power and pressure are analyzed. The attenuation effect of nitrogen CCP increases with the increasing RF power, and it is interesting that the influence of pressure on the attenuation of EM waves is not monotonically increasing, and the related mechanism is discussed. Finally, discussion of skin depth under different RF power and pressure validates the above conclusions. The absorption band of nitrogen CCP under the best parameters in this work can reach the X-band, which shows great application potential in plasma stealth. [ABSTRACT FROM AUTHOR]

This paper extends the analysis first presented in Jardin et al. [Phys. Rev. Lett. 128, 245001 (2022)] to more thoroughly examine the stability of spherical torus equilibrium to ideal magnetohydrodynamic (MHD) infernal modes and their nonlinear consequences. We demonstrate that in a 3D resistive magnetohydrodynamic (MHD) simulation of a NSTX discharge, anomalous transport can occur due to these instabilities. We generate a family of equilibrium of differing β and use this to show that these instabilities could explain the experimentally observed flattening of the electron temperature profile at modest β. The modes studied in this paper are found to occur with poloidal mode number m and toroidal mode number n when the ratio m/n is in the range of 1.2–1.5, when the central safety factor is in this range or slightly lower, and when the central region has very low magnetic shear. Our analysis gives some insight as to why the unstable linear growth rates are oscillatory functions of the toroidal mode number n. We present a simulation of an initially stable configuration that passes through a stability boundary at a critical β as it is heated. We also show that a particular NSTX discharge is unstable to these modes over a timescale of several hundred ms. We conclude that these modes must be taken into account when performing predictive modeling. An appendix shows that similar modes can be found in R / a = 4 tokamaks for certain q-profiles and β values. [ABSTRACT FROM AUTHOR]

In order to overcome the problem of efficiency decrease in the relativistic backward wave oscillator (RBWO) operating at low magnetic field, an S-band klystron-like RBWO with a three-period slow-wave cavity-chain and a dual-cavity extractor is proposed and investigated in detail in this paper. In the device, several measures are taken to enhance the conversion efficiency at low magnetic field, which include increasing the beam bunching depth by a two-stage modulation structure comprised of a resonant reflector upstream and a three-period cavity-chain modulator downstream, strengthening the energy exchange process from the electron beam to the microwave by a dual-cavity extractor, and optimizing the envelope distribution of the electron beam in the interaction region by adjusting the drift length before the resonant reflector. Under the condition of the guiding magnetic field of 0.28 T, the device could generate a microwave with a power of 4.3 GW, a frequency of 3.79 GHz, and the conversion efficiency of 43.3% in the simulation. [ABSTRACT FROM AUTHOR]

In this paper, we propose a relativistic quantum many-body theory for the collective modes in spinor quantum electrodynamic plasma. Different from the usual quantization scheme, we use the self-consistency nontrivial background field method in the framework of thermo field dynamics, in which the resulting quanta are temperature-dependent particles instead of the observable ones such as electrons, positrons, and photons. The theory provides a general scheme for many-body physics, which overcomes the disadvantages of random phase, Hartree–Fock, or other equivalent mean-field approximations. The essential point for our theory is to exactly evaluate the background fields. In this paper, we propose a general and efficient method to determine them, which we name as the “classical limit method” for convenience. To demonstrate how to apply the theory, we discuss the collective modes in unmagnetized electron–positron plasma, in both the low-energy and high-energy limits. It yields the well-known dispersion relations of longitudinal and transverse modes for non-relativistic degenerate plasmas, at zero and nonzero temperature. Furthermore, it gives the additional relativistic and vacuum fluctuation corrections, including increasing mass, decreasing effective charge, finite light velocity influence on the dispersion relation, and virtual charge redistribution. The last effect is reported for the first time. [ABSTRACT FROM AUTHOR]

The purpose of the developed plasma jet generator is to study the effect of jet plasma on electromagnetic wave propagation, simulating the plasma sheath environment encountered during space vehicle reentry. Because the temperature and velocity of the plasma jet are high, it is difficult to measure temperature and electron density by the contact method. In addition to the normal flow of the entire apparatus, high-power magnetic field energy (generated by the power supply) is injected into the inductively coupled plasma (ICP) generation region. The energy of the magnetic field excites the gas and generates plasma. In this paper, the whole apparatus is calculated numerically, the energy term is added to the corresponding area of ICP, and the enthalpy distribution of the whole apparatus is calculated. The heat flux and total pressure are measured by slug calorimeter (heat flux probe) and total pressure probe, and then, the enthalpy is obtained. When the calculated enthalpy is consistent with the measured enthalpy, the value of the energy term in the numerical calculation process is the injected energy value. The ratio of the energy injected into the ICP region to the total energy provided by the power supply is the power injection proportion. The power injection proportion of the apparatus in this paper obtained by the above method is between 25% and 30%. [ABSTRACT FROM AUTHOR]

This paper reports plasma behavior in an un-magnetized, co-axial electrode geometry DC glow discharge plasma system. Fluctuations and hysteresis in discharge characteristics have been observed when the electrode system has a central anode configuration. The important fact is that fluctuations and hysteresis in discharge characteristics are not observed in a central cathode configuration. The radial profile of plasma potential shows that it is less than the anode potential, so current continuity is maintained in this current-driven system. This paper also attempts to identify the source of order-to-chaos-to-order in floating potential oscillations with respect to the discharge characteristics. When discharge current (Id) increases after the first negative differential resistance region, the system self-organizes and stabilizes into a state of periodic oscillations. Chaotic behavior is a possible development of new dynamical states in the discharge, which develops from an initial high frequency, low amplitude oscillations (in the range 11.6 mA < Id < 15 mA) and, thereafter, transits to low frequency, large amplitude oscillations at Id >15 mA. In the reverse path of discharge characteristics, the oscillations are more regular than in the forward path. Before the production of low frequency, large amplitude oscillations, the current oscillations follow a similar pattern to the floating potential oscillations. As it transits from chaotic to low frequency, large amplitude floating potential oscillations, discharge current oscillations show a chaotic type of behavior. [ABSTRACT FROM AUTHOR]

This paper extends the evaluation of ignition metrics to include the impact of hohlraum cooling before peak implosion velocity in radiation driven implosions. First, we provide an extension of the results for the key hot spot stagnation quantities from the 2018 paper [Lindl et al., Phys Plasmas 25, 122704 (2018)]. The modified analytic expressions presented here match the Hydra results for these National Ignition Facility scale implosions both with and without hohlraum cooling before peak velocity if the effective ablation pressure Pabl(effective) = Pabl(tpv − 0.5 ns) is used in the analytic formulas, where tpv is the time of peak implosion velocity. Second, we provide an analysis that enables a comparison of the Hydra radiation hydrodynamics code calculations utilized here with the predictions of the analytic piston model [Hurricane et al., Phys. Plasmas 29, 012703 (2022)] of an ICF implosion, which focused on sensitivity to time duration of the hohlraum cooling phase before peak velocity (often called the "coast time") and the shell radius at peak velocity Rpv. Third, we provide a set of ignition metrics that are valid across a wide range of capsule designs valid for implosions both with and without hohlraum cooling before peak implosion velocity is reached. [ABSTRACT FROM AUTHOR]

A method to analyze the scattering characteristics of a Laguerre–Gaussian (LG) vortex beam by a low-velocity charge in a steady applied magnetic field is investigated in this paper. Based on the plane wave angular spectrum representation and the electromagnetic radiation theory of a moving charge, the expressions of the scattered field and scattered power per unit solid angle are presented. Considering a low-velocity electron, the distribution of the scattered power per unit solid angle is numerically simulated. The effects of electron motion parameters, beam parameters, and applied magnetic field are discussed in detail. The results show that the longitudinal motion of the electron, which is parallel to the direction of the applied magnetic field, makes the distribution of the scattered power no longer maintain radial consistency but has a concave–convex distribution. Due to the periodicity of the circular motion of the electron in the applied magnetic field, the scattering power distribution pattern consists of many annular lobes. The spectral characteristics of the backscattered field are analyzed by fast Fourier transform. It is confirmed that the scattered field satisfies the rotational and the linear Doppler effects, and the accuracy of the formula provided in this paper is verified. This work lays a foundation for further study of the scattering characteristics of plasma on vortex electromagnetic waves and helps to promote the in-depth development of vortex beams in the field of plasma diagnosis. [ABSTRACT FROM AUTHOR]

The field-reversed configuration (FRC) is a compact toroidal plasma system related to the research of alternative fusion reactors. Improving the FRC formation, which is critical to the improvement of its overall quality, is reported in this paper by using a plasma gun to assist the pre-ionization process. For the single-translated FRC, the poloidal magnetic flux increases around 30%, accompanied by an increase in the separatrix radius and plasma density, while its translation speed is found to decrease slightly. The estimated increase in particle inventory is more than 60%. The improvement of these parameters also extends the lifetime of the FRC. [ABSTRACT FROM AUTHOR]

In a recent paper [P. H. Yoon and G. Choe, Phys. Plasmas 28, 082306 (2021)], the weak turbulence theory for incompressible magnetohydrodynamics is formulated by employing the method customarily applied in the context of kinetic weak plasma turbulence theory. Such an approach simplified certain mathematical procedures including achieving the closure relationship. The formulation in the above-cited paper starts from the equations of incompressible magnetohydrodynamic (MHD) theory expressed via Elsasser variables. The derivation of nonlinear wave kinetic equation therein is obtained via a truncated solution at the second-order of iteration following the standard practice. In the present paper, the weak MHD turbulence theory is alternatively formulated by employing the pristine form of incompressible MHD equation rather than that expressed in terms of Elsasser fields. The perturbative expansion of the nonlinear momentum equation is carried out up to the third-order iteration rather than imposing the truncation at the second order. It is found that while the resulting wave kinetic equation is identical to that obtained in the previous paper cited above, the third-order nonlinear correction plays an essential role for properly calculating derived quantities such as the total and residual energies. [ABSTRACT FROM AUTHOR]

This paper considers a pure electron plasma, with a small admixture of negative ions, confined in a Penning–Malmberg trap. When a diocotron mode is excited on the plasma, the end sheaths of the plasma are azimuthally distorted. During reflection at a distorted end sheath, an ion steps off of the surface characterizing the drift motion in the plasma interior, and this step produces transport. The diocotron mode transfers canonical angular momentum to the ions, and in response damps. These transport mechanism and associated damping are called rotational pumping. It is particularly strong when the axial bounce motion and the rotational drift motion, in the rotating frame of the mode, satisfy a resonance condition. This paper calculates the transport flux of ions and the associated damping rate of the mode in the resonant regime. Previous papers have discussed the theory and the experimental observation of rotational pumping for the special case of a diocotron mode with azimuthal wave number l = 1, and this paper extends the theory to modes with l ≠ 1 , which may sound like a trivial extension, but in fact is not. [ABSTRACT FROM AUTHOR]

This paper develops a unified linear theory of cross field plasma instabilities, including the Farley–Buneman, electron thermal, and ion thermal instabilities, in spatially uniform collisional plasmas with partially unmagnetized multi-species ions. Collisional plasma instabilities in weakly ionized, highly dissipative, weakly magnetized plasmas play an important role in the lower Earth's ionosphere and may be of importance in other planetary ionospheres, stellar atmospheres, cometary tails, molecular clouds, accretion disks, etc. In the Earth's ionosphere, these collisional plasma instabilities cause intense electron heating. In the solar chromosphere, they can do the same—an effect originally suggested from spectroscopic observations and modeling. Based on a simplified 5-moment multi-fluid model, the theoretical analysis presented in this paper produces the linear dispersion relation for the combined Thermal Farley–Buneman Instability with an important long-wavelength limit analyzed in detail. This limit provides an easy interpretation of different instability drivers and wave dissipation. This analysis of instability, combined with simulations, will enable us to better understand plasma waves and turbulence in these commonly occurring collisional space plasmas. [ABSTRACT FROM AUTHOR]

This paper is aimed at investigating the role of electrons in creation of currents in plasma equilibria with high plasma pressure (β ≈ 1). Despite the long history of studies of these equilibria, there is still no consensus on what kind of particle species is responsible for the creation of the diamagnetic current and what characteristic size the current layer should have. For example, simulations of isothermal plasma injection into a multi-cusp magnetic trap [J. Park et al., Front. Astron. Space Sci. 6, 74 (2019)] demonstrate the formation of a transition layer with a thickness comparable to the electron Larmor radius, where the equilibrium current is carried by electrons. At the same time, studies of a diamagnetic bubble created by a hot-ion plasma in a mirror trap [I. Kotelnikov, Plasma Phys. Control Fusion 62, 075002 (2020)] assume ion dominance and completely ignore electron currents. In this paper, we show that the equilibrium initially governed by the ion diamagnetic current is unstable against perturbations at the ion-cyclotron frequency harmonics, and this instability forces the plasma to come to a new equilibrium state in which the current is mainly created by the E × B -drift of electrons. The same type of equilibrium is also found to form in a more realistic problem setup when plasma is continuously injected into the uniform vacuum magnetic field. [ABSTRACT FROM AUTHOR]

In a pair of linked articles (called Papers I and II, respectively), we apply the concept of Lagrangian Coherent Structures borrowed from the study of Dynamical Systems to chaotic magnetic field configurations in order to separate regions where field lines have different kinds of behavior. In the present article, Paper II, by means of a numerical procedure, we investigate the Lagrangian Coherent Structures in the case of a two-dimensional magnetic configuration with two island chains that are generated by magnetic reconnection and evolve nonlinearly in time. The comparison with previous results, obtained by assuming a fixed magnetic field configuration, allows us to explore the dependence of transport barriers on the particle velocity. [ABSTRACT FROM AUTHOR]