Electron Beam Plasma Research Articles

Stimulated Raman scattering by circularly polarized quadruple Gaussian laser beam and co-propagating electron beam in plasma

This study investigates the interplay between a co-propagating relativistic electron beam and a quadruple Gaussian laser beam in plasma, focusing on the suppression of stimulated Raman scattering (SRS) growth. The presence of the laser beam induces the excitation of a pair of plasma waves and side-scattered electromagnetic waves. As the side-scattered wave and pump wave couple together, they exert a ponderomotive force on the electron beam and plasma electrons, resulting in an enhancement of the plasma wave amplitude. Nonlinear coupling between the density perturbation in the plasma, induced by the plasma wave, and the pump wave leads to the excitation of a nonlinear current responsible for the growth of the side-scattered electromagnetic wave associated with SRS. Furthermore, the growth rate of SRS is shown to be highly sensitive to the phase matching between the relativistic electron beam and the plasma wave. In cases of phase mismatch, the growth rate experiences a significant reduction. Additionally, the effectiveness of the electron beam in driving the stimulated Raman process is greatly affected by the energy spread of the electron beam. A substantial reduction in effectiveness is observed due to this energy spread.

Ferroelastic rare‐earth tantalates for multifunctional thermal/environmental barrier coatings: A perspective

AbstractThis perspective outlines the research directions of ferroelastic rare‐earth (RE) tantalates (RETaO4), which have been studied as multifunctional thermal/environmental barrier coatings (T/EBCs) with working temperatures above 1600°C. Ferroelastic RETaO4 ceramics exhibit several distinct features, including the reversible second‐order ferroelastic phase transition, high toughness, low thermal conductivity, low oxygen ion conductivity, and adjustable thermal expansion coefficients. This perspective provides a concise summary of the research progress on tantalate coatings synthesized via air plasma spraying and electron beam physical vapor deposition. The service performance of tantalate coatings is typically evaluated through thermal fatigue and shock measurements. Uncovering the failure mechanisms and understanding influencing factors are key aspects for future studies. In this regard, establishing the synthesis‐structure‐property relationship of RETaO4 coatings is essential. This brief perspective can serve as a guide for future work on RETaO4 coatings and further advancements in their applications across various fields, including aviation engines and gas turbines.

Research Progress of Surface Treatment Technologies on Titanium Alloys: A Mini Review

Titanium alloys are important strategic structural materials with broad application prospects in the industries of aerospace, space technology, automobiles, biomedicine, and more. Considering the different requirements for the diverse applications of titanium alloys, the modification of physicochemical properties, mechanical properties, and biocompatibility are required, including novel composite materials, novel design, novel manufacturing methods, etc. In this review, the surface treatment technologies utilized on titanium alloys are summarized and discussed. Regarding surface modification of titanium alloys, the methods of laser treatment, electron beam treatment, surface quenching, and plasma spraying are discussed, and in terms of the surface coatings on titanium alloys, thermal spraying, cold spraying, physical vapor deposition, and chemical vapor deposition are also summarized and analyzed in this work. After surface treatments, information on microstructures, mechanical properties, and biocompatibility of titanium alloys are collected in detail. Some important results are summarized according to the aforementioned analysis and discussion, which will provide new thinking for the application of titanium alloys in the future.

Effect of frictional treatment and low temperature plasma carburizing on the microhardness and electromagnetic characteristics of metastable austenitic steel

Microhardness and electromagnetic characteristics of corrosion-resistant chromium-nickel (wt. %: 16.80 Cr; 8.44 Ni) austenitic steel subjected to electron beam plasma carburizing at temperatures of 350 and 500°C, frictional treatment with a sliding indenter and combined treatments, including frictional treatment and plasma carburizing have been investigated. It has been found that plasma carburizing increases the microhardness of the steel surface from 200 to 1100 HV0.025. The total hardening depth was 25 microns after carburizing at T = 350°C and 300 microns after carburizing at T = 500°C. Frictional treatment increases the microhardness of the steel to 600 HV0.025 with a total hardening depth of 500 microns. It has been shown that the diffusion-active layer with a dispersed structure formed during preliminary frictional treatment contributes to additional hardening of the steel (up to 1275 HV0.025) during subsequent low-temperature (350°C) carburizing. Combined treatment with carburizing at a temperature of 500 °C increases the microhardness of the steel to 820 HV0.025, and the total hardening depth is 500 microns for both combined treatments. It has also been found that plasma carburizing of the steel leads to a decrease in the eddy-current readings compared to the quenched steel and their growth compared to the steel subjected to frictional treatment, which can be used to develop quality control techniques for such treatments.

Instability of Langmuir-beam waves: Kappa-distributed electrons

In space plasmas, electron populations exhibit non-equilibrium velocity distributions with high-energy tails that are reproduced by the Kappa power-laws and contrast with the Maxwellian distributions often used in theoretical and numerical analyses. In this work, we investigate typical electron beam-plasma systems and show the influence of Kappa tails on the linear dispersion and stability spectra of Langmuir-beam waves. The most common scenarios invoke instabilities of Langmuir waves at the origin of radio emissions in solar flares and interplanetary shocks. However, the parametric domain of these instabilities is narrow (i.e., energetic beams but with very low density, nb/ne≲10−3), making their analytical and numerical characterization not straightforward, while the approximations used may lead to inconclusive results. Here, we provide exact numerical solutions of the Langmuir-beam mode, which distinguish from the classical ones (unaffected by the beam), and also from electron beam modes destabilized by more energetic and/or denser beams. Langmuir-beam solutions are only slightly modified by the Kappa distribution of the beam component, due to its very low density. However, if the main (core) population is Kappa distributed, the instability of the Langmuir-beam mode is strongly inhibited, if not suppressed. New analytical solutions are derived taking into account the more or less resonant involvement of the electron core and beam populations. As a result, the analytical solutions show an improved match with the exact solutions, making them applicable in advanced modeling of weak (weakly nonlinear) turbulence.

Doping-induced Ti3+ state and oxygen vacancies in TiO2: A single-chip combinatorial investigation

TiO2 is widely recognized as a high performance photocatalyst for photocatalytic applications. Oxygen vacancies (VO) and titanium defects are known to make a significant contribution to the enhanced photocatalytic efficiency of TiO2, accordingly control of these two centers is pivotal to optimizing the surface photochemical activity. In this work, the formation of VO and Ti3+ ions induced by n-type doping of TiO2 with Nb is demonstrated using a combinatorial investigation approach. Chemical Beam Vapour Deposition (CBVD) is used to fabricate Nb concentration-graded (NbxTi1-x)O2 anatase films with 0.009 ≤ x ≤ 0.033 over a 5 mm length on a single chip. Cathodoluminescence (CL) microanalysis shows the luminescence intensity decreases with increasing Nb concentration; however, the presence of a self-trapped exciton (STE) emission, characteristic of anatase TiO2, indicates that the Nb incorporation does not affect the structural properties of TiO2. Notably, the introduction of Nb donors induces the formation of the signature luminescence bands of VO and Ti3+ at 2.05 and 2.60 eV at 80 K, respectively, and their intensities rise by up to 28% with increasing Nb content. The formation of VO and Ti3+ is attributed to the effect of excess electrons locally produced by Nb donor doping. The thermal activation energies for the STE and defect-related emissions are found to be identical at 32 ± 4 meV, suggesting that the recombination kinetics is mediated by Nb donors. Significantly, we demonstrate that the near-surface VO density can be further increased by two different post-growth treatment approaches: (i) remote hydrogen plasma and (ii) low-energy electron beam irradiation (LEEBI), without effecting the valence state of Ti. Our results open opportunities to optimize the photocatalytic properties of TiO2 by defect engineering.

Optical properties of N2/Ar plasma generated by electron beams with silicon nitride transmission window at high pressures

In this paper, we report the generation of nitrogen/argon electron beam plasmas with a 0.4 μm-thick silicon nitride transmission window. The measured transmittance of the electron beam is about 92% when the incident energy of electron beam is 40 keV. The optical properties of the electron beam plasma are investigated at high pressures. The luminescence intensity distribution of nitrogen and argon electron beam plasmas shows a good similarity with changing the gas pressure, suggesting that electron beam ionization is independent of background gas. At the same gas pressure, the nitrogen plasma with conical structure has a longer length along the incident direction of the electron beam and a smaller divergence cone angle compared with the argon plasma. In the nitrogen discharge, it is found that the intensities I380.4, I399.7, and I391.4 corresponding to characteristic lines at 380.4, 399.7, and 391.4 nm decrease along the incident direction of the electron beam, which is correlated with the reduction of the electron density along the incident direction of the electron beam. There is no change in the ratio of I399.7 to I380.4, indicating the spatial uniformity of the electron temperature. When the pressure increases, the ionization process induced by primary electron is enhanced, generating more plasma electrons, which is responding to the increase in the characteristic line intensity. At the same time, the neutral particle collision processes are enhanced and the electron temperature decreases with the increase in the pressure, which is believed to contribute to the observed reduction of the I399.7/I380.4 ratio.

Research Progress of the Heliospheric Radio Emissions

The heliospheric radio emissions are the strongest radio emissions phenomenon in the solar system, with a radiation power of at least 1013 W, which can provide important physical information of high energy electron beam and magnetic plasma structure near the heliospheric boundary. Since the first detection by the Voyager spacecraft in 1983, those radio emissions have widely and continuously attracted much attention from researchers. There are generally two types of the heliospheric radio emissions: instantaneous or drifting emission with relatively high frequency, and continuous emission or non-drifting emission with relatively low frequency. Usually, both types of emissions start from about 2 kHz. For the drifting emission, it has the characteristic of drifting toward high frequency, the drifting rate is about 1–3 kHz/yr, the frequency range is 1.8–3.6 kHz, and the duration is about 100–300 days. For the non-drifting emission, it has no obvious frequency drift, the frequency range is 1.8–2.6 kHz, and the duration is about 3 yr. It is generally believed that the heliospheric radio emissions are related to shock. In this paper, the possible source region of the radio emissions, the emission mechanisms, and the source of shock related to the emissions are introduced. Furthermore, the existing scientific problems and the future perspectives on the research of heliospheric radio emissions are discussed.

Thermionic coating method with preliminary bombardment of the substrate surface with a stream of low energy ions

Relevance. Vacuum-plasma methods of applying functional coatings are widely used to increase the reliability and durability of machine and mechanism parts, cutting tools, and technological equipment, as well as in modern micro- and nanoelectronics for applying conductive and dielectric layers of various thicknesses. The study presents a method of thermionic coating that combines in one technological cycle the processes of surface cleaning by a stream of low-energy ions and plasma electron beam evaporation of a substance under conditions of thermionic plasma formation. Aim. The research aims to determine the possibility of using the presented methodology to create and process functional coatings without radiation damage to the substrate surface. Methodology. The experimental studies were carried out in a plasma electron beam system with a primary plasma source based on an arc discharge with a filament cathode. The samples were diagnosed using a scanning electron microscope. Results. The ion current density from the primary plasma was investigated to determine the efficiency of the surface cleaning mechanism by ion bombardment. The dependences of the ionic current density on the initial parameters of the experiment were determined. The results of the treatment of the (TiZr/TiSi) N sample surface with a plasma ion stream are presented. The obtained scanning electron microscope images showed that such treatment leads to the cleaning of the surface layer from various contaminants without damage and creates a substrate for further thermionic deposition of a coating with a high degree of adhesion. The mechanism of thermionic deposition of a titanium monolayer on a stainless-steel substrate previously cleaned by ion bombardment was studied. The revealed order of magnitude higher values of the ionic current to the substrate during the formation of thermionic plasma indicate a significant increase in the rate of the deposition process and contribute to the formation of a high-quality ion-plasma coating. Conclusions. The scanning electron microscope images of the sample surface showed that the titanium coating during thermionic deposition was uniformly distributed over the substrate surface, without any droplet phase, which indicates the suitability of this technique for applying functional coatings without radiation damage to the substrate surface

Branching of High-Current Relativistic Electron Beam in Porous Materials.

Propagation of high-current relativistic electron beam (REB) in plasma is relevant to many high-energy astrophysical phenomena as well as applications based on high-intensity lasers and charged-particle beams. Here, we report a new regime of beam-plasma interaction arising from REB propagation in medium with fine structures. In this regime, the REB cascades into thin branches with local density a hundred times the initial value and deposits its energy 2 orders of magnitude more efficiently than that in homogeneous plasma, where REB branching does not occur, of similar average density. Such beam branching can be attributed to successive weak scatterings of the beam electrons by the unevenly distributed magnetic fields induced by the local return currents in the skeletons of the porous medium. Results from a model for the excitation conditions and location of the first branching point with respect to the medium and beam parameters agree well with that from pore-resolved particle-in-cell simulations.

The Influence of Frictional Treatment and Low-Temperature Plasma Carburizing on the Structure and Phase Composition of Metastable Austenitic Steel

The features of the structure and phase composition of corrosion-resistant austenitic chromium–nickel steel (16.80 wt % Cr, 8.44 wt % Ni) subjected to carburizing in electron beam plasma at temperatures of 350 and 500°C, frictional treatment with a sliding indenter, and a combination of frictional treatment and plasma carburizing have been considered. It has been established that plasma carburizing results in the formation of a modified surface layer consisting of carbon-saturated austenite and carbides (Cr23C6, Fe3C); in this case, the formation of γC-phase occurs only at a temperature of 350°C. The depth of a modified layer increases with an increase in the carburizing temperature. It has been shown that it is useful to perform combined frictional treatment and plasma carburizing at a carburizing temperature of 350°C, since in this case the deformation-induced structure formed as a result of frictional treatment is preserved, and the precipitated carbides remain highly dispersed. In this case, frictional treatment should provide the formation of the deepest possible diffusion-active layer with a dispersed structure.

The Influence of Frictional Treatment and Low-Temperature Plasma Carburizing on the Structure and Phase Composition of Metastable Austenitic Steel

The features of the structure and phase composition of corrosion-resistant austenitic chromium–nickel steel (16.80 wt % Cr, 8.44 wt % Ni) subjected to carburizing in electron beam plasma at temperatures of 350 and 500°C, frictional treatment with a sliding indenter, and a combination of frictional treatment and plasma carburizing have been considered. It has been established that plasma carburizing results in the formation of a modified surface layer consisting of carbon-saturated austenite and carbides (Cr23C6, Fe3C); in this case, the formation of γC-phase occurs only at a temperature of 350°C. The depth of a modified layer increases with an increase in the carburizing temperature. It has been shown that it is useful to perform combined frictional treatment and plasma carburizing at a carburizing temperature of 350°C, since in this case the deformation-induced structure formed as a result of frictional treatment is preserved, and the precipitated carbides remain highly dispersed. In this case, frictional treatment should provide the formation of the deepestpossible diffusion-active layer with a dispersed structure.

Kinetic Theory of Instability of the Electron Beam-Plasma System Taking into Account the Elastic Electron-Atomic Collisions for an Arbitrary Scattering Indicatrix

A kinetic theory of stability of a fast electron beam-gas-discharge plasma system under conditions when the electron mean free path relative to elastic collisions with atoms is of the order of the plasma dimension along the direction of the beam propagation is developed. It is assumed that the cross section of elastic electron-atom collisions is considerably higher than the cross section of inelastic processes with electrons. The dispersion equations for an arbitrary indicatrix of elastic electron-atom scattering are obtained. Despite the smallness of the cross section for inelastic scattering in comparison with elastic one, it is also necessary to consider inelastic processes when the plasma Knudsen numbers are less than 0.3. As the Knudsen number decreases beneath 0.3 the growth rate considerably decreases in the range of instability, because the role of elastic scattering of electrons by atoms increases.

Local wavelength evolution and Landau damping of electrostatic plasma wave driven by an ultra-relativistic electron beam in dense inhomogeneous plasma

Evolution of an electrostatic plasma wave driven by a low-density ultra-relativistic electron beam in dense inhomogeneous plasma is considered. In particular, the wavelength variation as observed at fixed locations in the plasma is analyzed in terms of the wave characteristics. It is shown that for a negative density gradient, the observed local wavelength decreases monotonically with time, but for a positive density gradient, it first increases and then decreases with time, accompanied by reversal of the wave phase. However, in both cases the local wavelength eventually decreases with time since Landau damping becomes significant as the wavelength becomes of the order of the plasma Debye length. Results from particle-in-cell simulations agree well with theoretical analyses of the wavelength variation.

Solar Electron Beam Velocities That Grow Langmuir Waves in the Inner Heliosphere

Solar accelerated electron beams, a component of space weather, are emitted by eruptive events at the Sun. They interact with the ambient plasma to grow Langmuir waves, which subsequently produce radio emission, changing the electrons’ motion through space. Solar electron beam–plasma interactions are simulated using a quasilinear approach to kinetic theory to probe the variations in the maximum electron velocity [Xi ] responsible for Langmuir wave growth between the Sun’s surface and 50 R⊙ above the surface. We find that it peaks at 5 R⊙ at 0.38 c and decreases as r^{-0.5} to 0.16 c at 50 R⊙. The role of the initial beam density [n_{mathrm{beam}}] and velocity spectral index [alpha ] on the energy density of the beam and Xi is extensively studied. We show that a high spectral index yields a lower Xi , while a high n_{mathrm{beam}} yields a higher Xi , and vice versa. We observe at different energy channels that below 60 keV, electrons arrive up to 0.75 minutes earlier than expected at 13 R⊙ while higher energy electrons propagate scatter free in the plasma. A special focus on the associated Type III radio burst shows that the energy range [Delta E] of electrons producing Langmuir waves evolves from 7 keV to 1 keV between 0 and 28 R⊙. Understanding the transport effect on the electron beam kinetics and arrival time at Earth has space weather implications. The results of this simulation can be tested against readily available in-situ data from Solar Orbiter and Parker Solar Probe.

EBM Technique Study on Microstructural Characterization of Al-Zr-N Coating

Through the implementation of the electron beam physical vapour deposition (EB-PVD) technique, an aluminium zirconium nitrate (Al-Zr-N) coating has been created in the current work on high speed steel (E19) substrates. Through the use of X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), nano indentation, and scratch tests, the structural morphological and mechanical properties of the substrate are investigated. The cause of tension relaxation and vacancy concentration is explained by the fluorite phase's lattice constant decreasing with rising deposition temperature. As the temperature of the substrate rises, the coating's increased surface roughness is explained by an increase in crystallite size [1]. TBCs are frequently applied to metal substrates using the Atmospheric Plasma Spraying (APS) and Electron Beam Physical Vapour Deposition (EB-PVD) methods. For the next generation of turbine engines, the high costs and relatively high thermal conductivities of EB-PVD coatings, as well as the short thermal lifetime of APS coatings, are significant drawbacks. Suspension Plasma Spraying (SPS) was evaluated in this study to enhance the thermal properties of TBC. The SPS process enables the creation of columnar micro-structures that are easily adjustable in terms of thermal conductivity and columnar structure compaction.

Contribution of thermal dissociation during steel nitriding in electron beam plasma

We report the results of measurements of mass-to-charge ion composition of the beam plasma generated by a forevacuum plasma-cathode electron source in a nitrogen atmosphere during electron beam interaction with the surface of a steel sample. It has been found that as the sample surface temperature increases from 540 ℃ to 930 ℃, the fraction of atomic nitrogen ions in the spectrum increases by 4-10%. This increase in atomic nitrogen occurs at the backdrop of decreasing number of molecular nitrogen monoxide ions and is associated with thermal dissociation of its molecules.

Effect of cyclic thermal load on beryllium

The paper presents data on the behavior of TGP-56 beryllium after exposure to an electron beam and hydrogen plasma. The experiments were conducted with different numbers of pulses at surface temperatures of ∼ 360 °C, ∼800 °C, and ∼ 1200 °C. The temperature mode is determined by the operating conditions of the first wall coating at a standard thermal load. To assess the changes in beryllium after testing, microanalysis, X-ray diffraction analysis, and microhardness measurements were performed. It has been found that the beryllium coating is resistant to normal International Thermonuclear Experimental Reactor (ITER) operation modes, but at temperatures above 800 °C, critical damage to the material is possible over the time of operation of the thermonuclear facility.

LOW-TEMPERATURE CATALYZED GROWTH AND PLASMONIC PROPERTIES OF COLUMNAR Au-SiOx NANOCOMPOSITE THIN FILMS

The optical properties of noble metal nanoparticles (NPs) can be efficiently controlled by their incorporation into host matrix films. Here, we report on the fabrication of composite films of gold NPs in a silicon suboxide matrix by a novel approach using a combination of pulsed laser deposition for NP production and gas-jet, electron-beam plasma chemical vapor deposition for low-temperature (300°C) synthesis of a SiO<sub>x</sub> (x = 0.38-1.55) thin film as a matrix for the NPs. The produced nanocomposite exhibits unexpected plasmonic properties, non-monotonically dependent on the matrix thickness, due to a porous columnar matrix structure grown from the NPs with variable oxygen content along the columns. This implies that low-temperature, gold-catalyzed oxidation of silicon occurs during the structure growth. Calculations based on Mie theory show that the refractive index of the obtained SiO<sub>x</sub> matrix can be as low as 1.2 at certain film thicknesses. Mechanisms of the columnar structure formation at different deposition stages are discussed. The synthesis approach can be used for the fabrication of optical thin-film materials with controllable low refractive index.

Solitons in a cold electron beam plasma

Necessary and sufficient conditions for the existence of dissipative electron-acoustic solitons in a cold electron beam plasma with superthermal trapped electrons described by the Schamel equation are derived in this paper. Soliton solutions to the Schamel equation are constructed using formal analytical techniques which yield counter-intuitive conditions for the existence of these solutions. The existence conditions are derived in terms of system parameters and initial conditions. Computational experiments are used to validate the obtained results.