High-current Electron Beam Research Articles

Modification of the Structure, Phase Composition, and Properties of an Intermetallic-Matrix Composite by Low-Energy High-Current Electron Beam Irradiation

Modification of the Structure, Phase Composition, and Properties of an Intermetallic-Matrix Composite by Low-Energy High-Current Electron Beam Irradiation

Influence of Low-Energy High-Current Electron Beam Exposure on the Phase Composition and Corrosion Resistance of the AM60 Magnesium Alloy

The surface of an AM60 (Al – 5.5, Zn – 0.2, Cu – 0.009, Fe – 0.005, Si – 0.1; Ni – 0.002, Mn – 0.3 wt.%, Mg – the rest) magnesium alloy was exposed to a low-energy high-current electron beam. After the irradiation, the content of the β-phase (Mg17Al12) decreases and the aluminum content increases in the alloy surface layer. After the exposure to the electron beam, the corrosion resistance of the alloy in a 1-molar NaCl solution increases significantly compared to the initial state. The physical reason for the increase in the alloy corrosion resistance after exposure to the electron beam is the higher corrosion resistance of the oxide film formed on the alloy surface due to the increased aluminum content.

Surface modification of Al-15Al2O3-0.3G powder metallurgical alloy induced by high-current pulsed electron beam

This paper investigates the effect of high-current pulsed electron beam (HCPEB) surface treatment with two, five, and eight pulses on Al-15Al2O3-0.3G prepared by powder metallurgy. The results show that the presence of graphene during HCPEB irradiation effectively controls the extension of microcracks. The surface hardness of the samples increased by 66.56% and the wear rate decreased by 68.98% after eight-pulse HCPEB treatment. The increase in hardness is attributed to the uniform dispersion of hard particles, fine grain strengthening, dislocation strengthening, and amorphous structure formation by XRD, SEM, and TEM analysis during HCPEB irradiation. The improvement in wear resistance was attributed to the increase in hardness. The corrosion current density in 5 wt. % NaCl solution decreased from 1.212 × 10−4 to 3.353 × 10−5 after eight-pulse HCPEB treatment; the improved corrosion resistance performance is attributed to the equilibrium structure induced by HCPEB treatment.

Effect of the energy density of pulsed electron beam on the microstructure and properties of Mo-Zr surface alloys

Lasers and electron beams have been widely used to synthesize various surface alloys (SAs) but no data have been reported so far on the molybdenum-zirconium (Mo-Zr) ones. To partially fill this knowledge gap, Mo-Zr SAs were formed by processing molybdenum films on zirconium substrates with low-energy high-current electron beams (LEHCEBs). The effect of the energy density of LEHCEBs on the microstructure, phase composition, nanohardness and corrosion resistance of the Mo-Zr SAs were investigated. Basically, the Mo-Zr SAs consisted of a solid solution of Mo in the β-Zr phase, Mo2Zr second phase particles (SPPs) and a solid solution Zr in Mo. Increasing in the energy density decreased the concentration of the SPPs and enhanced the content of the β-Zr phase. Also, it affected the depth of the highest concentration of the SPPs. In the zones of the highest molybdenum contents, the nanohardness values reached 9.4–12.7 GPa, which was higher by 3.2–4.4 times than that of the zirconium substrates. In a 3.5 % NaCl solution at room temperature, the corrosion current densities and the corrosion potentials were greater than those of the zirconium substrates by six and almost two times, respectively.

The refined microstructure and enhanced properties of the Al-Mo laser-alloyed layer after high-current pulsed electron beam irradiation

The aim of this study is to investigate the microstructure and properties of the AlMo laser-alloyed layer induced by high-current pulsed electron beam (HCPEB) irradiation. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were utilized to investigate the microstructures of the modified layer. The microhardness and friction properties were also measured. The microstructural observation shows that HCPEB irradiation led to the formation of a modified layer approximately a dozen microns thick, which was the absence of the pores. It was found that the flower- and strip-like AlMo particles were dissolved to form nano-size particles consisting of Al5Mo (h2), Al12Mo, and Al17Mo4 phase after HCPEB irradiation. Additionally, the slip bands and high-density dislocations were formed in the modified layer. The refined microstructure significantly enhanced the microhardness of the laser-alloyed layer. A quantitative evaluation was conducted to investigate the individual contributions of four strengthening mechanisms to the strength of the modified layer, which indicated that dislocation and grain boundary strengthening were dominant. The results of sliding wear tests show that the modified layer exhibited superior properties compared to the laser alloying layer, which was attributed to the formation of crystal defects, solid solutions, and nanoparticles.

Upper-hybrid oscillations of high current relativistic electron beam under conditions of magnetic self-insulation

Upper-hybrid oscillations of high current relativistic electron beam under conditions of magnetic self-insulation

Two-dimensional space charge limited current in regime between accelerating diode and drift space for sheet and circular beam

We develop a general electrostatic steady-state model to calculate the two-dimensional (2D) space-charge-limited current (SCLC) with an initial velocity v0 (i.e., kinetic energy eKV=mv02/2) injected from a cathode into a vacuum diode with a spacing D and a potential difference of Vg. We consider two types of beam cross section: (a) a sheet beam with a width W and (b) a circular beam with a radius R, where both W and R are larger than D in the calculation. By introducing a parameter ε≡KV/Vg≥0, we can tune the operating regime to be in between the accelerating diode (ε≪1) and drift space (ε≫1). Hence, we verify the 2D SCLC model by converging to some prior analytical findings such as the 2D Child–Langmuir law at ε = 0, 2D SCLC at drift space at ε≫1, and their 1D limits at W/D≫1 or R/D≫1. Our 2D SCLC model indicates that there is a maximal value at ε∼1/60, which is independent of W/D or R/D. Furthermore, the hysteresis behavior is also studied when the injected current density is beyond the SCLC threshold and its dynamics are mainly influenced by ε instead of geometrical effect. This model is useful in high current electron beam emission with a finite emission area and with a non-negligible arbitrary injection kinetic energy.

Mechanisms of deformation induced by high-current pulsed electron beam irradiation

AA2024 aluminum alloy was irradiated by a high-current pulsed electron beam with the following parameters: beam energy ∼0.3 MeV, current ∼2000A, pulse duration ∼5·10−6 s, beam diameter ∼3 cm. The thickness of the surface remelted layer reached 100 μm. Dynamic thermal stresses caused by irradiation, induced the development of deformation processes in the irradiated layer. Based on the study of surface morphology and structural state of the remelted layer, it was shown that deformation processes occur in the surface layer by the grain boundary sliding mechanism. The level of residual stresses in the irradiated layer was low and amounted to 34 MPa.

Status of the High-Current Electron-Beam Ion Source Charge Breeder for the Facility for Rare-Isotope Beams

The Reaccelerator (ReA) of the Facility for Rare-Isotope Beams (FRIB) employs an Electron-Beam Ion Trap (EBIT) as a charge breeder to reaccelerate rare-isotope beams up to 12 MeV/u. The ReA EBIT produces an electron current of 300 – 600 mA. The maximum trap capacity of the ReA EBIT is 1010 elementary charges. FRIB production rates are expected to exceed 1010 particles/s in some cases in the future. There is also a user demand for reaccelerated stable-isotope beams of more than 1010 pps. To handle these rates and provide redundancy, a High Current Electron-Beam Ion Source (HCEBIS) has been built and is now being commissioned. An electron-beam current of 2 A with a 50 % duty cycle has been transported through a 4-T field. An upcoming upgrade to increase the electron-beam current up to 4 A will allow for a maximum trap capacity of 2.4×1011 elementary charges. We present the status of the HCEBIS, including the results of the electron-beam commissioning and systematic studies.

High-Current Capability and Upgrades of the EBIS/T Charge-Breeding System in the Reaccelerator at the Facility for Rare-Isotope Beams

The Reaccelerator (ReA) of the Facility for Rare-Isotope Beams (FRIB) at Michigan State University uses a Beam Cooler/Buncher (BCB) and an Electron-Beam Ion Trap (EBIT) as a charge-breeding injector system. The rare isotopes produced by In-flight Separation are selected by the Advanced Rare Isotope Separator (ARIS) and stopped in a helium gas cell. Long-lived and stable-isotope beams can also be extracted from a Batch-Mode Ion Source (BMIS). The continuous beams transported at low energy to ReA are injected into the BCB. The pulsed beams are then injected into the EBIT, charge bred, ejected, and accelerated by ReA’s LINAC. The EBIT electron current (300 - 600 mA) is a factor that limits its capacity to ∼2×1010 elementary charges, which restricts the maximum EBIT-extracted rates to less than 2×1010 particles per second for light ions. An upgrade of the EBIT electron gun is expected to provide 2 A in current. In parallel, a High-Current Electron-Beam Ion Source (HCEBIS) is being commissioned. The HCEBIS can presently provide an electron current of 2 A. An upgrade will increase the current to 4 A. The implementation of these two upgrades is expected to allow for maximum rates to be ∼1011 pps, compatible with FRIB projected rates and user demands. We review the high-current capabilities and upgrades of ReA’s charge-breeding system.

High-current pulsed electron beam modification on microstructure and performance of Cu/CuW diffusion bonding joints

High-current pulsed electron beam modification on microstructure and performance of Cu/CuW diffusion bonding joints

On the correspondence of bump relief on the surface of materials processed with low-energy high-current electron beam to their grain structure

One of the features that appears on the pre-polished surface of metals and alloys as a result of processing with low-energy high-current electron beam is a bump surface relief with the bump size varying from several tens to several hundred nanometers. Some researchers consider these bumps as the trace of the grain structure of the near-surface modified layer of material. The aim of the present work was to show experimental results proving that the bump relief is not related to the grain size in the near-surface layer. The microstructure was studied using reliable complementary methods of transmission electron microscopy and backscattered electron diffraction using Inconel 718 alloy and stainless steel obtained by additive manufacturing and processed with low-energy high-current electron beam.

Sources of Non-Relativistic, High-Current Electron Beams Based on the Cathodes with Built-in Arc Plasma Sources

Sources of Non-Relativistic, High-Current Electron Beams Based on the Cathodes with Built-in Arc Plasma Sources

Microstructure and Properties of TiN/TiCN/Al2O3/TiN Coating Enhanced by High-Current Pulsed Electron Beam

In this work, a TiN/TiCN/Al2O3/TiN coating deposited onto cemented carbide matrix by chemical vapor deposition was irradiated by high-current pulsed electron beam (HCPEB). The influence of pulse times on the phase composition, microstructure, and mechanical properties of the coating investigated. The results showed that no new phase was produced, the grain size of the coating surface was refined, the surface became flat, and the surface roughness decreased after HCPEB treatment. The TiN/TiCN/Al2O3/TiN coating presented a smooth surface with good mechanical performance after HCPEB. A maximum hardness was obtained after 15 pulses, and the 15-pulse irradiated coating showed better wear resistance. The improvement in the coating’s performance after irradiation was mainly attributed to the formation of grain refinement and crystal defects, as well as the change of stress field inside the coating. The objective of this study was to evaluate the potential of HCPEB modification in the preparation of high-performance coating by analyzing the microstructure and property of coating under different pulses.

Influence of Low-Energy High-Current Electron Beam Exposure on the Phase Composition and Corrosion Resistance of the AM60 Magnesium Alloy

Influence of Low-Energy High-Current Electron Beam Exposure on the Phase Composition and Corrosion Resistance of the AM60 Magnesium Alloy

Development of a high current electron beam facility for compact accelerator neutron source target thermal tests

Target thermal capabilities are one of the major key points for CANS (Compact Accelerator-based Neutron Source) developments. Indeed, high energy (few MeV) and high average current (few tens of mA) proton or deuteron beams are required to produce high thermal neutron flux of 101³ n.cm⁻2.s⁻1 or greater. The targets must therefore absorb and dissipate a high thermal power. In order to make progress on their designs without deuteron or proton beams, we developed a compact electron beamline based on an Electron Cyclotron Resonance (ECR) source that permits testing of targets under relevant thermal conditions at power densities up 3 kW. cm⁻2.

TEM and X-ray diffraction studies of structure of TiNi SMA treated by low-energy high-current electron beam

Advanced scientific and technological achievements in the surface engineering of TiNi shape memory alloys are closely related with their mechanical performance. Electron-beam treatments could be applied in order to modify surface properties of smart materials and promote stress-induced martensitic transformations. The fundamental issue of electron-beam processing is residual elastic stresses arising from the ultrafast quenching (∼108 K/s) of thin (∼2–4 μm) surface layers. We report the experimental results on phase composition, structure and residual elastic stresses formed in the binary TiNi SMA irradiated by a low-energy (< 25 keV) high-current (∼ 25 kA) electron beam. Microstructure, fracture mechanisms and phase analysis of the as-cast and deformed tensile specimens have been studied by X-ray diffraction and electron microscopy. After electron-beam treatment, both martensitic B19′ and R phases are found in the near surface layer. The X-ray diffraction studies indicate that compressive stresses in the B2 phase of the irradiated TiNi alloy reach –460 MPa. In the fractured specimen (after tensile test) the residual stresses decrease to –160 MPa and release through the B2→B19′→B2 martensitic transformation. In-depth gradient distribution of the defect substructures responsible for the mechanical behavior of TiNi alloys was revealed.

Surface Modification of Diatomite-Based Micro-Arc Coatings for Magnesium Implants Using a Low-Energy High-Current Electron Beam Processing Technique

The present study showcases a novel effective technique for the surface modification of micro-arc diatomite coatings using low-energy, high-current electron beams (LEHCEBs). A variety of methods such as scanning electron microscopy, energy-dispersive X-ray spectroscopy, the X-ray diffraction method, scratch testing, the potentiodynamic polarization method, immersion testing in SBF, and flow cytometry have been used to study the coatings. During processing, the electron beams’ energy density ranged between 2.5–7.5 J/cm2. After the LEHCEB treatment, the surface morphology of the coatings changed completely. The corrosion resistance of the LEHCEB-treated coated samples increased significantly, as evidenced by the decrease in corrosion current to 4.6 × 10−10 A·cm−2 and the increase in polarization resistance to 1.4 × 108 Ω·cm2. The electron beam treatment also increased the adhesion strength of the coatings to the magnesium substrate by 1.8–2.5 times compared to untreated coatings. Additionally, biological studies have shown the high viability of the NIH/3T3 cell line after contact with the samples of the coating extracts.

Characteristics of branched flows of high-current relativistic electron beams in porous materials

Branched flow is a universal phenomenon in which treebranch-like filaments form through traveling waves or particle flows in irregular mediums. Branched flow of high-current relativistic electron beams (REBs) in porous materials has been recently discovered [Jiang et al., Phys. Rev. Lett. 130, 185001 (2023)]. REB branching is accompanied by extreme beam focusing, up to a hundred times the initial value, at predictable caustic locations. The energy coupling efficiency between the beam and porous material surpasses that in homogeneous targets by two orders of magnitude. This paper examines REB branching, focusing on how beam parameters (e.g., Lorentz factor and density) and characteristics of the porous materials (e.g., pore size, skeleton thickness, and density) influence branching patterns. Analyses of the dynamics of individual beam electrons are also provided. The findings pave the way for further understanding REB branching and its potential applications in the future.

Energy Density Distribution in the Cross Section of a Radially Converging Low-Energy High-Current Electron Beam

Energy Density Distribution in the Cross Section of a Radially Converging Low-Energy High-Current Electron Beam