High-current Electron Beam Research Articles

Effect of CeO2 on Corrosion Resistance of High-Current Pulsed Electron Beam Treated Pressureless Sintering Al-20SiC Composites

In this paper, the effect of rare earth Ce on the corrosion resistance of Al-20SiC composites treated with high-current pulsed electron beams is investigated, and the corresponding corrosion mechanism is proposed. The scanning electron microscope (SEM) results show that cracks arise on the surface of Al-20SiC composites prepared by pressureless sintering. After electron beam treatment, the pores on the surface are reduced because of the filling of Al liquid. After adding CeO2 to Al-20SiC composites, the wettability between Al and SiC phases is improved, thus realizing metallurgical bonding of the two phases, and microcracks generated after HCPEB treatment are significantly eliminated. Glancing X-ray diffraction (GIXRD) results show that after electron beam treatment, aluminum grains tend to grow more favorably with the stable and dense crystal plane of Al(111), thus improving corrosion resistance. The electrochemical test results show that the corrosion current density decreases by one order of magnitude with increase in the number of pulses because of rare earth Ce compared to the initial Al-20SiC composite specimens, indicating that the corrosion resistance of the Al-20SiC-0.3CeO2 composite is improved. This is because rare earth not only eliminates microcracks, but also changes the type of corrosion from localized to uniform, thus improving corrosion resistance. The Al-based composite material modified by electron beam and rare earth has many potential applications and development prospects.

Synthesis and Characterization of Ti-Nb Alloy Films Obtained by Magnetron Sputtering and Low-Energy High-Current Electron Beam Treatment.

The aim of the present work is to investigate the synthesis of Ti–Nb alloy films obtained by the physical vapor deposition (PVD) magnetron sputtering of Nb films on Ti substrates, followed by low-energy high-current electron beam (LEHCEB) alloying treatment. Ti–Nb alloys were synthetized under two different regimes, one by varying the deposited amount of Nb (from 25 to 150 nm) and treating samples with low applied voltages and a number of pulses (three pulses at either 20 or 25 kV), the second by setting the amount of Nb (100 nm) and alloying it at a higher applied voltage with a different number of pulses (from 10 to 50 at 25 and 30 kV). The synthetized Ti–Nb alloys were characterized by XRD and GDOES for phase identification and chemical composition; SEM and optical microscopy were employed for morphology evaluation; compositional investigation was done by EDS analysis and mechanical properties were evaluated by microindentation tests. LEHCEB treatment led to the formation of metastable phases (α′, α″ and β) which, together with the grain refinement effect, was responsible for improved mechanical properties.

Versatile, high brightness, cryogenic photoinjector electron source

Since the introduction of the radio-frequency (rf) photoinjector electron source over thirty years ago, peak performance demands have dictated the use of high accelerating electric fields. With recent strong advances in obtainable field values, attendant increases in beam brightness are expected to be dramatic. In this article, we examine the implementation of very high gradient acceleration in a high frequency, cryogenic rf photoinjector. We discuss in detail the effects of introducing, through an optimized rf cavity shape, rich spatial harmonic content in the accelerating modes in this device. Higher spatial harmonics give useful, enhanced linear focusing effects, as well as potentially deleterious nonlinear transverse forces. They also serve to strongly increase the ratio of average accelerating field to peak surface field, thus aiding in managing power and dark current-related challenges. We investigate two scenarios which are aimed at unique exploitation of the capabilities of this source. First, we investigate the obtaining of extremely high six-dimensional brightness for advanced free-electron laser applications. We also examine the use of a magnetized photocathode in the device for producing unprecedented low asymmetric emittance, high-current electron beams that reach linear collider-compatible performance. As both of the scenarios demand an advanced, compact solenoid design, we describe a novel cryogenic solenoid system. With the high field rf and magnetostatic structures introduced, we analyze the collective beam dynamics in these systems through theory and multi-particle simulations, including a particular emphasis on granularity effects associated with microscopic Coulomb interactions.

Comparison of microstructure and oxidation behavior of NiCoCrAlYSi laser cladding coating before and after high-current pulsed electron beam modification

In this study, NiCoCrAlYSi coatings prepared via laser cladding were modified using a high-current pulsed electron beam (HCPEB) technique. The microstructural modifications and the effects that the HCPEB treatment had on the high-temperature oxidation resistance were investigated. Microstructural observations reveal that the cladding coating surface, which was initially porous and composed of dendritic segregations, was totally changed after HCPEB irradiation; specifically, the microstructure became rather dense, and the composition became uniform. The grain refinement and high density of dislocations were obtained in the remelted layer. After oxidation for 100 h, the original coating showed relatively poor oxidation resistance, presented as severe internal oxidation. After HCPEB irradiation, the modified coating samples promoted the rapid formation of a stable, continuous, and slow-growing α-Al2O3 scale, which effectively prolonged the high-temperature life of the cladding coating.

Electron Microscopy Study of Alumina Ceramics Irradiated with a Low-Energy High-Current Electron Beam

Electron Microscopy Study of Alumina Ceramics Irradiated with a Low-Energy High-Current Electron Beam

The features of the structural state and phase composition of the surface layer of aluminum alloy Al-Mg-Cu-Zn-Zr irradiated by the high current electron beam

The structural and phase changes in the surface layer of the 1933 aluminum alloy caused by the irradiation of a high-current relativistic electron beam are studied. The impact of the electron beam leads to the formation of a remelted surface layer with surface relief and microcracks. The structural phase state of this layer is determined by the complex impact of the electron beam and the kinetics of melt crystallization under ultrafast cooling. Via X-ray diffraction studies and the results of energy dispersive X-ray microanalysis it became possible to make a conclusion that submicron sizes of magnesium oxide are present in the remelted layer. MgO inclusions are distributed homogeneously in the remelted layer. The presence of MgO inclusions leads to hardening of the surface layer of the alloy. The nature of formation of MgO during the impact of a pulsed electron beam are discussed

A study of the effect of electron-beam processing on the surface of samples obtained by additive technologies from cobalt-chromium powder

Products made of cobalt-chromium made by additive manufacturing methods are widely used in many branches of modern industry (aviation, mechanical engineering, shipbuilding and instrumentation, energy, medicine, etc.). Surface treatment with high-current pulsed electron beams (HPEB) is a promising method for further expanding the scope of these alloys. The article presents studies of the structural and phase state of the surface layer of samples before and after treatment with high-current pulsed electron beams.

Influence of technological factors on porosity in the mass production of inlet guide vanes using additive technologies

Stainless steel products manufactured using additive technologies are widely used in many branches of modern industry (aviation, medicine, engineering, etc.). One of the main defects in this type of production is porosity. Surface treatment with high-current pulsed electron beams (HPEB) allows not only to increase microhardness and corrosion resistance, but also to reduce surface roughness and porosity in the recrystalized layer. This article presents studies of the microstructure of stainless steel samples, as well as the structural and phase state of the surface layer of samples before and after irradiation with HPEB.

The Role of Graphene Admixtures in the Stability of Aluminum Oxide to Brittle Fracture under Pulsed Electrophysical Actions

We report the results of testing the dynamic strength of Al2O3 nanoceramics with different concentrations of five-layer graphene under the action of a high-current nanosecond electron beam and a high-voltage electric discharge of the same nanosecond duration. It is found that, under pulsed loading, an increase in the graphene content in the composite increases the brittleness of the nanocomposite.

Electron lenses: historical overview and outlook

The first electron lenses — understood as “lenses made of electrons” rather than “lenses to focus electrons” — were envisioned in the mid-1990s and built in the early 2000s for compensation of beam-beam effects in the Tevatron proton-antiproton collider. Since then, the lenses — a novel instrument for high-energy particle accelerators — have been added to the toolbox of modern beam facilities, being particularly useful for the energy frontier superconducting hadron colliders (“supercolliders”). In this article we briefly present the history of ideas and developments toward effective use of low-energy high-current bright electron beams in high energy accelerators and discuss the promise of their future applications.

Long lifetime of bialkali photocathodes operating in high gradient superconducting radio frequency gun

High brightness, high charge electron beams are critical for a number of advanced accelerator applications. The initial emittance of the electron beam, which is determined by the mean transverse energy (MTE) and laser spot size, is one of the most important parameters determining the beam quality. The bialkali photocathodes illuminated by a visible laser have the advantages of high quantum efficiency (QE) and low MTE. Furthermore, Superconducting Radio Frequency (SRF) guns can operate in the continuous wave (CW) mode at high accelerating gradients, e.g. with significant reduction of the laser spot size at the photocathode. Combining the bialkali photocathode with the SRF gun enables generation of high charge, high brightness, and possibly high average current electron beams. However, integrating the high QE semiconductor photocathode into the SRF guns has been challenging. In this article, we report on the development of bialkali photocathodes for successful operation in the SRF gun with months-long lifetime while delivering CW beams with nano-coulomb charge per bunch. This achievement opens a new era for high charge, high brightness CW electron beams.

Extremely Dense Gamma-Ray Pulses in Electron Beam-Multifoil Collisions.

Sources of high-energy photons have important applications in almost all areas of research. However, the photon flux and intensity of existing sources is strongly limited for photon energies above a few hundred keV. Here we show that a high-current ultrarelativistic electron beam interacting with multiple submicrometer-thick conducting foils can undergo strong self-focusing accompanied by efficient emission of gamma-ray synchrotron photons. Physically, self-focusing and high-energy photon emission originate from the beam interaction with the near-field transition radiation accompanying the beam-foil collision. This near field radiation is of amplitude comparable with the beam self-field, and can be strong enough that a single emitted photon can carry away a significant fraction of the emitting electron energy. After beam collision with multiple foils, femtosecond collimated electron and photon beams with number density exceeding that of a solid are obtained. The relative simplicity, unique properties, and high efficiency of this gamma-ray source open up new opportunities for both applied and fundamental research including laserless investigations of strong-field QED processes with a single electron beam.

InSitu Generation of High-Energy Spin-Polarized Electrons in a Beam-Driven Plasma Wakefield Accelerator.

Insitu generation of a high-energy, high-current, spin-polarized electron beam is an outstanding scientific challenge to the development of plasma-based accelerators for high-energy colliders. In this Letter, we show how such a spin-polarized relativistic beam can be produced by ionization injection of electrons of certain atoms with a circularly polarized laser field into a beam-driven plasma wakefield accelerator, providing a much desired one-step solution to this challenge. Using time-dependent Schrödinger equation (TDSE) simulations, we show the propensity rule of spin-dependent ionization of xenon atoms can be reversed in the strong-field multiphoton regime compared with the non-adiabatic tunneling regime, leading to high total spin polarization. Furthermore, three-dimensional particle-in-cell simulations are incorporated with TDSE simulations, providing start-to-end simulations of spin-dependent strong-field ionization of xenon atoms and subsequent trapping, acceleration, and preservation of electron spin polarization in lithium plasma. We show the generation of a high-current (0.8kA), ultralow-normalized-emittance (∼37 nm), and high-energy (2.7GeV) electron beam within just 11cm distance, with up to ∼31% net spin polarization. Higher current, energy, and net spin-polarization beams are possible by optimizing this concept, thus solving a long-standing problem facing the development of plasma accelerators.

Experimental plasma maser as a broadband noise amplifier. II. Short pulse

This paper presents an experimental plasma maser driven by a 2-ns long, high-current electron beam with a typical particles energy of 270 ± 10 keV, a pulsed power of 450 ± 30 MW, and a total energy of 0.85 ± 0.03 J. Tunable plasma characteristics define variations in the spectral maxima of excited high-power microwaves in the range from 3 to 25 GHz. The short beam current pulse has provided the device operation in the mode of a noise amplification with the energy efficiency of 26% ± 3%, mean microwave power over the beam current pulse of 117 ± 10 MW, and an instant (peak) power of up to 430 ± 30 MW.

Adhesive Strength of Ni–Cu Surface Alloy Formation by Low-Energy High-Current Electron Beam

The paper presents the adhesive strength measurements of the Ni–Cu surface alloy formed on a copper substrate at a different thickness of the transition layer. The formation of the surface alloy is provided by the low-energy high-current electron beam of a microsecond duration; the different thickness of the transition layer is varied by the thickness of the nickel film sputtered. The multiple deposition-irradiation process is performed during one vacuum cycle. It is found that the cross-section of the film (Ni)-substrate (Cu) interface is rather developed and curved. The transition layer thickness reduces with increasing thickness of the deposited nickel film. Scratch testing shows that the adhesive strength of the Ni–Cu surface alloy obtained by using the low-energy high-current electron beam, is higher than that of the sputter-deposited surface alloy. The highest adhesion is observed for the Ni–Cu surface alloy obtained by the nickel film deposition 0.125 μm thick. In this case, the crack formation and localized film delamination occur under the critical loads of 15 and 17 N, respectively. Nevertheless, a complete delamination of the surface alloy is not observed.

Microstructure and properties of CoCrFeNiMo0.2 high-entropy alloy enhanced by high-current pulsed electron beam

Abstract Recently, high-entropy alloys have drawn lots of attention due to their outstanding properties. In this paper, a promising new surface modification technique was acted on CoCrFeNiMo0.2 high-entropy alloy to improve its mechanical and corrosion properties. CoCrFeNiMo0.2 high-entropy alloys were synthesized via vacuum arc melting then, their surfaces were processed by high-current pulsed electron beam (HCPEB). Microstructure, microhardness, wear and corrosion resistance were studied systematically by means of X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Before and after HCPEB irradiation, CoCrFeNiMo0.2 high-entropy alloy had a face-centered cubic (FCC) structure, and the surface of the irradiated samples revealed preferential orientation on the (111) and (200) planes. In addition, a compact and homogenization surface layer formed after irradiation. Also, high-amplitude stress caused high-density dislocations and stacking faults on the surface. After HCPEB irradiation, the properties of the samples were significantly improved, the maximum microhardness (392.9 HV) and lowest wear rate (0.92 × 10−4 mm3·N−1·m−1) was obtained after 35-pulsed irradiation. Furthermore, corrosion resistance was obviously enhanced after 25-pulsed irradiation.

Microstructural modifications and high-temperature oxidation resistance of arc ion plated NiCoCrAlYSiHf coating via high-current pulsed electron beam

A NiCoCrAlYSiHf coating prepared via arc ion plating was irradiated using a high-current pulsed electron beam (HCPEB) technique. The self-quenching and polishing effect induced by HCPEB treatment normalized the defects, re-melted the surface, refined the grains, introduced the dislocations, and changed the elemental distributions. After oxidation for 200 h, severe spalling of the oxide scale and internal oxidation occurred in the original coating. The restructuring of the remelted layer contributed to a very stable, continuous, slow-growing, and uniform α-Al2O3 scale during the entire oxidation stage. HCPEB technique is an effective way to dramatically improve the service life of an MCrAlYX-type coating.

ИССЛЕДОВАНИЕ ФАКТОРОВ, СПОСОБСТВУЮЩИХ НЕCАНКЦИОНИРОВАННОМУ ИНИЦИИРОВАНИЮ ЭНЕРГОНАСЫЩЕННЫХ МАТЕРИАЛОВ

The results of experimental studies on the initiation of compositions containing energy-saturated materials by high-current electron beams and electrodischarge plasma are presented. Experimental studies simulate the effects on energy-saturated materials of electromagnetic fields of natural and man-made origin. The threshold voltage of the electrical breakdown of the compositions during a high-voltage electric discharge was determined and the possibility of initiation of the compositions by high-current electron beams of nanosecond duration using a pulsed high-current electron accelerator GKVI-300 was studied. Four compositions were selected as objects of study: a composition based on potassium picrate, a composition containing ammonium perchlorate, a composition based on lead minium with zirconium and colloxylin additives, and ballistite composition SBK-3. It is shown in the work that the initiation of compositions by a high-current electron beam is potentially possible only for compositions with low ignition temperatures, ignition of compositions with high ignition temperatures is possible due to the introduction of a powdery nanoscale additive, particles of which have specific heat less than particles of an energy-saturated material, and ignition of ammonium perchlorate is possible only if the particles of the additive have lower thermal conductivity than the particles of perchlorate ammonium.

An Axial Foilless Diode Guided by Composite Magnetic Field for the Production of Relativistic Electron Beams

Foilless diode are widely used in high-power microwave devices, but the traditional foilless diodes have large volume, heavy weight, and high power consumption, which are not conducive to the application of high-power microwave system on mobile platform. In order to reduce the size of the foilless diode, improve the transmission efficiency of electron beams, and reduce the weight and power consumption of the guiding magnetic field system, an axial foilless diode with a composite guiding magnetic field system is developed in this paper. By adjusting the structure size and magnetic field parameters of solenoid coil, permanent magnet, and soft magnet, the configuration of the composite magnetic field is optimized. The diameter of the anode tube is about 40% smaller than that of the original structure, and the weight and power consumption of the guiding magnetic system are about 40% lower than that of the original system when the same axial magnetic field intensity in the uniform region is generated. When the magnetic field strength of the permanent magnet is set as 1.4 T and that of the solenoid coil is in the range of 0.5 T∼1 T, the electron beam transmission efficiency is 100%, and the diode impedance is adjustable in the range of 100 Ω∼240 Ω. The experimental results verify the correctness of the simulation analysis. The experimental results show that when the magnetic field strength of the solenoid coil is 0.98 T (0.5 T) and that of the permanent magnet is 1.4 T, the transmission efficiency of the high-current annular electron beam with a peak voltage of 636 kV (590 kV) and a peak current of 3.3 kA (2.6 kA) is 100%, and the diode impedance is about 194 Ω (220 Ω).

Усталостные свойства никелида титана и их повышение с использованием низкоэнергетического сильноточного электронного пучка

It is shown that it is possible to an almost double increase nickel titanium fatigue characteristics using a low-energy high-current electron beam surface treatment of microsecond duration with the following parameters - energy density E s = 1.5 and 3.7 J/cm2, the number of pulses n = 5. Due to surface cleaning from particles/inclusions of Ti2Ni, TiC(O) and the presence of residual compressive stresses in the rapidly quenched surface layer of TiNi oriented perpendicular to the irradiation surface.