Pulsed Electron Beam Research Articles

Photoassisted electron emission from planar-type electron source based on graphene/oxide/silicon structure

This paper reports on photoassisted electron emission from a planar-type electron emission source based on a graphene/oxide/p-Si structure under visible laser light irradiation. The electron source is expected to be useful as a photocathode with a high quantum efficiency and an ultrafast pulsed electron beam. The electron emission efficiency is found to be 12%, independent of laser light irradiation. Without a negative electron affinity surface, the emission current generated by irradiation shows an increase of several orders of magnitude compared with that in the dark, and a quantum efficiency of 0.3% is achieved. This electron source exhibits advanced photoassisted electron emission characteristics with high photosensitivity in the order of milliamps per watt. The photoassisted emission from the device shows a photoresponse with a rise and fall time of 70 μs at a wavelength of 633 nm, which is determined by the diffusion process of photoexcited electrons in the bulk. The use of a heavily doped p-type silicon substrate provides a practical route for further improvement.

Comparative Study on Structural Differences in Monosaccharide Layers Using PLD and PED Techniques.

To demonstrate the feasibility of obtaining low-molecular-weight organic films (below 200 Da) using non-solvent PVD processes, glucose layers were produced via pulsed laser deposition (PLD) and pulsed electron beam deposition (PED) methods. Glucose was chosen due to its fundamental role in various biological processes, and because this low-molecular-weight compound is a solid at room temperature, which is required for both techniques. The physical and chemical structures of the deposited glucose layers were characterized by optical, scanning electron, and atomic force microscopy, as well as by X-ray diffraction, X-ray photoelectron, and infrared spectroscopy. Both PLD and PED methods resulted in glucose layers with good chemical structure preservation (with minor oxidation observed in PED) while yielding films with distinct physical properties. This opens up the possibility of tailoring organic layers with specific characteristics depending on the application, by choosing the deposition method.

Investigation on the Properties of Anodic Oxides Formed on Aluminium–Silicon Alloys Irradiated by Pulsed Electron Beam

Investigation on the Properties of Anodic Oxides Formed on Aluminium–Silicon Alloys Irradiated by Pulsed Electron Beam

Relativistic Electrons from Vacuum Laser Acceleration Using Tightly Focused Radially Polarized Beams.

We generate a tabletop pulsed relativistic electron beam at 100Hz repetition rate from vacuum laser acceleration by tightly focusing a radially polarized beam into a low-density gas. We demonstrate that strong longitudinal electric fields at the focus can accelerate electrons up to 1.43MeV by using only 98GW of peak laser power. The electron energy is measured as a function of laser intensity and gas species, revealing a strong dependence on the atomic ionization dynamics. These experimental results are supported by numerical simulations of particle dynamics in a tightly focused configuration that take ionization into consideration. For the range of intensities considered, it is demonstrated that atoms with higher atomic numbers like krypton can favorably inject electrons at the peak of the laser field, resulting in higher energies and an efficient acceleration mechanism that reaches a significant fraction (≈14%) of the theoretical energy gain limit.

Enhanced thermomechanical fatigue resistance in W10Re alloys: Microstructural and surface engineering approaches

Thermomechanical fatigue of refractory metals is commonly observed in high-temperature environments like first walls and divertors for proposed fusion reactors or X-ray anodes for medical imaging. Typically, alloying with rhenium or optimized microstructures are employed to counteract or delay the detrimental effects of fatigue in tungsten. Additionally, a novel concept is the utilization of surface structures to compensate cyclic thermal stresses. This work aimed to investigate the combination of these approaches, by comparing two W10Re alloys with vastly different microstructures, as well as engineered surface conditions of varying scales. Samples were subjected to thermocyclic fatigue under pulsed electron beam exposure, mimicking the surface temperatures typically encountered in a rotating X-ray anode. Analysis of several in-situ data streams, post-mortem investigations by metallography, and finite element methods revealed the interplay between microstructure and surface modifications. The columnar microstructure exhibited higher resistance to severe surface damage compared to the globular one, linked to the deflection of cracks along grain boundaries and subsequent melting. Coarse structuring was found to partly relieve the surface stresses during thermal cycling, preventing most of the damage accumulation. A full damage relief and performance equivalence between columnar and globular microstructure was achieved by engineering fine-structured surfaces, which led to a ten-fold increase in fatigue resistance over the non-structured condition.

Evaluation of the Low-Energy Ultrashort Pulsed Electron Beam Irradiation-Induced Oxidative Stress and Adaptive Response of Select Enzymes in a Rat Brain

Evaluation of the Low-Energy Ultrashort Pulsed Electron Beam Irradiation-Induced Oxidative Stress and Adaptive Response of Select Enzymes in a Rat Brain

Complex electron-ion-plasma surface modification of high-alloy stainless steel

The work is devoted to identification and analysis of patterns of change in the elemental and phase composition, defective substructure, mecha­nical (microhardness) and tribological (wear resistance and friction coefficient) properties of stainless high-chromium steel subjected to complex processing, combining vacuum irradiation of the samples surface layer with an intense pulsed electron beam of submillisecond exposure duration and subsequent nitriding under electron-ionic heating conditions. High-chromium steel AISI 310S, which in the initial state is a polycrystalline aggregate based on γ-iron, was used as the research material. Pulsed electron beam treatment of steel was carried out on a “SOLO” installation equipped with an electron source with a plasma cathode based on a low-pressure pulsed arc discharge with grid stabilization of the cathode plasma boundary and an open anode plasma boundary. Steel nitriding was carried out on a “TRIO” installation with a chamber size of 600×600×600 mm, equipped with a switching unit to implement the electron-ionic processing mode. Nitriding was carried out at 723, 793, and 873 K temperatures for 1, 3 and 5 h. It was found that electron-ionic nitriding of the samples pre-irradiated with an electron beam (10 J/cm2, 200 μs, 3 pulses at 723 and 793 K for 3 h) is accompanied by the formation of a ceramic layer containing only iron and chromium nitrides. The highest values of steel wear resistance after electron-ionic nitriding, exceeding the wear resistance of the initial steel by more than 700 times, are observed at nitriding parameters of 793 K, 3 h.

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.

Technologies to decontaminate aflatoxins in foods: a review

SummaryAflatoxins are toxic secondary metabolites produced by Aspergillus spp., found in staple food commodities. Aflatoxins are carcinogenic, teratogenic, and mutagenic and pose a serious threat to the health of humans. The identification and quantification of aflatoxins in foods is a major challenge to guarantee food safety. Therefore, developing feasible, sensitive, and robust methods for decontamination is paramount, with short processing time and negligible impact on quality. This review evaluates recent novel technologies for aflatoxins decontamination by physical methods (microwave heating, Gama and electron beam irradiation, pulse light and ultraviolet), chemical methods (ozone, natural plant extracts, and organic acids), and biological methods (atoxigenic Aspergillus strains, Trichoderma spp., and bacteria and yeast). The study highlights on the cutting‐edge technologies of smart packaging and artificial intelligence (AI). To achieve more efficiency and adaptability to different food matrices in aflatoxins decontamination, the study suggests integrating multiple strategies. The study also recommends integrating Partnership for Delivery (P4D) to share the responsibility to increase the chance for success and control aflatoxins in foods.

Symmetrical vortices and laminar dust flow induced by an intense electron beam interacting with a strongly coupled dusty plasma

A strongly coupled quasi-two-dimensional dusty plasma confined electrostatically in the plasma sheath of a radio frequency (RF) plasma is irradiated by a collimated and mono-energetic pulsed electron beam (e-beam) with an energy of 13 keV and a high peak current per pulse of 30 mA. A stream of rapidly moving charged dust particles is created inside the dust crystal due to the drag force of the electrons in the e-beam. The dust flow is split into two symmetrical branches when it reaches the boundary of the round dust crystal, each following the limit of the circular confining region. This results in the formation of a double vortex flow pattern with the dust particles being transported along the irradiation direction and then aside, eventually back to the entrance position of the e-beam. The observed flow regime is laminar at all times, with the speed in the central region increasing up to 12 mm s−1 in the first 200 ms and then diminishing gradually to a steady value of about 5–6 mm s−1 during a stress relaxation time period of 360 ms. The vorticity follows a similar trend with peak values −3.8 and 3.8 s−1 and steady state values between −2.5 and 2.5 s−1 in the two symmetrical vortices. Time-resolved particle-image-velocimetry and particle-tracking-velocimetry are used to characterize the flow. Molecular dynamics simulations confirm qualitatively the experimental observations showing dust stream and double vortex formation.

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.

Complex Modification of the Surface Layer of a High-Entropy Al-Cr-Fe-Co-Ni Alloy by Electron-Ion-Plasma Treatment

Using the technology of wire-arc additive manufacturing (WAAM – wire arc additive manufacture), a high-entropy alloy (HEA) of non-equiatomic composition Al, Cr, Fe, Co, Ni was manufactured. Using the methods of modern physical materials science, an analysis of the elemental and phase composition, defective substructure, mechanical and tribological properties of the HEA surface layer, formed as a result of complex modification, combining the deposition of a film (B + Cr) and irradiation with a pulsed electron beam in an argon medium, was carried out. In the initial state, the alloy has a simple cubic lattice with a lattice parameter of 0.28795 nm; the average grain size of the HEA is 12.3 µm. Chemical elements (at. %) 33.4 Al; 8.3 Cr, 17.1 Fe, 5.4 Co, 35.7 Ni, which form HEA, are distributed quasi-periodically. The irradiation regime was revealed (energy density of the electron beam ES = 20 J/cm2, pulse duration 200 µs, number of pulses 3 pulses, frequency 0.3 s more than 5 times), allowing to increase microhardness (almost 2 times) and wear resistance (more than 5 times), reduce the coefficient of friction by 1.3 times. Regardless of the value of ES, HEA is a single-phase material and has a simple cubic crystal lattice. High-speed crystallization of the surface layer leads to the formation of a subgrain structure (150–200) nm. It is shown that an increase in the strength and tribological properties of HEA is due to a significant (4.5 times) decrease in the average grain size, the formation of particles of chromium and aluminum oxyborides, and the incorporation of boron atoms into the crystal lattice of HEA.

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.

Acoustic Oscillations on Piezoelectric Materials Excited by a GHz Pulsed Electron Beam

Acoustic Oscillations on Piezoelectric Materials Excited by a GHz Pulsed Electron Beam

The study of interaction of the high energetic plasma and electron pulses with multicomponent alloy surface

This paper investigates the impact of high-energy sources, namely, high-energy plasma pulses and high-energy electron beam pulses, on materials in the form of layer through separate and combined exposures. Experimental setups utilizing a Rod Plasma Injector (RPI) and an electron gun were employed for irradiation tests. The studies involved pre- and post-treatment analysis of morphology, chemical, and phase composition using scanning electron microscopy and x-ray diffraction measurements. Surface modifications under different exposure conditions were characterized, revealing that both sources induced significant alterations in surface composition and crystal structure. These interactions result in a more uniform chemical composition, reduced surface roughness, and a shift from an amorphous phase to a nanocrystalline or amorphous-nanocrystalline state. The results underscore the potential of high-energy sources for efficient surface engineering, offering opportunities for customized material surface modifications through meticulous adjustment of these generation parameters.

Emission characteristics of a forevacuum plasma-cathode source of wide-aperture pulsed electron beam with layer (mesh) stabilization of emission plasma

Research of emission characteristics of a pulsed forevacuum plasma electron source with layer (mesh) stabilization of emission plasma boundary has been carried out. Generation of a pulsed wide-aperture electron beam is provided by DC accelerating voltage (1–10 kV) and pulse-periodic formation of emission plasma by a cathodic arc with current 5–80 A, pulse duration 500–600 μs. Pressure (4–30 Pa) and the type of working gas (N2, O2, Ar, He, Kr) significantly influence on the emission characteristics of the forevacuum plasma electron source. An increase in the gas pressure and the use of gas with larger ionization cross-section provide an increase in the electron emission current. At low pressure (below a certain threshold value, which determined by the type of gas) an increase in the discharge current leads to an increase in the efficiency of electron emission. But at pressures more than the threshold value the emission efficiency decreases as the discharge current increases. The influence of pressure and type of gas on the emission characteristics are caused by the ion flux from the beam plasma which is formed due to ionization of gas by accelerated beam's electrons.

Average dose rate is the primary determinant of lipid peroxidation in liposome membranes exposed to pulsed electron FLASH beam

BackgroundLipid peroxidation, a self-propagating chain reaction that oxydates lipid molecules, contributes to harmful effects of ionizing radiation. A decrease in peroxidation at higher dose rates could play a role in the FLASH sparing effect. PurposeWe explored how lipid peroxidation induced by FLASH (>100 Gy/s) and conventional (CONV, <0.2 Gy/s) radiation depends on lipid concentration and content of polyunsaturated fatty acids (PUFA). Additionally, we investigated the correlation between the lipid peroxidation and the main beam parameters characterizing pulsed electron beams, namely the dose per pulse (DRp) and the average dose rate (DRav). MethodsWe employed phosphatidylcholine (PC) liposomes as a model of biological membranes. Suspensions of liposomes containing different proportions of linoleic acid (LA) were prepared at various concentrations and irradiated at FLASH and CONV dose rates. Additionally, the liposomes were exposed to beams characterized by diverse combinations of DRp and DRav. The extent of lipid peroxidation was assessed by monitoring oxygen consumption (ΔpO2) and measuring the yield of malondialdehyde (MDA), and in certain instances, of lipid peroxides (LOOH). ResultsRegardless of the radiation dose, liposome concentration or LA content, ΔpO2 and the yield of MDA were significantly lower for FLASH than for CONV irradiation. Increase in the proportion of readily oxidizable LA in the lipid had negative effect on the MDA yield but correlated positively with ΔpO2 and LOOH yield. Exposing liposomes to beams operating at different pulse repetition frequencies, while keeping the total dose and DRp constant, resulted in markedly different ΔpO2 and MDA yields. In contrast, DRav was found to exhibit stable correlation with both MDA yield and ΔpO2. ConclusionsIrradiation at FLASH dose rates produces lower yield of lipid peroxidation in PUFA-containing artificial PC membranes than CONV irradiation under all tested conditions. Time-averaged dose rate, in contrast to pulse dose rate, was the critical parameter determining the level of lipid peroxidation induced by pulsed electron beams.

Modification of ZrO2 ceramic by continuous and pulsed electron beams in the forevacuum pressure range

We describe our study of the treatment of ceramics based on zirconium dioxide (ZrO2), partially stabilized with yttrium oxide (Y2O3) (5.15 % wt.), by continuous and pulsed electron beams in the forevacuum pressure range. We find that continuous electron beam treatment at certain heating rates can lead to changes in the surface structure, with increase in roughness and change in crystalline phase composition. High heating rate leads to increase in the cubic phase of ZrO2. The results of irradiation by a pulsed electron beam depends on the pulse energy density and pulse power of the beam, with noticeable changes in the surface characteristics when the energy density reaches about 10 J/cm2; increased roughness of the ceramic surface is observed at this energy density. Further increase in pulse energy density (>10 J/cm2) and/or power can lead to increase in roughness by an order of magnitude. A change in color of the ceramic surface and formation of a layer with a columnar structure is observed when the energy density reaches 21 J/cm2 at a pulse power of 320 kW. These results show the suitability of electron beam treatment for controlled modification of zirconium dioxide ceramic materials.

Comprehensive dosimetric characterization of novel silicon carbide detectors with UHDR electron beams for FLASH radiotherapy.

The extremely fast delivery of doses with ultra high dose rate (UHDR) beams necessitates the investigation of novel approaches for real-time dosimetry and beam monitoring. This aspect is fundamental in the perspective of the clinical application of FLASH radiotherapy (FLASH-RT), as conventional dosimeters tend to saturate at such extreme dose rates. This study aims to experimentally characterize newly developed silicon carbide (SiC) detectors of various active volumes at UHDRs and systematically assesses their response to establish their suitability for dosimetry in FLASH-RT. SiC PiN junction detectors, recently realized and provided by STLab company, with different active areas (ranging from 4.5 to 10mm2) and thicknesses (10-20µm), were irradiated using 9MeV UHDR pulsed electron beams accelerated by the ElectronFLASH linac at the Centro Pisano for FLASH Radiotherapy (CPFR). The linearity of the SiC response as a function of the delivered dose per pulse (DPP), which in turn corresponds to a specific instantaneous dose rate, was studied under various experimental conditions by measuring the produced charge within the SiC active layer with an electrometer. Due to the extremely high peak currents, an external customized electronic RC circuit was built and used in conjunction with the electrometer to avoid saturation. The study revealed a linear response for the different SiC detectors employed up to 21Gy/pulse for SiC detectors with 4.5 mm2/10µm active area and thickness. These values correspond to a maximum instantaneous dose rate of 5.5 MGy/s and are indicative of the maximum achievable monitored DPP and instantaneous dose rate of the linac used during the measurements. The results clearly demonstrate that the developed devices exhibit a dose-rate independent response even under extreme instantaneous dose rates and dose per pulse values. A systematic study of the SiC response was also performed as a function of the applied voltage bias, demonstrating the reliability of these dosimeters with UHDR also without any applied voltage. This demonstrates the great potential of SiC detectors for accurate dosimetry in the context of FLASH-RT.

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.