High-energy Electron Irradiation Research Articles

Vacancy formation modulating the local atomic environment for remarkable Multi-functional Magnetic properties in Ni–Co–Mn–In alloy

Defect (mainly vacancy) engineering has shown its potential for modulating the functional behavior of magnetic materials. In this work, dense Ni vacancies are introduced in Ni45Mn36.5In13.5Co5 alloy and the effect of these vacancies on the magnetic properties is both theoretically and experimentally clarified. In detail, Ni vacancy with the lowest formation energy is introduced by high energy electron irradiation, which shortens the distance between adjacent Mn atoms to strengthen the interaction between them and increase the corresponding magnetic moments, leading to the dTm/dH increase from −2.89 to 6.28 KT−1. As a result, a breakthrough in the magnetocaloric performance is correspondingly achieved, i.e., the entropy change (ΔSM) increases up to an ultra-high value of 48.15 J/(kg·K), much higher than all other reported values. Moreover, the reversible magnetostrain is also improved from 80 to 200 ppm. In summary, this work provides strong guidance for optimizing the magnetic performance of Ni–Mn based Heusler alloys via vacancy modulation.

Effect of High-Energy Electron Irradiation on the Microstructure and Properties of Polyetherimide

Effect of High-Energy Electron Irradiation on the Microstructure and Properties of Polyetherimide

MOSkin dosimetry for an ultra-high dose-rate, very high-energy electron irradiation environment at PEER

FLASH radiotherapy, which refers to the delivery of radiation at ultra-high dose-rates (UHDRs), has been demonstrated with various forms of radiation and is the subject of intense research and development recently, including the use of very high-energy electrons (VHEEs) to treat deep-seated tumors. Delivering FLASH radiotherapy in a clinical setting is expected to place high demands on real-time quality assurance and dosimetry systems. Furthermore, very high-energy electron research currently requires the transformation of existing non-medical accelerators into radiotherapy research environments. Accurate dosimetry is crucial for any such transformation. In this article, we assess the response of the MOSkin, developed by the Center for Medical Radiation Physics, which is designed for on-patient, real-time skin dose measurements during radiotherapy, and whether it exhibits dose-rate independence when exposed to 100 MeV electron beams at the Pulsed Energetic Electrons for Research (PEER) end-station. PEER utilizes the electron beam from a 100 MeV linear accelerator when it is not used as the injector for the ANSTO Australian Synchrotron. With the estimated pulse dose-rates ranging from (7.84±0.21)×105 Gy/s to (1.28±0.03)×107 Gy/s and an estimated peak bunch dose-rate of (2.55±0.06)×108 Gy/s, MOSkin measurements were verified against a scintillating screen to confirm that the MOSkin responds proportionally to the charge delivered and, therefore, exhibits dose-rate independence in this irradiation environment.

Dosimetric studies of e-, γ-, n- Irradiation fields of the M-30 microtron (18.5 mev)

The results of the implementation and study of the radiation characteristics of high-energy electron (e-), gamma (γ-), and neutron (n-) radiation fields of the M-30 microtron with a maximum energy of 18.5 MeV are presented. Dosimetric characteristics were studied using the method of thermally stimulated luminescence (TSL) and using samples TLD-100H (LiF: Mg,Cu,P) and TLD-500K (Al2O3:C). Three e-, γ-, and n-experiments were performed at the same M-30 electron flux; the dosimetric indicators Yγ,n;e = Dγ,n/De, where Dγ,n is the intensity of the dosimetric peaks of TSL after γ- or n-irradiation, and De is, respectively, e-irradiation. We discuss the relative stability of these dosimeters' Yγ,e parameters at gamma irradiations and the presence of a partial correlation of Yn,e values in neutron fields. The latter is associated with the peculiarity of radiation defect formation in the material of dosimeters when interacting with nuclear particles of different types. The research results confirm the general ideas about the physics of electron radiation conversion into beams of nuclear particles of different natures. The data obtained are important in developing methods for dosimetric support of radiation technologies that use beams of mixed high-energy nuclear radiation, particularly for radiation therapy.

The Effect of High-Energy Electron Irradiation of Saline Solution on Its Optical Characteristics and Cytotoxic/Cytodynamic Activity

The Effect of High-Energy Electron Irradiation of Saline Solution on Its Optical Characteristics and Cytotoxic/Cytodynamic Activity

Electron irradiation effects on the optical properties of Hf- and Zn-doped β-Ga2O3

Optical and electrical properties of Hf- and Zn-doped β-Ga2O3 samples, which are n-type and insulating, respectively, were altered via high-energy electron irradiation at 2.5 or 0.5 MeV. The β-Ga2O3:Hf samples irradiated with 2.5 MeV electrons experienced a color change from blue to yellow and a large drop in conductivity, attributed to the creation of gallium vacancies, which compensate donors. This irradiation resulted in the absence of free carrier absorption and the presence of Cr3+ photoluminescence (PL). PL mapping prior to irradiation revealed optically active ZnO precipitates that formed during the growth of β-Ga2O3:Zn. These precipitates have a 384 nm (3.23 eV) stacking fault emission in the core; in the outer shell of the precipitate, the PL blue-shifts to 377 nm (3.29 eV) and a broad defect band is observed. After 0.5 MeV electron irradiation, the defect band broadened and increased in intensity. The blue PL band (435 nm) of β-Ga2O3 was enhanced for both Hf- and Zn-doped samples irradiated with 0.5 MeV. This enhancement is correlated with an increase in oxygen vacancies.

Photoluminescence of bulk α -In2Se3 crystals irradiated by high-energy electrons

The photoluminescence (PL) spectra of bulk α-In2Se3 crystals before and after 10 MeV electrons irradiation with the 1015 and 1017 cm−2 fluences were studied in the temperature range from 7 to 340 K. Three main types of radiative recombinations corresponding to band-to-tail (BT), deep defects, and band-to-band (BB) recombination were manifested in the non-irradiated α-In2Se3 crystals. Also recombinations that can be associated with exciton recombinations at temperatures below 45 K are observed. After electron irradiation, noticeable changes in the PL spectra are observed. We detected a slight increase in activation energy of the BT recombination. An increase in the concentration of deep defects is also noted. The significant decrease in PL intensity of the BB recombinations indicates the formation of non-radiative recombination centers after electron irradiation with the 1017 cm−2 fluence. Our study may be useful for understanding the effects of high-energy electrons irradiation on the performance of electronic and photovoltaic devices based on α-In2Se3.

Electron Irradiation-Induced Degradation of TiN Thin Films on Quartz and Sapphire Substrates.

In this contribution, we investigated the properties of magnetron-sputtered TiN thin films on sapphire and quartz substrates before and after 5 MeV electron irradiation with a fluence of 7 × 1013 e/cm2. Structural, morphological, optical, and electrical properties were analyzed to observe the impact of electron irradiation on the TiN thin films. The results showed improved electrical properties of the TiN thin films due to high-energy electron irradiation, resulting in increased specific conductivity compared to the as-deposited thin films on both sapphire and quartz substrates. The structural features of the TiN thin films on the sapphire substrate transformed from polycrystalline to amorphous, while the TiN thin films deposited on the quartz substrate remained unchanged. Chemical state analysis indicated changes in the metallic bonding between Ti and N in the deposited TiN on the sapphire substrate, while TiN deposited on the quartz substrate retained its Ti-N bonding. This study provides insights into the effects of electron irradiation on TiN thin films, emphasizing the importance of investigating radiation resistance for the reliable operation of optoelectronic devices and photovoltaic systems in extreme ionizing radiation environments.

Influence mechanisms of electron beam irradiation on surface flashover in vacuum: Electron modification, deposition, and migration

In surface science, surface flashovers are discharge phenomena that occur at the gas/vacuum-solid interface. Spacecraft in the universe suffers from high-energy electron irradiation while it works under a high DC operating voltage, and thus, surface flashover threatens the safe operation of spacecraft and limits human’s deeper exploration of the universe. To unravel the influence mechanisms of electron beam irradiation (EBI), surface flashover voltages (Vf) of epoxy composites during EBI, short-term after EBI, and long-term after EBI are investigated, and the behaviors of molecular structure, deposited electrons near chains, and radiation electrons under EBI and their effects on Vf are separately clarified. For long-term after EBI, EBI induces crosslinking of molecular chains and introduces deep traps to the solid surface, which impedes electron emission and surface charging, and thus Vf increases. For short-term after EBI, the deposited electrons suppress charge injection to the solid, and Vf further increases. During EBI, the high-energy radiation electrons stimulate gas desorption and directly participate in plasma propagation, leading to a sharp decrease in Vf. This work comprehensively explains the influence mechanisms of EBI electron modification, deposition, and migration on the Vf, which offers a theory to guide the prevention of flashover for spacecraft.

Atomic imaging reveals in-situ growth behavior of bi nanoparticles by high-energy electron irradiation

Herein, we present an in-situ investigation of Bi nanoparticles (NPs) growth on BiVO4 substrates using high-energy electron beams in transmission electron microscopy (TEM). High-Resolution (HR)TEM images at atomic level reveal a four-step growth mechanism in which Bi NPs transform from metastable droplets to solid nanocrystals. The disappearance behavior is essentially opposite to the growth behavior, with the exception that the Bi particles do not exhibit droplet-like morphology throughout the disappearance. As demonstrated, the aggregation behavior is significantly influenced by particle size, lattice matching degree and interparticle distance. These findings are significant for the practical use of bismuth-based materials in irradiation environments.

Space radiation environment adaptability of the domestic 5056 high-performance aluminum honeycomb

In order to investigate the influence of space radiation environment on the performance of domestic 5056 high-performance aluminum honeycomb core, the effects of different irradiation effects and different radiation doses on the nodal strength and mechanical properties of domestic 5056 high-performance aluminum honeycomb core were studied through space radiation environmental tests and mechanical property tests such as high-energy electron irradiation, γ-ray irradiation, ultraviolet irradiation, hot and cold shock test, vacuum volatilization test. The results show that under multiple environmental conditions such as high-energy electron irradiation γ-ray irradiation, ultraviolet irradiation, and hot and cold shock environment, the domestic high-performance aluminum honeycomb core shows excellent adaptability to the irradiation environment and can be used for a long time in the extravehicular environment. However, when the radiation dose is greater than 2 × 109rad, the strength of honeycomb core nodes decreased significantly. The vacuum volatilization test results sindicate that the material meets the gas requirements of aerospace raw materials and has extremely low vacuum pollution characteristics.

Electron irradiation: From test to material tailoring

In this article, we report some examples of how high-energy electron irradiation can be used as a tool for shaping material properties turning the generation of point-defects into an advantage beyond the presumed degradation of the properties. Such an approach is radically different from what often occurs when irradiation is used as a test for radiation hard materials or devices degradation in harsh environments. We illustrate the potential of this emerging technique by results obtained on two families of materials, namely semiconductors and superconductors.

Electron Beam Induced Enhancement and Suppression of Oxidation in Cu Nanoparticles in Environmental Scanning Transmission Electron Microscopy.

We have investigated the effects of high-energy electron irradiation on the oxidation of copper nanoparticles in environmental scanning transmission electron microscopy (ESTEM). The hemispherically shaped particles were oxidized in 3 mbar of O2 in a temperature range 100-200 °C. The evolution of the particles was recorded with sub-nanometer spatial resolution in situ in ESTEM. The oxidation encompasses the formation of outer and inner oxide shells on the nanoparticles, arising from the concurrent diffusion of copper and oxygen out of and into the nanoparticles, respectively. Our results reveal that the electron beam actively influences the reaction and overall accelerates the oxidation of the nanoparticles when compared to particles oxidized without exposure to the electron beam. However, the extent of this electron beam-assisted acceleration of oxidation diminishes at higher temperatures. Moreover, we observe that while oxidation through the outward diffusion of Cu+ cations is enhanced, the electron beam appears to hinder oxidation through the inward diffusion of O2- anions. Our results suggest that the impact of the high-energy electrons in ESTEM oxidation of Cu nanoparticles is mostly related to kinetic energy transfer, charging, and ionization of the gas environment, and the beam can both enhance and suppress reaction rates.

Assessing the Long-Term Performance of Adhesive Joints in Space Structures during Interplanetary Exploration.

Spacecraft experience minimal mechanical loads in space, but with the development of reusable spacecraft for interplanetary exploration and repeated landings, structures will be subjected to increased mechanical stress. The impact of the space environment on the aging of adhesive materials used in space structures over long-term applications is not well understood. This study investigates two commonly used adhesives in spacecraft assembly, namely Scotch-Weld™ EC-2216 and Scotch-Weld™ EC-9323-2, under two aging conditions: (1) high-energy electron irradiation using a Van de Graaf accelerator, and (2) thermal vacuum cycling. The research evaluates the evolution of intrinsic adhesive properties and adhesion to CFRP (carbon fiber-reinforced polymer) and aluminum adherents before and after exposure to these environmental conditions through tensile tests, peel tests, double-cantilever beam (DCB) tests, and dynamic mechanical analysis (DMA).

Time evolution of temporal, spatial and spectral distribution of high-energy electron radiation in intense laser pulses

To study the time evolution of high-energy electron radiation in circularly polarized intense laser pulses in detail, a model of the interaction between the high-energy single electron and intense laser pulses is constructed based on the Lagrangian equation and the electron energy equation. Through simulation, this article vividly displays the evolution process of radiation in the spatial, frequency and time domain. By modulating the interaction time between the laser and electron and referring to the spatial distribution image of energy, the value and direction of the maximum radiation energy per unit solid angle are calculated. In addition, in specific directions, this paper discusses the effects of interaction duration on the energy frequency distribution and the power variation pattern. The results prove that the maximum radiation energy per unit solid angle will appear when the interaction time comes to about 450 fs, which is also the boundary moment when the frequency and time spectrum no longer change obviously. Therefore, by modifying the duration of the electron–laser interaction, it is possible to produce the electron radiation with desired characteristics more precisely.

Secondary radiation dose modeling in passive scattering and pencil beam scanning very high energy electron (VHEE) radiation therapy.

Electrons with kinetic energy up to a few hundred MeV, also called very high energy electrons (VHEE), are currently considered a promising technique for the future of radiation therapy (RT) and in particular ultra-high dose rate (UHDR) therapy. However, the feasibility of a clinical application is still being debated and VHEE therapy remains an active area of research for which the optimal conformal technique is also yet to be determined. In this work, we will apply two existing formalisms based on analytical Gaussian multiple-Coulomb scattering theory and Monte Carlo (MC) simulations to study and compare the electron and bremsstrahlung photon dose distributions arising from two beam delivery systems (passive scattering with or without a collimator or active scanning). We therefore tested the application of analytical and MC models to VHEE beams and assessed their performance and parameterization in the energy range of 6-200MeV. The optimized electron beam fluence, the bremsstrahlung, an estimation of central-axis and off-axis x-ray dose at the practical range and neutron contributions to the total dose, along with an extended parameterization for the photon dose model were developed, together with a comparison between double scattering (DS) and pencil beam scanning (PBS) techniques. MC simulations were performed with the TOPAS/Geant4 toolkit to verify the dose distributions predicted by the analytical calculations. The results for the clinical energy range (between 6 and 20MeV) as well as for higher energies (VHEE range between 20 and 200MeV) and for two treatment field sizes (5×5 and 10×10 cm2 ) are reported, showing a reasonable agreement with MC simulations with mean differences below 2.1%. The relative contributions of photons generated in the medium or by the scattering system along the central-axis (up to 50% of the total dose) are also illustrated, along with their relative variations with electron energy. The fast analytical models parametrized in this study allow an estimation of the amount of photons produced behind the practical range by a DS system with an accuracy lower than 3%, providing important information for the eventual design of a VHEE system. The results of this work could support future research on VHEE radiotherapy.

Surface Defects of Electron Irradiation Engineering for Graphene/Polymer Composite-Based Flexible Humidity Sensors

A facile approach for surface defect engineering based on high-energy electron irradiation is proposed here to produce a graphene/polymer composite flexible humidity sensor with high humidity resistance and responsiveness. The responsiveness of the graphene/polymer composite humidity sensor following electron irradiation was ∼22.4-fold greater than the unirradiated humidity sensor. When the relative humidity was 97.3%, the responsiveness of the sensor was 1.2 × 105. In addition, the irradiated humidity sensor maintained an excellent response after 10 water resistance tests. Furthermore, material characterization techniques demonstrated that graphene/polymer composite materials with low crosslinking density could be produced by electron irradiation at the appropriate fluence. Concurrently, the specific surface area of the graphene/polymer composite material was increased, and several oxygen-containing functional groups were generated, providing more active sites for water molecules to enhance the stability and responsiveness of the sensor. Thus, the irradiated graphene/polymer composite humidity sensor has potential applications in human respiratory monitoring and noncontact switching. Moreover, the surface defect engineering of electron irradiation provides a facile strategy for obtaining graphene/polymer composite flexible humidity sensors with high comprehensive properties.

Modification of Macromolecules of Polyimide Films by Electron Irradiation.

New polymeric materials formation by controlling their properties is the primary and most challenging problem in developing a methodology for synthesizing a chosen technology and its use. The combined effect of high-energy electron radiation and tensile stress will cause a decrease in crystallinity and the breakage of chemical bonds in polyimide film macromolecules and is a new approach in their production technology. The effect of uniaxial tension and electron irradiation on the modification of polyimide film at room temperature was studied. Irradiation of the films caused an increase in the intensity of the IR spectrum by ~2-6 times and an increase in the width of the bands. The intensity in the range of 1700-3500 cm-1 increased, indicating an increase in the content of radicals as a result of irradiation. The amplitudes of the electron paramagnetic resonance signal from non-irradiated films increased from 3 × 103 to 5 × 103 as a result of uniaxial tension to fracture, indicating an increase in radicals in the material. The lines of the electron paramagnetic resonance spectrum shifted from 3475.0 cm-1 to 3512.5 cm-1, with a simultaneous decrease in the signal's amplitude from 6 ×103 to 4 × 103, as a result of the electron irradiation of the films, followed by their subjection to tension. This was due to a decrease in the concentration of the radicals of the =N-H and -N-H2 groups until their disappearance and the formation of new ones.

Electron and Neutron Beam Irradiation Effects in Homogeneous and Nanostructured Oxides.

Oxide-based materials have a variety of applications in chemical sensing and photocatalysis, thin-film transistors, complex-oxide field-effect transistors, nonvolatile memories, resistive switching, energy conversion, topological oxide electronics, and many others. The radiation resistance of these materials in such devices plays an important role in device operation in radiation environment, and this attracts much attention in the research area. In spite of damage in a number of cases high-energy particles may have a beneficial effect on the target. In this mini-review article examples of both creation of defects and beneficial changes in the structure and properties of homogeneous and nanostructured oxides caused by high-energy electron and neutron irradiation are given by considering some recently published results. First, the attention is turned to ionizing and displacement effects of electron and neutron irradiation in homogeneous bulk and thin-film oxides reported in the literature. Then, the effect of electron and neutron irradiation on nanostructured oxides and semiconductor nanoparticles embedded in an oxide matrix is regarded. Considerable attention is paid to silicon oxide layers since they are widely used in microelectronic products, which are among the most manufactured devices in human history. Processes of irradiation-induced lattice rearrangement, compositional changes, growth of nanoparticles and their size reduction, creation of point defects and their complexes, electron-hole generation, and charge trapping are discussed.

Crossing the ballistic-ohmic transition via high energy electron irradiation

The delafossite metal ${\mathrm{PtCoO}}_{2}$ is among the highest-purity materials known, with low-temperature mean free path up to 5 $\ensuremath{\mu}\mathrm{m}$ in the best as-grown single crystals. It exhibits a strongly faceted, nearly hexagonal Fermi surface. This property has profound consequences for nonlocal transport within this material, such as in the classic ballistic-regime measurement of bend resistance in mesoscopic squares. Here, we report the results of experiments in which high-energy electron irradiation was used to introduce pointlike disorder into such squares, reducing the mean free path and therefore the strength of the ballistic-regime transport phenomena. We demonstrate that high-energy electron irradiation is a well-controlled technique to cross from nonlocal to local transport behavior and therefore determine the nature and extent of unconventional transport regimes. Using this technique, we confirm the origins of the directional ballistic effects observed in delafossite metals and demonstrate how the strongly faceted Fermi surface both leads to unconventional transport behavior and enhances the length scale over which such effects are important.