High-energy Electron Irradiation Research Articles

Improving NV centre density during diamond growth by CVD process using N2O gas

Nitrogen-vacancy (NV) centres in diamond are point-like defects that have attracted a lot of attention as promising candidates for quantum technologies particularly for sensing and imaging nanoscale magnetic fields. For this application, the use of a high NV density within a high-quality diamond layer is of prime interest. In previous works, it has been demonstrated that in situ doping with N2O rather than N2 during chemical vapour deposition (CVD), limits the formation of macroscopic defects and improves NV's photostability. In this work, we focus on the optimization of the CVD growth conditions to obtain a high NV density keeping a constant N2O concentration in the gas phase (100 ppm). For this purpose, freestanding CVD layers are prepared varying two main growth parameters: methane content and substrate temperature. High energy electron irradiation followed by annealing is finally carried out in order to increase the NV yield through partial conversion of N impurities. Defect concentrations and spin properties are investigated. We find that growth under lower methane concentrations and lower temperatures enhances NV doping. NV ensembles with a density of the order of 2 ppm are finally obtained with narrow spin resonance linewidth. In addition, higher annealing temperatures of 1200 °C following irradiation are found to efficiently remove defects thus improving spin properties.

Structural rod-like particles for highly efficient radiative cooling

Passive daytime radiative cooling (PDRC) has attracted tremendous interest for the merit of zero energy consumption and free-pollution. While state-of-the-art PDRC techniques are still confined to specific application scenarios for the limited applicability and non-ideal environmental stability. We report an unconventional method of devising structural rod-like particle (RLP) with the textured surface embedding random nanopores for fabricating highly efficient radiative cooling coating. Our structural particle coating (SPC) containing the RLPs exhibits ultrahigh solar reflectance (97%) and long wave thermal emittance (95%), contributing to optimal average sub-ambient temperature drop of 5.7 °C in the nighttime and 4.3 °C in the daytime under solar intensity of nearly 1000 W/m2. It is a noteworthy finding because our SPC possesses paint-like simple structure and process, straightforward manufacturability, and offers a promising route for terrestrial radiative cooling. The superb insensitivity to space extreme temperature, high-energy electron irradiation and ultraviolet endows our SPC with even potential application under harsh space conditions.

Microstructure and properties analysis of accumulative-roll-bonding-processed Mg–Li/Ta composites for shielding of high-energy electron

The rational combinations of low/high-density metallic materials have been proved to be effective in shielding high-energy electron radiation, however, little has been studied and reported about their synthesis, microstructure, properties and stability against irradiation. In present work, Mg–Li alloy and pure Ta sheets were used to prepare such a novel low/high-density shielding composite by accumulative roll bonding (ARB). Results showed that a uniformed microstructure of composite could be produced after four ARB cycles. Both ARB process and irradiation caused no obvious change in phase compositions of raw materials. In larger areal mass 8.2–12.3 g/cm2, the Mg–Li/Ta composite is a more efficient shield than pure Mg–Li and Ta. Treated by irradiation, a notable number of cavities accompanied by dislocations were formed as main defects in α-Mg phase. The induced dislocations facilitated the nucleation and growth of {1 0–1 2} twins, which in turn acted as sinks of defects. By contrast, Ta phase exhibited good radiation stability as no signs of visible cavities. During ARB process and irradiation, the textures of α-Mg and Ta in composite all varied distinctly. The average micro-hardness of Mg–Li and Ta phase increased with ARB cycles. Treated by irradiation, Mg–Li matrix was sharply hardened while hardness of Ta was slightly decreased. The tensile strength of Mg–Li/Ta composite increased in ARB process and reached the maximum after four cycles. After irradiation, composite exhibited same strength but severe loss of ductility.

High energy electron irradiation in Ni41Mn43Co6Sn10 for obtaining large magnetostrain under a relatively low magnetic field

Promising magnetostrain effect endows the Ni-(Co)-Mn-X (X = Sn, In, Sb) based Heusler alloys large potential for the application on intelligent-drive field. However, the over high driving magnetic field always requires cumbersome attaching devices, which restricts the further promotion of such materials. In this work, a large number of point defects are formed in Ni41Mn43Co6Sn10 alloys by high energy electron irradiation, which could simultaneously increase the structural and magnetic difference between the parent phase and martensite phase. As a result, a high reversible magnetostrain of 0.22% is accordingly obtained in the transformation process only under a relatively low magnetic field of 4 T, which are comparable to the maximum values obtained under high fields in other Ni-Mn-based alloys.

Trevor Evans. 26 April 1927—10 October 2010

Trevor Evans was responsible for revealing the main physical processes which take place in natural diamond both in the upper mantle of the earth, where it is stabilized by high pressure and temperature, and as it is ejected by volcanic action to the surface. By measuring the activation energies required for graphitization, he clarified the reason for its very long life as a metastable crystal, valuable both as a gemstone and as an industrial abrasive. He learned how to make diamond specimens for examination in the transmission electron microscope, which enabled his discovery of dislocation loops and platelet precipitates in nitrogen-containing (type 1) stones. In a series of exacting laboratory experiments under geologically relevant conditions he pioneered the study of the emergence of nitrogen from solution to precipitation during the ejection process. In synthetic diamonds, using high-energy electron irradiation, he was able to reproduce the sequence of all the various types of nitrogen aggregation found in natural diamond. His work played a major role underpinning the characterization of gemstones, explaining many features of their colour. For many years he led diamond research in the UK, supported by De Beers. His work stimulated and has been confirmed by research in many other laboratories around the world.

Defect Engineering: Electron-Exchange Integral Manipulation to Generate a Large Magnetocaloric Effect in Ni41Mn43Co6Sn10 Alloys.

A promising magnetocaloric effect has been obtained in Ni-(Co)-Mn-X (X = Sn, In, Sb)-based Heusler alloys, but the low isothermal magnetic entropy change ΔSM restricts the further promotion of such materials. Defect engineering is a useful method to modulate magnetic performance and shows great potential in improving the magnetocaloric effect. In this work, dense Ni vacancies are introduced in Ni41Mn43Co6Sn10 alloys by employing high-energy electron irradiation to adjust the magnetic properties. These vacancies bring about intense lattice distortion to change the distance between adjacent magnetic atoms, leading to a significant enhancement of the average magnetic moment. As a result, the saturation magnetization of ferromagnetic austenite is accordingly improved to generate a high isothermal magnetic entropy change ΔSM of 20.0 J/(kg K) at a very low magnetic field of ∼2 T.

Ionizing Radiation Induced Formation of CeO2 Mesocrystals: γ-Irradiation versus High-Energy Electron Irradiation

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Spectroscopic behavior of various materials in a GEO simulated environment

Artificial objects currently populating Earth orbital regimes can be distinguished by comparing remote observational data to that of optical measurements within the visible (VIS) and near infrared (NIR) spectral regions of materials obtained in the laboratory. Careful comparison of spectrally resolved observations with laboratory-based material irradiation experiments can provide a tool for remote diagnosis and anomaly resolution. However, the spectral signatures of many materials change as a function of exposure to radiation in geosynchronous Earth orbit (GEO). In order for remote characterization to be a viable characterization technique, the evolution of material optical properties (VIS-NIR) upon exposure to the GEO environment must be understood. To this end, we have studied the reflectance of several commonly used spacecraft materials including organic polymers, solar cell coverglasses, black thermal control paint, and carbon-carbon (C–C) matrix composite as a function of exposure to high energy electron irradiation in order to mimic the harsh environment of GEO. It was found that different classes of materials exhibit large variation in radiation stability resulting in the development of unique spectral characteristics.

Analysis of the Effects of High-Energy Electron Irradiation of GaN High-Electron-Mobility Transistors Using the Voltage-Transient Method

The effects of high-energy (1 MeV) electron irradiation on the electrical and trapping properties of AlGaN/GaN high-electron-mobility transistors (HEMTs) are investigated systematically. When the irradiation fluence increases from 5 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> to 1 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , the drain-source current also increases and the threshold voltage shifts toward the negative direction. A Raman spectroscopy study shows that electron irradiation induces strain relaxation in the HEMT, which results in an improvement in the device's electrical characteristics. In particular, three traps in the device are identified using the voltage-transient method and the trapping effects in the HEMT are investigated after the final irradiation. When compared with the transient voltages during the pristine stage, the absolute amplitudes of the three traps in the device decrease after irradiation, which indicates a reduction in the density of the traps. Furthermore, it is proposed that the time constants of the three traps increase while the energy levels remain unchanged, which is ascribed to the strain relaxation and the structural ordering of the defects after electron irradiation. The observed changes in the trapping behaviors are consistent with the improvement in the electrical properties of the device and the shift in the Raman spectra.

High-resolution planar electron beam induced current in bulk diodes using high-energy electrons

Understanding the impact of high-energy electron radiation on device characteristics remains critical for the expanding use of semiconductor electronics in space-borne applications and other radiation harsh environments. Here, we report on in situ measurements of high-energy electron radiation effects on the hole diffusion length in low threading dislocation density homoepitaxial bulk n-GaN Schottky diodes using electron beam induced current (EBIC) in high-voltage scanning electron microscopy mode. Despite the large interaction volume in this system, quantitative EBIC imaging is possible due to the sustained collimation of the incident electron beam. This approach enables direct measurement of electron radiation effects without having to thin the specimen. Using a combination of experimental EBIC measurements and Monte Carlo simulations of electron trajectories, we determine a hole diffusion length of 264 ± 11 nm for n-GaN. Irradiation with 200 kV electron beam with an accumulated dose of 24 × 1016 electrons cm−2 led to an approximate 35% decrease in the minority carrier diffusion length.

B0AT1 Amino Acid Transporter Complexed With SARS-CoV-2 Receptor ACE2 Forms a Heterodimer Functional Unit: In Situ Conformation Using Radiation Inactivation Analysis.

The SARS-CoV-2 receptor, angiotensin-converting enzyme-2 (ACE2), is expressed at levels of greatest magnitude in the small intestine as compared with all other human tissues. Enterocyte ACE2 is coexpressed as the apical membrane trafficking partner obligatory for expression and activity of the B0AT1 sodium-dependent neutral amino acid transporter. These components are assembled as an [ACE2:B0AT1]2 dimer-of-heterodimers quaternary complex that putatively steers SARS-CoV-2 tropism in the gastrointestinal (GI) tract. GI clinical symptomology is reported in about half of COVID-19 patients, and can be accompanied by gut shedding of virion particles. We hypothesized that within this 4-mer structural complex, each [ACE2:B0AT1] heterodimer pair constitutes a physiological “functional unit.” This was confirmed experimentally by employing purified lyophilized enterocyte brush border membrane vesicles exposed to increasing doses of high-energy electron radiation from a 16 MeV linear accelerator. Based on radiation target theory, the results indicated the presence of Na+-dependent neutral amino acid influx transport activity functional unit with target size molecular weight 183.7 ± 16.8 kDa in situ in intact apical membranes. Each thermodynamically stabilized [ACE2:B0AT1] heterodimer functional unit manifests the transport activity within the whole ∼345 kDa [ACE2:B0AT1]2 dimer-of-heterodimers quaternary structural complex. The results are consistent with our prior molecular docking modeling and gut–lung axis approaches to understanding COVID-19. These findings advance understanding the physiology of B0AT1 interaction with ACE2 in the gut, and thereby contribute to translational developments designed to treat or mitigate COVID-19 variant outbreaks and/or GI symptom persistence in long-haul postacute sequelae of SARS-CoV-2.

Real-Time Identification of Oxygen Vacancy Centers in LiNbO3 and SrTiO3 during Irradiation with High Energy Particles

Oxygen vacancies are known to play a central role in the optoelectronic properties of oxide perovskites. A detailed description of the exact mechanisms by which oxygen vacancies govern such properties, however, is still quite incomplete. The unambiguous identification of oxygen vacancies has been a subject of intense discussion. Interest in oxygen vacancies is not purely academic. Precise control of oxygen vacancies has potential technological benefits in optoelectronic devices. In this review paper, we focus our attention on the generation of oxygen vacancies by irradiation with high energy particles. Irradiation constitutes an efficient and reliable strategy to introduce, monitor, and characterize oxygen vacancies. Unfortunately, this technique has been underexploited despite its demonstrated advantages. This review revisits the main experimental results that have been obtained for oxygen vacancy centers (a) under high energy electron irradiation (100 keV–1 MeV) in LiNbO3, and (b) during irradiation with high-energy heavy (1–20 MeV) ions in SrTiO3. In both cases, the experiments have used real-time and in situ optical detection. Moreover, the present paper discusses the obtained results in relation to present knowledge from both the experimental and theoretical perspectives. Our view is that a consistent picture is now emerging on the structure and relevant optical features (absorption and emission spectra) of these centers. One key aspect of the topic pertains to the generation of self-trapped electrons as small polarons by irradiation of the crystal lattice and their stabilization by oxygen vacancies. What has been learned by observing the interplay between polarons and vacancies has inspired new models for color centers in dielectric crystals, models which represent an advancement from the early models of color centers in alkali halides and simple oxides. The topic discussed in this review is particularly useful to better understand the complex effects of different types of radiation on the defect structure of those materials, therefore providing relevant clues for nuclear engineering applications.

Impact of high-energy electron irradiation on mechanical, structural and chemical properties of agarose hydrogels

Due to their excellent biocompatibility and biodegradability, natural hydrogels are highly demanded biomaterials for biomedical applications such as wound dressing, tissue engineering, drug delivery or three dimensional cell culture. Highly energetic electron irradiation up to 10 MeV is a powerful and fast tool to sterilize and tailor the material's properties. In this study, electron radiation treatment of agarose hydrogels was investigated to evaluate radiation effects on physical, structural and chemical properties. The viscoelastic behavior, surface hydrophilicity and swelling behavior in a range of typical sterilization doses of 0 kGy to 30 kGy was analyzed. The mechanical properties were determined by rheology measurements and decreased by more than 20% compared to the initial moduli. The number average molecular weight between crosslinks was estimated based on rubber elasticity theory to judge on the radiation degradation. In this dose range, the number average molecular weight between crosslinks increased by more than 6%. Chemical structure was investigated by FTIR spectroscopy to evaluate the radiation resistance of agarose hydrogels. With increasing electron dose, an increasing amount of carbonyl containing species was observed. In addition, irradiation was accompanied by formation of gas cavities in the hydrogels. The gas products were specified for CO2, CO and H2O. Based on the radiolytic products, a radiolysis mechanism was proposed. Electron beam treatment under high pressure conditions was found to reduce gas cavity formation in the hydrogels.

Self-Organized Nanostructures Generated on Metal Surfaces under Electron Irradiation

Irradiation of high-energy electrons can produce surface vacancies on the exit surface of thin foils by the sputtering of atoms. Although the sputtering randomly occurs in the area irradiated with an intense electron beam of several hundred nanometers in diameter, characteristic topographic features can appear under irradiation. This paper reviews a novel phenomenon on a self-organization of nanogrooves and nanoholes generated on the exit surface of thin metal foils irradiated with high doses of 360–1250 keV electrons. The phenomenon was discovered firstly for gold irradiated at temperatures about 100 K, which shows the formation of grooves and holes with widths between 1 and 2 nm. Irradiation along [001] produces grooves extending along [100] and [010], irradiation along [011] gives grooves along [100], whereas no clear grooves have been observed for [111] irradiations. By contrast, nanoholes, which may reach depths exceeding 20 nm, develop mainly along the beam direction. The formation of the nanostructures depends on the irradiation temperatures, exhibiting an existence of a critical temperature at about 240 K, above which the width significantly increases, and the density decreases. Nanostructures formed for silver, copper, nickel, and iron were also investigated. The self-organized process was discussed in terms of irradiation-induced effects.

Кинетические закономерности синтеза литий-цинкового феррита в условиях нагрева пучком электронов

The paper considers kinetic studies lithium-zinc ferrite synthesis under heating by high-energy electron beam of mixtures of the initial Fe2O3 – Li2CO3 – ZnO reagents of different prehistory. We used samples of bulk density and compressed in hydraulic press. Radiation-thermal synthesis of samples was carried out an ILU-6 pulsed electron accelerator by heating of high-energy electrons with 2.4 MeV energy. Was spending heating to 600, 700, 750 °C and kept at 0 to 120 minutes. Formation of ferrite in conventional thermal annealing at similar temperature and time conditions was studied for comparison. Characterized method for studying synthesized samples was X-ray diffraction analysis. It is found that the rate of ferrite formation depends on both the heating method and the density of the initial mixture. It is shown that heating the mixture with an electron beam significantly accelerates the process of obtaining ferrite, which is manifested in a decrease of the kinetic parameters of ferrite synthesis. The increase the rate of ferrite formation under high-energy electron irradiation is due to a significant decrease in activation energy of synthesis process and decrease in pre-exponential multiplier in temperature dependence.

Optical Characterization of Native Defects in 4H–SiC Irradiated by 10 MeV Electrons with Subsequent Annealing

Low-temperature photoluminescence was employed to investigate the defects of 4H–SiC crystals after high-energy electron irradiation, and the annealing characteristics and dependence of the detecting temperature and irradiation doses were investigated. Results showed that the emission, associated with carbon antisite–vacancy (VCCSi)+ defects was dominant in the electron-irradiated 4H–SiC crystal. With increase in detecting temperature, the emission decreased demonstrating red-shifted, and the full width at half-maximum broadened, which was attributed to the increase in the concentration of carriers arising from thermal activation at high temperature. The emission intensity was the highest value at an irradiation dose of 7.9 × 1018 e/cm2, and then began to decrease. This revealed the lattice damage caused by long-term high-energy irradiation, which reduced the intensity of the defect radiation in the spectrum.

Effects of High Energy Electron and X-Ray Irradiation on the Morphology, Microstructure and Reflectivity of Cast Speculum Metal Mirror

Effects of High Energy Electron and X-Ray Irradiation on the Morphology, Microstructure and Reflectivity of Cast Speculum Metal Mirror

Laboratory predictions for the night-side surface ice glow of Europa

Europa’s surface continuously experiences high fluxes of charged particles due to the presence of Jupiter’s strong magnetic field. These high-energy charged particles, including electrons, interact with the ice- and salt-rich surface, resulting in complex physical and chemical processes. Here, we report that Europa ice analogues emit characteristic spectral signatures in the visible region when exposed to high-energy electron radiation. The strongest emission (ice glow) we observed was centred at ~525 nm. We found that the presence of sodium chloride and carbonate strongly quenched, while epsomite enhanced, the radiation-induced ice glow. These emission characteristics could be used to determine the chemical composition of Europa’s surface during night-time low-altitude fly-bys of spacecraft such as the Europa Clipper. We estimate that the Europa Clipper Wide Angle Camera could record between 500 and 280,000 counts per second through different colour filters, depending on the chemical composition of Europa’s surface. Though we focus here on Europa, our study may be relevant to other bodies exposed to high doses of ionizing radiation, such as Io and Ganymede. With its extreme radiation environment, rich surface geology and compositional diversity, the radiation-induced ice glow on Europa could enable more precise surface characterization and provide unique night-time views. Based on laboratory experiments and predictions, the Europa Clipper mission is expected to detect the surface ices on the night side of Jupiter’s moon Europa glowing in the dark, with an intensity that can be used to determine their composition.

Review on the treatment of organic wastewater by discharge plasma combined with oxidants and catalysts.

Discharge plasma technology is a new advanced oxidation technology for water treatment, which includes the effects of free radical oxidation, high energy electron radiation, ultraviolet light hydrolysis, and pyrolysis. In order to improve the energy efficiency in the plasma discharge processes, many efforts have been made to combine catalysts with discharge plasma technology. Some heterogeneous catalysts (e.g., activated carbon, zeolite, TiO2) and homogeneous catalysts (e.g., Fe2+/Fe3+, etc.) have been used to enhance the removal of pollutants by discharge plasma. In addition, some reagents of in situ chemical oxidation (ISCO) such as persulfate and percarbonate are also discussed. This article introduces the research progress of the combined systems of discharge plasma and catalysts/oxidants, and explains the different reaction mechanisms. In addition, physical and chemical changes in the plasma catalytic oxidation system, such as the effect of the discharge process on the catalyst, and the changes in the discharge state and solution conditions caused by the catalysts/oxidants, were also investigated. At the same time, the potential advantages of this system in the treatment of different organic wastewater were briefly reviewed, covering the degradation of phenolic pollutants, dyes, and pharmaceuticals and personal care products. Finally, some suggestions for future water treatment technology of discharge plasma are put forward. This review aims to provide researchers with a deeper understanding of plasma catalytic oxidation system and looks forward to further development of its application in water treatment.

Effect of circularly polarized laser pulse beam waist radius on the dynamic and radiation characteristics of collided electrons

In this paper, the trajectory as well as the temporal and spatial characteristics of the electromagnetic radiation of high-energy electrons collided by fields of relativistically circularly polarized laser pulses are studied theoretically and calculated numerically, based on Lorentz equation, energy equation of electrons, and the basic equations of electron radiation. Results shows that the head-on collision of a single counter-streaming electron and an intense circularly polarized laser pulse can produce an ultra-intense pulse with zeptosecond duration in the direction where the azimuth angle and the polar angle . The amplitude of the electron trajectory and the peak power of its radiation are positively related to the beam waist radius. However, as the radius of the laser beam increases, its influence on the dynamic and radiation characteristics of the electron weaken gradually and become negligible when the beam waist radius is greater than 4 times the laser wavelength.