Electron Beam Applications Research Articles

Stable Field Emission from Single-Crystalline Zirconium Carbide Nanowires.

The <100> oriented single-crystalline Zirconium Carbide (ZrC) nanowires were controllably synthesized on a graphite substrate by chemical vapor deposition (CVD) with optimized growth parameters involving Zirconium tetrachloride (ZrCl4), flow of methane (CH4), and growth temperature. The length of nanowires is above 10 µm while the diameter is smaller than 100 nm. A single ZrC nanowire was picked up and fixed on a tungsten tip for field emission measurement. After surface pretreatments, a sharpened and cleaned ZrC nanowire emitter showed a high emission current density of 1.1 × 1010 A m-2 at a low turn-on voltage of 440 V. The field emission is stable for 150 min with a fluctuation of 1.77%. This work provides an effective method for synthesizing and stabilizing single-crystalline ZrC nanowire emitters as an electron source for electron-beam applications.

A coupling method for rapid, continuous and extremely wide-temperature measurement of total hemispherical emissivity and conversion efficiency of the kinetic energy of an electron beam to the thermal energy of a material based on a scanning electron beam

Precise measurements of a material's total hemispherical emissivity and conversion efficiency of the Kinetic energy of an Electron beam to the Thermal energy of a Material (KETM) are crucial for the advancement of new materials and electron beam applications. We propose a coupling method for the rapid and continuous measurements of the above parameters across an extremely broad temperature range, the basic idea of which is that a thin plate sample is uniformly heated to a high-temperature state by a scanning electron beam and naturally cooled, and equations of the transient heat transfer process in the cooling section and the heating section are solved separately based on the assumption of the lumped heat capacity, and the above parameters varying with temperature are obtained in turn. The characterization experiments of the wire-drawn and polished 304 stainless steel are carried out. The emissivities of two surface states increase monotonically in the ranges of [0.17(400K), 0.26(954K)] and [0.12(400K), 0.20(983K)], respectively, aligning well with trends and values reported in the literature. Oxidation on both surfaces worsens as the preset temperature rises, resulting in a corresponding increase in the emissivity. Considering the impact of oxidation on emissivity, KETM is calculated in various regions within the considered temperature ranges. The results indicate a slight variation around 0.819 in KETMs of wire-drawn and polished 304 stainless steel within the temperature range of 400∼1000 K, aligning well with the value reported in the literature. This efficient measurement method can provide potential support for the application of the above two parameters.

Advanced Laser–Plasma Diagnostics for a Modular High-Repetition-Rate Plasma Electron Accelerator

We present a laser–plasma electron accelerator module designed to be driven by high-repetition-rate lasers for industrial applications of laser-driven electron beams. It consists of a single vacuum chamber containing all the necessary components for producing, optimizing, and monitoring electron beams generated via laser wakefield acceleration in a gas jet when driven by a suitable laser. The core methods in this paper involve a comprehensive metrological assessment of the driving laser by rigorous temporal laser pulse characterization and contrast measurements, supplemented by detailed spatiotemporal distribution analyses of the laser focus. Results demonstrate the good stability and reproducibility of the laser system, confirming its suitability for advanced scientific and industrial applications. We further demonstrate the functionality of the laser–plasma accelerator module diagnostics, perform target density characterizations, and time-resolved laser–plasma shadowgraphy. Current limitations of the set-up preventing first electron acceleration are analyzed and an outlook for future experiments is given. Our work is a first step towards the wide dissemination of fully integrated laser–plasma accelerator technology.

Beam characterization of mid-infrared free electron laser to drive high-harmonic generation

The maximum energy of photons from high-harmonic generation (HHG) increases with the wavelength of the driving laser. A free electron laser (FEL) is a continuously tunable light source in the mid-IR wavelength range and it is useful for investigating the extension of the accessible photon energy in HHG. Recently, the undulator magnets of the IR FEL at the Laboratory for Electron Beam Research and Application (LEBRA), Nihon University, have been replaced, and then the output power of the FEL has increased. Here, we evaluate the pulse duration and focal beam size of the FEL and show that the LEBRA FEL with 2 and 3 μm laser wavelengths under a 44 MHz bunch repetition mode can drive HHG.

Changes in Telomere Length in Leukocytes and Leukemic Cells after Ultrashort Electron Beam Radiation

Application of laser-generated electron beams in radiotherapy is a recent development. Accordingly, mechanisms of biological response to radiation damage need to be investigated. In this study, telomere length (TL) as endpoint of genetic damage was analyzed in human blood cells (leukocytes) and K562 leukemic cells irradiated with laser-generated ultrashort electron beam. Metaphases and interphases were analyzed in quantitative fluorescence in situ hybridization (Q-FISH) to assess TL. TLs were shortened compared to non-irradiated controls in both settings (metaphase and interphase) after irradiation with 0.5, 1.5, and 3.0 Gy in blood leukocytes. Radiation also caused a significant TL shortening detectable in the interphase of K562 cells. Overall, a negative correlation between TL and radiation doses was observed in normal and leukemic cells in a dose-dependent manner. K562 cells were more sensitive than normal blood cells to increasing doses of ultrashort electron beam radiation. As telomere shortening leads to genome instability and cell death, the results obtained confirm the suitability of this biomarker for assessing genotoxic effects of accelerated electrons for their further use in radiation therapy. Observed differences in TL shortening between normal and K562 cells provide an opportunity for further development of optimal radiation parameters to reduce side effects in normal cells during radiotherapy.

Dosimetry for low-energy electron beam applications at Fraunhofer FEP

Abstract Accelerating electrons to achieve chemical and biological effects is a well-established competence of Fraunhofer FEP. Today, there is a large variety of low-energy electron beam applications with a broad range of absorbed doses, e.g. modification of plastics, plasma-chemical syntheses, pollutant removal in wastewaters and exhaust gases, sterilization of medical products, disinfection of seeds, biocompatible functionalization of implants and stimulation of biotechnological processes. This calls for reliable, sensitive, and flexible methods for dosimetry. Radiochromic films are suitable tools to measure electron dose distributions for the characterization and quality control of Fraunhofer FEP’s irradiation facilities. Risø B3 radiochromic film from DTU Health Tech, the dosimeter of choice at FEP, reliably detects doses in the range of 10–100 kGy. However, with new upcoming applications, doses in the single-digit kGy range and even lower come to the fore. Hence, the palette of dosimeters at FEP must be extended. Gafchromic’s HD-V2 film is a welcome complement and widens the accessible dose range down to 10 Gy. Using a UV-VIS spectrophotometer for read-out of the films and custom analysis algorithms further increase the sensitivity of the dosimetric setup. Additionally, dosimeters based on the optically stimulated luminescence (OSL) of beryllium oxide offer a wide dose range and high sensitivity. They were used to measure doses induced by secondary X-ray components to gain more information about a specific radiation field. The work gives an overview of the dosimetric toolbox at Fraunhofer FEP and the efforts to implement new methods of detection for low-dose applications and X-ray dosimetry.

Design and experimental study of electron beam treatment for composite insulator sheds

Composite insulators, widely used in high-voltage transmission lines, feature silicone rubber sheds that age in complex natural environments. Applying electron beam irradiation to the silicone rubber can enhance their ageing resistance and hydrophobic properties. To advance the study of sheet silicone rubber to the entire insulator, this study proposes a method utilising a 5 MeV Dynamitron accelerator for treating a irregularly structured insulator. The insulator is irradiated in a state of tilted placement and rotation about its axis to achieve a uniform and consistent dose across the sheds. The irradiation process of the insulator with electron beams is simulated using Geant4, considering both instantaneous and cumulative states separately. The deflected particles from scattering and reflection of high-energy electrons interacting with insulator components have a significant impact on the dose distribution in each shed. Moreover, an optimal tilt of 20° ensures similar irradiation doses and high uniformity across all sheds. An experimental platform is developed for rotational irradiation of the insulator to ensure stable operation. Preliminary experimental results confirm that the doses across all sheds are uniform and consistent.

Impacts of e-beam irradiation on microbial contamination and quality of Chinese medical formulas QingXuan tablets

Applying electron beam irradiation (EBI) technology to remove microbial contamination is a potential way to improve the efficiency of Chinese medical formula preservation. In this study, Qingxuan tablets (QXT) were irradiated at doses of 3, 5, 9, and 13 kGy of the electron beam, to investigate the impacts of EBI on the microbial load, physical properties, color, bioactive content, antioxidant activity, chromatograms, and spectral similarity of QXT. The results showed that EBI treatment at 13 kGy reduced the population of the total aerobic bacteria and the total molds and yeast of QXT to <200 CFU/g. Irradiation had no significant (P > 0.05) effect on the physical properties and color of QXT. However, the bioactive content of QXT was significantly lower at a dose of 13 kGy compared to unirradiated samples. The free radical scavenging capacity of QXT remained preserved after irradiation. High-performance liquid chromatography (HPLC), Fourier transforms infrared spectroscopy (FTIR), and ultraviolet–visible spectroscopy (UV–Vis) analyses showed that the difference in the chemical content between irradiated QXT and unirradiated samples gradually increased as the dose was increased from 0 kGy to 13 kGy. These results suggest that EBI can be used to sterilize and preserve Chinese medical formulas, but the irradiation dose should be controlled to prevent changes in quality.

Feasibility assessment of polycrystalline CsPbI3 relative dosimeters in photon and electron beam radiotherapy

Volumetric modulated arc therapy represents the latest technology in radiotherapy. It involves continuous modification of the multi-leaf collimator spatial distribution, dose rate, and gantry rotational speed, necessitating a dosimeter with high spatial resolution and exceptional sensitivity per unit volume. In particular, cesium-based inorganic perovskites have been studied for various applications, spanning from photoconductor solar cells to radiation detectors. These perovskites are renowned for their outstanding attributes, including thermal stability, inorganic stability, and light absorption capacity. Despite such advantageous characteristics, CsPbI3 materials have only been investigated in radiodiagnostics, with limited exploration in radiotherapy. To address this gap, this study verified the viability of CsPbI3 materials, note for their outstanding radiation detection efficiency, as dosimeters capable of measuring the radiation detection performance for radiotherapy devices. The reproducibility, linearity, and percent depth dose (PDD) were evaluated under the application of photon and electron beams in linear accelerators. The reproducibility assessment revealed impressive results, with the relative standard deviation registering at 0.53%, 0.32%, and 0.38% under electron beam energies of 6, 9, and 12 MeV and 0.45%, and 0.89% under photon beam energies of 6 and 15 MV. Moreover, the linearity test revealed an R 2 value of 0.9999, indicating high linearity, at 6, 9, and 12 MeV and at 6 and 15 MV. The PDD graphs drawn for the CsPbI3 dosimeter fabricated in this study showed that the D max points were consistent. The novel CsPbI3 dosimeter demonstrated a level of detection performance that satisfied all criteria; reproducibility, linearity, and PDD. The results collectively indicated that the CsPbI3 dosimeter can be used for dosimeters in radiotherapy devices.

Ultrafast electron beam compression using chirped pulse beating laser

High-brightness ultrafast electron beams are of significant interest to researchers because of their diverse applications. In order to further improve the quality of ultrafast electron beams, we propose a novel method in this paper, which involves compressing electron beams by using the beating laser generated from two chirped radially polarized lasers. This proposed method allows for the compression of electron beams with different pulse widths. Furthermore, it employs two lasers from the same source, which minimizes the impact of laser’s transverse position offset on bunch compression at the modulation point. This method reduces the requirement of laser system and increases its robustness under non-ideal conditions, making it highly valuable for the generation and application of ultrashort electron beams.

Experimental realization of near-critical-density laser wakefield acceleration: Efficient pointing 100-keV-class electron beam generation by microcapillary targets

We experimentally demonstrated the generation of a pointing stable, low-divergence, low-energy electron beam driven by near-critical-density laser wakefield acceleration using a moderate low-intensity laser pulse. Electron beams with a half-beam divergence angle of ∼30 mrad were generated at laser intensities of 4 × 1016–1 × 1018 W/cm2 from a microcapillary hole. The pointing fluctuation of the electron beam was 1.8 mrad (root-mean-square) at the maximum laser intensity of 1 × 1018 W/cm2. The energies of the electron beam were up to 400 keV at 1 × 1018 W/cm2 and 50 keV even at 1 × 1016 W/cm2. We confirmed that the peak energy of the hump or cutoff energy of the electron beams was reproduced in particle-in-cell simulation. Such low divergence electron beam generation at sub-relativistic intensity (1016 to 1017 W/cm2 order) will lead to various applications of laser-driven keV-class electron beams, such as advanced radiotherapy.

Effects of Irradiation Dose of Sheet-Like Electron Beam and its Cathode Voltage on Impact Strength of Carbon Fiber Reinforced Thermoplastic Polyamide just before Shipping

Achieving a strong bond between carbon fiber (CF) and recyclable thermoplastic polymer (TP) has always been highly sought after. So far, applying electron beam (EB) irradiation with optimal dose and cathode potential (Vc) has shown success in increasing mechanical properties of interlayered CFRTPs. However, with concern for durability and safety, higher strength is desired. Therefore, EB setting applying electron beam (EB) irradiation with cathode potential (Vc) to 170, 210, 225 or 250 kV was applied to CFRTPA (carbon fiber reinforced thermoplastic polyamide) articles just before shipping. Specimens were 9 CF plies alternating between 10 PA (polyamide) sheets, designated [TPA]10[CF]9. When optimal EB dose of 43.2 kGy is applied to both finished specimen surfaces after fabrication, experimental results show higher Vc setting of 250 kV can increase impact strength of the [TPA]10[CF]9 over that at 170 kV. In summary, the 250 kV-EB (250 kV) strengthens [TPA]10[CF]9 significantly, about 25 to 27% larger than that of 170 kV and zero (untreated). Based on Christenhusz and Reimer equation to calculate penetration depth, Dth of EBI into polymers, increasing Vc to 250 kV increased Dth to more than 2 times that at 170 kV.

Experimental study of the electron beam application for evaporation of cobalt, tin and copper

Studies on the kinetic theory of the evaporation of metals in vacuum have already existed, and there have been various applications, such as evaporation filming and powder making in vacuum. However, the vast amount of needed physical parameters has become an obstacle in achieving an accurate measurement, which limits their applications in turn. In addition, there is a lack of experimental research data and simple measurements about the intensive evaporation with the electron beam technology at high temperatures. In this study, a new thermogravimetric analysis (TGA) measuring device was designed for evaporation with the electron beam technology, to track the temperature and mass of the molten pool in real time and obtain abundant and instantaneous experimental data with complete details during the evaporation process. The starting evaporation temperature and the evaporation rate of cobalt, tin, and copper have been measured. In this study, the starting evaporation temperatures of cobalt, tin, and copper are 2173±5 K, 1970±5 K, and 1523±5 K respectively. At 2200–2271 K, the evaporation coefficient of Co is stabilized at around 0.5 with a decreasing tendency; at 1873–2050K, the evaporation coefficient of Cu decreases rapidly from 0.88 to 0.39; at 1979–2038 K, the evaporation coefficient of Sn increases from 0.27 to 0.64.

Temporal resolution in transmission electron microscopy using a photoemission electron source.

Temporal resolution in transmission electron microscopy (TEM) has progressed to the sub-picosecond level with the stroboscopic method using a photoemission mechanism with an ultrafast laser for the electron gun. Time-resolved TEM in conjunction with a photocathode (PC)-type electron source pumped by a pulsed laser has been actively developed to exceed sub-nanosecond time resolution. Here, we provide an overview of the trends in this field and discuss the measurement targets that can be obtained by time-resolved measurements. Furthermore, we consider the types and characteristics of PC materials and their related physical quantities for evaluation of electron beam properties. Experimental results obtained by time-resolved TEM using a semiconductor PC that has a surface with a negative electron affinity are presented, and application results based on quantum mechanics are given. We also describe new techniques for improving the time resolution and new applications of pulsed electron beams in electron microscopy and discuss the measurement targets that are expected for time-resolved electron microscopy.

Improved treatment of home-made glow discharge ion source

For a better treatment, a new class of DC ion source (DCIS) was developed and adapted to provide low-power, highly-density plasma and ion-current applications. Such an ion source operates under the mode of abnormal glow discharge being of the self-extraction category, with specific features such as simple operation, stable discharge, and the ability to use for a variety of plasma, ion, and electron beam applications. A teflon disc with different diameters has been installed in between the two electrodes. This disc covered the cathode area, reducing the discharge area on the cathode surface for discharge confinement, and thus allowing for a higher output ion beam current. Pressures of 10−4 mbar, a 3 mm gap between the electrodes, and a 5 mm teflon diameter were observed to be the optimal operating conditions. At this ideal distance, hydrogen, nitrogen, and argon gases were used to investigate internal and external operational parameters. Finally, the Paschen curves were determined for hydrogen, air, as well as nitrogen gases.

The effect of electron beam irradiation on the microbial stability and quality characteristics of vacuum‐packaged ready‐to‐eat potato

We studied the microbial stability and quality of vacuum-packaged ready-to-eat (RTE) potatoes irradiated by different doses of electron beam during storage. Results showed that irradiation effectively reduced the total bacterial count of samples, with a maximum reduction of 7.08 log units by irradiation at 5 kGy. Irradiation at dose ≥7 kGy completely inactivated the microorganisms. Potato color and texture were affected when the irradiation dose was ≥3 and ≥5 kGy, respectively, which may be due to the reduction of a* value and chewiness of samples. An electronic nose could effectively distinguish the odor of the irradiated samples from the non-irradiated ones. Irradiation significantly reduced potato Vc content but it had no effect on the moisture and total protein content. Potato DPPH activities were increased by irradiation at dose ≤5 kGy but decreased when the dose was ≥7 kGy. The FRAP values were reduced in all irradiated samples. Novelty impact statement This work investigated the effect of electron beam irradiation on microbial stability and quality characteristics, including sensory quality, texture, odor, nutritional properties, and antioxidant capacity of vacuum-packaged RTE potatoes. Based on the results, an optimum dose for RTE potatoes decontamination was also suggested. Results would provide the basic data for the wider application of electron beams in RTE vegetable preservation.

First full-scale application of electron beam technology for treating dyeing wastewater (30,000 m3/d) in China

Electron beam technology has been widely investigated for the degradation of recalcitrant organic pollutants in water and wastewater in laboratory scale. However, it needs verification in practical application for long-term operation. Strikingly, for the first time, we have successfully applied electron beam technology to treat the actual dyeing wastewater in capacity of 30,000 m3/d in Jiangmen city, Guangdong Province, China. The continuous monitoring data of the effluent water quality showed that electron beam technology can be used as advanced treatment process to effectively improve the removal efficiency of COD and color. The effluent COD of electron beam unit stayed between 20 and 50 mg/L when the influent COD ranged from 180 to 280 mg/L, and the color of the treated dyeing wastewater decreased to about 10 times. The operational cost of whole wastewater treatment processes was about 2.0–2.5 ¥/m3, including electron beam unit. Based on the monitoring data of more than one year's operation, it can be concluded that electron beam technology could provide a solution for refractory industrial wastewater treatment, which is a high efficient and cost-effective advanced treatment process.

Investigation of the degradation rate of electron beam processed and friction stir processed biocompatible ZKX50 magnesium alloy

Together with the mechanical properties, the degradation rate is an important factor for biodegradable implants. The ZKX50 Mg alloy is a suitable candidate to be used as a biodegradable implant due to its favorable biocompatibility and mechanical properties. Current research investigates the degradation rate and corrosion behavior of the ZKX50 as a function of the microstructure constituents and their morphology. Since grain refinement is the main strengthening mechanism for the ZKX50, the effect of the microstructure refinement on the corrosion rate was studied by applying electron beam processing (EBP) and friction stir processing (FSP) on the ZKX50 cast alloy. To study the effect of the microstructure constituents and their morphology a subsequent solution heat treatment (HT) was applied to the processed samples. The results show that the EBP and FSP lead to a uniform and remarkably refined microstructure of the ZKX50 alloy and homogeneous distribution of the intermetallic phases. The results of electrochemical corrosion tests together with the microstructure characterization show that microgalvanic corrosion is the predominant mechanism that occurs between the Ca 2 Mg 6 Zn 3 intermetallic phase and α-Mg matrix. According to the results attained through the electrochemical tests, the EBPed-HT ZKX50 alloy shows higher corrosion resistance compared to all other conditions immersed in 0.5 wt.% NaCl solution. The dissolution and spheroidizing of Ca 2 Mg 6 Zn 3 particles during the solution heat treatment provides higher corrosion resistance mainly by decreasing the microgalvanic corrosion. The microstructure of the heat-treated samples does not show a significant grain coarsening which can degrade the enhancement of the mechanical properties achieved by the EBP and FSP.

Effect of Structural and Phase Changes under Relativistic Electron Pulsed Beam Irradiation on the Aluminum Alloys Micro-hardness

The paper studies the distinctive features of micro-hardness value changes in the zone of industrial aluminum alloy 1933 and alloy 1380 irradiated by the relativistic electron beam. The surface layer was modified under the relativistic electron beam injected along with the equal energy parameters. However, we have to claim that some physical and technological properties of the irradiated alloys layer came with some differences. The modified layer micro-hardness increased over 30% in 1933 aluminum alloy and decreased by 10% in 1380 aluminum alloy. The mechanisms affecting the metal material strengthening transformation after a pulsed electron beam application are analyzed. Thus it was established that one of the core impacts to increase the micro-hardness of 1933 aluminum alloy surface layer was fine MgO impurities being absent in the initial alloy and caused by the irradiation, whilst the micro-hardness of the irradiated layer of the 1380 aluminum alloy decreases due to the dissolution during irradiation of the strengthening phases, which were identified in the initial state.

Research on Solenoidal Permanent Magnet for Guiding and Focusing Annular Electron Beams

The vacuum oscillators generally utilize high current annular relativistic electron beams to generate high-power microwaves. The annular electron beams are usually guided and focused by strong axial magnetic fields. A permanent magnet is developed for the application of annular electron beams. The configuration of the permanent magnet is based on the Halbach structure. A new method is proposed to design this solenoidal permanent magnet. The permanent magnet flux source can generate a 0.88 T axial magnetic field at the interaction region and a peak field of 0.94 T. The diameter of its clear bore is 50 mm. The total weight of the permanent magnet is 320 kg. The design, fabrication, and test results are presented in this article.