Electron Beam Research Articles

Observation of an Extraordinary Type V Solar Radio Burst: Nonlinear Evolution of the Electron Two-Stream Instability

Solar type V radio bursts are associated with type III bursts. Several processes have been proposed to interpret the association, electron distribution, and emission. We present the observation of a unique type V event observed by e-CALLISTO on 7 May 2021. The type V radio emission follows a group of U bursts. Unlike the unpolarized U bursts, the type V burst is circularly polarized, leaving room for a different emission process. Its starting edge drifts to higher frequency four times slower than the descending branch of the associated U burst. The type V processes seem to be ruled by electrons of lower energy. The observations conform to a coherent scenario where a dense electron beam drives the two-stream instability (causing type III emission) and, in the nonlinear stage, becomes unstable to another instability, previously known as the electron firehose instability (EFI). The secondary instability scatters some beam electrons into velocities perpendicular to the magnetic field and produces, after particle loss, a trapped distribution prone to electron cyclotron masering (ECM). A reduction in beaming and the formation of an isotropic halo are predicted for electron beams continuing to interplanetary space, possibly observable by Parker Solar Probe and Solar Orbiter.

Reduction of the Downward Energy Flux of Nonthermal Electrons in the Solar Flare Corona due to Cospatial Return-current Losses

High-energy electrons carry much of a solar flare’s energy. Therefore, understanding changes in electron beam distributions during their propagation is crucial. A key focus of this paper is how the cospatial return current reduces the energy flux carried by these accelerated electrons. We systematically compute this reduction for various beam and plasma parameters relevant to solar flares. Our 1D model accounts for collisions between beam and plasma electrons, return-current electric-field deceleration, thermalization in a warm target approximation, and runaway electron contributions. The results focus on the classical (Spitzer) regime, offering a valuable benchmark for energy flux reduction and its extent. Return-current losses are only negligible for the lowest nonthermal fluxes. We calculate the conditions for return-current losses to become significant and estimate the extent of the modification to the beam’s energy flux density. We also calculate two additional conditions that occur for higher injected fluxes: (1) where runaway electrons become significant, and (2) where current-driven instabilities might become significant, requiring a model that self-consistently accounts for them. Condition 2 is relaxed and the energy flux losses are reduced in the presence of runaway electrons. All results are dependent on beam and cospatial plasma parameters. We also examine the importance of the reflection of beam electrons by the return-current electric field. We show that the interpretation of a number of flares needs to be reviewed to account for the effects of return currents.

Bone-seeking tumor cells alter bone material quality parameters on the nanoscale in mice

Bone metastases related to breast and prostate cancer present with multiple challenges and skeletal related events like fragility fractures impair the quality of life of the patients significantly. To determine local alterations in bone material quality with bone metastasis, we subjected murine tibial specimens, generated after intratibial injections of either RM-1 prostate cancer cells or EO771 breast cancer cells into male and female mice respectively, to high-resolution imaging modalities. Small and wide-angle X-ray scattering showed unaltered mineral characteristics in the more osteosclerotic prostate cancer model, while the quantification of calcium weight percentage via backscattered electron microscopy determined minor differences along the perilacunar bone matrix. Further analyses of mineral and collagen characteristics were performed using Raman spectroscopy and focused ion beam electron microscopy. Our study indicates that alterations in nanochannel properties occur due to the presence of bone seeking tumor cells with more prevalent nanopores in the perilacunar matrix.

On the modulated fifth order dressed electron acoustic electrostatic and energy features in auroral plasma

In this work, the higher order electrostatic and solitonic EA energy plasma in auroral plasma has been investigated. The perturbed KdV form has been solved. The modulated soliton speed, energy of the cold beam electrons, and the associated higher fifth order electrostatic field have been mathematically derived. The effect of perturbed beam density as well as beam temperature parameters on the dressed electrostatic and energy properties has been discussed. The auroral plasma results in this work may be important in space applications.

(Invited) Consideration on Gate Stack Formation Processes of Ultrawide Bandgap Ga2O3 with SiO2 Dielectric Layer

MOSFETs on β-Ga2O3 are expected to be a high-efficient and cost-effective alternative option of high-voltage power devices. Taking account of the reliability and the large conduction-band offset against β-Ga2O3, it would be reasonable to employ SiO2 as the gate dieletric. In this study we investigated the effects of post-deposition annealing (PDA) on SiO2/β-Ga2O3 MOS gate stacks, in terms of the MOS electrical characteristics and the band alignment.β-Ga2O3 (001) wafers with ~2×1016 cm-3 n-type doped epitaxial layers were cleaned in diluted HF solution, and SiO2 films were deposited by electron-beam (EB) evaporation of Si in O2 ambient of ~1×10-2 Pa, followed by PDA at various temperatures from 600 to 1000℃ in either O2 or N2 ambient. Au was evaporated as gate electrode to form MOS capacitors. X-ray photoelectron spectroscopy (XPS) was conducted on the stacks with ~3nm-thick SiO2 for the evaluation of band alignment. Ultraviolet photoelectron spectroscopy (UPS) was also employed to determine the band diagram of β-Ga2O3 (001).Nearly-ideal capacitance-voltage characteristics were obtained for the MOS capacitor fabricated with O2-PDA at 1000℃. The interface state density (Dit) determined by conductance method decreased down to ~1010 cm-3 at the energy level of EC−0.2 eV by PDA at higher temperature. The hysteresis width (ΔVhys) of C-V curves was smaller for the samples annealed at higher temperatures. The flatband voltage (VFB) shift after O2-PDA resulted in VFB close to the ideal value estimated from the physical properties of Au and Ga2O3, suggesting that fixed charge density at the interface would be minimized. However, PDA in N2 at 1000℃ resulted in a negative shift of VFB, which indicates the formation of positive fixed charges in the stack. The beneficial influences of O2-PDA on those characteristics suggest that an oxygen deficiency introduced near the interface is one of the origins of interface defect states. It is noteworthy that Ga3d XPS on the surface of Ga2O3 substrate always shows a tailing in lower binding energy side, which is indicating oxygen deficiency on the surface. The intensity of this lower-binding-energy component reduced significantly when a bare-Ga2O3 substate was annealed in O2, however, it did not decrease efficiently even after O2-PDA when the surface was covered with SiO2. This is probably due to the oxygen rearrangement at SiO2/Ga2O3 interface determined by the difference of material properties of those oxides. This fact suggests that the Ga2O3 surface easily forms oxygen vacancies when it is covered with SiO2. This would be the reason why the formation of interface defect states is not suppressed without O2-PDA.Next the band diagram of β-Ga2O3 (001) substrate was investigated by UPS analysis where the energy level of valence band edge referring to the vacuum level was evaluted from the energy difference between minimum (cut-off) and maximum edges of the obtained kinetic energy spectra of photoelectrons. As a result we found the valence band edge of of β-Ga2O3 (001) was ~8.2 eV below the vacuum level, where the influences of O2 annealing at 1000℃ on the valence band edge energy level was limited to the shift within ~0.1eV. This would tell us the valence band offset between SiO2 and Ga2O3 should be around ~1.1eV, and the conduction band offset between them is to be around 2.8-2.9eV, by taking account of the well-reported SiO2 band diagram and assuming the bandgap of β-Ga2O3 as 4.7eV. On the other hand, the valence band offset estimated from the deconvolution of the XPS valence band spectrum for a ~3nm-thick SiO2/β-Ga2O3 stack from the energy edge difference between the deconvoluted spectra corresponding to SiO2 and Ga2O3, was a few hundreds of mV smaller than the above expected value (~1.1eV). This discrepancy is indicating the formation of an interface dipole layer between SiO2 and Ga2O3 with a pair of nagative and positive charges aligned at the interface to cause a shift in the band alignment. The magnitude of such dipole was indicated to be more significant (~0.5eV) for the stack after PDA at 1000℃, whereas it was less (0.2~0.3eV) after PDA at 600℃.In conclusion, we demonstrated that SiO2/β-Ga2O3 (001) MOS capacitors showed nearly-ideal electrical characteristics with significantly reduced interface defect density and small fixed charge density by applying O2-PDA. The band alignment of SiO2/β-Ga2O3 (001) MOS stack was clarified by photoelectron spectroscopy to confirm a very large conduction band offset of the stack, but an influence of the formation of interface dipole layer between SiO2 and Ga2O3 on the band alighment was also indicated.

Microstructural Analysis of Deposited Alkali Metal in “Anode-Free” Solid-State Batteries

Lithium metal as an anode material can greatly boost energy and power density in solid-state batteries.[1] However, challenges like local contact loss and dendrite growth limit the applicable current density. It was shown previously that the lithium microstructure can greatly influence the electrochemical performance of lithium, e.g. the stripping capacity until pore formation occurs.[2]Solid-state-batteries (SSBs) manufactured without the use of an alkali metal reservoir are under intense investigation, as they may enable unmatched energy densities without the need to handle reactive and inherently unsafe alkali metal foils. In these reservoir-free cells (RFCs) the alkali metal is usually stored in the discharged cathode active material upon assembly and thus only deposited at the anode current collector within the first charging step. However, despite its expected influence on the electrochemical performance, the microstructure of freshly deposited lithium has yet to be analyzed. Up to now, the lack of a combination of suitable preparation and analyses tools restrict any study of the microstructure of thin alkali metal films.Within this study, we designed a workflow to reliably analyze the microstructure of thermally processed lithium and sodium films. Using a combination of cryogenic focused ion beam (FIB) preparation and electron back-scatter diffraction (EBSD), we were able to exclude any recrystallization during room temperature storage or FIB preparation. Therefore, this newly developed workflow was further used to study the microstructure of otherwise buried alkali metal films, which were deposited in so called “anode-free” or reservoir free cell designs.Our analyses show that the grain size of plated alkali metal films is independent on the microstructure of used current collector and generally consists of very large grains, albeit not as large as as-bought foil. Even more interesting, every single deposited film consists solely of columnar grains with grain boundaries oriented perpendicular to the solid electrolyte interface, marking a clear difference to using an alkali metal foil as the anode. Our results are confirmed at two different RFCs, namely Cu|LLZO|Li and Steel|LPSCl|Li. Generally, we believe our research on metal anodes will open up the possibility of tackling more advanced scientific questions previously impossible to answer.(1) Krauskopf, T., Richter, F. H., Zeier, W. G. & Janek, J. Physicochemical Concepts of the Lithium Metal Anode in Solid-State Batteries. Chem. Rev. 120, 7745–7794 (2020).(2) Singh, D. K., Fuchs, T. et al. Origin of the lithium metal anode instability in solid-state batteries during discharge. Matter 6, 1463–1483 (2023).

Current-Dependent Lithium Metal Microstructure in ‘Anode-Free’ Solid-State Batteries at the Steel|LPSCI Interface

Further improvement of energy densities of state-of-the-art batteries could be achieved with the utilization of lithium metal anodes.1 Due to the reactivity of the alkali metal, the fabrication process needs to be monitored carefully. To circumvent degradation during storage as well as the handling of lithium metal, reservoir-free cells (RFCs) are investigated.2 Using accessible lithium stored within lithiated cathode materials, the lithium anode is formed in a formation step during the first charging cycle. The electrochemical properties of the electrodeposited lithium film are strongly dependent on its microstructure, and can, for example, influence the resoluble amount of lithium during subsequent cycling.3,4 Until now, the microstructure of electrodeposited lithium and how to control it is elusive.To observe and characterize the microstructure of electrodeposited lithium at the stainless steel|LPSCl interface, a combination of electrochemical impedance spectroscopy, focused ion beam and scanning electron microscopy as well as electron backscatter diffraction was used. With this setup, the correlation between deposition current density and resulting microstructure of the lithium film was investigated. For higher current densities, a twenty times smaller grain size was observed, while the grain density showed a twelvefold increase, which could have a major influence on the subsequent dissolution of lithium. Furthermore, the microstructural evolution during prolonged lithium deposition was investigated.1 J. Janek and W. G. Zeier, Nat. Energy, 2016, 1, 16141.2 M. J. Wang, E. Carmona, A. Gupta, P. Albertus and J. Sakamoto, Nat Commun., 2020, 11, 1–9.3 S. E. Sandoval and M. T. McDowell, Matter, 2023, 6, 2101–2102.4 D. K. Singh, T. Fuchs, C. Krempaszky, B. Mogwitz, S. Burkhardt, F. H. Richter and J. Janek, Adv. Funct. Mater., 2023, 33, 2211067.

Generation of Rapid and High-Quality Serum by Recombinant Prothrombin Activator Ecarin (RAPClot™).

We recently reported the potential application of recombinant prothrombin activator ecarin (RAPClot™) in blood diagnostics. In a new study, we describe RAPClot™ as an additive to develop a novel blood collection prototype tube that produces the highest quality serum for accurate biochemical analyte determination. The drying process of the RAPClot™ tube generated minimal effect on the enzymatic activity of the prothrombin activator. According to the bioassays of thrombin activity and plasma clotting, γ-radiation (>25 kGy) resulted in a 30-40% loss of the enzymatic activity of the RAPClot™ tubes. However, a visual blood clotting assay revealed that the γ-radiation-sterilized RAPClot™ tubes showed a high capacity for clotting high-dose heparinized blood (8 U/mL) within 5 min. This was confirmed using Thrombelastography (TEG), indicating full clotting efficiency under anticoagulant conditions. The storage of the RAPClot™ tubes at room temperature (RT) for greater than 12 months resulted in the retention of efficient and effective clotting activity for heparinized blood in 342 s. Furthermore, the enzymatic activity of the RAPClot™ tubes sterilized with an electron-beam (EB) was significantly greater than that with γ-radiation. The EB-sterilized RAPClot™ tubes stored at RT for 251 days retained over 70% enzyme activity and clotted the heparinized blood in 340 s after 682 days. Preliminary clinical studies revealed in the two trials that 5 common analytes (K, Glu, lactate dehydrogenase (LD), Fe, and Phos) or 33 analytes determined in the second study in the γ-sterilized RAPClot™ tubes were similar to those in commercial tubes. In conclusion, the findings indicate that the novel RAPClot™ blood collection prototype tube has a significant advantage over current serum or lithium heparin plasma tubes for routine use in measuring biochemical analytes, confirming a promising application of RAPClot™ in clinical medicine.

Electron Imaging of Nanoscale Charge Distributions Induced by Femtosecond Light Pulses.

Surface charging is ubiquitously observable during in situ transmission electron microscopy of nonconducting specimens as a result of electron beam/sample interactions or optical stimuli and often limits the achievable image stability and spatial or spectral resolution. Here, we report on the electron-optical imaging of surface charging on a nanostructured surface following femtosecond multiphoton photoemission. By quantitatively extracting the light-induced electrostatic potential and studying the charging dynamics on relevant time scales, we gain insights into the details of the multiphoton photoemission process in the presence of an electrostatic background field. We study the interaction of the charge distribution with the high-energy electron beam and secondary electrons and propose a simple model to describe the interplay of electron- and light-induced processes. In addition, we demonstrate how to mitigate sample charging by simultaneously optically illuminating the sample.

Investigation of optical polarization characteristics of ultraviolet-C AlGaN multiple quantum wells by angle-resolved cathodoluminescence

AlGaN-based ultraviolet-C (UV-C) light-emitting diodes (LEDs) face challenges related to their extremely low external quantum efficiency, which is predominantly attributed to the remarkably inadequate transverse magnetic (TM) light extraction efficiency (LEE). In this study, we employ angle-resolved cathodoluminescence (ARCL) spectroscopy to assess the optical polarization of (0001)-oriented AlGaN multiple quantum well (MQW) structures in UV-C LEDs, in conjunction with a focused ion beam and scanning electron microscopy (FIB/SEM) system to etch samples with various inclination angles (θ) of sidewall. This technique effectively distinguishes the spatial distribution of TM- and transverse electric (TE)-polarized photons contributing to the luminescence of the MQW structure. CL spectroscopy confirms that UV-C LEDs with a θ of 35° exhibit the highest CL signal compared to samples with other θ. Furthermore, we establish a model using finite difference time domain (FDTD) simulation to validate the mechanism of the outcomes. The complementary contribution of TM and TE photons at different specific angles are distinguished by ARCL and confirmed by simulation. At angles near the sidewall, the CL is dominated by the TM photons, which mainly contribute to the increased LEE and the decreased degree of polarization (DOP) to make the spatial distribution of CL more uniform. Additionally, this method allows us to analyze the polarization of light without the need for polarizers, enabling the differentiation of TE and TM modes. This distinction provides flexibility for selecting different emission mode based on various application requirements. The presented approach not only opens up new opportunities for enhanced UV-C light extraction but also provides valuable insights for future endeavors in device fabrication and epitaxial film growth.

Mechanical Milling – Induced Microstructure Changes in Argyrodite LPSCl Solid‐State Electrolyte Critically Affect Electrochemical Stability

AbstractMicrostructure of argyrodite solid‐state electrolyte (SSE) critically affects lithium metal electrodeposition/dissolution. While the stability of unmodified SSE is mediocre, once optimized state‐of‐the‐art electrochemical performance is achieved (symmetric cells, full cells with NMC811) without secondary interlayers or functionalized current collectors. Planetary mechanical milling in wet media (m‐xylene) is employed to alter commercial Li6PS5Cl (LPSCl) powder. Quantitative stereology demonstrates how milling progressively refines grain and pore size/distribution in the SSE compact, increases its density, and geometrically smoothens the SSE‐Li interface. Mechanical indentation demonstrates that these changes lead to reduced site‐to‐site variation in the compact's hardness. Milled microstructures promote uniform early‐stage electrodeposition on foil collectors and stabilize solid electrolyte interphase (SEI) reactivity. Analysis of half‐cells with bilayer electrolytes demonstrates the importance of microstructure directly contacting current collector, with interface roughness due to pore and grain size distribution being key. For the first time, short‐circuiting Li metal dendrite is directly identified, employing 1.5 mm diameter “mini” symmetrical cell and cryogenic focused ion beam (cryo‐FIB) electron microscopy. The branching sheet‐like dendrite traverses intergranularly, filling the interparticle voids and forming an SEI around it. Mesoscale modeling reveals the relationship between Li‐SSE interface morphology and the onset of electrochemical instability, based on underlying reaction current distribution.

A study on the resist performance of inorganic-organic resist materials for EUV and electron-beam lithography

In the realization of further miniaturization at scales of 10 nm and below in semiconductor devices, it is essential to create new resist designs, such as hybrid inorganic-organic resist materials for ionizing radiation, in order to clarify the effect the structure of metal resist on resist performance. In this study, some hybrid inorganic-organic resist materials known as metal-oxo clusters were synthesized, and their lithographic characteristics were investigated to clarify the relationship between resist performance, such as sensitivity, resolution, and their absorption coefficient or cross section, and the density of their elements by using EUV and electron-beam (EB) exposure. Our results indicated that the sensitivity in Hf-based oxo clusters was higher than that of Ti-based and Zr-based oxo clusters in both EB and EUV exposure. Although the exposure dose was not optimized, the patterns of Ti-based, Zr-based, and Hf-based oxo clusters showed 100, 50, and 32 nm line-and-space patterns at doses of 250, 80, and 25 μC cm−2, respectively. We clarified that it is very important for new resist designs such as hybrid inorganic-organic resists to increase the photo-absorption cross section and density of elements for EUV and EB without degradation of film quality. In addition, the size and homogeneity of the building blocks and film quality are very important for the resist performance of hybrid inorganic-organic resist materials. Furthermore, it is clarified that the etch durability of metal-oxo clusters is higher than conventional resist materials, and this is much increased by annealing them at 800 °C.

Exploring self-consistent 2.5D flare simulations with MPI-AMRVAC

Context. Multidimensional solar flare simulations have not yet included a detailed analysis of the lower atmospheric responses, such as downflowing chromospheric compressions and chromospheric evaporation processes. Aims. We present an analysis of multidimensional flare simulations, including an analysis of chromospheric upflows and downflows that provides important groundwork for comparing 1D and multidimensional models. Methods. We followed the evolution of a magnetohydrodynamic standard solar flare model that includes electron beams and in which localized anomalous resistivity initiates magnetic reconnection. We varied the background magnetic field strength to produce simulations that cover a large span of observationally reported solar flare strengths. Chromospheric energy fluxes and energy density maps were used to analyze the transport of energy from the corona to the lower atmosphere, and the resultant evolution of the flare. Quantities traced along 1D field lines allowed for detailed comparisons with 1D evaporation models. Results. The flares produced by varying the background coronal field strength between 20 G and 65 G have GOES classifications between B1.5 and M2.3. All produce a lobster claw reconnection outflow and a fast shock in the tail of this flow with a similar maximum Alfvén Mach number of ∼10. The impact of the reconnection outflow on the lower atmosphere and the heat conduction are the key agents driving the chromospheric evaporation and “downflowing chromospheric compressions”. The peak electron beam heating flux in the lower atmospheres varies between 1.4 × 109 and 4.7 × 1010 erg cm−2 s−1 across the simulations. The downflowing chromospheric compressions have kinetic energy signatures that reach the photosphere, but at subsonic speeds they would not generate sunquakes. The weakest flare generates a relatively dense flare loop system, despite having a negative net mass flux, through the top of the chromosphere, that is to say, more mass is supplied downward than is evaporated upward. The stronger flares all produce positive mass fluxes. Plasmoids form in the current sheets of the stronger flares due to tearing, and in all experiments the loop tops contain turbulent eddies that ring via a magnetic tuning fork process. Conclusions. The presented flares have chromospheric evaporation driven by thermal conduction and the impact and rebound of the reconnection outflow, in contrast to most 1D models where this process is driven by the beam electrons. Several multidimensional phenomena are critical in determining plasma behavior but are not generally considered in 1D flare simulations. They include loop-top turbulence, reconnection outflow jets, heat diffusion, compressive heating from the multidimensional expansion of the flux tubes due to changing pressures, and the interactions of upward and downward flows from the evaporation meeting the material squeezed downward from the loop tops.

3D morphology of the petal-like precipitates in Cu-Fe alloys: Experimental study and phase field modelling

Precipitation hardening is a well-known phenomenon which is widely harnessed in alloy design strategy. In particular, the microstructural features such as shape, size, precipitate number density and volume fraction determine the mechanical behaviour of materials. During service, the morphology of precipitates sometimes achieves a complex 3D shape upon displaying branching and/or splitting patterns. Unfortunately, the detailed information about this intricate morphology cannot be retrieved through traditional experimental techniques based on 2D visualization. Here, we report the implementation of a 3D analysis technique combining Focused Ion Beam (FIB) and Scanning Electron Microscopy (SEM) tomography to visualize the atypical petal-like morphology of Fe-rich precipitates in a Cu-Fe alloy. Using Phase-Field modelling (PFM), we identify the mechanism responsible for the unusual morphologies of Fe-rich particles. Our work highlights the significance of 3D characterization of precipitates and provides a fascinating pathway for refining understanding of precipitation mechanisms in metals and alloys.

Microstructural and phase evolution of Ti6Al4V in electron beam wire additive manufacturing and on the subtransus quenching and normalization

Structural evolution of electron beam wire additively manufactured Ti–6Al–4V subjected to quenching and normalization from the subtransus temperatures 900 °C has been studied. Different phase states and structures have been obtained in the as-built sample such as grain-boundary (allotriomorphic) α-GB, Widmanstatten (basket-weave) α/β as well as α/α′′ and α/α2. Quenching resulted in retaining the α-GB and α/α2 structures while α/β transformed into α/α′. Normalization caused formation of α′′-Ti and ω-Ti phases in addition to the primary α. The α-Ti variant selection depended on the intensity of heating so that the number of Type-4-2 grain boundaries with misorientation angles 60, 60.8, 63.3° increased from the as-built to normalized sample. Quenching provided improvement of both tensile strength and plasticity.

Techno-economic analysis of electron beam irradiation pretreatment of corn straw for anaerobic digestion

The complexity of anaerobic digestion process and the risks of investing in new technologies are the main obstacles to improving anaerobic digestion technology. There is still a gap between research results and commercial applications. This study investigated the techno-economic feasibility and bottlenecks of introducing electron beam irradiation pretreatment technology into the commercial-scale anaerobic digestion plant. Model construction, parameter initialization and economic analysis were performed in SuperPro Designer software. The parameters used in the model were derived from experimental results, software built-in model and recent literature. The results show that the gross margin, return on investment, payback time, internal rate of return, and net present value of the system with electron beam irradiation pretreatment are 4.4 %, 9.8 %, 10.1 years, 8.0 % and $0.6 million, respectively. The corresponding values of the system without electron beam irradiation pretreatment are 9.9 %, 11.1 %, 8.9 years, 9.7 % and $1.5 million, respectively. The main factor affecting gross profit is tipping fee of liquid anaerobic digestion effluent, followed by plant size of anaerobic digestion, degradation efficiency of corn straw, and compost price. This study has guiding significance for the application of electron beam irradiation pretreatment technology in the production of renewable energy from lignocellulosic biomass.

Microstructure and Properties of TiN/TiCN/Al2O3/TiN Coating Enhanced by High-Current Pulsed Electron Beam

In this work, a TiN/TiCN/Al2O3/TiN coating deposited onto cemented carbide matrix by chemical vapor deposition was irradiated by high-current pulsed electron beam (HCPEB). The influence of pulse times on the phase composition, microstructure, and mechanical properties of the coating investigated. The results showed that no new phase was produced, the grain size of the coating surface was refined, the surface became flat, and the surface roughness decreased after HCPEB treatment. The TiN/TiCN/Al2O3/TiN coating presented a smooth surface with good mechanical performance after HCPEB. A maximum hardness was obtained after 15 pulses, and the 15-pulse irradiated coating showed better wear resistance. The improvement in the coating’s performance after irradiation was mainly attributed to the formation of grain refinement and crystal defects, as well as the change of stress field inside the coating. The objective of this study was to evaluate the potential of HCPEB modification in the preparation of high-performance coating by analyzing the microstructure and property of coating under different pulses.

Mathematical modelling of the emission characteristics of a field electron cathode in a scanning electron microscope under biosampling conditions

Currently, the use of electron microscopes in medicine is developing intensively, including scanning electron microscopes (SEM), which are designed to solve a huge number of problems in various fields with a wide range of electron accelerating voltages and electron beam energies. The development of an SEM with certain emission characteristics, with a range of lower beam energies for the study of biological samples, is an urgent task because modifying the SEM to solve problems in medicine, for example, would make it possible to obtain higher-quality images of biospecimens for diagnostics and monitoring the effectiveness of therapy. To develop new SEMs with certain characteristics, it is proposed to conduct less expensive research using numerical methods based on mathematical models of processes in electron-optical SEM systems. In this regard, this work sets the task of determining the size and shape of the beam, the main emission characteristics of the field electron cathode (FEC) of the SEM, which is under the influence of the electric field that excites electron emission and the external longitudinal magnetic field by studying the movement of the outermost electron of the beam, taking into account the influence of space charge beam electrons, external magnetic field. In the model, the FEC is approximated by a paraboloid of rotation, and the concept of a boundary “outermost” electron is introduced, the trajectory of which determines the shape and size of the beam. The problem of calculating the emission characteristics along the trajectory of the outermost electron of a FEC is solved using a mathematical model that includes the following equations: motion of the “outermost” electron, Maxwell outside and inside the beam, continuity of the current density, Fowler-Nordheim equation. As a result, a system of 18 first-order ordinary differential equations was obtained, the numerical calculation of which using the 4th order Runge-Kutta method allows us to obtain the emission characteristics of the FEC. As a result, it is suggested that it would be feasible to modify SEMs for more effective use in the medical field, taking into account their increasing use in disease diagnosis and the possible improvement of image quality through the development of FEC SEMs with more suitable characteristics.

A comprehensive investigation of the performance of a commercial scintillator system for applications in electron FLASH radiotherapy.

Dosimetry in ultra-high dose rate (UHDR) beamlines is significantly challenged by limitations in real-time monitoring and accurate measurement of beam output, beam parameters, and delivered doses using conventional radiation detectors, which exhibit dependencies in ultra-high dose-rate (UHDR) and high dose-per-pulse (DPP) beamline conditions. In this study, we characterized the response of the Exradin W2 plastic scintillator (Standard Imaging, Inc.), a water-equivalent detector that provides measurements with a time resolution of 100Hz, to determine its feasibility for use in UHDR electron beamlines. The W2 scintillator was exposed to an UHDR electron beam with different beam parameters by varying the pulse repetition frequency (PRF), pulse width (PW), and pulse amplitude settings of an electron UHDR linear accelerator system. The response of the W2 scintillator was evaluated as a function of the total integrated dose delivered, DPP, and mean and instantaneous dose rate. To account for detector radiation damage, the signal sensitivity (pC/Gy) of the W2 scintillator was measured and tracked as a function of dose history. The W2 scintillator demonstrated mean dose rate independence and linearity as a function of integrated dose and DPP for DPP ≤ 1.5Gy (R2>0.99) and PRF ≤ 90Hz. At DPP>1.5Gy, nonlinear behavior and signal saturation in the blue and green signals as a function of DPP, PRF, and integrated dose became apparent. In the absence of Cerenkov correction, the W2 scintillator exhibited PW dependence, even at DPP values<1.5Gy, with a difference of up to 31% and 54% in the measured blue and green signal for PWs ranging from 0.5 to 3.6 µs. The change in signal sensitivity of the W2 scintillator as a function of accumulated dose was approximately 4%/kGy and 0.3%/kGy for the measured blue and green signal responses, respectively, as a function of integrated dose history. The Exradin W2 scintillator can provide output measurements that are both dose rate independent and linear in response if the DPP is kept ≤1.5Gy (corresponding to a mean dose rate up to 290Gy/s in the used system), as long as proper calibration is performed to account for PW and changes in signal sensitivity as a function of accumulated dose. For DPP>1.5Gy, the W2 scintillator's response becomes nonlinear, likely due to limitations in the electrometer related to the high signal intensity.

Preparation and properties of a bismaleimide resin modified with a propargyl compound for electron beam irradiation curing

N, N, N′, N′ -Tetrapropargyl- p, p′-diaminodiphenylmethane (TPDDM) is synthesized and used to blended with 4,4′-bismaleimide diphenylmethane (BDM) as propargyl compound in a molten state to obtain a TPDDM modified bismaleimide (BTP) resin. The BTP resins are cured under electron-beam (EB) irradiation as well as heat. The cure degree and reactions of BTP resins are studied. The thermal stability and mechanical properties of the cured BTP resins are further investigated. The results show that the BTP resins can be cured under EB irradiation and have over 82% degree of cure, which increases with the increase of EB irradiation dose. The cure reactions of EB-cured BTP resin are similar to that of heat-cured BTP resin. The temperature at 5% weight loss ( Td5) and mechanical properties of the cured BTP resins are close analogies between EB and heat cure processes although the cure degrees of EB-cured BTP resins are lower. The glass transition temperature ( Tg) and flexural modulus of the EB-cured BTP resin are higher than that of the heat-cured BTP resin. The Tg of the EB-cured BTP resin can reach over 385°C. The TPDDM-modified BDM is a candidate bismaleimide resin for the EB irradiation curing process in advanced manufacturing technology.