Inelastic Energy Loss Research Articles

Breakage dynamics and scaling of wet aggregates of rigid particles

The mechanical behaviour of wet particle aggregates is crucial in many granular processes such as wet granulation and soil degradation. However, the interplay of capillary and viscous forces for aggregate stability and breakage have remained elusive due to the complexity of granular dynamics. We use particle dynamics simulations to analyse the deformation and breakage of wet aggregates colliding with a flat wall. The aggregates are composed of spherical particles and the effect of liquid bonds is modelled through capillary and lubrication forces acting between particles. We perform an extensive parametric study by varying surface tension, impact velocity and liquid viscosity in a broad range of values. We show that when lubrication force is neglected, aggregate breakage is fully controlled by the reduced kinetic energy $\xi$ , defined as the ratio of incident kinetic energy to the initial capillary energy. At low values of $\xi$ , the aggregate deforms without breakage due to inelastic energy loss induced by rearrangements and loss of capillary bonds, whereas above a critical value of $\xi$ it breaks into smaller aggregates due to the transfer of kinetic energy from aggregate to fragments. In the presence of lubrication forces, the crossover from capillary to viscous regime is controlled by the capillary number, defined as the ratio of viscous dissipation to capillary energy. We find that the critical value of $\xi$ for aggregate breakage in the viscous regime increases as a power law with capillary number while the effective restitution coefficient follows the same trend as in the capillary regime.

Assessing trajectory-dependent electronic energy loss of keV ions by a binary collision approximation code

The inelastic energy deposition of energetic ions is a decisive quantity for numerous industrial-scale applications, such as sputtering and ion implantation, yet the underlying physics being governed by dynamic many-particle processes is commonly only qualitatively understood. Recently, transmission experiments on single-crystalline targets (Phys. Rev. Lett. 124, 096601 & Phys. Rev. A 102, 062803) revealed a complex energy scaling of the inelastic energy loss of low-energy ions heavier than protons along different trajectories. We use a Monte Carlo like binary collision approximation code equipped with an impact-parameter-dependent modeling of the inelastic energy losses to assess the role of local contributions to electronic excitations in these cases. We compare angular intensity distributions of calculated trajectories with experimental results for 50-keV 4He and 100-keV 29Si ions transmitted in a time-of-flight setup through single-crystalline silicon (001) foils with nominal thicknesses of 200 and 50 nm, respectively. In these calculations, we employ different models of electronic energy loss, i.e., local and nonlocal forms for light and heavy projectiles. We find that the vast number of projectiles are eventually channeled along their trajectories, regardless of the alignment of the crystal with respect to the incident beam. It is, however, only when local electronic energy loss is considered that the simulated two-dimensional maps and energy distributions show excellent agreement with the experimental results, where channeling leads to significantly reduced stopping, especially for heavier projectiles. We demonstrate the relevance of these effects for ion implantations by assessing the nonlinear and nonmonotonic scaling of the ion range with the thickness of a random surface layer. Published by the American Physical Society 2024

Nitrogen admixture-driven electron cooling and plasma bullet dynamics in atmospheric-pressure dc nanosecond-pulsed argon jet plasmas

We present experimental measurements of the electron temperature and density profiles and analyze the dynamics of a plasma bullet at volumetric concentrations of nitrogen admixture, 0%–3%, in an atmospheric-pressure nanosecond-pulsed argon jet plasma. Time-resolved Thomson scattering measurements taken 2.5 mm from the exit plane reveal that the temporal maximum of electron temperature and density reduced by as much as 55% and 29%, respectively, when mixing only 3% nitrogen to pure argon. These trends were consistent across axial locations from 2.5 to 14 mm from the exit plane for both electron temperature and density at nitrogen admixture plasmas. Moreover, the propagation velocity and length of the plasma bullet decreased by 13% while the radius by 23% at 3%-nitrogen admixture when compared to the pure argon jet case. The analysis suggests that the nitrogen admixture causes electron cooling due to inelastic energy losses, which results in a reduced electron density and propagation velocity due to a decrease in the electron-impact ionization rate. It is therefore inferred that the electron cooling mechanism and reduced density at nitrogen admixture will significantly impact the electron-impact excitation rate coefficient of nitrogen as well as the concentration of the precursor species such as N2(A3Σu+).

Influences of Graphene Oxide on Mechanical Properties and Mesoscopic Deformation and Failure Process of Concrete

In this research, graphene oxide (GO) was integrated into concrete to assess its effectiveness as an additive. Triaxial compression permeability experiments, variable‐angle (30°, 45°, and 60°) shear experiments, and dynamic compression experiments were conducted on graphene oxide concrete (GOC) and normal concrete (NC). The Holmquist–Johnson–Cook model and LS‐DYNA software were utilized to simulate the mesoscopic failure of NC and GOC under impact loading. The mechanism of GO was examined through scanning electron microscope (SEM) microscopic scanning and energy dispersive spectroscopy (EDS) energy spectrum testing. The findings demonstrate that the contain of GO significantly enhances the destruction resistance of concrete under triaxial compression. The permeability of both NC and GOC exhibits a negative exponential decrease with increasing confining pressure, and carbon fiber reduces concrete permeability by 17.79%–60.9%. Compared to NC, the cohesion and internal friction angle of GOC increased by 7.80% and 8.55%, respectively. GO also improves energy conversion and storage capacity during the elastic stage of concrete, reducing inelastic energy loss during shear processes. Although, both NC and GOC exhibit strain rate sensitivity, the DIF value of GOC surpasses that of NC and the disparity between the two intensifies with increasing impact pressure. Simulation results indicate that the number of crushing units in GOC is significantly lower than in NC, maintaining integrity. Analysis of SEM microscopic test results reveals that the distribution of cement hydration products in NC is uniform, whereas in GOC, it displays regional characteristics, a phenomenon corroborated by EDS energy spectrum test results.

Contribution of molecular orbital promotion to the electronic stopping cross section at slow atom solid collisions

The autoionization states formation due to MO promotion during collisions of keV-energy ions with solids produces a dominant contribution to inelastic energy losses and, accordingly, to the electronic stopping powers dE/dx. The correlations of emitted electron numbers δ with the values of inelastic energy losses Q are shown. When corresponding distances of closest approach are reached, the MO orbital promotion produces a stepwise increase in values of Q and δ. Based on the measured ionization cross-sections and Q values, electronic stopping powers can be calculated. For the case when such measurements are not available, the scaling for the ionization cross section in the case of K, L and M shell excitation can be used.We have proposed a new model for calculating electronic stopping power in which the formation of autoionization states in atomic collisions makes a dominant contribution to the inelastic energy loss and ionization of colliding atoms. Using data on the values of energy losses and ionization cross sections, it is possible to calculate the values of electronic stopping. The model predicts the threshold character of the dE/dx dependence versus the collision velocity and an increase in inelastic energy losses at the collision energies at which the threshold for the corresponding MO promotion occurs.

Contribution of molecular orbital promotion to the electronic stopping cross section at slow atom solid collisions

The autoionization states formation due to MO promotion during collisions of keV-energy ions with solids produces a dominant contribution to inelastic energy losses and, accordingly, to the electronic stopping powers dE/dx. The correlations of emitted electron numbers δ with the values of inelastic energy losses Q are shown. When corresponding distances of closest approach are reached, the MO orbital promotion produces a stepwise increase in values of Q and δ. Based on the measured ionization cross-sections and Q values, electronic stopping powers can be calculated. For the case when such measurements are not available, the scaling for the ionization cross section in the case of K, L and M shell excitation can be used.We have proposed a new model for calculating electronic stopping power in which the formation of autoionization states in atomic collisions makes a dominant contribution to the inelastic energy loss and ionization of colliding atoms. Using data on the values of energy losses and ionization cross sections, it is possible to calculate the values of electronic stopping. The model predicts the threshold character of the dE/dx dependence versus the collision velocity and an increase in inelastic energy losses at the collision energies at which the threshold for the corresponding MO promotion occurs.

Obrazovanie i raspad avtoionizatsionnykh sostoyaniy - osnovnoy mekhanizm neuprugikh poter' pri stolknoveniyakh atomov keV-energiy

It has been shown that the formation of autoionization states makes the dominant contribution to inelastic energy loss and to ionization in keV atomic collisions, i.e., at velocities lower than the velocities of atomic electrons. Scaling laws have been proposed to calculate the cross sections for the formation of vacancies in inner K and L electron shells of colliding atoms. A model has been proposed to relate ionization processes and the observed inelastic energy losses. Auger transitions in a short-lived quasimolecule formed by two atoms approaching each other have been studied. The nature of the continuous component in electron spectra emitted in collisions has been determined. It has been shown that the excitation of autoionization states determines the stopping cross sections for keV atoms in matter.

Formation and Decay of Autoionization States as the Main Inelastic Energy Loss Mechanism in keV Atomic Collisions

Formation and Decay of Autoionization States as the Main Inelastic Energy Loss Mechanism in keV Atomic Collisions

New model of the excess charge generation by nuclear reaction products in electronic components

A method for calculating the cross-section for single event effect (SEE) in the electronics operation is proposed; it is caused by secondary ions — products of the interaction between a high-energy proton with the atomic nucleus of one of the materials of an integrated circuit. To estimate the excess charge generated in this case, the contribution of all secondary ions, including those born outside the sensitive layer, is taken into account in the model. Along with the traditional approach based on inelastic energy losses, the model considers the process of atom ionization in the approximation of the effective ion charge. The new method gives lower values of the number of electron–hole pairs and the SEE cross-section.

3D Nanoprinting Replication Enhancement Using a Simulation-Informed Analytical Model for Electron Beam Exposure Dose Compensation.

3D nanoprinting, using focused electron beam-induced deposition, is prone to a common structural artifact arising from a temperature gradient that naturally evolves during deposition, extending from the electron beam impact region (BIR) to the substrate. Inelastic electron energy loss drives the Joule heating and surface temperature variations lead to precursor surface concentration variations due, in most part, to temperature-dependent precursor surface desorption. The result is unwanted curvature when prescribing linear segments in 3D objects, and thus, complex geometries contain distortions. Here, an electron dose compensation strategy is presented to offset deleterious heating effects; the Decelerating Beam Exposure Algorithm, or DBEA, which corrects for nanowire bending a priori, during computer-aided design, uses an analytical solution derived from information gleaned from 3D nanoprinting simulations. Electron dose modulation is an ideal solution for artifact correction because variations in electron dose have no influence on temperature. Thus, the generalized compensation strategy revealed here will help advance 3D nanoscale printing fidelity for focused electron beam-induced deposition.

Revealing two-stage phase transition process in defective KTaO3 under inelastic interactions

The interactions of ions with defective KTaO3 has been studied by irradiating pre-damaged single crystal KTaO3 with 5 MeV C, 7 MeV Si and 12 MeV O ions at 300 K. By exploring these processes in KTaO3, the results show that, for a pre-damaged fractional disorder level of 0.3 and inelastic electronic energy loss, Se, ≥ 4.65 keV/nm (7 MeV Si ions), the synergistic interaction of Se with defects enables amorphous ion track creation. At lower values of Se (5 MeV C and 12 MeV O), minor increases in disorder are observed initially over a region of depth at an ion fluence of 10 ions/nm2, which may be due to dissolution of pre-existing interstitial or amorphous clusters; however, with further increase in ion fluence, a transition from irradiation-induced disorder production to ionization-induced damage recovery processes, not previously reported in KTaO3, is observed.

Bandgap modulation and electrical characteristics of (AlxGa1−x)2O3/4H-SiC thin film heterostructures

In this work, (AlxGa1−x)2O3 thin films were grown on a 4H-SiC substrate by radio frequency (RF) sputtering. (AlxGa1−x)2O3 targets with different nominal Al content xt: 0, 0.1, 0.4, 0.8, and 1 were used for RF sputtering. Samples were subsequently annealed at 800 °C to enhance film crystallinity. X-ray diffraction analysis revealed the improved crystallinity for increased Al content (xt), ranging from a ratio of 0 to 0.4 (in relation to Al+Ga content). The films with Al content of 0.8 and 1 exhibited poor crystallinity. The chemical compositions of the Al, Ga, and O atoms were consistent with those of the sputtering targets. Furthermore, the analysis of the inelastic energy loss from X-ray photoelectron spectroscopy confirmed that bandgap tuning is possible for (AlxGa1−x)2O3 using the RF sputtering method. Hall mobility improved up to 17.1%, from 21.90 (xt: 0) to 25.65 (xt: 0.4) cm2V−1s−1. I−V characteristics corresponded well with the Hall measurement. Therefore this study effectively demonstrated the tuning of the bandgap of (AlxGa1−x)2O3 by varying the Al composition. Further, the electrical properties of the (AlxGa1−x)2O3 can be improved or maintained from that of conventional Ga2O3 devices by optimizing the growth ambient.

Thermal non-equilibrium simulation of diffuse and constricted anode attachments of a high intensity transferred arc

The arc attachment modes on anode of a high intensity argon arc with water-cooled constrictor are numerically investigated by a two-temperature model. An inelastic electron energy loss factor, representing the energy loss due to non-equilibrium chemical kinetic processes, is introduced to the electron energy equation. Two different attachment modes, i.e., diffuse and constricted anode attachments, are obtained based on the experimental conditions. Results for both anode attachment modes indicate that the temperature discrepancy between electrons and heavy particles is very pronounced in the arc fringes and in the regions close to the anode. By comparing the axial and radial Lorentz forces between the diffuse and constricted anode attachments, it is found that the larger axial and radial Lorentz forces in a constricted anode attachment are the main cause for the formation and maintenance of anode jet. The effects of inelastic electron energy loss on different anode attachment modes are discussed and the results indicate that it is very important to consider the chemical non-equilibrium processes in an appropriate way for predicting arc attachment modes on anode reasonably.

Cone-Size Dependence of Jet Suppression in Heavy-Ion Collisions.

The strong suppression of high-p_{T} jets in heavy-ion collisions is a result of elastic and inelastic energy loss suffered by the jet multiprong collection of color charges that are resolved by medium interactions. Hence, quenching effects depend on the fluctuations of the jet substructure that are probed by the cone-size dependence of the spectrum. In this Letter, we present the first complete, analytic calculation of the inclusive R-dependent jet spectrum in PbPb collisions at LHC energies, including resummation of energy loss effects from hard, vacuumlike emissions occurring in the medium and modeling of soft energy flow and recovery at the jet cone. Both the geometry of the collision and the local medium properties, such as the temperature and fluid velocity, are given by a hydrodynamic evolution of the medium, leaving only the coupling constant in the medium as a free parameter. The calculation yields a good description of the centrality and p_{T} dependence of jet suppression for R=0.4 together with a mild cone-size dependence, which is in agreement with recent experimental results. Gauging the theoretical uncertainties, we find that the largest sensitivity resides in the leading logarithmic approximation of the phase space of resolved splittings, which can be improved systematically, while nonperturbative modeling of the soft-gluon sector is of relatively minor importance up to large cone sizes.

Measuring Energy Gaps of Organic Semiconductors by Electron Energy Loss Spectroscopies

Herein is explored the use of electron energy loss due to π–π* transition to measure energy gaps of organic semiconductors. Sources of kinetic electrons studied include an external electron gun (reflection electron energy loss spectroscopy (REELS)) and an internal core shell excitation by X‐rays (i.e., X‐ray photoelectron spectroscopy (XPS)). To obtain the bandgap accurately, a data analysis method is proposed to extract the optical bandgap from the π–π* inelastic electron energy loss spectra. This method uses a Gaussian function to fit experimental data yielding a peak width w and position E0. The energy gap of an organic semiconductor, i.e., the onset of the π–π* transition peak, can then be calculated by . Through examination of 11 organic semiconductors, it is found that the bandgaps measured by REELS agree well with optical bandgaps. The bandgaps measured by XPS, however, do not always agree with optical gaps. This indicates that the XPS π–π* inelastic peak in some material systems may convolute with other core shell processes such as shake‐up. In addition, it is shown that all key energy structures of an organic semiconductor can be measured concurrently by REELS and ultraviolet photoemission spectroscopy.

Low temperature growth of Beryllium Oxide thin films prepared via plasma enhanced atomic layer deposition

Beryllium oxide (BeO) is a unique metal oxide that exhibits high thermal conductivity and a high dielectric constant, even though it has a large bandgap energy. These characteristics can potentially address the electromagnetic issues associated with contemporary nanoscale electronic devices. However, BeO is mainly used as a heat-dissipating and refractory layer in sintering powders. To extend the use of BeO in semiconductor front-end-of-line processes, we developed nanoscale BeO thin films by using state-of-the-art atomic layer deposition (ALD). The physical and electrical properties of the BeO thin films were evaluated by introducing O2 plasma and H2O vapor as oxidation sources for the ALD process. A controlled plasma-enhanced ALD (PEALD) process led to the production of c-axis grown crystalline wurtzite BeO (002) films with a high growth rate per cycle at low substrate temperatures. The plasma energy was found to be adequately compensate for the high substrate temperature required for thermal ALD (ThALD). The bandgap energy (7.9 eV), calculated via inelastic energy loss analysis, and the dielectric constant (8.75) and breakdown voltage (10.3 MV/cm), obtained from MOS capacitors, are optimal for nanoscale electronic device applications.

Anisotropy of the Runaway Electron Generation Process in Strongly Inhomogeneous Electric Fields

An investigation of runaway electron (RE) kinetics under the influence of a strongly inhomogeneous electric field was carried out by means of 2-D analytical and 2-D numerical Monte–Carlo approaches. Several shapes of cathodes generating an inhomogeneous electric field were studied. Within the developed 2-D analytical model, blade-shaped and cone-shaped cathodes were considered. The voltage values which allow electrons to scatter at large angles close to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula> /2 near a blade-shaped cathode were determined. Also, it was shown that the RE scatter angles are larger for the blade (in comparison with the ones for the cone) due to the electric field defocusing effect. Within the framework of the numerical 2-D Monte–Carlo model, a cathode was assumed to have a parabolic shape. Inapplicability of the classical runaway criterion in strongly inhomogeneous electric fields was demonstrated. Also, it was shown that the cathode surface domain of electron emission and an initial direction of electron motion have a strong influence on their energy balance and, hence, on the probability for electrons to transit into the continuous accelerating regime. Energy losses of REs were estimated. A correlation between the full-width at half-maximum of the RE energy spectrum and an inelastic energy loss value was proposed.

An investigation of maximum particle velocity as a universal invariant-Defined by a statistical measure of failure or plastic energy loss for acoustofluidic applications.

Materials under vibration experience internal stress waves that can cause material failure or energy loss due to inelastic vibration. Traditionally, failure is defined in terms of material acceleration, yet this approach has many drawbacks, principally because it is not invariant with respect to scale, type of vibration, or material choice. Here, the likelihood of failure is instead considered in terms of the maximum vibration or particle velocity for various metals, polymers, and structural materials. The exact relationship between the maximum particle velocity and the maximum induced stress may be derived, but only if one knows the details of the vibration, material, flaws, and geometry. Statistical results with over thousands of individual trials are presented here to demonstrate a wide variety of vibrations across a sufficient variety of these choices. Failure in this context is defined as either fracture or plastic yield, the latter associated with inelastic deformation and energy loss during vibration. If the maximum permissible cyclical stress in material vibration is known, to at least an order of magnitude, the probability of this type of failure may be computed for a range of vibration velocities in each material. The results support the notion that a maximum particle velocity on the order of 1 m/s is a universal and critical limit that, upon exceeding, causes the probability of failure to become significant regardless of the details of the material, geometry, or vibration. We illustrate this in a specific example relevant to acoustofluidics, a simple surface acoustic wave device. The consequences of particle velocity limit analysis can effectively be used in materials and structural engineering to predict when dynamic material particle velocity can cause inelastic losses or failure via brittle fracture, plastic deformation, or fatigue failure.

Inelastic energy losses for ions with pre-equilibrium charge distribution

Method for evaluation of inelastic energy losses of ions with pre-equilibrium charge distribution is proposed. The ion energy losses in various inelastic processes are studied. In this model the difference between the energy losses of ions with different charges are taken into account. The process of target atom ionization is the main contribution to inelastic energy losses and the energy losses in charge-changing processes for ions with pre-equilibrium charge distribution can be considered as a correction.

Inelastic energy loss of Ar ions scattered Al2O3 surface under grazing incidence

In this paper presents the investigation of the surface Al2O3 by ion scattering spectroscopy. The trajectory of small angle scattered ions calculated by the method of binary collision approximation. It was found dependence of inelastic energy loss and trajectories of scattered ions. The value of inelastic energy loss scattered ions almost depend to the angle of incidence and the geometrical parameters of surface semichannels.