Projectile Energy Research Articles

Theoretical study of electron impact single ionization of neon by multicenter three distorted-wave method at low projectile energy: an overall agreement with experiment

Universal theoretical description of electron impact single ionization process for complex atoms and molecules is a long-standing challenge. A perturbative approach named multicenter three distorted wave method (MCTDW) has recently been developed by our group, aiming at calculating (e, 2e) fully differential cross sections for molecular target. In MCTDW method, the incident, scattered and ejected electrons are described by distorted waves using single center expansion technique. The continuum wave functions of the incident and two outgoing electrons are solved in the potential of neutral molecule and ion, respectively. The accuracy and generality of this method has been demonstrated for water molecule as well as simple two-electron atom helium (2018 Phys. Rev. A 98 042710) . Here MCTDW is extended to investigate more complex multi-electron atom neon of electron impact ionization from its 2p orbital at projectile energy of 100 eV and 65 eV. The results are compared with the internormalized experiments reported in the literatures (2013 Phys. Rev. Lett. 110 153202; 2015 Phys. Rev. A. 91 032707). An overall agreement has been achieved with experimental data for different scattering angles and energies, as well as theoretical calculations employing nonperturbative B-spline R-matrix with pseudostates approach.

Triple-differential cross sections for (e,2e) electron-impact ionization dynamics of tetrahydrofuran at low projectile energy

We study the triple-differential cross section (TDCS) for the electron-impact ionization of the highest occupied molecular orbital of tetrahydrofuran at a projectile energy ${E}_{0}=91\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$. The experimental data were measured using a reaction microscope, which covers a large part of the full solid angle for the secondary electron emission with energies ranging from 6 to 15 eV, and projectile scattering angles ranging from $\ensuremath{-}{10}^{\ensuremath{\circ}}$ to $\ensuremath{-}{20}^{\ensuremath{\circ}}$. The experimental TDCSs are internormalized across all measured scattering angles and ejected energies. They are compared with predictions from the multicenter distorted-wave (MCDW) approximation and a modified MCDW-Nee method which includes the postcollision interaction (PCI) using the Ward-Macek factor. Additional calculations were obtained using a molecular three-body distorted-wave (M3DW) approach which accounts for PCI in an exact treatment. Generally, the MCDW-Nee and M3DW models show better agreement with experiment than the MCDW calculations. This shows the importance of accounting for PCI for low-energy outgoing electrons in electron-impact ionization processes.

Influence of the incident energy of the projectile and of different targets on the production of neutron-rich nuclei

The multinucleon transfer reaction is treated as a diffusion process by solving four-variable master equations within the dinuclear system (DNS) concept. The reaction systems $^{136}\mathrm{Xe}+^{208}\mathrm{Pb}$ and $^{136}\mathrm{Xe}+^{198}\mathrm{Pt}$ are investigated and compared to the experimental data. The calculated results correctly describe the magnitude and maxima of the observed transfer cross sections for a wide range of transfers. One finds that the neutron richness of the reaction products is strongly dependent on the projectile energy near the Coulomb barrier. By comparing the obtained results for the above two reaction systems, the absolute cross sections from the $^{208}\mathrm{Pb}$ target predict smaller production cross sections for neutron-deficient nuclei and moderately neutron-rich nuclei as compared to $^{198}\mathrm{Pt}$.

X-ray Computed Tomography for the Development of Ballistic Composite.

This paper presents the results of research on ballistic panels made of polymer–matrix composites (PMCs). The analysis covers two types of composites produced by the authors based on high-density polyethylene (PEHD) and polypropylene (PP) reinforced with aramid fabric. Ballistic tests were carried out with the use of two types of projectile: 0.38 Special, and 9 × 19 Parabellum, which are characterized by different velocity and projectile energy. The study presents the X-ray computed tomography (XCT) analysis for structure assessment of ballistic panels and its impact behavior, further compared to the results of computer simulations conducted using the numerical analysis. The quality of the manufactured panels and their damage caused by a ballistic impact was assessed using a multi-scale geometry reconstruction. The mesoscale XCT allowed the internal composite geometry to be analyzed, as well as a unit cell of the representative volume element (RVE) model to be built. The RVE model was applied for homogenization and finite element (FEA) simulation of projectile penetration through the ballistic panel. The macroscale XCT investigation allowed for the quantitative description of the projectile’s impact on the degree of delamination and deformation of the panels’ geometry.

Electron-capture cross sections from atoms to hydrogen-like projectiles

State-selective total and projectile angular-differential cross sections for single-electron transfer to the ground state from atoms in collisions with hydrogen-like projectiles are calculated by means of the four-body distorted wave approximation in the energy range from 25 to 2500 keV amu−1. In the initial channel, the effect of the dynamic electron–electron correlation is explicitly taken into account through the complete perturbation potentials. Distortion in the initial channel due to the Coulomb continuum states of the target and the active electron in the field of the residual projectile ion is included. The quantum-mechanical prior and post transition amplitudes for single-electron capture for symmetric and asymmetric collisions are then derived in terms of three-dimensional real integrals. The role of dynamic inter-electron correlation on the cross sections as a function of the impact energy is examined. Only for He+–He collisions, the projectile angular-differential cross sections for ground state capture are calculated at different impact energies. We investigate the effect of the total cross section as well as the projectile angular-differential cross sections to the choice of different ground state wavefunction of the projectile in the final state. It is observed that although the shape of the differential cross section does not change significantly for these functions, there is a significant change of the differential cross sections due to the choice of the target description. The differential cross section reveals pronounced minima and maxima in the projectile scattering angles as the projectile energy decreases. The observed structure demonstrates the analogy of atomic de Broglie’s matter-wave scattering and Fraunhofer-type diffraction. Finally the validity of our results is assessed by comparison with available experimental data.

Numerical Calculation and Uncertain Optimization of Energy Conversion in Interior Ballistics Stage

Gun firing is a process that converts propellant chemical energy to projectile kinetic energy and other kinds of energies. In order to explore the energy conversion process, firstly, the interior ballistics mathematical model and the barrel-projectile finite element model are built and solved. Then, the related variable values and energy values are obtained and discussed. Finally, for improving energy efficiency, the interval uncertainty optimization problem is modeled, and then solved using the two-layer nested optimization strategy and back-propagation (BP) neural network surrogate model. Calculation results show that, after optimization, the heat efficiency raises from 31.13% to 33.05% and the max rifling stress decreases from 893.68 to 859.76 Mpa, which would improve the firing performance and prolong the lifetime of the gun barrel.

Graphdiyne family-tunable solution to shock resistance

The excellent mechanical properties of Graphdiyne (GDY) family has enabled it as an appealing candidate in the field of impact protection. In this in silico study, Monolayer GDY nanosheets of different morphology including GDY, GY-3, GY-4, GY-5 and GY-6 are assessed under hypervelocity impacts (from 1 to 6 km s−1). Tracking the deformation mechanisms under impacts as well as the Probability density function based on atomic Von Mises stress distribution, the length of acetylenic chain clearly alters ductile behavior as well as the energy dissipation/delocalization rate of GDY family during the impact. Results also suggest the penetration energy is not only determined by the energy delocalization rate but also sensitive to impact velocity for nanosheet with various acetylenic chain length. GY-5 with a much lower energy delocalization rate presents a close penetration energy comparing with GDY at a low impact at ∼2.0 km s−1, its superior ductility granted by long acetylenic chain not only dissipates kinetic energy of projectile via deformation, but also extends time for acceleration during the contact with projectile. Considering the impact resist performance of GDY family in terms of Specific penetration energy, GY-5 with the perfect balance between material density, ductility and Young’s modulus makes it the superior anti-ballistic material for impact velocity at <5 km s−1. For impact velocity >5 km s−1, it induces severer local deformation, and leaves no time for a well-developed distributed pattern as observed in a lower impact velocity scenario. As such, extensive elastic deformation of the nanosheet is not captured under impact, nanosheets with shorter acetylenic chains and hence greater material strength demonstrates superior impact resist. This study provides a fundamental understanding of the deformation and penetration mechanisms of monolayer GDY nanosheets under impact, which is crucial in order to facilitate their emerging applications for impact protection.

Similarities in the penetration depth of concrete impacted by rigid projectiles

Similarity can reflect common laws in the mechanism of rigid-body penetration. In this paper, the similarities in rigid-body penetration depth are demonstrated by three non-dimensional but physically meaningful quantities, i.e., $$ \rho_{\text{kinetic}} $$ , $$ I_{ \ln }^{*} $$ and $$ N^{\prime}_{1} $$ . These three quantities represent the non-dimensional areal density of projectile kinetic energy, the effect of nose geometry, and the friction at the interactive cross section between projectile and target respectively. It is shown that experimental data of rigid projectile penetration, from shallow to deep penetration, can be uniquely unified by these three similarity quantities and their relationships. Furthermore, for ogival nose projectiles, their penetration capacities are dominated by $$ \rho_{\text{kinetic}} $$ , which is consisted by non-dimensional effective length $$ L_{\text{eff}} $$ and non-dimensional quantity $$ D_{\text{n}}^{\text{p}} = \frac{{\rho_{\text{p}} v_{0}^{2} }}{AY} $$ which has the same form as Johnson’s damage number. On the sacrifice of minor theoretical accuracy, the non-dimensional penetration depth $$ P/d $$ can be understood as directly controlled by $$ D_{\text{n}}^{\text{p}} $$ , enhanced by projectile effective length $$ L_{\text{eff}} $$ under a multiplication relation, and optimized by projectile nose geometry in the formation of $$ I_{ \ln }^{*} $$ .

Alignment of the projectile 2p3/2 state created by nonradiative electron capture in 95- and 146-MeV/u Xe54+ with Kr and Xe collisions

Anisotropic distributions of the Lyman-${\ensuremath{\alpha}}_{1}$ transition of the down-charged $\mathrm{X}{\mathrm{e}}^{53+*}$ ions are observed in fast $\mathrm{X}{\mathrm{e}}^{54+}$ with Kr and Xe collisions, in which the electron is transferred by the nonradiative electron capture mechanism. At the energy of 95 MeV/u, the alignment parameter of the projectile $2{p}_{3/2}$ state, ${\mathcal{A}}_{20}$, is determined to be \ensuremath{-}0.35 \ifmmode\pm\else\textpm\fi{} 0.02 for both targets. While the projectile energy is 146 MeV/u, the parameter for the Kr and Xe target is \ensuremath{-}0.28 \ifmmode\pm\else\textpm\fi{} 0.02 and \ensuremath{-}0.29 \ifmmode\pm\else\textpm\fi{} 0.04, respectively. The present results demonstrate that the electron capture to the ${m}_{j}=\ifmmode\pm\else\textpm\fi{}1/2$ magnetic substates is about two times more probable than to the ${m}_{j}=\ifmmode\pm\else\textpm\fi{}3/2$ ones.

Актуальные вопросы систематизации научных знаний об условиях выстрела в судебной баллистике

In this research, there was considered a challenge of constructing a system of scientific knowledge of the shot conditions in judicial ballistics. It was observed that there are underlying factors that are intended to ensureits [scientific knowledge] consistency: identification of the list of shot conditions, which require consideration when solving expert-level research tasks on weapons, cartridges and traces of their action; determination of the communication systems in the course of objects’ interaction, which present the result of exposure to the conditions of the shot; classification of the shot conditions based on the grounds significant for solving scientific and practical problems. The article contains the characteristics of a constructive, functional factor (condition) of weapons and cartridges influence, environmental and fire factors, the structure of the target and its physical properties, situational and spatial factors, and projectile energy characteristics. Highlighted are the forms of connections formed in the course of objects’ interaction, proposed are the author’s classifications of forensically significant shooting conditions with them being divided on the basis of the following criteria: production from the object of interaction, production from a natural phenomenon, production method, results weapon operation and utilization, duration of exposure, type of structural connections between interaction objects, number of conditions that apply when firing and the forming traces.

Stopping and straggling of 60–250-keV backscattered protons on nanometric Pt films

The stopping power and straggling of backscattered protons on nanometric Pt films were measured at low to medium energies (60--250 keV) by using the medium-energy ion scattering technique. The stopping power results are in good agreement with the most recent measurements by Primetzhofer Phys. Rev. B 86, 094102 (2012) and are well described by the free electron gas model at low projectile energies. Nevertheless, the straggling results are strongly underestimated by well-established formulas up to a factor of two. Alternatively, we propose a model for the energy-loss straggling that takes into account the inhomogeneous electron-gas response, based on the electron-loss function of the material, along with bunching effects. This approach yields remarkable agreement with the experimental data, indicating that the observed enhancement in energy-loss straggling is due to bunching effects in an inhomogeneous electron system. Nonlinear effects are of minor importance for the energy-loss straggling.

Variance in the radial distribution of nuclear matter between 56Ni and 58Ni inferred from a model-independent Sum-of-Gaussian analysis of elastic proton scattering data

Differential cross sections for p-Ni56 and p-Ni58 elastic scattering, measured at low momentum transfer and at projectile energies of about 400 MeV/u with beams stored in the Experimental Storage Ring (ESR) at GSI, Darmstadt, have been analyzed up to |t|=0.06 (GeV/c)2 applying the model-independent Sum-of-Gaussians (SOG) method based on the Glauber multiple-scattering theory. The rms point matter radius of the self-conjugate doubly magic radioactive Ni56 nucleus was deduced to be 3.62(6) fm, to be compared to the known radius of the stable Ni58 nucleus, 3.67(7) fm. Although the radii of both nuclei differ only slightly, and there is close agreement of the matter radii of Ni58 from former analyses using phenomenological parametrizations of the matter distribution, the SOG method was capable of elucidating pronounced differences in the shapes of the radial matter distributions between both nuclei. Consequences for the understanding of nuclear structure in the vicinity of the N=Z=28 magic shell are briefly discussed.

Ab initio leading order effective potentials for elastic nucleon-nucleus scattering

Background: Calculating microscopic effective interactions (optical potentials) for elastic nucleon-nucleus scattering has already in the past led to a large body of work. For first-order calculations a nucleon-nucleon (\textit{NN}) interaction and a one-body density of the nucleus were taken as input to rigorous calculations of microscopic full-folding calculations. Purpose: Based on the spectator expansion of the multiple scattering series we employ a chiral next-to-next-to-leading order (NNLO) nucleon-nucleon interaction on the same footing in the structure as well as in the reaction calculation to obtain an in leading-order consistent effective potential for nucleon-nucleus elastic scattering, which includes the spin of the struck target nucleon. Methods: The first order effective folding potential is computed by first deriving a nonlocal scalar density as well as a spin-projected momentum distribution. Those are then integrated with the off-shell Wolfenstein amplitudes $A$, $C$, and $M$. The resulting nonlocal potential serves as input to a momentum-space Lippmann-Schwinger equation, whose solutions are summed to obtain the nucleon-nucleus scattering observables. Results: We calculate elastic scattering observables for $^4$He, $^6$He, $^8$He, $^{12}$C, and $^{16}$O in the energy regime between 100 and 200 MeV projectile kinetic energy, and compare to available data. We also explore the extension down to about 70 MeV, and study the effect of ignoring the spin of the struck nucleon in the nucleus. Conclusions: In our calculations we contrast elastic scattering off closed-shell and open-shell nuclei. We find that for closed-shell nuclei the approximation of ignoring the spin of the struck target nucleon is excellent. We only see effects of the spin of the struck target nucleon when considering $^6$He and $^8$He, which are nuclei with a $N/Z$ ratio larger than 1.

Charge state distribution and energy loss for 100 keV protons moving in discharge H plasmas

Ab initio theoretical simulations are performed for charge state distribution and energy loss of a 100 keV proton beam propagating in partially ionized discharge H plasmas. In the simulation, all transition processes are calculated accurately among eight main projectile electronic configurations including the most relevant excited states. Projectile configuration evolution is computed by solving rate equations, and the effective charge state Zeff is obtained during all discharge stages. A new way is suggested to get the projectile energy loss with the contributions of all configurations considered separately. Such obtained energy losses are in the best agreement with experimental measurements among all the related models. However, both traditional empirical models with estimated Zeff and the standard stopping model are found invalid in this case, and relevant reasons are explored. Projectile capture and ionization processes in plasmas are found to be especially important in the stopping process. We predict that projectile excited states would make a much larger difference in energy deposition when a higher atomic number projectile is chosen, which has not been deeply recognized in plasmas yet.

Experimental Investigation of the Crater Caused by Hypervelocity Rod Projectile Impacting on Rocks

To investigate the cratering effects of hypervelocity rod projectile impacting on rocks, a two-stage light gas gun was used to carry out 10 groups of small-scale experiments, whose velocity ranges from 1.5 km/s to 4.1 km/s. After each experiment, the morphology and size of the hypervelocity impacting crater were accurately obtained by using a device for image scanning. According to the morphology of the final crater, the impact crater can be divided into crushing area, spallation area, and radial crack area. Based on the experimental results of steel projectile vertical impacting on granite targets, the relationship between the depth and the diameter of the crater is analyzed, i.e., h/D≈0.1∼0.2; it shows that the depth of the crater is much smaller than the diameter of the crater, and the crater seems to be a shallow dish. The relation between the kinetic energy of the projectile and the size of the crater was discussed. With the increase of the projectile kinetic energy, it is uncertain whether the depth of the crater increases, but the volume of the crater will increase. Lastly, dimensionless analysis of the impact crater was carried out. Specifically, the limitations of point source solutions to hypervelocity rod projectile impact cratering have been proved, and there is no essential difference to calculate the final crater by using the energy scale or the momentum scale.

MD study of surface collision cascades in nickel

Collision cascades initiated by fast Ni projectiles with energy E = 5, 10, 15 and 20 keV at the surface of nickel target at temperature T = 100, 300, 600, 900 and 1200 K were studied by molecular dynamics simulations. Representative sampling of 24 surface collision cascades per E,T set was generated to get the statistically reliable number of Frenkel pairs NFP and the fraction of vacancies σvac and self-interstitial atoms (SIAs) σSIA in point defect clusters as functions of the projectile energy and irradiation temperature. It was established that NFP,σvac and σSIA in surface collision cascades in nickel averaged over cascade series with the same E,T are higher than those produced in collision cascades in the bulk of the material under the same simulation conditions. Point defects generated in surface cascades predominantly agglomerate into clusters. Spatial separation of vacancies and SIAs due to the interaction of collision cascades with the free surface is the major driving mechanism responsible for the increased number of NFP,σvac and σSIA produced in surface collision cascades in nickel.

Contrast modes in a 3D ion transmission approach at keV energies

We present options for visualizing contrast maps in 3D ion transmission experiments. Simultaneous measurement of angular distributions and flight time of ions transmitted through self-supporting, single-crystalline silicon foils allows for mapping of intensity and different energy loss moments. The transmitted projectiles were detected mainly for random beam-sample orientation using pulsed beams of He ions and protons with incident energies 50 and 200 keV. Differences in contrast, observed when varying the projectile type and energy, can be attributed to sample nuclear and electronic structure and bear witness to impact parameter dependent energy loss processes. Our results provide a base for interpretation of data obtained in prospective transmission studies when for example using a helium ion microscope.

Ionization Cross Sections in the Collision between Two Ground State Hydrogen Atoms at Low Energies

The interaction between two ground state hydrogen atoms in a collision was studied using the four-body classical trajectory Monte Carlo method. We present the total cross sections for the dominant channels, namely for the single ionization of the target, the ionization of the projectile, resulting from pure ionization, and also from the electron transfer (capture or loss) processes. We also present cross sections for the complete break of the system, resulting in the final channel for four free particles. The calculations were carried out at low energies, relevant to the interest of fusion research. We present our cross sections in the projectile energy range between 2.0 keV and 100 keV and compare them with previously obtained theoretical and experimental results.

Electron emission from CH4 molecules in collisions with fast bare C ions

We present the energy and angular distributions of electron emission from a ${\mathrm{CH}}_{4}$ molecule in collisions with fast bare C ions with energies 3.5 and 5.5 MeV/u. The absolute double differential cross sections (DDCS) are measured for the ejected electrons having energies from 11 eV to 330 eV for $3.5\ensuremath{-}\mathrm{MeV}/\mathrm{u}$ projectiles and from 5 eV to 330 eV for 5.5 MeV/u bare C ions. The emission is measured in the angular range from ${20}^{\ensuremath{\circ}}$ to ${160}^{\ensuremath{\circ}}$. The forward-backward angular asymmetry, the single differential cross sections (SDCS), and the total cross section are deduced from the measured DDCS values. The energy and angular distributions of the DDCS and SDCS are compared with those calculated using a theoretical model based on the prior form of the continuum distorted wave--eikonal initial state (CDW-EIS) approximation. The dynamics of the process is considered within the CDW-EIS approximation, while the initial orbitals of the molecular target are represented using the complete neglect of the differential overlap approximation. The calculations are found to be in very good agreement with the measured cross sections. The angle dependence of the carbon K-LL Auger emission and the total Auger emission cross section are also derived for both projectile energies.

Neutron elastic scattering on calcium isotopes from chiral nuclear optical potentials

We formulate microscopic neutron-nucleus optical potentials from many-body perturbation theory based on chiral two- and three-body forces. The neutron self energy is first calculated in homogeneous matter to second order in perturbation theory, which gives the central real and imaginary terms of the optical potential. The real spin-orbit term is calculated separately from the density matrix expansion using the same chiral interaction as in the self energy. Finally, the full neutron-nucleus optical potential is derived within the improved local density approximation utilizing mean field models consistent with the chiral nuclear force employed. We compare the results of the microscopic calculations to phenomenological models and experimental data up to projectile energies of $E = 200$ MeV. Experimental elastic differential scattering cross sections and vector analyzing powers are generally well reproduced by the chiral optical potential, but we find that total cross sections are overestimated at high energies.