Incident Projectile Research Articles

Mechanical responses and damage characteristics of the high-velocity impact of ice projectiles on foam sandwich structure

The integration of composite sandwich structures in aircraft design necessitates consideration of hail impacts within aerospace applications. This investigates the dynamic response and damage characteristics of a carbon fibre/PMI foam sandwich structure under hail impact through both experimental and numerical simulation methods. These methods analyse the impact velocity, fibre panel thickness, and angle of incidence of the ice projectiles. The study establishes relationships among various parameters such as ice projectile impact force, foam absorption energy, and target plate deformation in relation to the impact velocity and angle of incidence. The damage sustained by the carbon fibre/PMI foam sandwich (CPS) structure due to ice projectile impact was systematically categorized and examined. Additionally, the effects of normal and tangential impact velocities on the target plate's dynamic response during oblique impacts were investigated. This research serves as a valuable reference for understanding the dynamic response and damage characteristics of composite foam sandwich structures subjected to ice projectile impacts, With a focus on the carbon fibre/PMI foam sandwich structure.

Data-driven modeling for residual velocity of projectile penetrating reinforced concrete slabs

The penetration of projectiles into reinforced concrete (RC) structures is crucial for defense technology. However, accurately estimating the resistance of RC structures to projectile penetration is challenging due to complex parameter nonlinearities. This paper proposes a data-driven modeling methodology that combines validated finite element (FE) simulations with machine learning (ML) algorithms to investigate the penetration resistance of RC slabs against projectiles. The methodology employs an extreme learning machine (ELM) network to identify extreme conditions characterizing penetration resistance, reducing data requirements, and improving prediction efficiency. Predicted results from the ELM network are then used as input for a recurrent neural network (RNN) to predict residual velocity curves over time, a crucial metric for evaluating penetration resistance. To cover various loading scenarios, 64 sets of FE models with different incident velocities, caliber-radius-head (CRH), and projectile masses are developed based on available experimental studies. The Johnson-Holmquist II model and Johnson-Cook model are employed for concrete and steel, respectively, to describe material behavior at high strain rates. The FE prediction results form a training sample database, and ML models are established using CRH, incident velocity, and projectile mass as input layers and projectile residual velocity as the output layer. The results demonstrate high Pearson correlation coefficients of 0.984 and 0.991 for the ELM and RNN prediction results, respectively, with numerical simulation results. The proposed networks provide accurate and efficient alternatives to time-consuming FE simulations for predicting projectile penetration performance. This strategy offers a new ML-based method for rapid evaluation, particularly for in-situ applications.

Study of state-selective single-electron capture in slow Ne7+ colliding with He and H2 target

Using the cold target recoil-ion momentum spectroscopy, we measured the state-selective single electron capture in collisions of 3.5–6.3 keV u−1 Ne7+ ions and He and H2. The Q-value spectra and angular distributions as a function of the projectile incident energy were obtained. The results show that the single electron capture into n = 4 states is the dominant reaction channel for the Ne7+-He system, while the capture into n = 4 and n = 5 states both are dominant processes for the Ne7+-H2 system. The molecular coulombic barrier model and the potential energy curves can qualitatively explain the measured state populations for both systems.

Systematic study of fusion suppression and its dependency on projectile breakup threshold energy

Measurements of the excitation function (EF) of the observed evaporation residues (ERs) populated in the 20Ne + 93Nb reaction at E lab ≈ 91−145 MeV are carried out to explore the systematic of fusion suppression and its dependency on projectile breakup threshold energy, by employing the offline γ-ray detection method. The EF of the observed ERs populated through complete and/or incomplete fusion processes are analysed in the framework of statistical mode code PACE4. The fusion function, derived from the experimentally measured fusion cross section data, is compared with the universal fusion function (UFF) to estimate the degree of fusion incompleteness. Based on the observed results, an empirical formula is proposed to interrelate the degree of fusion suppression and breakup threshold energy of the incident projectile.

Comprehension of breakup fusion reactions using forward recoil range distribution measurements

To understand the break-up fusion reaction dynamics, the forward recoil range distribution (FRRD) measurements of 12C + 165Ho system at the incident projectile energy of ≈ 88 MeV has been performed. The recoil catcher activation technique followed by the off-line gamma ray spectroscopy was implemented. It is observed that the FRRD measurements of the evaporation residues (ERs) populated via xn and pxn channels have a single Guassian peak at large cumulative thickness. This is attributed to complete momentum transfer from the projectile to the target nucleus. However, in case of the FRRD measurements of the ERs populated via αxn, αpxn and 2αxn emitting channels, in addition to peak corresponding to complete momentum transfer, the Gaussian peaks at lower cumulative thicknesses are also observed. This is accredited to the breakup fusion. Moreover, the effect of projectile breakup on complete fusion cross section is also studied. The suppression in fusion cross section is observed when compared with the universal fusion function, thus indicating the breakup probability of 12C projectile.

Helium and Proton Particle-Induced X-Ray Emission (PIXE) for Characterization of PM2.5 from Surabaya, Indonesia

Generally, particle-induced X-ray emission (PIXE) analysis is performed using protons as the incident projectiles. In this study, helium ions were used for inducing X-ray emission to improve the detection limit for the characterization of light elements in the PM2.5 fine fraction. The sampling was conducted for 24 h using a Gent stacked filter unit sampler at an industrial site in Surabaya, Indonesia. The samples were analyzed by PIXE using a 4-MV Van de Graaff accelerator at Kyoto University. Both helium and protons were used in the analysis to obtain optimal results, and 21 elements were detected in the samples. Notably, the use of helium particle-induced X-ray emission was more suitable for Na, Mg, Al, and Si than protons. Moreover, the sensitivity and limit of detection for these elements were enhanced using helium ions. Validation was performed using standard reference material NIST 2783 air particulates on filter media, and the results were in good agreement. Using both He-PIXE and H-PIXE, heavy metals, crustal elements, and other elements were identified that exhibited the characteristics of PM2.5 collected in Surabaya, Indonesia. Further statistical analysis and receptor modeling are required to identify the possible pollutant sources of PM2.5.

Analysis of Projectile Impact Resisting Characteristics of Hollow Triangular Matrix Structure

The numerical simulation of engineering structural elements and spatial combination form of the polarizing body using common engineering materials is carried out, and the triangular hole matrix space combination structure is proposed. The penetration depth and deflection angle of the projectile under different projectile velocities and incident positions are obtained by numerical simulation of the projectile impacting the composite structure under various working conditions. At the same time, through the comparative study of ordinary solid shell shielding structures, it is found that the higher the projectile velocity, the higher the shell shielding effectiveness of triangular hole matrix space composite structure.

Fractional calculus within the optical model used in nuclear and particle physics

The optical model is a fundamental tool to describe scattering processes in nuclear physics. The basic input is an optical model potential, which describes the refraction and absorption processes more or less schematically. Of special interest is the form of the absorption potential. With increasing energy of the incident projectile, a derivation of this potential must take into account the observed energy dependent transition from surface to volume type. The classic approach has weaknesses in this regard. We will discuss these deficiencies and will propose an alternative method based on concepts developed within the framework of fractional calculus, which allows to describe a smooth transition from surface to volume absorption in an appropriate way.

Facets of reaction mechanism in 6Li+181Ta system

More focused investigations are required to better understand the different modes of fusion phenomena in weakly bound projectiles. In order to comprehend the reaction mechanism of weakly bound projectiles, a new measurement of the evaporation residue cross sections from the 6Li-induced reaction on 181Ta in the 4.5–7.1 MeV/nucleon energy range has been reported in this article. The γ-ray spectrometry has been employed to identify the 183m,g Os, 182Os, 183Re, and 183,182m2,180Ta residues produced in the reaction via different evaporation channels. The EMPIRE-3.2.2 code, which houses both the equilibrium and pre-equilibrium models in its framework, and PACE4 have been tasked to analyze the measured excitation functions. Out of the two, EMPIRE-3.2.2 demonstrates better agreement with the data. A systematic analysis of the measured data and theoretical background indicates that the complete and incomplete fusion of 6Li contribute to the residual cross sections. Thus, the strength of the partial fusion has been inferred. Further, the neutron transfer channels have been found to contribute significantly to the reaction dynamics; hence they are investigated using the coupled reaction channel calculations and discussed in detail. The isomeric cross section ratio obtained from the measured residual cross sections of the isomeric pair of 183Os highlights the significance of angular momentum and relative spins of the ground and isomeric states as a function of projectile incident energy.

Impact of projectile incidence angle with obstacle during ricochet on the damage characteristics formed in smoothbore weapon shot

The aim of this study was to establish the degree of projectile incidence angle with obstacle on forensic medical characteristic of gunshot injuries arising from smoothbore weapon fire and bullet ricochet. Based on the comprehensive forensic study results of experimental entry gunshot injuries, statistically significant differences in the following morphological signs were found for two ranges of incidence angle values (10-20° and 30-50°): «Number of MD», «Length 1 MD», «Length 2 MD», «Width 1 MD», «Orientation of AD to the conventional clock face relative to MD 1 or to the group of largest MD (max. value)». The medians and limits of 99% confidence intervals of these features values were observed depending on the range of incidence angle values. The revealed patterns can be used in expert practice during forensic medical examination of gunshot injuries formed as a result of a projectile ricochet after smoothbore weapon fire, as well as to develop a methodology for conducting a forensic study of this gunshot injury type.

Role of neutron transfer in the reaction mechanism of 9Be+169Tm, 181Ta, 187Re and 197Au systems

The contribution of one neutron stripping cross section to the total reaction cross section has been studied for 9Be projectile incident on 169Tm, 181Ta, 187Re and 197Au targets around Coulomb barrier energy. The measured one neutron stripping cross sections for these systems have been compared with the coupled channel calculations. The recently developed global set of optical model potential parameters for 9Be projectile has been used in the present calculations. The cumulative of measured complete fusion (CF), incomplete fusion (ICF), one neutron stripping and calculated non-capture breakup (NCBU) cross sections is found to explain almost the reaction cross sections for all the targets. A very small contribution from target inelastic states and elastic breakup may contribute to the remaining part. The percentage fraction of cross section for CF, ICF, one neutron stripping, and NCBU over reaction cross section show the dominance of neutron transfer and NCBU at below barrier energies while CF and ICF processes have the major contribution at above barrier energies.

A study on the capabilities and accuracy of Kapton based TOF space dust and debris detectors

The growing population of space debris in the near-Earth environment means there is an increased need for space-based detectors, capable of measuring and distinguishing natural space dust and anthropogenic orbital debris populations, to monitor and quantify the relative threat they pose. This has led to much research into the development of new detectors, including those based on time of flight (TOF) designs which can give impact speed and direction. Kapton’s favourable properties (e.g. its low mass and ability to be manufactured as thin films) and tried and tested space applications, suggest it may be suitable for use in TOF detectors where impactor speed is measured by passage through several films with known separation. To test the measurement accuracy of such a detector, a prototype Kapton based TOF space dust and debris detector was constructed, and impacted at 2 and 4 km s−1. For a Kapton film thickness of 12.5 μm and projectiles of 1 mm in size, within experimental uncertainties of ∼1%, there was no difference between incident projectile speed (as measured independently) and that measured by the TOF detector. This, confirms that Kapton based TOF detectors are capable of measuring particle speed to a high degree of accuracy, making them suitable for measuring the near-Earth particle environment.

Ballistic resistance and energy dissipation of woven-fabric composite targets: Insights on the effects of projectile shape and obliquity angle

This study aims at investigating the ballistic resistance and energy absorption in woven E-glass composite panels, considering different projectile nose shapes and oblique incidence angles. To that scope, three-dimensional finite element (FE) models of both projectiles and the laminated target are developed and numerical investigations are carried out using Abaqus Explicit solver. The composite damage model's constitutive law encompasses nonlinear material response, material properties degradation, progressive failure, and an element deletion strategy. The cohesive surface technique is used to represent the interface between two adjacent plies in the laminate, and the traction-separation law is used to characterize the behaviors of interlaminar degradation and failure. Material responses attributable to fiber rupture, matrix cracking, and plasticity caused by micro-matrix cracking due to shear loading are taken into account with suitable damage evolution laws. The computational framework is first validated against the experimental results reported in the literature by performing ballistic impact tests on the target laminate with conical, hemispherical and blunt-ended projectile, and the numerical results showed a good comparison in terms of residual velocity. Subsequently the framework is explored in simulating more complex failure mechanisms, with particular emphasis on the influence of the impact angle of obliquity, a parameter that is not usually analyzed in the literature. In that regard, the effects of normal and oblique impact on the damage morphologies and ballistic behavior of the fabric composite target in terms of energy absorption, impact contact force, and projectile residual velocity are conducted and analyzed, comparatively. The findings showed that the ballistic impact behavior of target composite is substantially influenced by projectile nose shape and incidence angle obliquity.

Single and double electron detachment absolute cross sections of H− and D− in collisions with SF6 and CF4

Collisional single electron detachment (SED) and double electron detachment (DED) absolute cross sections of H− and D− with sulfur hexafluoride (SF6) and carbon tetrafluoride (CF4) were measured by using the growth rate method. The energy used in the experiment ranged from 10 to 30 keV. By combining with the available data in references, it was found that SED absolute cross sections reach saturation in the experimental velocity range, while DED absolute cross sections continue to increase as the velocity increases. The SED absolute cross sections of CH4, SF6, and CF4 were proportional to their bond lengths and the radius of the incident anionic projectile within the error range in the present velocity region.

A Microscopic View of Macromolecule Transfer in the Vacuum Using Gas and Bismuth Clusters

Transferring large nonvolatile molecules in the vacuum is key to both their characterization by mass spectrometry (ion mobility, etc.) and their use as nanofabrication building blocks in soft-landing-type experiments. Recently, our group performed the successful transfer and redeposition of intact and bioactive lysozyme (14 kDa) with large gas cluster ion beams, in the absence of a solvent or matrix, demonstrating that such beams could serve as tools for macromolecule manipulation. A number of fundamental questions arose in relation with this experimental proof-of-concept, concerning for instance the maximum molecular size for successful transfer, the effect of the cluster projectile incidence angle, the dependence of molecular dissociation on the projectile energy and size, the internal energy uptake ultimately leading to metastable decay reactions, or the influence of the surface interactions on desorption. To address these questions, a series of molecular dynamics simulations were conducted involving cluster impacts on an adsorbed globular polystyrene (PS) macromolecule of 60 kDa, with a mass and shape comparable to those of a protein such as bovine serum albumin. Conditions of intact desorption of this PS molecule by Ar clusters are identified, in terms of energy per atom and incidence angle, and the results are compared to 30 keV Bi5 impacts, commonly used for molecular analysis and 2D imaging in our time-of-flight secondary ion mass spectrometry experiments. When Ar cluster impact conditions are appropriate for intact desorption, the take-off angle of the macromolecule is larger than the projectile incidence. Bombardment by a massive methane projectile (6.6 × 104 methane molecules) does not induce qualitatively different results, and in general, the energy per atom or energy per unit mass remains the deciding factor concerning the survival or dissociation of the bombarded molecule. In contrast with large gas clusters, Bi5 projectiles largely fail at desorbing the intact macromolecules, because of the detrimental effect of the collision cascade and the insufficient momentum transferred by the crater expansion for molecular lift off. Additionally, 10 keV Ar5000 projectiles with 45–75° incidence with respect to the surface normal directly transfer momentum to the macromolecule via their backscattered Ar atoms and small clusters, inducing molecular desorption with center-of-mass velocities of the order of 1 km/s. The implications for future experiments are discussed.

RADIATION-INDUCED SURFACE MIGRATION OF TUNGSTEN: CHANNELING ALONG ATOMIC STEPS

The interaction of accelerated helium atoms with the atomic-smooth surface of tun+gsten single crystals was investigated using the low-temperature field-ion microscope, equipped with the source of helium atoms with an energy of 5 keV together with the techniques of molecular dynamics. It was observed the effect of the surface channeling of fast atoms of a target along the surface steps which occurs as a result of the collision cascade induced by the incident projectile. A substantial part of these displaced atoms in the target gains momentum oriented along the < 111 > close-packed crystallographic directions. The fine morphology of the trajectory of an excited tungsten atom reveals the transverse oscillations of the W atom normally to the < 111 > surface atomic step. The rate of the kinetic energy loss during the surface channeling of fast tungsten atoms does not exceed 0.4 eV/Å. This provides relatively large displaced surface atom ranges along the close-packed atomic steps. The found out results can be regarded as a special case of the correlation mechanism of the radiation-induced surface mass transfer.

Perturbation theory of scattering for grazing-incidence fast-atom diffraction.

Recent grazing-incidence, fast atom diffraction (GIFAD) experiments have highlighted the well known observation that the distance between classical rainbow angles depends on the incident energy. The GIFAD experiments imply an incident vertical scattering angle, facilitating an analytic analysis using classical perturbation theory, which leads to the conclusion that the so called "dynamic corrugation" amplitude, as defined by Bocan et al., Phys. Rev. Lett., 2020 125, 096101 is, within first-order perturbation theory, proportional to the tangent of the rainbow angle. Therefore it provides no further information about the interaction than is gleaned from the rainbow angle and its energy dependence. Perhaps more importantly, the resulting analytic theory reveals how the energy dependence of rainbow angles may be inverted into information on the force field governing the interaction of the incident projectile with the surface.

Penetration dynamics of steel spheres into a ballistic gelatin: Experiments, nondimensional analysis, and finite element modeling

Ballistic gelatin is widely used as a simulant of soft tissues, and its dynamic responses to high-speed projectile penetration are critical for understanding soft tissue damage, wound ballistics, and protection gear design. Here, we investigate penetration dynamics of spherical steel projectiles with different diameters into a ballistic gelatin at different incident velocities. The projectile diameter ranges from 1 mm to 5 mm, and the incident velocity, from 50 m s−1 to 400 m s−1. Penetration dynamics is captured with high-speed photography. A power-law relation is found between the maximum penetration depth and projectile kinetic energy at high incident velocities, but not at intermediate and low velocities. Nondimensional analysis is applied to the penetration depth; a general relation is established for nondimensional maximum penetration depth as a function of projectile density, projectile diameter and projectile incident velocity for low-, intermediate- and high-speed penetration, and this relation can accurately describe the experiments. The drag force of projectile is analyzed to explain the relation between projectile acceleration and velocity. In addition, a calibrated finite element model reproduces well experimental observations such as the maximum penetration depth and projectile trajectory.

Differential Condensation of Methane Isotopologues Leading to Isotopic Enrichment under Non-equilibrium Gas-Surface Collision Conditions.

We examine the initial differential sticking probability of CH4 and CD4 on CH4 and CD4 ices under nonequilibrium flow conditions using a combination of experimental methods and numerical simulations. The experimental methods include time-resolved in situ reflection–absorption infrared spectroscopy (RAIRS) for monitoring on-surface gaseous condensation and complementary King and Wells mass spectrometry techniques for monitoring sticking probabilities that provide confirmatory results via a second independent measurement method. Seeded supersonic beams are employed so that the entrained CH4 and CD4 have the same incident velocity but different kinetic energies and momenta. We found that as the incident velocity of CH4 and CD4 increases, the sticking probabilities for both molecules on a CH4 condensed film decrease systematically, but that preferential sticking and condensation occur for CD4. These observations differ when condensed CD4 is used as the target interface, indicating that the film’s phonon and rovibrational densities of states, and collisional energy transfer cross sections, have a role in differential energy accommodation between isotopically substituted incident species. Lastly, we employed a mixed incident supersonic beam composed of both CH4 and CD4 in a 3:1 ratio and measured the condensate composition as well as the sticking probability. When doing so, we see the same effect in the condensed mixed film, supporting an isotopic enrichment of the heavier isotope. We propose that enhanced multi-phonon interactions and inelastic cross sections between the incident CD4 projectile and the CH4 film allow for more efficacious gas–surface energy transfer. VENUS code MD simulations show the same sticking probability differences between isotopologues as observed in the gas–surface scattering experiments. Ongoing analyses of these trajectories will provide additional insights into energy and momentum transfer between the incident species and the interface. These results offer a new route for isotope enrichment via preferential condensation of heavier isotopes and isotopologues during gas–surface collisions under specifically selected substrate, gas-mixture, and incident velocity conditions. They also yield valuable insights into gaseous condensation under non-equilibrium conditions such as occur in aircraft flight in low-temperature environments. Moreover, these results can help to explain the increased abundance of deuterium in solar system planets and can be incorporated into astrophysical models of interstellar icy dust grain surface processes.

Radiative double-electron capture by fully stripped and one-electron ions in gas and thin-foil targets

Radiative double-electron capture (RDEC), in which two-electron capture is accompanied by simultaneous emission of a single photon, was investigated for fully stripped and one-electron projectiles colliding with gaseous and thin-foil targets. RDEC can be considered the inverse of double photoionization by a single photon. For the gaseous targets, measurements were done for 2.11 MeV/u ${\mathrm{F}}^{9+}$ and ${\mathrm{F}}^{8+}$ ions interacting with ${\mathrm{N}}_{2}$ and Ne, while for the thin-foil target the measurements were done for 2.11 MeV/u ${\mathrm{F}}^{9+}$ and ${\mathrm{F}}^{8+}$ and 2.19 MeV/u ${\mathrm{O}}^{8+}$ and ${\mathrm{O}}^{7+}$ ions striking thin C targets. Reports on this work were already published separately in shorter accounts by La Mantia et al. [Phys. Rev. Lett. 124, 133401 (2020) for the gas targets and Phys. Rev. A 102, 060801(R) (2020) for the thin-foil targets]. The gas targets were studied under single-collision conditions, while the foil targets suffered unavoidable multiple collisions. The measurements were carried out by detecting x-ray emission from the target at ${90}^{\ensuremath{\circ}}$ to the beam direction in coincidence with outgoing ions undergoing double, single, and, in the case of the foil targets, no charge change inside the target. Striking differences between the gaseous and foil targets were found from these measurements, with RDEC for the gaseous targets occurring only in coincidence with q-2 outgoing projectiles as expected, while RDEC for the foil targets was seen in each of the outgoing q-2, q-1, and no charge-change states. The no charge-change result was totally unexpected. The cross sections for RDEC for the fully stripped ions on gas targets were found to be about six times larger than those for the one-electron projectiles. For the foil targets, the RDEC cross sections for the fully stripped and one-electron projectiles differ somewhat from one another but not to the the extent they did for the gas targets. In this work the cross sections for all of the projectiles for the foil targets were adjusted due to the target contaminant background from potassium and calcium atoms that existed in the spectra. Also, the cross sections for the incident one-electron projectiles were modified due to a correction for the fraction of these ions that becomes fully stripped in passage through the foil. These differences are attributed to the effects of the multiple collisions that occur for the foil targets. The differential cross sections at ${90}^{\ensuremath{\circ}}$ determined for each of the projectiles interacting with each of the targets are compared with each other and with the previous measurements. To the extent that the cross sections follow a ${sin}^{2}\ensuremath{\theta}$ dependence, the total cross sections are compared with theoretical calculations [E. A. Mistonova and O. Yu. Andreev, Phys. Rev. A 87, 034702 (2013)], for which the agreement is poor, with the measured cross section exceeding the predicted ones by about an order of magnitude. Possible reasons for this discrepancy will be discussed.