Projectile-target Interaction Research Articles

Systematic Study of Neutron-Rich Rare Isotope Production in Peripheral Heavy-Ion Collisions at Beam Energies 15–25 MeV/nucleon

The production cross sections of projectile-like fragments from collisions of 86Kr projectiles with 64,58Ni and 124,112Sn targets at 15 and 25 MeV/nucleon are studied systematically with emphasis on the neutron-rich isotopes. Our recent experimental data are compared with calculations for the above collisions employing a hybrid approach. The dynamical stage of the projectile-target interaction was described with either the phenomenological deep-inelastic transfer (DIT) model or with the the microscopic constrained molecular dynamics model (CoMD). Subsequently, for the de-excitation of the projectile-like fragments, the statistical multifragmentation model (SMM) or the binary-decay code GEMINI were employed. An overall good agreement with the experimental results was obtained. We point out that our current understanding of the reaction mechanism at beam energies below the Fermi energy suggests that such nuclear reactions, involving peripheral nucleon exchange, can be exploited as a novel route to access extremely neutron-rich rare isotopes toward the r-process path and the hard-to-reach neutron drip-line. For this purpose, we believe that the use of re-accelerated neutron-rich radioactive beams may offer unique and exciting opportunities toward unexplored regions of the nuclear landscape.

Laser-assisted (e,2e) ionization of atomic hydrogen in a quasi-Sturmian-Floquet approach

We study laser-assisted fast (e, 2e) collisions on atomic hydrogen both in perturbative and in nonperturbative regimes of laser radiation. We calculate multiphoton triple differential cross sections in asymmetric coplanar kinematics employing the first Born approximation in the projectile–target interaction. The study allows us to test the robustness of our recently formulated quasi-Sturmian-Floquet method to treat the dressing of the initial and final atomic states by the laser field. In both radiation regimes our method exhibits high efficiency for different net numbers of photons exchanged between the colliding system and the laser field.

Reliable extraction of the dB(E1)/dE for 11Be from its breakup at 520 MeV/nucleon

We analyze the breakup of the one-neutron halo nucleus 11Be measured at 520 MeV/nucleon at GSI on Pb and C targets within an eikonal description of the reaction including a proper treatment of special relativity. The Coulomb term of the projectile-target interaction is corrected at first order, while its nuclear part is described at the optical limit approximation. Good agreement with the data is obtained using a description of 11Be, which fits the breakup data of RIKEN. This solves the apparent discrepancy between the dB(E1)/dE estimations from GSI and RIKEN for this nucleus.

Effect of the impact geometry in the ballistic trauma absorption of a ceramic multilayered armor system

Ceramic armors are frequently used for protection against high energy projectiles, such as the 7.62mm and 5.56mm. Recently, it has been demonstrated that a modification in the geometry of the impact face, from flat to convex, enlarges the stress distribution zone created by the projectile-target interaction. This effect raises the projectile's energy absorption and might improve the user's safety. In the present work, the objective is to characterize ceramic armor plates with convex impact face, by means of the NIJ-0101.06 (2008) standard methodology, aiming to provide an eventual application in armor vests. The characterization is based on the measurement of the backface signature, a deformation behind armor imprinted in a reference material that simulates the consistency of the human body. The results showed significant improvement in the ballistic performance after the impact geometry modification.

Experimental impact cratering: A summary of the major results of the MEMIN research unit

AbstractThis paper reviews major findings of the Multidisciplinary Experimental and Modeling Impact Crater Research Network (MEMIN). MEMIN is a consortium, funded from 2009 till 2017 by the German Research Foundation, and is aimed at investigating impact cratering processes by experimental and modeling approaches. The vision of this network has been to comprehensively quantify impact processes by conducting a strictly controlled experimental campaign at the laboratory scale, together with a multidisciplinary analytical approach. Central to MEMIN has been the use of powerful two‐stage light‐gas accelerators capable of producing impact craters in the decimeter size range in solid rocks that allowed detailed spatial analyses of petrophysical, structural, and geochemical changes in target rocks and ejecta. In addition, explosive setups, membrane‐driven diamond anvil cells, as well as laser irradiation and split Hopkinson pressure bar technologies have been used to study the response of minerals and rocks to shock and dynamic loading as well as high‐temperature conditions. We used Seeberger sandstone, Taunus quartzite, Carrara marble, and Weibern tuff as major target rock types. In concert with the experiments we conducted mesoscale numerical simulations of shock wave propagation in heterogeneous rocks resolving the complex response of grains and pores to compressive, shear, and tensile loading and macroscale modeling of crater formation and fracturing. Major results comprise (1) projectile–target interaction, (2) various aspects of shock metamorphism with special focus on low shock pressures and effects of target porosity and water saturation, (3) crater morphologies and cratering efficiencies in various nonporous and porous lithologies, (4) in situ target damage, (5) ejecta dynamics, and (6) geophysical survey of experimental craters.

Theoretical study on collision dynamics of H+ + H2O at low energies

ABSTRACTScattering dynamics of a water molecule in collision with proton is studied based on a time-dependent density functional theory and coupled with the molecular dynamics method, in which the electrons are described by quantum mechanics and the nuclei are described by classical mechanics. Four different incident directions at 46 eV are chosen in order to investigate the orientations effect, and the energy-dependent effect in low energy region is explored under impact energies 27, 36 and 46 eV. Reaction channels, scattering angles and energy loss of protons are calculated. The differences between those characteristics are unobvious in large impact parameters, which are irrespective of the incident orientations due to weak projectile-target interaction. In small impact parameters, the results strongly depend on the collision energy and orientation.

Cross sections for electrons scattering from silver at low energies

SynopsisDifferential cross sections for scattering of electrons from silver atoms are calculated in the low energy region using the relativistic Dirac equation. The projectile target interaction is represented as sum of three local and real terms i.e. the static, a parameter free correlation polarization potential and the modified semi classical exchange potentials. We compare our results for differential cross sections with the available calculations and experimental measurements.

Stability of tungsten projectiles penetrating adobe masonry – Combined experimental and numerical analysis

We investigate the penetration of tungsten-heavy-alloy projectiles into adobe targets. The analysis rests on two complementary parts. Firstly, experimental data comprising impact experiments with five different projectile variants against finite-thickness adobe targets is available. Although the data stems from earlier work, it is presented in full detail here for the first time. The general phenomenology is discussed mainly with respect to projectile failure and stability of the penetration in adobe. Secondly, a recently published hydrocode model for adobe under impact loading is applied without further modification for complementing the experimental results with additional time-resolved insight into the penetration mechanics. For the regime without projectile failure or significant plastic deformation, this hydrocode model is capable of reproducing the experimentally observed projectile-target interaction with good overall agreement between experiments and simulation. While the test data covers different penetration regimes from rigid-body motion to projectile failure, the numerical analysis is restricted to linear-elastic behavior of the impactors, in order to avoid any ambiguity due to the less established projectile material description. With the information from the hydrocode simulations, we are able to reveal the origin of the projectile-specific magnitude of instability in the penetration in adobe. The thereby achieved understanding of the motion of the differently shaped impactors within the formed cavity allows us to discuss possible explanations for the particular projectile failure observed in the experimental data.

Positron Scattering from Molecules: An Experimental Cross Section Compilation for Positron Transport Studies and Benchmarking Theory

We present a compilation of recommended positron–molecule cross sections for a range of scattering processes including elastic scattering, vibrational excitation, discrete electronic-state excitation, positronium formation, ionization, and also for the grand total cross section. Where possible, in particular for possible application in positron transport simulations for a given molecule, we try and list data for energies in the range 0.1–1000 eV although in practice the actual energy is highly target–molecule and scattering process specific. Aside from being relevant to positron transport studies, through, for example, Monte Carlo simulations, the present compilation should also be germane for benchmarking the validity and accuracy of positron–molecule scattering calculations and, just as importantly, to allow a comparison with corresponding electron scattering results. That latter comparison can shed real light on the projectile–target interactions that underpin the scattering dynamics.

Double ionization of helium by proton impact: from intermediate to high momentum transfer

Fil: Ambrosio, Marcelo Jose. Kansas State University; Estados Unidos. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Astronomia y Fisica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomia y Fisica del Espacio; Argentina

Flash X-ray cinematography analysis of dwell and penetration of small caliber projectiles with three types of SiC ceramics

Abstract In order to improve the performance of ceramic composite armor it is essential to know the mechanisms during each phase of the projectile–target interaction and their influence on the penetration resistance. Since the view on the crater zone and the tip of a projectile penetrating a ceramic is rapidly getting obscured by damaged material, a flash X-ray technique has to be applied in order to visualize projectile penetration. For this purpose, usually several flash X-ray tubes are arranged around the target and the radiographs are recorded on film. At EMI a flash X-ray imaging method has been developed, which provides up to eight flash radiographs in one experiment. A multi-anode 450 kV flash X-ray tube is utilized with this method. The radiation transmitted through the target is then detected on a fluorescent screen. The fluorescent screen converts the radiograph into an image in the visible wavelength range, which is photographed by means of a high-speed camera. This technique has been applied to visualize and analyze the penetration of 7.62 mm AP projectiles into three different types of SiC ceramics. Two commercial SiC grades and MICASIC (Metal Infiltrated Carbon derived SiC), a C-SiSiC ceramic developed by DLR, have been studied. The influences, not only of the ceramic but also the backing material, on dwell time and projectile erosion have been studied. Penetration curves have been determined and their relevance to the ballistic resistance is discussed.

Target–projectile interaction during impact melting at Kamil Crater, Egypt

In small meteorite impacts, the projectile may survive through fragmentation; in addition, it may melt, and chemically and physically interact with both shocked and melted target rocks. However, the mixing/mingling between projectile and target melts is a process still not completely understood. Kamil Crater (45m in diameter; Egypt), generated by the hypervelocity impact of the Gebel Kamil Ni-rich ataxite on sandstone target, allows to study the target–projectile interaction in a simple and fresh geological setting. We conducted a petrographic and geochemical study of macroscopic impact melt lapilli and bombs ejected from the crater, which were collected during our geophysical campaign in February 2010. Two types of glasses constitute the impact melt lapilli and bombs: a white glass and a dark glass. The white glass is mostly made of SiO2 and it is devoid of inclusions. Its negligible Ni and Co contents suggest derivation from the target rocks without interaction with the projectile (<0.1wt% of projectile contamination). The dark glass is a silicate melt with variable contents of Al2O3 (0.84–18.7wt%), FeOT (1.83–61.5wt%), and NiO (<0.01–10.2wt%). The dark glass typically includes fragments (from few μm to several mm in size) of shocked sandstone, diaplectic glass, lechatelierite, and Ni–Fe metal blebs. The metal blebs are enriched in Ni compared to the Gebel Kamil meteorite. The dark glass is thus a mixture of target and projectile melts (11–12wt% of projectile contamination). Based on recently proposed models for target–projectile interaction and for impact glass formation, we suggest a scenario for the glass formation at Kamil. During the transition from the contact and compression stage and the excavation stage, projectile and target liquids formed at their interface and chemically interact in a restricted zone. Projectile contamination affected only a shallow portion of the target rocks. The SiO2 melt that eventually solidified as white glass behaved as an immiscible liquid and did not interact with the projectile. During the excavation stage dark glass melt engulfed and coated the white glass melt, target fragments, and got stuck to iron meteorite shrapnel fragments. This model could also explain the common formation of white and dark glasses in small impact craters generated by iron bodies (e.g., Wabar).

Meshfree modeling of concrete slab perforation using a reproducing kernel particle impact and penetration formulation

A meshfree formulation under the reproducing kernel particle method (RKPM) was introduced for modeling the penetration and perforation of brittle geomaterials such as concrete. RKPM provides a robust framework to effectively model the projectile-target interaction and the material failure and fragmentation behaviors that are critical for this class of problems. A stabilized semi-Lagrangian formulation, in conjunction with a multiscale material damage model for brittle geomaterials and a kernel contact algorithm, were introduced for penetration modeling. In this work, the accuracy of the meshfree impact and penetration formulation was studied using a series of large-caliber projectile concrete slab perforation experiments with impact velocities in the ballistic regime. These experiments were selected due to the challenging nature of concrete perforation, and the results were used to validate the effectiveness of the proposed method to model the penetration processes and the concrete target failure. Simulation results confirm the formulation's accuracy for this type of high-rate ballistic problem and establish a basis for extension to other types of impact problems. The results show the importance of properly formulating the method of domain integration to maintain accuracy in the presence of concrete fragmentation, and also highlight the method's ability to capture the fragmentation response without a need for non-physical treatments commonly used in conventional methods.

Influence of renormalization shielding on the electron-impact ionization process in dense partially ionized plasmas

The renormalization shielding effects on the electron-impact ionization of hydrogen atom are investigated in dense partially ionized plasmas. The effective projectile-target interaction Hamiltonian and the semiclassical trajectory method are employed to obtain the transition amplitude as well as the ionization probability as functions of the impact parameter, the collision energy, and the renormalization parameter. It is found that the renormalization shielding effect suppresses the transition amplitude for the electron-impact ionization process in dense partially ionized plasmas. It is also found that the renormalization effect suppresses the differential ionization cross section in the peak impact parameter region. In addition, it is found that the influence of renormalization shielding on the ionization cross section decreases with an increase of the relative collision energy. The variations of the renormalization shielding effects on the electron-impact ionization cross section are also discussed.

Electron impact excitation of helium in Debye plasma

The probability, differential, and integral scattering cross sections of the 11S→21S and 11S→21P transitions of helium have been calculated in the first Born approximation. The projectile-target interactions depending on the temperature and the density of plasma are described by the Debye-Hückel model. Wave functions of the target before and after collision were modeled by non orthogonal Hartree-Fock orbitals. The wave functions parameters are calculated with the Ritz variational method. We improve our unscreened first Born approximation integral cross sections by using the BE-scaled (B stands for binding energy and E excitation energy) method. The second Born approximation has also been used to calculate the excitation cross sections in Debye plasma. Our calculations are compared to other theoretical and experimental results where applicable.

Double ionization of helium by fast electrons with the Generalized Sturmian Functions method

The double ionization of helium by high energy electron impact is studied. The corresponding four-body Schrödinger equation is transformed into a set of driven equations containing successive orders in the projectile–target interaction. The first order driven equation is solved with a generalized Sturmian functions approach. The transition amplitude, extracted from the asymptotic limit of the first order solution, is equivalent to the familiar first Born approximation. Fivefold differential cross sections are calculated for (e, 3e) processes within the high incident energy and small momentum transfer regimes. The results are compared with other numerical methods, and with the only absolute experimental data available. Our cross sections agree in shape and magnitude with those of the convergent close coupling method for the (10+10) eV and (4+4) eV emission energies. To date this had not been achieved by any two different numerical schemes when solving the three–body continuum problem for the fast projectile (e, 3e) process. Though agreement with the experimental data, in particular with respect to the magnitude, is not achieved, our findings partly clarify a long standing puzzle.

Studies of cross sections for collisions of electrons from hydride molecules:NH3andPH3

A parameter-free spherical complex optical potential approach in the fixed-nuclei approximation is applied here to calculate elastic differential, integral, and momentum-transfer cross sections as well as total (elastic plus inelastic) cross sections for the scattering of electrons from $\mathrm{N}{\mathrm{H}}_{3}$ and $\mathrm{P}{\mathrm{H}}_{3}$ molecules (i.e., nonmetallic hydrides) in the electron energy range of 0.1--100 eV. The projectile-target interaction is represented by a sum of a real and an imaginary potential. Present calculated results are compared with the available calculations and the experimental measurements. The quantitative features of the scattering parameters (such as Ramsauer-Townsend minimum and shape resonance structure), as observed in experiments, are well reproduced in the present study.

Discrepancy between theory and experiment in double ionization of helium by fast electrons

We compute fully differential cross sections for double ionization of helium by electrons, within the high-impact-energy and low-momentum transfer regimes, using the generalized Sturmian functions approach. Our results are converged relative to the total angular momentum and variable domain size. The method shows very good agreement with convergent close coupling calculations performed by Kheifets et al. [J. Phys. B 32, 5047 (1999)] for all ejection angles for the two electron emission energies considered in the experiments reported in that contribution. Both theoretical methods provide fully differential cross sections that require the same upscaling factors to compare with experimental data and are based on a first-order Born model for the projectile-target interaction. Since that reference was published, there were several theoretical efforts to account for the absolute scale of the experimental results, but agreement in the cross-section magnitude was not achieved even between theories. With the present contribution we conclude that the first-order Born model is now adequately solved, shifting the magnitude controversy towards either the experimental data and/or the addition of higher degrees of projectile-target interaction to the calculation.

Channeling of protons through BN nanotubes

In this paper we study the angular and spatial distributions of protons channeled through boron–nitride (BN) nanotubes. The BN nanotubes have very similar structures like carbon nanotubes, but they are more thermally and chemically stable, and they also present good candidates for future channeling experiments. We present the angular and spatial distributions of MeV energy protons through the straight short (10,10) single-wall BN nanotubes (SWBNNs). They were generated by a computer simulation method Borka et al. (2011, 2012a,b). Also, the effect of focusing of channeled protons is observed. A possible application of the obtained results for characterization of BN nanotubes is discussed. Analysis of angular and spatial distributions could be used to provide detailed information on the projectile–target interaction potentials inside BN nanotubes. We also varied the proton incident angle and energy and demonstrate that we can get a significant rearrangement of the propagating protons within the BN nanotube. This investigation may be used for proton beam guiding, to locate atomic impurities in nanotubes as well as for creating nanosized proton beams to be used in materials science, biology and medicine.

Scattering of Spin Polarized Positrons from Heavy Atoms: Europium and Bismuth

We present calculations of di erential, integrated elastic, total momentum transfer cross-sections and spin polarization parameters S for scattering of positron from Eu and Bi atoms in the energy range 2.0 to 500.0 eV using relativistic approach. The target projectile interaction is represented both by real and complex parameter-free optical potentials in the solution of the Dirac equation for the scattered positrons. The theoretical results are obtained from relativistic approach based on solving the Dirac equation using Hartree Fock and Dirac Fock wave functions to calculate cross-sections at all the energies considered.