Simultaneous Projectile Research Articles

Evaluating the performance of ceramic/fabric composite panels against simultaneous steel projectile impacts: An experimental and numerical study

In order to evaluate the ballistic performance of ceramic/fabric composite panels developed using 99.5 % alumina, Kevlar® and carbon fiber fabrics; a series of experiments were performed on the physical samples. The composite-projectile interaction was investigated in detail by means of finite element analysis using LS-DYNA®. The validated numerical model of the ceramic/fabric composite system was tactically modified to investigate the composite/projectile interaction for simultaneous projectile impacts at different impact velocities. The numerical model predicted the failure mechanism of the composite panel and the exit velocity of the projectile piercing through the composite accurately. This study reveals the important aspects of ballistic impact on composites under simultaneous multiple projectile impact condition which in turn, is a much more complex and critical case as compared to sequential multiple projectile impacts.

Search for isotope effects in projectile and target ionization in swiftHe+onH2orD2collisions

Using the cold target recoil ion momentum spectroscopy (COLTRIMS) technique, we have measured the simultaneous projectile and target ionization in collisions of He$^+$ projectiles with a mixture of gaseous H$_2$ and D$_2$ for an incident projectile energy of 650 keV. Motivated by Cooper et al. [Phys. Rev. Lett. 100, 043204 (2008)], we look for differences in the ionization cross section of the two isotopes with the highest resolution and statistical significance. Contributions of the electron-electron and electron-nucleus interactions have been clearly separated kinematically by measuring the longitudinal and transverse momentum of the recoiling ion. We find no significant isotope effect in any of our momentum distributions.

Universal behavior of the electron-electron interaction in the simultaneous projectile and target ionization

The antiscreening contribution to the simultaneous projectile and target ionization is analyzed for He+ and C3+ projectiles impinging on noble gas targets. The energy dependence of the average number of target active electrons which contribute to the antiscreening is described by means of a simple function, which is "universal" for noble gases but whose parameters are projectile dependent. A method is presented to estimate the number of active electrons for each target subshell in the high-velocity regime.

Electron-capture cross sections of multiply charged slow ions of carbon, nitrogen, and oxygen in He

Experimental cross sections are presented for single- and double-electron capture by ${\mathrm{C}}^{q+}$, ${\mathrm{N}}^{q+}$, and ${\mathrm{O}}^{q+}$ $(q=2--6)$ ions from He at incident energies of $(1.0--1800)q\phantom{\rule{0.2em}{0ex}}\mathrm{eV}$. Measurements were performed by using a mini-electron-beam-ion-source apparatus in combination with an octopole-ion-beam-guide. The cross sections are found to vary significantly depending on the collision energy as well as on the projectile species. Some cross sections reveal minima at incident energies of a few $\mathrm{eV}∕\mathrm{u}$, below which the cross sections increase with decreasing incident energy. To account for the experimental results, we developed a formalism of velocity-dependent capture cross sections within the framework of the classical over barrier model by employing an induced dipole interaction potential between the collision partners. In the calculations, doubly excited levels of projectile ions, formed via simultaneous excitation of the outermost projectile electron, were taken into consideration. It is found that the present model can satisfactorily reproduce the experimentally obtained energy dependence as well as absolute values of the cross sections. We conclude that the attractive induced dipole potential and simultaneous projectile excitation are important in low energy electron-capture collisions.

Effective strength of the electron-electron interaction in simultaneous projectile and target ionization.

The determination of the right balance between the strong-field interaction of the screened target nucleus and the two-center electron-electron interaction has been controversial since the early attempts to describe the stripping of light, swift ions, by heavy targets. In this work, we find a region of influence for the electron-electron contribution which clearly indicates that this interaction is an essential contribution to the stripping process for both light and heavy targets.

Electronic stopping power for swift excited He-like ions with bound electrons in the 1s nl state ( n = 2,3 and l = 0,1)

Using the first Born approximation, analytical formulae of the electronic stopping cross section and the effective charge, , are presented for swift partially stripped ions in 1s2p and 1s3p states passing through a material of atomic number in the velocity range (: Bohr velocity). Under the frozen-charge condition, it was at first found that the axial direction of the spatial distribution of p electrons remarkably affects the stopping cross sections. The magnitudes of stopping cross sections and for the 1s2p and 1s3p states are compared with those for the ground state and the metastable states (1s2s and 1s3s). Secondly, as well as the target excitation above, the contributions of the projectile excitation and the simultaneous projectile - target excitation processes are briefly estimated using a harmonic oscillator model for the target. It was found that the frozen-charge state projectile loses its energy quite dominantly compared with the projectile-inelastic processes.

Electron-electron interaction in projectile ionization

For simultaneous projectile and target ionisation in He +He collisions the momentum distribution of the singly and doubly charged recoil ions has been measured. A new cold target recoil ion momentum spectrometer with a momentum resolution of ±0.13 a.u., based on a precooled supersonic He gas jet, has been used. The experimental doubly differential cross section shows two prominent structures which can be attributed to the two center electron-electron interaction and the nucleus-electron interaction. The contribution due to the electron-electron interaction is found to be negligible at 0.5 MeV impact energy and to be dominant at 2 MeV. The two center electron-electron interaction contributes much less to target double than to single ionisation.

Charge transfer and excitation in high-energy ion-atom collisions

Coincidence measurements of charge transfer and simultaneous projectile electron excitation provide insight into correlated two-electron processes in energetic ion-atom collisions. Projectile excitation and electron capture can occur simultaneously in a collision of a highly charged ion with a target atom; this process is called resonant transfer and excitation (RTE). The intermediate excited state which is thus formed can subsequently decay by photon emission or by Auger-electron emission. Results are shown for RTE in both the K-shell of Ca ions and the L-shell of Nb ions, for simultaneous projectile electron loss and excitation, and for the effect of RTE on electron capture.