Projectile

About: Projectile is a research topic. Over the lifetime, 13047 publications have been published within this topic receiving 115563 citations.

Quantum-mechanical impulse approximation for single ionization of hydrogenlike atoms by multicharged ions

Abstract: A quantum-mechanical approximation is developed for ionization of one-electron targets by charged-ion impact. The model is based on the nonrelativistic distorted-wave formalism valid for impact velocities larger than the electron orbital velocity in the initial state. The exact impulse wave function is used to describe the initial state, thus incorporating the projectile potential to all orders. The final state is represented by a product of continuum Coulomb wave functions around both centers, providing the correct asymptotic conditions and the projectile and target cusps. The theory is thought to be valid for large projectile charge, even larger than the ion velocity. The impulse approximation developed here is expensive in computing time, but it is probably one of the few models to deal with high projectile charges. Double-differential cross sections are computable in the forward and backward ejection angles. Comparisons with the experiments in different regions of interest are presented, including the binary sphere, capture to the continuum cusp, ridge electrons, and backward ejection angles. The theory proves to be quite successful, and it does not seem to deteriorate with increasing projectile charge.

Effective charge and related/unrelated quantities in heavy-ion stopping

Abstract: Stopping cross sections for swift heavy ions are commonly parameterized in terms of a velocity-dependent effective charge defined with reference to proton or helium stopping. This assumes projectile screening by core electrons to be a dominating factor governing the velocity dependence of the stopping cross section. In this note we demonstrate, on the basis of improved theoretical estimates of stopping cross sections, that projectile screening only affects the quantitative details of the velocity dependence of the effective charge while the general behavior reflects the transition from the Born to the classical regime. This is consistent with the experience that effective charges derived from measured stopping cross sections show dependencies on projectile and target atomic number which differ distinctly from those of the equilibrium projectile charge. It follows that there is no theoretical basis for the effective-charge concept as it is commonly used in heavy-ion stopping.

Friction and ablation measurements in a round bore railgun

Abstract: Detailed experiments were performed in order to determine electrode ablation and friction effects in a round-bore railgun. An accelerating model was developed which includes electrode-ablation effects, the viscous arc drag, and the mechanical friction of the projectile. In addition, a novel nonlinear electrode-ablation model was found to describe the experimental data very well. A model for the mechanical friction force between the projectile and bore wall was applied to the equation of motion. The position/time data of the projectile acceleration could be adjusted with quite reasonable friction effects. Theoretical and experimental results show that the 'ideal' projectile velocity is decreased by about 28%: 15% due to electrode ablation, 9% due to mechanical friction, and about 4% due to viscous arc drag. >

Hugoniot analysis of the ram accelerator

Abstract: The thermodynamic properties of a combustible propellant gas, after it has been processed by a ram accelerator propulsive mode, are related by a “ram accelerator Hugoniot” expression. These end states are determined from the 1-D conservation equations in a manner similar to that used for detonation waves, but with the addition of a force term in the momentum equation. Establishment of a region of potentially accessible thermodynamic end states that are consistent with ram accelerator operation at and above the Chapman-Jouguet detonation speed indicates that there are no fundamental constraints on accelerating projectiles over a wide range of Mach numbers in a single propellant mixture. Interpreting experimental data in the context of a genetalized ram accelerator process leads to relatively simple propulsive models which can predict the projectile acceleration of any propulsive mode. The projectile velocity and acceleration histories determined by the Hugoniot analysis for the thermally choked ram accelerator mode are in excellent agreement with experiments.