Fast-ion interaction in dense plasmas with two-ion correlation effects

Time evolution and energy deposition for ion clusters injected into magnetized two-component plasmas

A two-dimensional particle-in-cell simulation model is proposed to study the time evolution and energy deposition for ion clusters injected into magnetized two-component plasmas. The injection of an isolated ion cluster is studied in the case of weak and strong magnetic fields. For strong magnetic fields, the ions tend to deposit their energy smoothly along the trajectory of the cluster, due to the confinement by the strong magnetic fields. However, in the case of weak magnetic fields, a large amount of energy is deposited by the ions near the initial cluster injection position, where the cluster density is expected to be largest. We attribute these to the influences of interference effects between the cluster ions, which have close relations to the distances between the ions. Furthermore, the influences of various magnetic fields, injection angles, and injection velocities on the time evolution and energy deposition of a beam pulse, which contains several similar ion clusters, are investigated in detail. The influences of different magnetic fields on the beam pulse show similar to that of a single ion cluster. For increasing injection angles, the beam velocity perpendicular to the magnetic field increases, leading to increasing oscillations in the beam trajectory and energy deposition profile. Besides, the amount of energy that transferred from the beam pulse to the plasma increases as the beam injection velocity approaches the electron thermal velocity.

Coulomb explosions and energy loss of molecular ions in plasmas

Interactions of swift molecular ions with high-density plasma targets are studied by means of the linearized Vlasov-Poisson theory, allowing the dynamically screened interaction potential among the constituent ions to be expressed in terms of the classical plasma dielectric function. Coulomb explosions and the energy losses of a molecular ion are simulated by solving the equations of motion for the constituent ions. It is found that, due to the wakelike asymmetry of the interaction potential, the molecular axis tends to align itself along the beam direction. In addition, a strong enhancement of the energy loss of the molecular ion has been found in the initial stages of Coulomb explosions due to proximity of the constituent ions, but this effect diminishes at latter stages when the ions are sufficiently far apart.

Interaction of ions and ion clusters with a disordered electron gas: collective and single-particle excitations

In this paper, we report results on our theoretical studies of stopping power contributions from single-particle and plasmon excitations. We have introduced an equipartition ratio defined as the ratio of stopping contributions from plasmon and single-particle excitations, respectively. Within the linear response theory we have made a comprehensive investigation of this equipartition ratio for fast pointlike and extended projectile ions in a disordered electron gas; the latter is modeled by a degenerate electron gas of metallic densities and with disorder being incorporated within a relaxation-time approximation. As simple but useful examples of pointlike and extended projectiles we have considered proton and He+ ion, as well as diproton and He+ ion clusters. We present detailed and comparative results for the equipartition ratio corresponding to several values of the damping parameter which characterizes disorder in our model. The results are also compared, wherever applicable, with those for individual, i.e., uncorrelated projectiles.

Dicluster stopping in a degenerate electron gas

In this paper we report on our theoretical studies of various aspects of the correlated stopping power of two pointlike ions (a dicluster) moving in close but variable vicinity of each other in some metallic target materials, the latter being modeled by a degenerate electron gas with appropriate densities. Within the linear-response theory we have made a comprehensive investigation of correlated stopping power, vicinage function and related quantities for a diproton cluster in two metallic targets, aluminum and copper, and present detailed and comparative results for three approximations to the electron gas dielectric function, namely, the plasmon-pole approximation without and with dispersion as well as with the random-phase approximation. The results are also compared, wherever applicable, with those for an individual projectile.

Laser-assisted stopping power of a hot plasma for a system of correlated ions

The laser-assisted stopping power of a fully ionized plasma for the system of two correlated test charges is investigated. The general expressions for the stopping power are applied to a low-density and a low-temperature plasma in a low-energy beam-plasma experiment [J. Jacoby et al., Phys. Rev. Lett. 74, 1550 (1995)]. The effect of the interaction between the beam test charges, described by a correlation term, is to increase the stopping power of the laser-assisted plasma compared to the case where the charges are infinitely separated. However, the laser field affects the correlation between the test charges and contributes to decrease the plasma stopping power, as compared to the laser-free dicluster case.