ABSTRACT
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.
ABSTRACT
A two-dimensional particle-in-cell (PIC) model is proposed to study the wake field and stopping power induced by a nonrelativistic charged particle moving perpendicular to the external magnetic field in two-component plasmas. The effects of the magnetic field on the wake potential and the stopping due to the polarization of both the plasma ions and electrons are discussed. The velocity fields of plasma ions and electrons are investigated, respectively, in the weak and strong magnetic field cases. Our simulation results show that in the case of weak magnetic field and high ion velocity, the wakes exhibit typical V-shaped cone structures and the opening cone angles decrease with the increasing ion velocity. As the magnetic field becomes strong, the wakes lose their typical V-shaped structures and become highly asymmetrical. Similar results can be obtained in the case of low ion velocity and strong magnetic field. In addition, stopping power is calculated and compared with previous one-dimensional and full three-dimensional PIC results.
ABSTRACT
The behavior of nanoparticles in dual-frequency capacitively coupled silane discharges is investigated by employing a one-dimensional self-consistent fluid model. The numerical simulation tries to trace the formation, charging, growth, and transport of dust particles during the discharge, under the influences of the high- and low-frequency electric sources, as well as the gas pressure. The effects of the presence of the nanoparticles and larger anions on the plasma properties are also discussed, especially, for the bulk potential, electron temperature, and densities of various particles. The calculation results show that the nanoparticle density and charge distribution are mainly influenced by the voltage and frequency of the high-frequency source, while the voltage of the low-frequency source can also exert an effect on the nanoparticle formation, compared with the frequency. As the discharge lasts, the electric potential and electron density keep decreasing, while the electron temperature gets increasing after a sudden drop.
ABSTRACT
Energy losses of test particles in magnetized two-component plasmas are investigated within the framework of the linearized Vlasov-Poisson theory, taking into account the dynamic polarization effects of both the plasma ions and electrons. General expressions of the potential and stopping power are obtained and calculations are performed for protons in a magnetized hydrogen plasma. The influences of the magnetic field, the angle between the proton velocity and magnetic field, and certain plasma parameters on the stopping power are studied. Numerical results show that for low particle velocities and strong magnetic field the dynamic polarization effects of the plasma ions become obvious and contribute mainly to the stopping power.
