Ion beam charge neutralization by electron injection is a complex kinetic process.Recent experiments show that resulting self-potential of the beam after neutralization by plasma could be much lower than the temperature of plasma electrons [Physics of Plasmas 23, 043113 (2016)], indicating that kinetic effects are important and may affect the neutralization of ion beam. We performed a numerical study of the charge neutralization process of an ion beam making use of a two-dimensional electrostatic particle-in-cell code. The results show that the process of charge neutralization by electron injection is comprised of two stages. During the first stage, the self-potential of the beam is higher than the temperature of injected electrons (Te/e). Therefore, the neutralization of the ion beam is almost unaffected by Te, and all injected electrons are captured by the ion beam. At the second stage, with the decline of the beam potential (), hot electrons escape from the ion beam, while cold electrons are slowly accumulated. As a result,  can be much lower than Te/e. It is found in the simulations that during the accumulation of cold electrons,  scales as e T  . In addition, the results show that the transverse position of electron source has a great impact on ion beam neutralization. Slight shift of electron source leads to large increase of the beam potential because of increase in potential energy of injected electrons.

The charge neutralization of an ion beam by electron injection is investigated using a two-dimensional electrostatic particle-in-cell code. The simulation results show that electrostatic solitary waves (ESWs) can be robustly generated in the neutralization process and last for long time (for more than 30 μs); and therefore ESW can strongly affect the neutralization process. The ESWs propagate along the axis of the ion beam and reflect from the beam boundaries. The simulations clearly show that two ESWs can pass through each other with only small changes in amplitude. Partial exchange of trapped electrons in collisions of two ESWs is observed in the simulations and can explain interaction during collisions of two ESWs. Coalescence of two ESWs is also observed.

The reflection of an electromagnetic wave in a thin plasma layer attached to a metal plate at high pressure is investigated with the finite-difference time-domain method. The effects of the plasma thickness, the plasma density distribution function, the collision frequency between electrons and neutrals and the frequency of incident wave on the reflection coefficient of the electromagnetic wave are discussed. Numerical results indicate that the reflection coefficient of the wave depends on its frequency, the plasma thickness, the plasma density distribution and the collision frequency. The reflection coefficient is low only at the low band of the calculated frequency for different plasma distribution functions if the plasma layer is very thin, e.g. 10 mm. Plasmas with an excess of 20 mm for a high collision frequency such as 103 GHz are capable of absorbing microwave radiation over a wider frequency range for different plasma distributions.

The principle of surface wave plasma discharge in a rectangular cavity is introduced and the distribution of the electromagnetic field within a rectangular waveguide is analysed. A novel structure of a slot antenna array is presented. In comparison with the traditional slotantenna, it is shown that the designed slot antenna array can excite effectively the surface wave coupling into the chamber, and generate a stable large-area high-density plasma. These results are useful for exploring the optimized design of the slot-antenna for surface wave plasmas.

The excitation and propagation of electrostatic solitary waves (ESWs) are observed in two-dimensional particle-in-cell simulations of ion beam neutralization by electron injection by a filament. Electrons from the filament are attracted by positive ions and bounce inside ion beam pulse. Bouncing back and forth electron streams then starts to mix, creating the two-stream instability. The instability saturates with the formation of ESWs. These ESWs reach several cms in longitudinal size and are stable for a long time (≫τ b , the duration of the ion beam pulse). The excitation of large-amplitude ESWs reduces the degree of neutralization of the ion beam pulse. In addition, the dissipation of ESWs causes heating of neutralizing electrons and their escape from the ion beam, leading to further reduction of neutralization degree.

Finite-difference-time-domain arithmetic is applied to simulate the propagation of an electromagnetic (EM) wave in a two-dimensional atmospheric pressure plasma (APP) and a metal layer with strong electron-neutral collisions. The dependences of the EM wave attenuation on the parameters of the APP are provided. The two-dimensional numerical results indicate that when the profile of the electron density is given, the attenuation of an EM wave in APP is strongly affected by (a) the polarization mode (TM mode or TE mode), (b) the incident angle of the EM wave, (c) the EM wave frequency, (d) the width of the plasma layer, and (e) the collision frequency between electrons and neutrals. In this paper, the behaviour of the propagation of an EM wave inside the plasma layer is explained by the principle of wave interference. The relationship between the attenuation property and the above-mentioned parameters is also studied.

A self-consistent and three-dimensional (3D) model of argon discharge in a large-scale rectangular surface-wave plasma (SWP) source is presented in this paper, which is based on the finite-difference time-domain (FDTD) approximation to Maxwell's equations self-consistently coupled with a fluid model for plasma evolution. The discharge characteristics at an input microwave power of 1200 W and a filling gas pressure of 50 Pa in the SWP source are analyzed. The simulation shows the time evolution of deposited power density at different stages, and the 3D distributions of electron density and temperature in the chamber at steady state. In addition, the results show that there is a peak of plasma density approximately at a vertical distance of 3 cm from the quartz window.

A three-dimensional model of a surface-wave plasma (SWP) source is built numerically using the finite-difference time-domain (FDTD) method to investigate the structure of the surface wave propagation along the plasma-dielectric interface and the distributions of electromagnetic fields in the whole system. A good-performance excitation source technique for the waveguide which is pivotal to the simulation is presented. The technique can avoid the dc distortions of magnetic fields caused by the forcing electric wall. An example of simulation is given to confirm the existence of the surface waves. The simulation also shows that the code developed is a useful tool in the computer-aided design of the antenna of the SWP source.