| As is well-known,magnetic mirror structures can be observed in many magnetized plasmas,such as large devices for studying the thermonuclear fusion,the Earth’s magnetic field,etc.Therefore,research on magnetic mirrors is crucial.Examples of such research include the study of confinement properties of plasmas in magnetic mirrors,research on high-frequency heating of plasmas in magnetic mirrors,and research on plasma rotation control in magnetic mirrors.Currently,research on magnetic mirror plasmas mostly focuses on quasi-neutral plasmas,and relatively less attention has been paid to non-neutral plasmas.There are still some issues that need further investigation,among which the motion of non-neutral plasma beams in magnetic mirrors is one of the hot topics.In this study,the Particle-In-Cell method was used in conjunction with theoretical analysis to investigate the motion characteristics of non-neutral plasmas in magnetic mirrors,and the leakage of non-neutral plasmas in axisymmetric magnetic mirrors was studied in detail.The research on this issue helps to further our understanding of the confinement and motion properties of non-neutral plasmas in magnetic mirrors.The main contents of this paper are as follows:We first studied the confinement characteristics of non-neutral plasma beams in magnetic mirrors.The results showed that the loss rate of different types of ion beams increases with the increase of ion mass.We conducted theoretical analysis on this phenomenon and provided an analytical expression for the loss rate through force analysis on charged particles in magnetic mirrors.We found that the numerical results were consistent with the trends predicted by the theoretical analysis.Furthermore,we investigated the confinement of electron-ion non-neutral plasma beams by specific magnetic field configurations.Simulation results showed that both the electron leakage rate and ion leakage rate varied with the initial charge state of the plasma beam.When the initial electron number density was smaller than the ion number density,the leakage rates of both charged particles remained unchanged.However,when the initial electron number density was much larger than the ion number density,the ion leakage rate increased with increasing initial electron number density,whereas the electron leakage rate decreased with increasing initial electron number density.We compared and analyzed the simulation results with the loss cone theory of magnetic mirrors and found that the numerical and theoretical results were consistent.Subsequently,we investigated the effect of magnetic mirror field configurations on non-neutral plasma beams and studied the motion characteristics of non-neutral plasma beams in magnetic mirrors with different structures.We found that the ion and electron leakage rates of non-neutral plasma beams varied significantly with the initial electron number density of the beam under different magnetic mirror configurations.We also found that the distance between the two coils and the coil radius had a significant impact on the leakage rates of positive and negative charged particles,while the magnitude of the coil current had almost no effect on the ion and electron leakage rates.The research results of this paper help to understand the motion characteristics of non-neutral plasma beams in magnetic mirror fields.Furthermore,the difference in confinement properties of positively and negatively charged particles in magnetic mirrors may be utilized to aid in the design of a magnetic mirror for the separation of different types of charged particles. |
