| Interactions between intense proton beams and solid targets is one of the means to produce warm dense plasma. The research on this process is not only one of the important basic physical problems, but also helpful to understand the process of the proton beam assisted fast ignition, ion beam-driven inertial confinement fusion, and the astrophysics physics. Researches are particularly interested in the description and measurement of wake field distribution and energy loss processes, and the property of generated warm dense matter(WDM).This article focuses on the transmission in the target material under different proton beam intensity and different beam density, as well as the collective excitation process of the target electron and the description of wake field distribution.Warm dense plasma generated by beam-target interaction is between the strongly coupled quantum condensed matter system and the weak coupled classical high-temperature plasma. Therefore it can not be simulated y either classical plasma theories or quantum condensed matter theories. In previous simulations, both the proton beams and electron gas in the aluminum target are considered as quantum fluid. Quantum hydrodynamic model is a proper description for the electron gas, but not a proper model for the proton beam, because quantum effects are neglectable in beams. Particle in Cell is more suitable to describe the proton beam, so we use the Particle in Cell – Quantum Hydrodynamics(PIC–QHD) coupled model to investigate the process.The first chapter briefly introduces the background of the sdudy of the proton beam interactions with solid targets, as well as the current research status and illustrates the major physical problems of the beam-target interaction. We also give the contents and the arrangement of the thesis.The second chapter describes in detail the grounds for using PIC – QHD coupled Model of the beam-target interaction and emphasises on the QHD model, PIC model and the derivation of their numerical solving method. The nonlinear QHD equations are solved by the flux correction transport format(FCT) value, and a one-dimensional electrostatic explicit PIC model is used to describe the proton beam. Physical models and numericalmethods- nonlinear PIC–QHD coupled methods are also given.The third chapter verifies the reliability and advantages of the PIC–QHD coupled model which is described the beam-target interaction. The simulation shows the results of the proton beam density, target electron density and electric field using pure QHD methold and PIC–QHD coupled method respectively. Which show that results from PIC–QHD coupled method and pure QHD obtain agree well qualitatively. The pure QHD model has been validated by analytical models and experiment, thus PIC method is proved to describe the proton beam reliably. Secondly, PIC methold can show the effects which QHD methold can not: for example, with the increase of time, due tot he proton beam accumulated to a certain extent near the surface and the space charge repulsion, the proton beam can not enter the target medium, which embodies the superiority of PIC – QHD coupled model. In short, PIC–QHD coupled model can show more accurate results and have a wider application.In the fourth chapter, the one-dimensional nonlinear PIC–QHD coupled model is adopted to describe the proton beam density, speed, target electron density and wake field of the beam-target interaction. Simulation results indicate that: because of the space-charge effects, the proton beam presents the phenomenon of pulsed beam, as the speed increases, the target electron density and wake field increases larger. Furthermore,the density of the proton beam, the target electron density and the wake field are affected significantly by the quantum effects, the existence of quantum effects will reduce the magnitude of the disturbance, the spatial distribution of the field perturbations. Compared to the classic case, spatial distribution of the field perturbation is quite different. |
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