The Research On The Ionization Effect And 100MG Level Self-generated Magnetic Field In The Interaction Of The Ultra-intense Laser Pulse With Matters

The interaction of the ultra-intense laser pulse with matters has become one of the most important fields in the frontier research of physics with the development of the high power laser facilities.Various of electron source,ion source,and radiation source,produced by the interaction of ultra-intense laser with matters,have been used in high energy density physical experiment,and are expected to be used in material detection and cancer treatment.In this thesis,there are two important problems in relevant to the interaction of the ultra-intense laser pulse with matters have been studied in detail.One is the influence of ionization effect on the interaction of the ultra-intense laser pulse with CH gas.The other is the generation mechanism and influence of the self-generated magnetic field in the interaction of ultra-intense laser pulse with nanostructured target.The interaction of ultra-intense laser pulse with CH2 gas have been studied in detail by using the particle simulation(PIC)method which include the collision and ionization process.It is found that a magnetic-dipole vortex(with 100 MG level self-generated magnetic field)is formed and self-sustained by its magnetic field pressure inside the plasma channel after the laser energy is almost depleted.The plasma channel is formed due to the laser ponderomotive force before the laser energy is depleted,and continues to extend by the magnetic dipole vortex after the laser energy is depleted.We also found that for the case without ion-ization,the deflection of the plasma channel can easily occur during the forward movement of the magnetic dipole vortex,but for the case with ionization,the deflection of the plasma channel is suppressed by the ionization effect.Further analysis indicates that the ionization process can decrease of the plasma density steepening at the front of the plasma channel.The self-generated magnetic field of the order of 100 MG not only affects the formation of the plasma channel,but also affects the generation and transport efficiency of the relativistic electron beam.A fully relativistic analytical model of the intensity and distribution of the self-generated magnetic field based on the electron magneto-hydrodynamic description is presented here.The analytical model shows that this self-generated magnetic field originates in the nonparallel density gradient and fast electron current at the interfaces of nanolayered target.And the material has a small effect on the generation of the self-generated mag-netic field in the nanolayered target.The 2D-PIC simulation results are in good agreement with the theoretical analysis.The simulation results also indicate that the motion of electrons in the nanolayered target is greatly affected by the static magnetic field,and the motion of ions in the nanolayered target is greatly affect-ed by the static electric field.Through theoretical analysis,it was found that in the self-generated electromagnetic field,the evolution time for the ions to move from one nanowire to another nanowire is about 100 fs.So,the whole structural of the nanolayered target can maintain integrity within the time 50?100 fs.These research are beneficial to improving the quality of the energetic electrons and ions accelerated by the ultra-intense laser pulse in the nanolayered target.In this thesis,we first introduce the research background and some funda-mental physical concepts,including the basic concepts of laser fusion,the de-velopment of laser technology,the research progress of ultra-intense laser-driven particle sources and the introduction of particle in cell(PIC)simulation method.In chapter two,the kinetic model of the ionization in PIC simulations including the field ionization,the collisional ionization,the electron-ion recombination and the ionization potential depression by the surrounding plasmas is introduced in detail.In chapter three,the simulation results of the interaction of ultra-intense laser pulse with CH2 gas have been introduced in detail by using the particle simulation(PIC)method which include the ionization process.In chapter four,a fully relativistic analytical model of the self-generated magnetic field is intro-duced when the ultra-intense laser pulse interacts with the nanolayered target.The last capture is the summaxy and outlook.