Theory and PIC simulation about femtosecond intense laser pulse with free electrons and plasma

本论文主要进行了激光加速电子和相对论电子辐射以及超短超强激光脉冲与高密度等离子体相互作用的研究工作，具体如下： 1．研究了紧聚焦的线偏振飞秒超强高斯激光脉冲捕获并剧烈加速斜入射低能相对论电子的效应，发现被捕获的电子在激光脉冲纵向有质动力的强大加速作用下，可以获得GeV量级的能量。 2．研究了逆流相对论电子与激光脉冲相互作用获得激光同步辐射的频率上移、微分散射截面等特性。发现逆流相对论电子与短脉冲激光相互作用，可以获得阿秒X射线辐射脉冲。 3．研究了圆偏振和线偏振飞秒脉冲激光作用下电子振荡导致的谐波辐射的频谱的特性。研究发现随着激光强度的增加，电子在激光场中运动的相对论效应可以导致谐波辐射。 4．用两维PIC粒子模拟程序研究了相对论紧聚焦高斯激光脉冲在高密度（2倍临界密度）等离子体中的传输。 5．用两维PIC粒子模拟程序研究了相对论飞秒强激光与微米量级的固体小靶和薄膜靶相互作用加速离子的过程。通过对高能离子密度和发散角的比较，发现在相同的激光条件下，小靶比薄膜靶更有利于获得密度高、发散角好的高能离子。 6．用两维PIC粒子模拟程序研究了线偏振强激光和超薄纳米薄膜靶的相互作用。In this dissertation, femtosecond intense laser pulse interact with free electrons and plasma were studied theoretically and simulatively. The main results are as follows: 1. A low-energy relativistic free electron capture and violently acceleration by a tightly focused ultra-short ultra-intense laser pulse in vacuum is presented in this paper. The results show that the electron is mainly accelerated by the longitudinal pondero- motive force. 2. The frequency upshifting and differential cross section of the laser synchrotron source (LSS) based on the Thomson backscattering of intense laser radiation from a counter- streaming relativistic electron are considered. A counterstreaming relativistic electron interacting with an incident short pulse laser emits attosecond x-ray pulse. 3. The dynamics and harmonics emission spectra due to electron oscillation driven by intense laser pulses have been investigated considering a single electron model. The spectral and angular distributions of the harmonics radiation are numerically analyzed that demonstrates significantly different characteristics from those of the low-intensity field case. Higher order harmonic radiations are possible for a sufficiently intense driving laser pulse. 4. A tightly focused Gaussian laser pulse with relativistic intensity propagating in slightly overdense plasma of 2 times critical density is sdudied by means of 2D particle-in-cell simulation. 5. The comparative efficiency and beam characteristics of high-energy ions generated from the interaction of a petawatt laser pulse with thin foil and a small solid-density plasma bunch have been studied by particle-in-cell simulation under identical conditions. Using direct beam measurements, we find that small solid target acceleration produces higher energy particle with smaller divergence and a higher efficiency than thin foil acceleration. 6. The interaction of a linearly-polarized intense laser pulse with an ultrathin nanometer plasma layer is considered