超强激光与等离子体作用产生自生磁场的新机制  

A New Mechanism on Self-Generated Magnetic Field Produced by Action of Extra-intense Laser and Plasma

作　　者：皮小力[1] 高海林[1] 郝东山 

机构地区：[1]河南工业职业技术学院基础科学教学部,河南南阳473009 [2]郑州工业应用技术学院信息工程学院,河南新郑451100

出　　处：《激光与光电子学进展》2014年第10期110-115,共6页Laser & Optoelectronics Progress

基　　金：河南省基础与前沿技术研究(092300410227)

摘　　要：应用多光子非线性Compton散射模型和粒子模拟程序,研究了Compton散射对等离子体中自生磁场的影响,提出了将超强入射激光脉冲和Compton散射光形成的耦合光作为形成自生磁场的新热电机制,给出了自生磁场的修正方程,并进行了仿真实验验证。结果表明:入射激光的ω0t<350时(ω0和t分别是入射激光的圆频率和脉冲宽度),电子密度发生明显变化,这是由于散射使质子与电子碰撞频率增大,能量交换加快,超热电子获得更高能量,从而带动更多质子加速的缘故。自生磁场空间分布范围和强度增大,这是由于散射使等离子体碰撞频率及电子的温度和密度梯度增大的缘故。自生磁场先较快增加后指数增长,到达正饱和后缓慢减小,最后达到负饱和状态,形成对称结构。自生磁场最大值为5.3×103T,比散射前强。这是由于散射使更多粒子发生了二、三阶电离,更多超热电子形成了更强的电流,最后趋于稳定的缘故。强自生磁场处温度梯度最大,且沿y方向,电子有效温度为0.61 MeV,比散射前更接近理论结果0.63 MeV,这是散射对电子温度贡献的结果。By using the model of multi-photon nonlinear Compton scattering and particle-in-cell programme, the influences of Compton scattering to the self-generated magnetic field in plasma are studied, a new hot- electric mechanism of self-generated magnetic field formed by the coupling light from the extra-intense incident laser pulse and Compton scattering light is given and the revised equation of the self-generated magnetic field is given out with simulated experiment verification. The results show that when the incident laser toot 〈 350 （ t00 is angnlar frequency, t is pulse duration）, the electron density is clearly changed, the cause is that the collision frequency between the proton and electron is increased by Compton scattering, the energy exchanging is accelerated, the even high energy is got by the extra-hot electron, and even protons are accelerated. The sapace distribution area and intense of the self-generated magnetic field increase, the cause is that the plasma collision frequency and gradients of temperature and density of the electron are increased by Compton scattering. Firstly, the self-generated magnetic field increases fastly, then, it increases with exponential function, after the saturation, it slowly decreases, finally, it reaches negative saturation, and the symmetrical system is formed. The maximum of the self-generated magnetic field is 5.3 × 103 T, the magnetic field intense is stronger after scattering, and the cause is that the two and three step ionizations of the even more particles take place becanse of Compton scattering, the even stronger current is formed by the even more extra- hot electrons, and finally the current is steady. The temperature gradient near the strong self-generated magnetic field is the maximum, its direction is y direction, the effective temperature of the electron is 0.61 MeV which is close to the theorectical result 0.63 MeV after scattering, and the cause is that the Compton scattering has a contribution to electron temperature.

关 键 词：等离子体 超强激光 多光子非线性COMPTON散射 自生磁场 梯度 超热电子 

分 类 号：O434.12[机械工程—光学工程]