QQ客服 官方微博 反馈留言

题名	超强激光场与自由电子相对论性相互作用中的相位效应研究
作者	贺新奎
学位类别	博士
答辩日期	2005
授予单位	中国科学院上海光学精密机械研究所
导师	徐至展
关键词	相对论非线性光学 光场相位 强场电子相互作用
其他题名	Phase dependence of the laser electron interaction in relativistic regime
中文摘要	啁啾脉冲放大技术的发明使得激光器输出功率密度不断提高，现在的台式激光器的峰值功率已进入拍瓦量级，聚焦功率密度达到1021W／cm2。聚焦功率密度的大幅度提高使得物质与激光相互作用时电子的速度接近光速，传统的非线性光学进入了相对论领域—相对论非线性光学。相对论非线性光学主要研究超弧超短的激光脉冲与物质的相对论性高度非线性栩互作用，作为一个新兴的学科，已经成为光学领域的研究热点。由于光场非常强，脉宽非常短使得超强激光与物质相互作用表现出很强的相位依赖性。本文论文研究了超强激光与相对论电子相互作用中的相位依赖特性，取得了若干重要的创新性成果。恒定磁场中电子与超强激光的相互作用的研究，对于研究激光电子加速和惯性约束核聚变中的激光快点火都非常重要，因此本论文研究了这一过程中电子动力学行为以及辐射谱的相位依赖性。研究发现，对于非共振情况，不论是电子的运动行为还是辐射谱都表现出极强的相位依赖性。对于圆偏振光，发现由于初始相位的不同，电子作螺旋运动的轴线将不同，当初始相位从0变化到π／2，螺旋运动的轴线会以电子的初始位置为圆心画出一个柱面。对于线偏振光，电子的动力学行为以及辐射谱以r＝1为分界线两边对于初始相位表现出相反的依赖性。r＜1时，初相位由O变化到π／2，电子的螺旋运动半径减小、能量平均值减小、迎着激光方向的磁场线减弱、垂直于激光方向的平均辐射减弱；r＞1时，初相位由O变化到π／2，电子的螺旋运动半径增大、轨迹的小幅振荡的振幅增大、迎着激光方向的磁场线增强、垂直于激光方向的平均辐射增强。综合以上结论，对于线偏振光本文得到了这样的结论，r＜1时，初相位由O变化到π／2，电子对于激光场的能量吸收减弱。而r＞1，初相位做同样的变化电子对激光场的能量吸收增强。对于共振情况，本文发现电子在初始位相为万／2时能量吸收稍好于初相位为O时，但并没有本质的变化。电子的运动行为随着初始相位的不同几乎没有变化，同样可以推断电子的辐射谱也不会随初始相位的不同有大的改变。紧聚焦的激光束中的电子加速，是真空电子加速的重要模型。本论文研究了在长脉冲中，紧聚焦电子加速的可能性。发现在紧聚焦的超强激光束中，如果电子初始位置处于光束中心，电子加速对于初始相位呈现出很强的依赖性，随着初始相位的变化，加速效果呈以T／2为周期的周期性变化，T是光场周期。最理想的初始相位为Nπ附近，其中N=0，1，2，…，而当初始相位为（N＋1／2）π时，电子不能获得高效的加速。数值模拟发现，这种模型加速效果很好，应用10PW的超强激光束，初始能量小于1MeV的电子可以被加速到高达1.4Gev。本论文给出了应用这种模型加速的最佳参数。发现最佳初始位置处于焦后，这样对于脉冲激光可获得有效的脉冲前沿有质动力加速，而后沿的减速也会由于光束的扩展而大大减弱。
英文摘要	With the invention of chirped pulse amplification technology, tabletop lasers have undergone a quantum jump in peak power. The development of high-peak power lasers have led to the advanced petawatt systems. Those facilities can deliver superstrong laser pulses with focused intensities as high as 1021W/cm2. Because of the ultrahigh laser intensity at focus, the speed of the electron during laser matter interaction is close to c, the speed of light. Thus, a new field of nonlinear optics, has been explored Nonlinear Relativistic Optics. The field of the nonlinear relativistic optics is mainly on the ultra-high laser field and matter interaction. As a new field, it has become a hotspot of optics. Because of the ultrahigh intensity of the laser field and the ultra short duration of the laser pulse, the phase of the laserfield at which the electron experiences within the laser pulse will be important. In this thesis, the phase dependence of ultrahigh laser field electron interaction is investigated. We have investigated the phase dependence of the dynamics and emission spectra of a fully relativistic electron in the superposition of an ultra intense plane wave laser field and a strong uniform magnetic field. This problem is important for the understanding of laser-plasma interaction and the related problems of high-energy electron emission, as well as for the interpretation and understanding of current laser-driven fusion experiments. For the nonresonance case, both dynamic behavior of the electron and radiation spectrum are strong phase dependent. We have shown that the effect of changing the initial laser phase is quite different for the cases of circularly and linearly polarized laser fields. For circular polarization only the axis of the helical trajectory is changed with variation of the initial laser field phase. The axis of the helical trajectory of the electron will scan a cylinder when initial phase change from 0 to 2π . However, for linear polarization, the effect of changing the initial phase is different in the two parameter regions divided by the resonance condition r = 1. When r < 1, with the increasement in η0 from 0 to π/2 , the radius of the electron's helical trajectory, the height of the magnetic peak and the average value of radiation spectrum observed from both the direction of the electric field and magnetic field are reduced, and these physical values are increased when r > 1. The results indicate that the magnetic peak is decided by the helical trajectory of the electron's movement. We also studied the phase dependence of the electron's energy and velocity components and found that they show some beat structure when η0 = 0 and this structure is absent when η0=π/2. Based on all these phenomena, we may conclude that, for r < 1, the energy exchange between the laser field and the relativistic electron is decreased when the initial laser field phase changes from 0 to π/2, and the result is the contrary when r > 1. For resonance case, we find that there is a little increase in energy exchange between the laser field and the relativistic electron when initial phase of laser field changed from 0 to π/2, but the change is not essential. We also find that there is almost no change of the dynamic behavior of the electron with different initial laser field phase, so we can conclude that there will not be essential change in the radiation spectrum of the electron. Electron acceleration in a tightly focused intense laser beam is an important model of vacuum laser electron acceleration. When we investigated the possibility of electron acceleration in a long laser pulse, strong phase dependence is found in this model if the electron is at the axis of the laser beam initially. The acceleration is periodic to the variety of the initial laser field phase, the period is π/2. The optimal initial phase of the laser field is Nπ, where N = 0, 1, 2, .... Electron can't be accelerated efficiently when the initial phase is (N + l/2)π. The simulation results show that the acceleration is efficient. When appropriate condition is reached, the electron gains more than 1.4 Gev from interaction with the 10 PW beams and over 400 Mev from the 1 PW beams. We also found the optimal parameter of the acceleration. The optimal location of the electron is behind the focus point, this is convenient for acceleration using laser pulse, because the electron can be accelerated by the ponderomotive force of leading part of the pulse and the deceleration by the descending part of the pulse is ineffective due to the evolution of the Gaussian laser beam waist.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15558]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	贺新奎. 超强激光场与自由电子相对论性相互作用中的相位效应研究[D]. 中国科学院上海光学精密机械研究所. 2005.

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。