涡旋光驱动等离子体尾场加速电子束的强太赫兹波辐射

Due to its unique optical properties and promising applications in many fields, the intense Terahertz (THz) wave radiation source is one of the important light sources that people have been pursuing. In the way of intense laser driving, plasma-based intense THz source has been paid considerable attention due to plasma is free of optical damages. This proposal will utilize 3D-PIC to study the THz wave radiation of wakefield accelerating electron beam with vortex laser driving underdense plasma. Though optimizing the laser-plasma parameters to control dynamic processes of the electron beam, the intense THz wave radiation is generated. The mechanism of generating donut wakefield will be explored in the process of vortex laser driving plasma, and the dynamic processes about the energy, total charge, and movement of wakefield-accelerated electron beam be discussed and analysed. The dependence of the THz radiation power on the energy and total charge of the electron beam with helical motion will be emphatically discussed. Through numerically simulate, some fundamental rules will be revealed that THz radiation generate when the vortex laser drive plasma wakefield to accelerate electron beam.

具有独特光学特性、可应用在诸多领域的强太赫兹波辐射源是近来人们所追求的重要光源之一。在超强激光驱动的方式下，由于等离子体具有无损伤阈值的限制，基于等离子体的太赫兹辐射源已受到广泛关注。本项目将利用三维Particle-In-Cell (3D-PIC) 模拟方法对涡旋光驱动欠密等离子体尾场加速电子束的太赫兹发射进行研究。通过优化激光等离子体参数来调控电子束的动力学参量来获得强太赫兹波辐射。探索涡旋光激发等离子体环形尾场的形成机制，讨论和分析尾场加速电子束的能量、总电荷数、运动形态的动力学过程。着重讨论螺旋运动的电子束向外辐射太赫兹的强度与电子束能量、总电荷数的依赖关系。通过数值模拟揭示涡旋光驱动等离子体尾场加速电子束辐射太赫兹波的基本规律。

作为实现强太赫兹（THz）、极紫外（EUV）辐射源的重要途径之一，对激光气体等离子体相互作用的研究受到极大关注。本项目通过软件Vsim的粒子模拟方法研究了涡旋光激发等离子体尾场加速环形电子束的THz辐射过程，结果显示被加速的环形电子束能够产生THz辐射，但通过分析发现辐射的转换效率较低。考虑到静电场能够有效提高THz辐射的转换效率，另外还需要考虑等离子体电离过程的瞬态电流效应，为分析问题方便，我们开发了一维坐标三维速度的粒子模拟源代码（1D3V-PIC）。考虑等离子体中电子碰撞效应对瞬态电流的影响，利用重写的1D3V-PIC代码研究了在非均匀静电场下波纹等离子体产生THz辐射过程，研究发现该方案可以产生频率可调的混频THz辐射。另外，利用1D3V-PIC代码研究了在非均匀静磁场下激光电离气体产生THz辐射的过程，研究发现该方案可以产生可控啁啾的圆极化THz辐射。高次谐波（HHG）是获得EUV辐射源的重要手段之一，我们研究了非对称波形激光驱动氢原子产生HHG频移及控制。

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