基于激光尾场加速的自反射式全光汤姆孙散射的参数优化

Parameter optimization of self-reflecting all-laser-driven Thomson scattering based on laser wakefield acceleration

基于激光尾场加速的全光汤姆孙散射能够提供高质量X射线束并大大减小装置的尺寸.与分光式相比,自反射式的构架可以降低实验的时空同步难度,但是由于激光尾场电子加速和汤姆孙散射过程耦合, X射线优化难度大,目前缺乏参数优化的相关报道.本文用数值模拟修正解析理论的方法,定量分析了激光尾场电子加速和汤姆孙散射过程中激光和电子束的焦斑、脉宽、能量等参数变化情况,并给出了激光在等离子体镜上的反射率,从而实现了用解析公式计算而非数值模拟跟踪参数变化,在保证精度的同时节约了计算时间.另外,利用修正后的公式优化了给定激光条件下的自反射式全光汤姆孙散射X射线,通过改变等离子体密度和等离子体镜位置这两个参数给出了最优X射线亮度和光子产额,该方法为将来结合人工智能优化控制全光汤姆孙散射光源提供了理论基础.

All-laser-driven Thomson scattering based on laser wakefield acceleration can provide high quality X-ray and greatly reduce the source size.Compared with two-pulse setting,the self-reflecting setting can reduce the requirement for temporal and spatial synchronization in experiment.However,it is difficult to optimize X-ray because Thomson scattering is coupled with laser wakefield acceleration in this process.In this paper,we correct theory formula through numerical simulation,and analyze the parameters quantitatively in laser wakefield acceleration and Thomson scattering,such as spot size,duration and energy of laser and electron beam,and reflectivity of plasma mirror.Then we can trace the parameters by using the modified formula rather than the numerical simulation with similar accuracy and less time.The modified formula is also used to optimize the selfreflecting all-laser-driven Thomson scattering X-ray under the given laser conditions.The optimal X-ray luminance and photon number can be obtained by changing the plasma density and the position of the plasma mirror.