新型自注入真空激光电子加速机制研究

Generation of high-quality relativistic electrons is a promising application of the high-intensity lasers. Vacuum laser acceleration (VLA) has attracted broad attentions and interests for its most fundamental physics, the electric accelerating gradients higher than TV/m, which may produce high charge relativistic electrons. The injection of electrons into the accelerating field and the phase slippage are two key issues of VLA. Our group has proposed a new self-injected scheme for VLA, using high-intensity lasers to interact with tube targets or film gap targets. In this scheme, electrons were first accelerated by the laser longitudinal ponderomotive forces, then injected into the appropriate phase, and finally captured and accelerated by the longitudinal electric fields. Moreover, modification of the phase velocity made the capture easier and the phase slippage distance longer. We will forward the research on this new, valuable and applicable scheme for VLA supported by this funding project. In theory the physical model will be strengthened. Understanding on ponderomotive injection, modification of phase velocity and other crucial issues of VLA will be deepened via simulations. Experiments aiming at the generation and modification of the high-charge relativistic electrons will be performed based on the capacities of 45TW, XGIII and 5PW high-intensity laser facilities in our institute.

产生高品质相对论电子束是超强激光的一个重要应用方向。激光真空加速机制（VLA）由于其物理原理基础简单，可产生TV/m量级的加速梯度和nC量级的电量，在国际上引起了广泛的关注和研究兴趣。如何实现电子注入和捕获以及增加失相距离是VLA应用面临的两个关键物理难题。本项目团队提出了一种新型自注入VLA机制，利用超强激光与圆柱靶或平面间隙靶相互作用，通过纵向有质动力加速自然地实现了电子注入和捕获，通过对加速场相速度的选择增加了失相距离，实现了大电量相对论电子加速。通过本项目的支持我们将进一步研究这种具有重大应用价值的新型VLA机制。首先利用理论和数值模拟方法，完善物理模型，加深对有质动力注入、加速场相速度调控等物理过程的认识和理解；其次基于本单位45TW、星光和5PW等超强激光装置，实验上实现大电量相对论电子束的产生、测试以及对电子束品质的精确调控。

产生高品质相对论电子束是超强激光的一个重要应用方向。激光真空加速机制（VLA）由于其物理原理基础简单，可产生TV/m量级的加速梯度和nC量级的电量，在国际上引起了广泛的关注和研究兴趣。本项目团队在自然科学基金的资助下，优化、发展和完善了新型自注入真空激光电子加速机制的物理模型，获得了自注入VLA机制的关键物理特征，包括高能电子产额明显增多，电子温度显著增加，尤其是电子角分布上呈现紧聚焦高准直分布等，获得了激光强度、焦斑大小、脉冲宽度、预脉冲强度等激光参数对VLA 影响的规律性认识，获得了靶结构、内径大小、靶长度等靶参数对VLA 影响的规律性认识，获得了激光聚焦位置、激光入射角度、激光注孔位置等束靶耦合参数对VLA 影响的规律性认识，加深了对激光等离子体相互作用物理过程的认识和理解，为进一步获取清晰全面的物理过程图像以及实验验证方案的设计提供了依据；发展了基于45TW、星光和5PW 等超强激光装置的实验方法和技术，建立了微通道靶制备、高精度束靶耦合、对比度提升等实验能力，升级改造了X光针孔相机、电子堆栈谱仪、电子谱仪等关键诊断设备，完善了激光注孔、激光输运、激光透射等实验过程监测；实验上得到了电子能谱、电量及角分布随激光强度、脉冲宽度、靶内径、靶长度等激光参数、靶参数及激光入射角度变化规律的关键实验数据；获得了电量达16nC（>1MeV）、温度超过7MeV、发散角小于5度大电量高能高准直电子束，实现了nC 量级电量、MeV 级能量高品质相对论电子束的产生。