激光驱动强流电子束产生和控制

Laser-driven relativistic electron beam for fast ignition

在惯性约束聚变(ICF)电子束快点火物理方案中,需要超强拍瓦激光脉冲驱动MeV能量的强流电子束,并沉积数十kJ能量到压缩氘氚芯区。强流电子束的束流品质是影响点火成功的关键因素之一,为深入了解强流电子束产生物理过程,研制成了三维高性能、适应上万CPU核规模的并行粒子模拟程序,并开展了大规模数值模拟研究,探索了强流电子束的产生机制和输运规律。回顾了近几年来快点火研究团队围绕强流电子束产生和控制开展的研究,介绍了导致束流品质差的两大物理原因:预等离子体效应和束流不稳定性磁场的随机散射。针对这两个物理原因,提出了四种提高强流电子束品质的方法:(1)双层金锥靶减弱预等离子体的负面效应;(2)输运丝产生环向磁场准直强流电子束;(3)外加磁场导引强流电子束提高耦合效率;(4)抑制束流不稳定性以降低随机磁场对电子束流的散射。

In the scheme of electron-driven fast ignition of inertial confinement fusion（ICF）,MeV relativistic electron beams driven by ultraintense petawatt laser pulses are required and electron energy of several tens of kilojoules should be deposited in the compressed core of an imploded DT shell.The beam quality is crucial to the success of fast ignition.In order to study the generation and transport of the relativistic electron beam,a three-dimensional high-performance parallel particle-in-cell code is developed and improved.In this review,this paper shows the researches on the generation of high-quality electron beams and the method of beam divergence controlling of our research group.Two main reasons for poor beam quality are firstly introduced：preplasma effect and random scattering of the magnetic field produced by the beam instability.In addition,enhancement of electron beam flux and collimation of its propagation are investigated.Four ways to obtain collimated electrons are put forward：1）reduce the pre-plasma effect with a double cone target;2）collimate fast electrons in specially engineered targets with the spontaneously generated magnetic field during its transportation;3）collimate fast electrons with external magnetic field;4）control the beam instability at the laser-plasma interface.