非均匀等离子体对强激光传播及电子束输运的影响

Propagation of Intense Laser and Transport of Relativistic Electron Beam in Inhomogeneous Plasmas

本文介绍近期针对非均匀等离子体对强激光传播和电子束输运影响取得的研究进展,首先研究弱无序分布等离子体对强激光传播的影响,提出强激光在弱无序等离子体中存在非线性分支流传输机制,并阐明光电离效应及相对论效应对分支流的重要影响。此外,研究等离子体密度梯度对相对论电子束输运过程的影响,发现相对论电子束输运所激发的静电波在空间固定点处的波数或相速度随时间变化,并且不依赖于等离子体密度的上升或下降,静电波的局域空间波数最终随时间逐渐增大,这导致在非均匀等离子体中静电波通过朗道阻尼方式将能量耗散转移给背景电子,表现为一种由背景等离子体密度梯度引起的束流能量耗散新机制。

This work introduces our recent research works on the propagation of intense laser and transport of relativistic electron beam in inhomogeneous plasmas.First of all,we investigated the propagation of intense laser pulse in plasma with randomly uneven density distribution and found a new nonlinear branched flow regime of intense laser propagation in inhomogeneous plasma.In particular,we identify the important effects played by the laser photoionization and relativistic motion of electrons.In addition,we also investigated the plasma density gradient effect on evolution of electrostatic wave excited by ultra-relativistic electron beam in inhomogeneous plasma.It is found that the local region wavenumber and phase velocity of the excited wave varies with time because of the plasma inhomogeneity.Independent of the positive and negative density gradient,the wavenumber finally increases with time.As a result,Landau damping gradually becomes dominant in the whole region of inhomogeneous plasma,and leads to transfer of the wave energy to background plasma electrons,presenting a novel energy dissipation regime caused by the plasma density gradient.