有限长激光脉冲在部分离化等离子体中的传播

为了研究有限长激光脉冲在部分离化等离子体中的传播特性,采用变分法推导出有限长激光脉冲在部分离化等离子体中的参量演化方程,分析了尾波场、相对论自聚焦和部分离化非线性极化强度的影响因素;通过分析焦斑半径和脉冲宽度满足的耦合方程,讨论了横向和纵向尾波场影响下的激光脉冲传播特性。结果表明,由于焦斑半径和脉冲宽度的耦合,激光脉冲在部分离化等离子体中传播必须满足一定条件;在部分离化等离子体中,考虑激光传播时脉冲宽度的变化是有必要的;对给定强度的激光脉冲,等离子体密度不变时,随着电离程度增大,尾波场会进一步增强激光脉冲的自聚焦,其中纵向尾波场比横向尾波场对激光脉冲的自聚焦作用更明显。这一结果对有限长激光脉冲电离诱导自注入及尾波场加速电子的方案具有理论指导意义。

Propagation of short laser pulses in partially stripped plasma

In order to study the propagation characteristics of short laser pulses in partially stripped plasma, parameters evolution equation of short laser pulses in partially ionized plasma was derived using variational method. The effect parameters of wakefield, relativistic self-focusing and intensity of partially stripped plasma were analyzed. The coupled evolution equations of the laser spot size and the pulse length were derived and the propagation of a short laser pulse in partially stripped plasma was analyzed under the effects of transverse wakefield(TWF) and longitudinal wakefield(LWF). The results show that laser pulse can be allowed to propagate in patitally stripped plasma only when a certain condition is satisfied. The evolution of the pulse length should be considered in partially stripped plasma. When laser pulse and plasma density is constant, with the increasing of ionization degree, wakefield will enhance the self-focusing of the laser pulse further. Longitudinal wakefield has more obvious effect on self-focusing of laser pulse than transverse wakefield. The results may be significant theoretically to the mechanism of ionization-induced injection and acceleration by an intense laser pulse.