第二讲 激光尾波场加速中的准单能电子束的产生

自从激光尾波场加速电子方案提出以来，经过二十多年的理论和实验研究，人们在激光尾波场加速方面已经取得了重大进步，相继在电子束能量、电子单色性等束流性能上取得重大突破.特别是在2004年对电子束的单色性研究取得重大突破，国际上几个著名实验室相继报道了准单能电子束产生的实验观测，掀起了激光尾波场研究的新高潮.对于准单能电子束的产生机制，虽然尚未达成统一认识，但普遍认为空泡加速可能是其中非常重要的机制之一.文章介绍了激光尾波场的基本概念，着重介绍了单能电子束产生的空泡加速模式里的两个关键物理过程：波破和电子的自捕获，同时介绍国际上相关的一些重要实验结果和理论进展.

Quasi-monoenergetic electron bunches generated from laser wakefield acceleration

Significant progress has been achieved in enhancing the energy and quality of electron beams since the proposal of laser wakefield acceleration by Tajima and Dawson more than 20 years ago. Breakthroughs in the generation of quasi-monoenergetic electron beams in several laboratories in 2004 spurred new interest in this type of compact accelerator. Even though its mechanism is not yet completely understood, it is believed that the socalled bubble acceleration is one of the main mechanisms. The basic principle of the laser wakefield acceleratorwill be explained briefly and wavebreaking and self-injection in the bubble regime described, including recent experimental and theoretical progress.