Generation and acceleration of electron bunches from a plasma photocathode
Generation and acceleration of electron bunches from a plasma photocathode
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DOI：
10.1038/s41567-019-0610-9
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发表时间：
2019-11-01
期刊：
影响因子：
19.6
通讯作者：
Hidding, B.
中科院分区：
文献类型：
--
作者：
Deng, A.;Karger, O. S.;Hidding, B.
等离子体波产生于强烈的相对论激光束（1，2）或粒子束（3，4）的尾流中，可以在厘米级的距离内将电子束团加速到千兆电子伏的能量。这使得实现紧凑的加速器与新兴的应用范围从现代光源，如自由电子激光器的能量前沿轻子对撞机。在等离子体韦克菲尔德加速器中，这种每米数千兆伏的尾流场可以加速外部注入（5，6）或从背景等离子体（7，8）捕获的见证电子束。在这里，我们展示了光学触发注入（9-11）和加速电子束，产生在多组分氢和氦等离子体采用空间对齐和同步的激光脉冲。这种“等离子体光阴极”通过直接在等离子体腔内释放隧道电离的氦电子，使尾流激发注入，然后这些冷电子迅速提升到相对论速度。注入机制可以经由光学（11）密度下降斜坡注入（12-16）来访问，并且是朝向产生具有前所未有的低横向发射度、高电流和6D亮度的电子束的重要步骤（17）。这一实验路径为基于超高亮度光束的变革性等离子体韦克菲尔德加速器应用开辟了许多前景。
Plasma waves generated in the wake of intense, relativistic laser(1,2) or particle beams(3,4) can accelerate electron bunches to gigaelectronvolt energies in centimetre-scale distances. This allows the realization of compact accelerators with emerging applications ranging from modern light sources such as the free-electron laser to energy frontier lepton colliders. In a plasma wakefield accelerator, such multi-gigavolt-per-metre wakefields can accelerate witness electron bunches that are either externally injected(5,6) or captured from the background plasma(7,8). Here we demonstrate optically triggered injection(9-11) and acceleration of electron bunches, generated in a multi-component hydrogen and helium plasma employing a spatially aligned and synchronized laser pulse. This 'plasma photocathode' decouples injection from wake excitation by liberating tunnel-ionized helium electrons directly inside the plasma cavity, where these cold electrons are then rapidly boosted to relativistic velocities. The injection regime can be accessed via optical(11) density down-ramp injection(12-16) and is an important step towards the generation of electron beams with unprecedented low transverse emittance, high current and 6D-brightness(17). This experimental path opens numerous prospects for transformative plasma wakefield accelerator applications based on ultrahigh-brightness beams.