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arXiv 0708.2844physics.plasm-phphysics.acc-ph
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飞秒电子束团动力学

Dynamics of Femtosecond Electron Bunches

A. G. Khachatryan, A. Irman, F. A. van Goor, K. -J. Boller

摘要:

在激光尾流场加速器中,一束持续时间为等离子体波周期量级的短脉冲激光将激发出异常强的等离子体尾流波(激光尾流场)。最近关于激光尾场加速的实验[Nature(London)431,p.535,p.538,p.541(2004)]证明了具有百分之几数量级的相对低能量扩展的超短(具有几飞秒的持续时间)相对论性电子聚束的产生。我们研究了这种聚束在真空和激光尾流场中的动力学。结果表明,在这两种情况下,强大的聚束动力学已经在几毫米的传播距离。在真空中,束团半径和发射度迅速增长。后者是一群人的可聚焦性。我们发现,当飞秒束团在通道引导的激光尾流场中加速时,对于实际的束团长度,束团长度近似守恒。然而,在电子感应加速器频率的扩展导致快速电子感应加速器相位混合在轴上注入的聚束包络。当束团离轴注入激光尾流场中时,束团退相干导致束团归一化发射度的显著增加,在某些情况下,加速后束团的能量扩展也会增加。我们还讨论了一种可能的两级激光尾场加速器。

英文摘要:

In the laser wakefield accelerator (LWFA) a short intense laser pulse, with a duration of the order of a plasma wave period, excites an unusually strong plasma wake wave (laser wakefield). Recent experiments on laser wakefield acceleration [Nature (London) 431, p.535, p.538, p.541 (2004)] demonstrated generation of ultra-short (with a duration of a few femtoseconds) relativistic electron bunches with relatively low energy spread of the order of a few percent. We have studied the dynamics of such bunches in vacuum and in laser wakefield. The results show strong bunch dynamics already on a few millimeters propagation distance in both cases. In vacuum, the bunch radius and emittance quickly grow. The latter worsens the focusability of the bunch. We found that when a femtosecond bunch is accelerated in a channel-guided laser wakefield, for realistic bunch lengths, the bunch length is approximately conserved. However, the spread in betatron frequencies leads to fast betatron phase mixing in the bunch envelope for on-axis injection. When bunch is injected in a laser wakefield off-axis, the bunch decoherence results in considerable increase in the normalized bunch emittance, and, in some cases, in increase in the energy spread, after acceleration. We also discuss a possible two-stage laser wakefield accelerator.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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