Brynes A D, Akkermans I, Allaria E, Badano L, Brussaard S, Ninno G De, Gauthier D, Gaio G, Giannessi L, Mirian N S, Penco G, Perosa G, Rebernik P, Setija I, Spampinati S, Spezzani C, Trovò M, Veronese M, Williams P H, Wolski A, Mitri S Di
ASTeC, STFC Daresbury Laboratory, Daresbury, Warrington, WA4 4AD, Cheshire, United Kingdom.
Cockcroft Institute, Sci-Tech Daresbury, Keckwick Lane, Daresbury, Warrington, WA4 4AD, United Kingdom.
Sci Rep. 2020 Mar 19;10(1):5059. doi: 10.1038/s41598-020-61764-y.
The optimal performance of high-brightness free-electron lasers (FELs) is limited by the microbunching instability, which can cause variations in both the slice energy spread and longitudinal profile of electron beams. In this paper, we perform 2D Fourier analysis of the full bunch longitudinal phase space, such that modulations in both planes can be studied simultaneously. Unlike the standard 1D analysis, this method is able to reveal modulations in a folded phase space, which would otherwise remain uncovered. Additionally, the plasma oscillation between energy and density modulations is also revealed by this method. The damping of the microbunching instability, through the use of a laser heater, is also analysed with this technique. We confirm a mitigation of the amplitude of modulation and a red-shift of the microbunching frequency as the energy spread added increases. As an outcome of this work, a systematic experimental comparison of the development of the instability in the presence of different compression schemes is here presented for the first time.
高亮度自由电子激光器（FEL）的最佳性能受到微聚束不稳定性的限制，这种不稳定性会导致电子束的切片能量展宽和纵向分布发生变化。在本文中，我们对整个束团的纵向相空间进行二维傅里叶分析，以便能够同时研究两个平面中的调制情况。与标准的一维分析不同，这种方法能够揭示折叠相空间中的调制，否则这些调制将无法被发现。此外，这种方法还揭示了能量调制和密度调制之间的等离子体振荡。我们还使用该技术分析了通过激光加热器对微聚束不稳定性的抑制作用。我们证实，随着添加的能量展宽增加，调制幅度会减小，微聚束频率会发生红移。作为这项工作的成果，首次在此展示了在不同压缩方案下不稳定性发展的系统实验比较。
