The micro-bunching instability is a longitudinal instability that leads to dynamical deformations of the charge distribution in the longitudinal phase space. It affects the longitudinal charge distribution, and thus the emitted coherent synchrotron radiation spectra, as well as the energy distribution of the electron bunch. Not only the threshold in the bunch current above which the instability occurs, but also the dynamics above the instability threshold strongly depends on machine parameters, e.g. accelerating voltage, momentum compaction factor, and beam energy. All this makes the understanding and potential mitigation or control of the micro-bunching instability an important topic for the next generation of light sources and circular $e^+e^-$ colliders. This contribution will give an overview of the micro-bunching instability and discuss how technological advances in the turn-by-turn and bunch-by-bunch diagnostics are leading to a deeper understanding of this intriguing phenomenon.
Micro-bunching for generating tunable narrow-band THz radiation at the FAST photoinjector
本文介绍了费米实验室FAST（Fermilab Accelerator Science and Technology）电子注入器中使用狭缝掩模产生的微聚束电子束发射的THz辐射谱。我们的目的是在传统的光注入器中用一个简单的方案产生可调谐的窄带太赫兹辐射。在弯道处使用狭缝掩模，通过在具有水平色散的位置处横向切割能量啁啾的电子聚束，在弯道后产生纵向微聚束。本文讨论了微聚束结构、束流光学、微聚束的模拟结果和聚束因子的相关理论。计算并比较了相干跃迁辐射和摇摆器两种辐射源在太赫兹频率下的辐射能量。我们还讨论了一个简单的方法来观察微聚束上的横向屏幕监视器使用的斜四极放置在弯道的结果。
