Deutsches Elektronen-Synchrotron, Notkestraße 85, 22607 Hamburg, Germany.
Northern Illinois Center for Accelerator & Detector Development and Department of Physics, Northern Illinois University, DeKalb Illinois 60115, USA.
Phys Rev Lett. 2019 Feb 1;122(4):044801. doi: 10.1103/PhysRevLett.122.044801.
Temporally modulated electron beams have a wide array of applications ranging from the generation of coherently enhanced electromagnetic radiation to the resonant excitation of electromagnetic wakefields in advanced-accelerator concepts. Likewise producing low-energy ultrashort microbunches could be useful for ultrafast electron diffraction and new accelerator-based light-source concepts. In this Letter we propose and experimentally demonstrate a passive microbunching technique capable of forming a picosecond bunch train at ∼6 MeV. The method relies on the excitation of electromagnetic wakefields as the beam propagates through a dielectric-lined waveguide. Owing to the nonultrarelativistic nature of the beam, the induced energy modulation eventually converts into a density modulation as the beam travels in a following free-space drift. The modulated beam is further accelerated to ∼20 MeV while preserving the imparted density modulation.
时变调制电子束在从相干增强电磁辐射的产生到先进加速器概念中电磁尾流的共振激发等方面有着广泛的应用。同样，产生低能超短微束对于超快电子衍射和基于新加速器的光源概念可能是有用的。在这篇文章中，我们提出并实验证明了一种能够在约 6 MeV 下形成皮秒微束列的无源微束形成技术。该方法依赖于当束流在介质填充波导中传播时，激励电磁尾流。由于束流的非相对论性质，所诱导的能量调制最终会在束流在后续自由空间漂移中传播时转换为密度调制。调制后的束流在保持所施加的密度调制的同时被进一步加速到约 20 MeV。
