Sei Norihiro, Zen Heishun, Ohgaki Hideaki, Hajima Ryoichi
Research Institute for Measurement and Analytical Instrumentation, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan.
Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
iScience. 2024 Nov 16;27(12):111402. doi: 10.1016/j.isci.2024.111402. eCollection 2024 Dec 20.
Microbunching caused by free-electron laser (FEL) interactions in an electron bunch deforms the overall bunch shape. Recent reports indicate the timing of the electron bunch overlapping with the FEL micropulse affects deformation in resonator-type FELs. The electron bunch shape is expected to change with the FEL micropulse energy because the FEL micropulse energy is enhanced within the electron beam macropulse; however, this has not yet been investigated. We evaluated the temporal evolution of the electron bunch length during FEL oscillations by observing the coherent edge radiation generated by the resonator-type FEL device, KU-FEL, Kyoto University. Experimentally verification showed that the expansion and contraction of the electron bunch changed more clearly when the energy and net gain of the FEL micropulse were high. Furthermore, the expansion and contraction behavior was consistent with a one-dimensional FEL simulation based on a well-established unaveraged method.
由电子束中自由电子激光（FEL）相互作用引起的微聚束会使整个束团形状发生畸变。最近的报告表明，电子束与FEL微脉冲重叠的时间会影响谐振器型FEL中的畸变。由于FEL微脉冲能量在电子束宏脉冲内增强，因此预计电子束形状会随FEL微脉冲能量而变化；然而，这一点尚未得到研究。我们通过观察京都大学的谐振器型FEL装置KU-FEL产生的相干边辐射，评估了FEL振荡期间电子束长度的时间演化。实验验证表明，当FEL微脉冲的能量和净增益较高时，电子束的膨胀和收缩变化更为明显。此外，膨胀和收缩行为与基于成熟的非平均方法的一维FEL模拟结果一致。
