Yang X, Penn G, Yu L H, Smaluk V, Shaftan T
National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA.
Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
Sci Rep. 2022 Jun 8;12(1):9437. doi: 10.1038/s41598-022-13702-3.
Prebunching via echo-enabled harmonic generation (EEHG) is an efficient way to reduce the radiator length and improve the longitudinal coherence as well as output stability in storage-ring-based free-electron lasers. We propose a conceptual design, which uses two straight sections to seed coherent extreme-ultraviolet (EUV) and soft X-ray emission with nearly MHz repetition rate. To take the large energy spread (10) of a storage ring into account and utilize the existing bending magnets between the two straight sections as the first chicane, we implement a special modeling tool, named EEHG optimizer. This tool has been successfully applied to maximize the prebunching with a reasonably low energy modulation, thereby generating intense coherent X-ray pulses within a short undulator length (a few meters) limited by the available space of a storage ring. Numerical simulations confirm that the optimized EEHG parameters can be directly applied to generate a 10 MW scale peak power with fully coherent ultrafast EUV to soft X-ray pulses based on the NSLS-II parameters. This method can be easily extended to other types of diffraction-limited storage rings.
通过受激回声谐波产生（EEHG）进行预群聚是一种有效的方法，可减少基于储存环的自由电子激光器中的辐射器长度，提高纵向相干性以及输出稳定性。我们提出了一种概念设计，该设计使用两个直线段来产生重复频率接近兆赫兹的相干极紫外（EUV）和软X射线辐射。为了考虑储存环的大能量分散（10），并将两个直线段之间现有的弯曲磁铁用作第一个弯道，我们实现了一种名为EEHG优化器的特殊建模工具。该工具已成功应用于以合理的低能量调制最大化预群聚，从而在受储存环可用空间限制的短波荡器长度（几米）内产生强相干X射线脉冲。数值模拟证实，基于NSLS-II参数，优化后的EEHG参数可直接用于产生具有完全相干超快EUV到软X射线脉冲的10兆瓦级峰值功率。该方法可以很容易地扩展到其他类型的衍射极限储存环。
