论文标题
自我调制增强的高重复率播种自由电子激光
High-repetition-rate seeded free-electron laser enhanced by self-modulation
论文作者
论文摘要
最近，已经提出了一个弱预捆的电子束的自调制方案[Yan等人，物理审查字母126，084801（2021）]，这对于高重复种子的自由电子激光器（FELS）（例如高元素谐波生成（HGHG））非常有前途。在本文中，对自调制方案进行了系统的分析和优化，并且在种子激光器的第二个谐波中进行自调节剂具有共鸣的进一步实验。三维数值模拟表明，通过优化梁大小或峰值电流，自调制方案中所需的种子激光强度比标准HGHG的三个数量级左右。更重要的是，通过合理地设置初始能量调节和自调节器的共振，可以在单级HGHG中实现种子激光器第30次谐波的更突出的束束因子和Lase。此外，实验结果证实，改变自调节剂的共振条件仍然可以放大激光诱导的能量调节，即使在第12个谐波也可以观察到相干辐射。这些结果表明，自调制方案可以显着降低种子激光系统的要求，同时提高谐波上调效率，这为实现高重复率和完全相干的软X射线纤维铺平了道路。
Recently, the self-modulation scheme of a weakly pre-bunched electron beam has been proposed [Yan et al., Physical Review Letters 126, 084801 (2021)], which is of great promise for high-repetition-rate seeded free-electron lasers (FELs), such as high-gain harmonic generation (HGHG). In this paper, the self-modulation scheme is systematically analyzed and optimized, and further experiments in which the self-modulator is resonant at the second harmonic of the seed laser are conducted. The three-dimensional numerical simulations show that the required seed laser intensity in the self-modulation scheme is around three orders of magnitude lower than that of the standard HGHG through the optimization of the beam size or the peak current. More importantly, by reasonably setting the initial energy modulation and the resonance of the self-modulator, a more prominent bunching factor and lase at the 30th harmonic of the seed laser can be achieved in a single-stage HGHG. Moreover, the experiment results confirm that varying the resonance conditions of the self-modulator can still amplify the laser-induced energy modulation, where coherent radiation generated even at the 12th harmonic can be observed. These results indicate that the self-modulation scheme can remarkably reduce the requirements of the seed laser system while improving the harmonic up-conversion efficiency, which paves the way for realizing high-repetition-rate and fully coherent soft x-ray FELs.
