A high-harmonic generation source for seeding a free-electron laser at 38 nm
A high-harmonic generation source for seeding a free-electron laser at 38 nm
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用于播种 38 nm 自由电子激光的高次谐波发生源
DOI：
10.1007/s00340-013-5571-6
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
M. Drescher
中科院分区：
文献类型：
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作者：
Th. Maltezopoulos;M. Mittenzwey;A. Azima;J. Bödewadt;H. Dachraoui;M. Rehders;C. Lechner;M. Schulz;M. Wieland;T. Laarmann;J. Roßbach;M. Drescher
高谐波源的直接播种可以改善自由电子激光的光谱、时间和相干性，并减少强度和到达时间的波动。在汉堡FLASH的极紫外自由电子激光器上，在自放大自发发射模式（SASE）下进行了sFLASH播种实验，将800 nm激光的21次谐波重新聚焦到专用的播种波动器中。对于播种，外部光场必须克服SASE的噪声水平；因此，种子脉冲和电子束之间的有效耦合是必要的。因此，HHG光束需要具有适当的散度、宽度、光束质量、瑞利长度、指向稳定性、单次脉冲能量和21次谐波稳定性。在这里，我们介绍了在38.1 nm处种子sFLASH的HHG源的设置，优化程序和必要的诊断。
Direct seeding with a high-harmonic generation (HHG) source can improve the spectral, temporal, and coherence properties of a free-electron laser (FEL) and shall reduce intensity and arrival-time fluctuations. In the seeding experiment sFLASH at the extreme ultraviolet FEL in Hamburg FLASH, which operates in the self-amplified spontaneous emission mode (SASE), the 21st harmonic of an 800 nm laser is refocused into a dedicated seeding undulator. For seeding, the external light field has to overcome the noise level of SASE; therefore, an efficient coupling between seed pulse and electron bunch is mandatory. Thus, an HHG beam with a proper divergence, width, beam quality, Rayleigh length, pointing stability, single-shot pulse energy, and stability in the 21st harmonic is needed. Here, we present the setup of the HHG source that seeds sFLASH at 38.1 nm, the optimization procedures, and the necessary diagnostics.