A growing number of X-ray sources based on the free-electron laser (XFEL) principle are presently under construction or have recently started operation. The intense, ultrashort pulses of these sources will enable new insights in many different fields of science. A key problem is to provide x-ray optical elements capable of collecting the largest possible fraction of the radiation and to focus into the smallest possible focus. As a key step towards this goal, we demonstrate here the first nanofocusing of hard XFEL pulses. We developed diamond based Fresnel zone plates capable of withstanding the full beam of the world's most powerful x-ray laser. Using an imprint technique, we measured the focal spot size, which was limited to 320 nm FWHM by the spectral band width of the source. A peak power density in the focal spot of 4×1017 W/cm2 was obtained at 70 fs pulse length.
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机译:基于自由电子激光(XFEL)原理的越来越多的X射线源目前正在建设中或最近已开始运行。这些来源的强烈超短脉冲将为许多不同的科学领域带来新的见解。关键问题是提供能够收集最大可能的辐射份额并聚焦到最小可能的焦点的X射线光学元件。作为朝着这个目标迈出的关键一步,我们在这里展示了硬XFEL脉冲的首次纳米聚焦。我们开发了基于钻石的菲涅耳波带片,可以承受世界上最强大的X射线激光的全光束。使用压印技术,我们测量了焦斑大小,受光源光谱带宽的限制,焦斑大小限制为320 nm FWHM。在70 fs脉冲长度下,焦点处的峰值功率密度为4×10 17 sup> W / cm 2 sup>。
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