Table-top laser-driven hard x-ray sources with kilohertz repetition rates are an attractive alternative to large-scale accelerator-based systems and have found widespread applications in x-ray studies of ultrafast structural dynamics. Hard x-ray pulses of 100 fs duration have been generated at the Cu Kα wavelength with a photon flux of up to 109 photons per pulse into the full solid angle, perfectly synchronized to the sub-100-fs optical pulses from the driving laser system. Based on spontaneous x-ray emission, such sources display a particular noise behavior which impacts the sensitivity of x-ray diffraction experiments. We present a detailed analysis of the photon statistics and temporal fluctuations of the x-ray flux, together with experimental strategies to optimize the sensitivity of optical pump/x-ray probe experiments. We demonstrate measurements close to the shot-noise limit of the x-ray source.
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机译:具有千赫兹重复频率的台式激光驱动硬X射线源是大规模基于加速器的系统的有吸引力的替代方法,并且已在超快结构动力学的X射线研究中得到广泛应用。在Cu K α sub>波长下已产生了100 fs持续时间的硬X射线脉冲,每个脉冲的光子通量达到每个立体角最多10 9 sup>个光子,与驱动激光系统产生的100-fs以下的光脉冲完全同步。基于自发的X射线发射,此类源显示特定的噪声行为,这会影响X射线衍射实验的灵敏度。我们提供了对光子统计数据和X射线通量的时间波动的详细分析,以及优化光学泵浦/ X射线探针实验灵敏度的实验策略。我们证明测量值接近X射线源的散粒噪声极限。
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