Non-uniform thermal load causes performance degradation of crystal X-ray optics. With the development of high-brightness X-ray free-electron lasers, the thermal load on X-ray optics becomes even more severe. To mitigate the thermal load, a quantitative understanding of thermal effects on the optical performance is necessary. We derived an analytical model for monochromator performance under a non-uniform thermal load. This analytical model quantitatively describes the distortion of the rocking curve and attributes different contributions to different factors of thermal load. It provides not only monochromator design insights and considerations, but also a quick estimation of the rocking curve distortion due to thermal load for practical situations such as pump-probe experiments.

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热负荷下单色仪性能表征的分析模型

不均匀的热负荷会导致晶体X射线光学器件性能下降。随着高亮度X射线自由电子激光器的发展，X射线光学器件上的热负荷变得更加严重。为了减轻热负荷，必须定量了解热对光学性能的影响。我们导出了在非均匀热负荷下单色仪性能的分析模型。该分析模型定量描述了摇摆曲线的变形，并将不同的贡献归因于不同的热负荷因素。它不仅提供了单色仪的设计见解和考虑因素，而且还可以快速估算出在实际情况下（例如泵探针实验）由于热负荷导致的摇摆曲线失真。