IMCA-CAT, Hauptman-Woodward Institute, USA.
J Synchrotron Radiat. 2010 Sep;17(5):644-52. doi: 10.1107/S0909049510024337. Epub 2010 Jul 15.
Micro-focusing optical devices at synchrotron beamlines usually have a limited acceptance, but more flux can be intercepted if such optics are used to focus secondary sources created by the primary optics. Flux throughput can be maximized by placing the secondary focusing optics close to or exactly at the secondary source position. However, standard methods of beamline optics analysis, such as the lens equation or matching the mirror surface to an ellipse, work poorly when the source-to-optics distance is very short. In this paper the general characteristics of the focusing of beams with Gaussian profiles by a ;thin lens' are analysed under the paraxial approximation in phase space, concluding that the focusing of a beam with a short source-to-optics distance is distinct from imaging the source; slope errors are successfully included in all the formulas so that they can be used to calculate beamline focusing with good accuracy. A method is also introduced to use the thin-lens result to analyse the micro-focusing produced by an elliptically bent trapezoid-shaped Kirkpatrick-Baez mirror. The results of this analysis are in good agreement with ray-tracing simulations and are confirmed by the experimental results of the secondary focusing at the 18-ID Bio-CAT beamline (at the APS). The result of secondary focusing carried out at 18-ID using a single-bounce capillary can also be explained using this phase-space analysis. A discussion of the secondary focusing results is presented at the end of this paper.
在同步加速器光束线上，微聚焦光学器件通常具有有限的接收能力，但是如果使用这些光学器件来聚焦由初级光学器件产生的次级源，则可以拦截更多的通量。通过将次级聚焦光学器件放置在次级源位置附近或正好在次级源位置处，可以最大限度地提高通量传输率。然而，当源到光学器件的距离非常短时，标准的光束线光学分析方法（例如透镜方程或将镜面匹配到椭圆）效果不佳。在本文中，在相位空间中，在傍轴近似下分析了具有高斯轮廓的光束由“薄透镜”聚焦的一般特性，得出结论，对于具有短源到光学器件距离的光束聚焦与对源进行成像明显不同；斜率误差已成功包含在所有公式中，因此可以使用它们来计算具有良好精度的光束线聚焦。还介绍了一种方法，使用薄透镜结果来分析椭圆弯曲的梯形 Kirkpatrick-Baez 镜产生的微聚焦。该分析的结果与光线追踪模拟吻合良好，并通过在 APS 的 18-ID Bio-CAT 光束线进行的次级聚焦的实验结果得到证实。使用单次反射毛细管在 18-ID 进行的次级聚焦的结果也可以使用此相空间分析来解释。本文最后还讨论了次级聚焦的结果。
