High-efficiency and high-resolution broad-range fluorescent x-ray spectrometry using a two-dimensional position-sensitive counter

研究了一种由平板晶体和基于MBWC技术的二维位置灵敏正比计数器组成的X射线荧光光谱仪的性能。观测到的X射线能量分辨率一般表现出与晶体和PSPC之间的距离的非线性关系，并在等于X射线源和晶体之间的距离附近给出最小值。这种现象被解释为由于晶体的马赛克结构而导致的反射X射线的近似聚焦。测量了四种晶体：LiF(200)、Si(111)、石墨和Ge(111)的能量分辨率与PSPC-晶体距离的关系。在石墨晶体中观察到的“马赛克聚焦”最为强烈。在最小分辨率下可分辨出Fe Kα1和Kα2峰，尽管存在较大的马赛克扩散0.4°。随着PSPC-晶体距离的增加或减小，分辨率会随着马赛克扩散所预期的梯度而下降。这一结果对石墨晶体与现有光谱仪的结合尤为重要，因为这意味着在现有的光谱仪中，石墨的X射线反射率是所有其他晶体中最高的，具有中等高的能量分辨率。其他晶体也表现出不同程度的非线性。

Properties of a fluorescent x-ray spectrometer which consists of a flat crystal and a two-dimensional position-sensitive proportional counter based on the MBWC technique has been studied. Observed x-ray energy resolution generally shows non-linear dependence on the distance between a crystal and the PSPC and gives minimum around the distance equal to the distance between an x-ray source and the crystal. This phenomenon is interpreted as approximate focusing of reflected x-rays due to mosaic structure of the crystal. The dependence of the energy resolution on the PSPC-crystal distance has been measured for four crystals ; LiF (200), Si (111), graphite, and Ge (111). The "mosaic focusing" is observed most strongly for the graphite crystal. At a resolution minimum Fe Kα1 and Kα2 peaks are resolved, despite of the large mosaic spread 0.4°. As the PSPC-crystal distance increases or decreases apart from the resolution minimum, the resolution degrades with a gradient expected from the mosaic spread. This result fox a graphite crystal combined with the present spectrometer is specially important, because it means that the highest x-ray reflectivity of graphite among all the other crystals consists with moderately high energy-resolution in the present type of spectrometers. The other crystals also show the non-linearity to various extent.