LiF(200) diffraction crystals are commonly used in high-power wavelength-dispersive X-ray fluorescence (XRF) but seldom in benchtop energy-dispersive XRF instruments because of their low diffraction efficiencies. We herein describe a method of producing a double-curved crystal (DCC) from an LiF(200) plate crystal, wherein diverging X-rays onto the DCC can be totally diffracted and focused. This improves the performance of a monochromatic wavelength X-ray fluorescence (MWXRF) source. The characteristic 5.415 keV line of a chromium target was diffracted by an LiF(200) DCC; this MWXRF was used to detect weak signals of trace light elements with atomic numbers 11–22 because of the extremely low and continuous background spectrum. The MWXRF intensity approached 5.3 × 10⁸ cps, and it exhibited excellent focusing with a 0.24 × 0.52 mm focal spot. Trace- and high-concentration levels were calibrated respectively to ensure good accuracy. The lower limits of detection of sulfur and chlorine in oils were 1.75 and 0.63 μg/g, respectively. The MWXRF source could be developed into an integrated device including a mini-focus X-ray tube and an LiF(200) DCC. Designing the DCC to diffract characteristic MWXRF would provide a system of practical applicability, especially for some serious overlapping and interferential spectral lines.

中文翻译：

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用于改善单色 X 射线荧光源性能的 LiF(200) 双曲面晶体

LiF(200) 衍射晶体常用于高功率波长色散 X 射线荧光 (XRF)，但很少用于台式能量色散 XRF 仪器，因为它们的衍射效率低。我们在此描述了一种从 LiF(200) 板晶体生产双曲面晶体 (DCC) 的方法，其中可以完全衍射和聚焦发散到 DCC 上的 X 射线。这提高了单色波长 X 射线荧光 (MWXRF) 源的性能。铬靶的特征 5.415 keV 谱线被 LiF(200) DCC 衍射；由于背景光谱极低且连续，因此该 MWXRF 用于检测原子序数为 11-22 的痕量轻元素的微弱信号。MWXRF 强度接近 5.3 × 10 ⁸ cps，它以 0.24 × 0.52 mm 的焦斑表现出出色的聚焦效果。分别校准痕量和高浓度水平以确保良好的准确度。油中硫和氯的检出下限分别为 1.75 和 0.63 μg/g。MWXRF 源可以发展成一个集成设备，包括一个微型聚焦 X 射线管和一个 LiF(200) DCC。设计 DCC 来衍射特征 MWXRF 将提供一个具有实际适用性的系统，特别是对于一些严重重叠和干涉的谱线。