Zhao Wenyang, Sakurai Kenji
Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-0006, Japan and National Institute for Materials Science, 1-2-1, Sengen, Tsukuba, Ibaraki 305-0047, Japan.
Rev Sci Instrum. 2017 Jun;88(6):063703. doi: 10.1063/1.4985149.
As X-ray fluorescence radiation isotropically spreads from the sample, one of the most important requirements for spectrometers for many years has been a large solid angle. Charge-coupled device (CCD) cameras are quite promising options because they have a fairly large area size, usually larger than 150 mm. The present work has examined the feasibility of a commercially available camera with an ordinary CCD chip (1024 × 1024 pixels, the size of one pixel is 13 μm × 13 μm, designed for visible light) as an X-ray fluorescence detector. As X-ray photons create charges in the CCD chip, reading very quickly the amount is the key for this method. It is very simple if the charges always go into one pixel. As the charges quite often spread to several pixels, and sometimes can be lost, it is important to recover the information by filtering out the unsuccessful events. For this, a simple, versatile, and reliable scheme has been proposed. It has been demonstrated that the energy resolution of the present camera is 150 eV at Mn Kα, and also that its overall achievement in seeing minor elements is almost compatible with conventional X-ray fluorescence detectors. When the CCD camera is combined with a micro-pinhole collimator, full field X-ray fluorescence imaging with a spatial resolution of 20 μm becomes possible. Further feasibility in practical X-ray fluorescence analysis is discussed.
由于X射线荧光从样品各向同性地传播，多年来对光谱仪的最重要要求之一是大立体角。电荷耦合器件（CCD）相机是很有前景的选择，因为它们具有相当大的面积尺寸，通常大于150毫米。目前的工作研究了使用具有普通CCD芯片（1024×1024像素，一个像素的尺寸为13μm×13μm，设计用于可见光）的商用相机作为X射线荧光探测器的可行性。由于X射线光子在CCD芯片中产生电荷，快速读取电荷量是该方法的关键。如果电荷总是进入一个像素，那就非常简单。由于电荷经常会扩散到几个像素，有时还会丢失，通过滤除不成功的事件来恢复信息很重要。为此，提出了一种简单、通用且可靠的方案。已经证明，目前相机在Mn Kα处的能量分辨率为150 eV，并且其在检测微量元素方面的总体成效几乎与传统X射线荧光探测器相当。当CCD相机与微针孔准直器结合时，就有可能实现空间分辨率为20μm的全场X射线荧光成像。还讨论了在实际X射线荧光分析中的进一步可行性。
