This article presents a method for precisely measuring the charge spread inside a silicon sensor, before it is sampled by the pixels of an X-ray imaging detector. The shape of the charge spread or pre-sampled point spread function (PSF) of the silicon sensor was demonstrated with a sub-micrometer resolution. The measurement setup comprises quasi-monochromatic X-ray beams emitted by a synchrotron radiation source, 5-$\mathrm{\mu }\mathrm{m}$-diameter tungsten pinhole, sub-$\mathrm{\mu }\mathrm{m}$-resolution X-ray beam profiler, and photodiode array in automation mode for step-scanning measurements. We obtained a value of 16.5–17.1 $\mathrm{\mu }\mathrm{m}$ (full width at half-maxima; sensor thickness: 650 $\mathrm{\mu }\mathrm{m}$; bias voltage: 750 V) based on preliminary experiments using 7.3 keV X-rays at BL19LXU of SPring-8. This value is consistent with the expected value obtained from the convolution of the beam profiles and pre-sampled PSFs corresponding to multiple photons for a dopant density of $\sim 10^{12}$ ${\mathrm{cm}}^{-3}$ within a range of approximately 1 $\mathrm{\mu }\mathrm{m}$. We believe that our measurement method has sufficient potential for evaluating the pre-sampled PSF of a photodiode array with an accuracy of 1 $\mathrm{\mu }\mathrm{m}$ or less. The single-photon capability of imaging detectors depends on the detector noise as well as the pre-sampled PSF. Our measurement method, with high spatial resolution, is beneficial in the sense that it optimizes the pixel design of X-ray image sensors using a sample piece with a limited number of pixels.

本文介绍了一种在X射线成像检测器的像素采样之前，精确测量硅传感器内部散布的电荷的方法。以亚微米分辨率展示了硅传感器的电荷扩散或预采样点扩散函数（PSF）的形状。测量装置包括由同步加速器辐射源发射的准单色X射线束，5-$\mathrm{\mu }\mathrm{米}$-直径钨针孔，亚-$\mathrm{\mu }\mathrm{米}$分辨率的X射线光束轮廓仪和自动模式下的光电二极管阵列，用于逐步扫描测量。我们得出的值为16.5–17.1$\mathrm{\mu }\mathrm{米}$ （全宽为一半的最大值；传感器厚度：650 $\mathrm{\mu }\mathrm{米}$; 偏置电压：750 V）基于在SPring-8的BL19LXU处使用7.3 keV X射线进行的初步实验。该值与从光束轮廓和预采样的PSF的卷积获得的期望值一致，该预采样的PSF对应于多个光子，掺杂浓度为。$〜\mathrm{1个}{0}^{12}$ ${\mathrm{厘米}}^{-3}$ 在大约1的范围内 $\mathrm{\mu }\mathrm{米}$。我们认为，我们的测量方法具有足够的潜力来评估光电二极管阵列的预采样PSF，其精度为1$\mathrm{\mu }\mathrm{米}$或更少。成像探测器的单光子能力取决于探测器的噪声以及预采样的PSF。我们的测量方法具有很高的空间分辨率，这是有好处的，因为它可以使用像素数量有限的样品来优化X射线图像传感器的像素设计。