Single energy X-ray source for calibration of X-ray detectors
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摘要: 为提高X射线探测器的标定精度,在荧光X射线源的基础上,提出在荧光X射线出射通道设置滤光片的方法提高X射线纯度。通过蒙特卡罗建立仿真模型,分析了辐射体发生K层光电效应的概率与原子序数的关系,并得到荧光强度和纯度随滤光片厚度的变化曲线。在大气环境下,采用硅漂移半导体探测器测试了荧光X射线源的能谱分布和光子流量,分析X射线管管电压对光子流量和荧光纯度的影响。在辐射体材料为铜,滤光片(镍)厚度为0 μm、10 μm和30 μm时,测得的荧光X射线纯度分别为75.61%、85.38%和84.25%,光子流量分别为3425 phs/s、2023 phs/s和1192 phs/s,确认了滤光片厚度对荧光X射线纯度和强度的影响,为解决荧光X射线光源单色性不足难以对X射线探测器进行高精度标定的问题提供了方向。Abstract: To improve the calibration accuracy of X-ray detectors, this paper presents a method of placing filters in fluorescent X-ray emission channels to improve the purity of X-rays. Monte Carlo simulation model was established to analyze the relationship between the probability of photoelectric effect in K layer and the atomic number, and the curve of fluorescence intensity and purity with filter thickness was obtained. In atmospheric environment, the energy spectrum distribution and photon flux of fluorescent X-ray source were measured by silicon drift semiconductor detector, and the effect of X-ray tube voltage on photon flux and fluorescence purity was analyzed. When the radiator material is copper and the thickness of the filter (nickel) is 0 μm, 10 μm and 30 μm, the purity of fluorescence X-ray measured is 75.61%, 85.38% and 84.25%, and the photon flux is 3425 phs/s, 2023 phs/s and 1192 phs/s, respectively. The influence of filter thickness on the purity and intensity of fluorescent X-ray is confirmed, which provides a direction for solving the problem that it is difficult to calibrate X-ray detectors with high accuracy due to the lack of monochromatism of fluorescent X-ray light source.
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Key words:
- fluorescent X-ray source /
- filter /
- calibration of detector
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表 1 不同辐射体的荧光X射线源能谱仿真数据
Table 1. Spectral simulation data of fluorescence X-ray sources with different radiators
material Kα photons Kα proportion/% K photons K proportion/% scattered photons scattered photon proportion/% Cr 46622 79.791 53529 82.426 64941 17.574 Fe 100289 80.270 114567 91.698 10373 8.302 Cu 252727 85.466 286400 96.853 9304 3.147 表 2 测得的不同辐射体材料的能谱数据
Table 2. Measured spectral data of different radiation materials
material $ {\rm{K}}_ {\text{α}} $ photons $ {\rm{K}}_ {\text{α}}$ proportion/% K photons K proportion/% scattered photons scattered photon proportion/% Cr 15410 45.72 18273 54.215 15432 45.785 Fe 39177 64.017 46347 75.733 14850 24.267 Cu 155442 75.642 183030 89.067 22466 10.933 Ge 177050 77.485 208868 91.410 19627 8.59 Zr 298287 79.044 351258 93.081 25733 6.819 表 3 不同
$ {\mathit{V}}_{\rm{a}} $ 下测得的辐射体Cu的光子流量数据Table 3. Photon flux data of radiator Cu measured under different
$ {\mathit{V}}_{\rm{a}} $ Ia/μA Va/kV Kα counting rate/(phs·s−1) Kα proportion/% scattered photon proportion/% 200 20 45 79.147 7.856 200 25 231 78.247 8.360 200 30 600 77.253 9.182 200 35 1007 76.568 9.734 200 40 1509 76.013 10.437 200 45 2047 75.815 10.491 200 50 2589 75.608 10.932 -
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