Mathematical model establishment, simulation and reconstruction of PGAI
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摘要: 瞬发伽马活化成像中，样品内部的中子自屏蔽和伽马自吸收效应会使测量结果产生不均匀分布。针对成像单元响应不一致的问题，研究了样品内部中子场不均匀分布和伽马自吸收效应的影响，并进行了理论推导，建立了用于修正成像单元响应和图像重建的数学模型，利用数学模型对Fe，H元素瞬发伽马活化成像的蒙特卡罗模拟进行了元素图像重建。 结果显示，样品内中子场和γ自吸收对成像的影响得到明显改善，Fe和H元素的含量分布使用此模型可以被精确重建，验证了数学模型的有效性。Abstract: In the prompt gamma activation imaging, the neutron self-shielding and gamma self-absorption effect inside the sample will cause uneven distribution of the measurement results. To solve the problem of the biased distribution in the prompt gamma activation imaging, the influence of the neutron field inside the sample and the self-absorption effect of gamma were studied, and the transport process of neutrons and gamma rays was theoretically deduced. A mathematical model for correcting the biased distribution and image reconstruction was established. The Monte Carlo method was used to simulate the prompt gamma activation imaging of Fe and H elements, and the mathematical model was used to reconstruct the element images. The results show that the influence of neutron self-shielding and γ self-absorption effect in prompt gamma activation imaging has been significantly corrected, and the content distribution of Fe and H elements can be accurately reconstructed using this mathematical model, which verify the validity of the mathematical model.
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图 4 Fe元素瞬发伽马射线计数在样品不同位置的分布图
Figure 4. Prompt gamma ray counting distribution of Fe in different positions of the sample
图 5 H元素瞬发伽马射线计数在样品不同位置的分布图
Figure 5. Prompt gamma ray counting distribution of H in different positions of the sample
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