质子照相中成像磁透镜系统对次级质子的消除

为了解成像磁透镜系统使用对提高质子照相品质的作用，研究了成像磁透镜系统对核反应产生的次级质子的消除作用。利用MCNPX模拟了次级质子的能谱，结果表明：次级质子的平均能量不足照相质子束的50%。从次级质子的能量特性和成像系统质子运动学方面的分析表明：成像磁透镜系统可消除次级质子的影响。利用程序MCNPX对含成像磁透镜系统的质子照相进行了模拟，结果显示：成像磁透镜系统将次级质子对光程的影响减小到2%以下，显著提高了图像品质。

Secondary proton removing effects of imaging lenses in proton radiography

In order to understand the effect of imaging lenses on imaging quality of proton radiograph, the research on the secondary proton-removing effect of imaging lenses has been carried out. The analytical results show that, the secondary protons’ energy is below one half of the original protons’ and the imaging lenses have the ability to remove secondary protons out of the detecting area. The simulation of the whole proton radiography system shows that the imaging lenses have decreased the relative optical path difference caused by secondary protons to less than 2%，and thus the image quality has been improved greatly. Thus the imaging lenses are important components in proton radiography.