质子照相中容器引起的模糊

Blur caused by container in proton radiography

为了弄清质子照相中容器引起模糊的大小,以质子与吸收体的多次库仑相互作用为基础,结合负幺阵成像磁透镜系统的特性,推导出了容器模糊的半高全宽表达式。研究表明:容器的模糊半高全宽与容器至客体的距离成正比,与容器厚度的均方根成正比,与质子的动量成反比;容器的前后壁都对模糊有贡献;相同条件下,计算得到Al制容器的模糊小于Fe制容器的模糊;半径200 cm、厚5 cm的Al制容器的模糊为1.30 mm,大于客体的模糊,同时蒙特卡罗程序的模拟也得到了相同的结果。

In order to investigate the blur caused by the container in proton radiography, the expression of blurring FWHM of the container was deduced on the base of the multiple Coulomb scattering and the characteristic of the lens imaging system. The results show that the blurring FWHM is proportional to the distance between the object and the container and root mean square of container＇s thickness, and inverse proportional to the proton momentum. The front wall and back wall of container will cause the blur. And on the same situation, the container made of aluminum has smaller blur than that of the iron one. The blurring FWHM of aluminum container （radius 200 cm , thickness 5 cm） is 1.30 mm, larger than the object＇s. The analytic results agree with the simulation one by MC program.