不锈钢和铝外壳材料对宇宙射线辐射成像的对比研究

Comparison Between Stainless-steel and Aluminum Shell Applying in Cosmic Rays Radiation Imaging

利用宇宙射线进行辐射成像,已经成为近年发展的无损成像技术。美国决策科学公司采用铝外壳的漂移管开发出无源探测系统(Passive Detection System,PDS)用于大型集装箱检测,本文依据实际工程需要,模拟宇宙射线中μ介子和电子直射铝外壳和不锈钢外壳PDS时沉积能量、能谱和位置分布的区别,用以研究不锈钢外壳代替铝外壳的可行性。研究结果显示,直射μ介子在两种外壳PDS中探测效率均接近1,经过两种外壳PDS后,能谱均有少许偏移和展宽,出射角度均有少许偏转。相比而言,不锈钢外壳PDS的能量沉积更大,能谱展宽和角度偏转也稍大,但均与铝外壳差距很小;直射电子在两种外壳PDS中探测效率均接近1,但相当一部分电子会被两种外壳PDS阻挡,未被阻挡电子能谱也有明显的偏移和展宽,出射位置偏移大,其中不锈钢造成的影响比铝外壳要更明显。因此若宇宙射线辐射成像时只考虑μ介子,从能量沉积、能谱和位置分布角度来说,不锈钢外壳代替铝外壳是完全可行的;但若考虑电子,不锈钢外壳和铝外壳对电子影响都不容忽视,不锈钢影响更大。

Using cosmic rays for radiation imaging has become a novel non-destructive imaging technology recently.Passive detection system(PDS)with drift tubes of aluminum shell was developed by Decision Sciences International Corporation for large container detection.However,compared to the aluminum shell,the stainless-steel shell is stronger and easier to process,which makes it more suitable to practical application.Based on the actual engineering needs,the differences between cosmic rays,including muons and electrons,incidenting PDS with aluminum shell and the stainless steel shell directly are simulated,containing the detection efficiency,the energy deposition in the gas of the drift tubes,and the energy spectrum and the position distribution through the PDS,so as to study the feasibility of replacing the aluminum shell with the stainless steel shell.It is showed that when the muons incident directly,the detection efficiency is close to 1,the energy spectrum shows shift and broadening,and the position distribution shows a little deviation for PDS with two kinds of shell.In comparison,the energy deposition,the shift and broadening of the energy spectrum,and the deviation of the position distribution are also slightly larger for PDS with stainless-steel shell,but the differences between PDS with two kinds of shell are very small.When the electrons incident the PDS directly,the detection efficiency is also close to 1,but a considerable part of the electrons will be blocked by the PDS with two kinds of shell;for the outgoing electrons,the energy spectrum has a large shift and broadening and the position distribution has a large deviation,among which the influence of PDS with stainless-steel shell is greater than that with aluminum shell.Therefore,if only muons are taken into account for the radiation imaging using cosmic rays,it is completely feasible for PDS with the stainless-steel shell to replace that with the aluminum shell;if the electrons are also considered,the influences of the PDS with two kinds of shell cannot be ignored,among which the influence of PDS with stainless-steel shell is greater.