γ射线旋转调制器成像系统的研制  

Development of a rotating modulator gamma-ray imager

作　　者：魏星[1] 王锋[1] 王英[1] 肖无云[1] 艾宪芸[1] 张斌[1] 徐红鹃[1] 张磊[1] 马新华[1] 

机构地区：[1]防化研究院国民核生化灾害防护国家重点实验室,北京102205

出　　处：《核技术》2014年第4期41-45,共5页Nuclear Techniques

摘　　要：可对硬X射线、γ射线等成像的旋转调制器(Rotating Modulator,RM)成像技术是一种探测效率高、能量范围宽、能量分辨能力高的技术,可满足核辐射监测中对高性能γ射线成像系统的需求。为此,研制了一台基于RM技术的γ射线成像系统样机。该样机主要包括一个由8条铅条组成的旋转准直器、7个NaI(Tl)探测器、步进电机和相应的读出及控制电路。样机视场角±14.6°,角度分辨率2°,在662 keV处能量分辨率为7%,对662 keVγ射线的探测效率达到22.2%。Background： In nuclear monitoring applications, a gamma-ray imager based on coded aperture （CA） technology can get a 2-D source intensity distribution map, which is superimposed on a corresponding video camera image, to visualize an object scene indicating the location, activity and even the type of radionuclide of radioactive sources. Though the CA imager has some advantages, it is still limited to imaging sources at large standoff distance or with high energy photon emission. There are two main barriers. One is that increasing the area of position-sensitive detector brings unacceptable additional system complexity and cost. Another is that thicker detector induces image blurring. Purpose： In order to overcome the disadvantages of CA imager, a novel gamma-ray imager prototype based on rotating modulator （RM） technique is built in our laboratory. Methods： The laboratory prototype consists of a rotating collimator, a NaI（T1） detectors array, readout and control circuit, a stepping motor, and their supporting frame Experimental tests were carried out. Results： The field of view （FOV） of this prototype is ±14.6°. An angular resolution of 2° is achieved. The energy resolution of the NaI（T1） detectors is 7%@662 keV and their average detection efficiency to 662-keV gamma-rays is 22.2%. Conclusion： ARM imager is capable of imaging gamma-rays and measuring the incident photon specmma simultaneously. Thus it can form radioactive map of different radionuclide. Through temporal modulation and image reconstruction, the angular resolution of RM imager is comparable to that of a CA imager. Using non-position-sensitive detectors, the detector area and thickness can be increased to improve the detection efficiency with relatively low cost. The study is still in progress and the performance of the RM imager is expected to be improved for further development.

关 键 词：旋转调制器 γ射线成像 图像重建 探测效率 

分 类 号：TL812[核科学技术—核技术及应用]