一种新型的液闪阵列成像屏空间分辨特性

针对低强度射线成像,自主研制了一种像元为0.1 mm高探测效率的液闪阵列屏.为此,基于倾斜刀口边缘响应的测量原理,建立了理论模拟方法和实验研究方法,对该液闪阵列屏开展了空间分辨性能研究.通过理论模拟,给出了液闪阵列屏在14 MeV中子和1.25 MeV伽马射线激发下的调制传递函数,并与像元为0.1,0.3和0.5 mm的闪烁纤维阵列屏进行了理论对比.在60Co伽马射线源上,对液闪阵列屏和像元为0.3和0.5 mm的两种国产闪烁纤维阵列屏进行了调制传递函数实测研究.理论模拟和实验结果一致,均表明液闪阵列的空间特性优于闪烁纤维阵列屏,而且具有更好的均匀性,对1.25 MeV伽马,空间分辨接近0.9 lp/mm,而其他两种纤维阵列屏仅达到0.5 lp/mm,对于14 MeV中子,液闪阵列屏的空间分辨可达到1.8 lp/mm.

Spatial resolution of novel liquid scintillating capillary array

Scintillating array image plates are allowed high resolution through a thicker detector which increases quantum efficiency without degrading the imaging resolution substantially.Due to limitations imposed by process capability,scintillator fiber array with pixel diameter less than 0.2 mm is hardly manufactured to improve performance.Therefore,a liquid scintillator capillary array with 0.1 mm pixel is developed to improve the detection efficiency and spatial resolution of image plate for low intensity radiation imaging.Its performances are studied and tested by simulation and experiment,and are compared with those of scintillating fiber array.Especially in order to gain high fidelity representation of modulation transfer function of the array image plate,a method of simulating and measuring the slanted knife edge response and an iterative algorithm are introduced.For 14 MeV neutron and 1.25 MeV gamma,the slanted knife edge responses of these array image plates with pixel dimensions in a range from 0.1 mm to 0.5 mm are respectively simulated by MCNPx program and the modulation transfer function(MTF)are obtained.The simulation results show that compared with scintillating fiber array,the liquid scintillator capillaries array has an obvious merit in spatial resolution because of greater stopping power for secondary charged particle in the capillary quartz glass wall with 0.02 mm in thickness.Its ultimate resolution can reach to 1.8 lp/mm for 14 MeV neutron by simulation.At the 4000 Ci 60Co facility,a 5-cm-thick tungsten bar,one side of which has a curvature of 0.1 radian to minimize the misalignment effect,is made a knife edge.The MTF of the scintillating fiber array with 0.3 mm and 0.5 mm pixel and newly developed liquid scintillator capillary array is measured through this tungsten knife edge.Experimental measurement results have also verified that the liquid scintillator capillary array performs well in spatial resolution and luminescent uniformity for 1.25 MeV gamma.The ultimate spatial resolution,0.9 lp/mm is gained,and those of other scintillating fiber arrays are all less than 0.5 lp/mm.Moreover,experimental test validates the simulating method and simulated results,although the measured value is slight less than the simulated value because of the effect of dimension of 60Co source.