Simulation of the effect of hole shape on performance of CsI: Tl scintillation screens based on silicon microchannel arrays
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摘要: 使用Geant4程序模拟了微孔形状对基于硅微通道阵列的CsI:Tl像素化X射线闪烁屏性能的影响。模拟的闪烁屏性能参数包括：闪烁光子数、底光输出、传输效率、n次全反射占比、调制传递函数(MTF)与空间分辨率的关系。模拟过程中设定微孔的形状分别为方形和圆形，两种孔形的微通道阵列周期相同，均为10 μm。模拟结果显示：方形微孔的闪烁光子数优于圆形微孔，闪烁光子数正比于微孔横截面积；闪烁屏厚度小于400 μm时，方形微孔的底光输出优于圆形微孔，厚度大于400 μm时，圆形微孔的底光输出优于方形微孔；圆形微孔的传输效率优于方形微孔；厚度为40和200 μm的方形微孔闪烁屏空间分辨率优于相同厚度的圆形微孔闪烁屏。制备了方形微孔的CsI:Tl闪烁屏样品，测量了其MTF与空间分辨率的关系，当MTF为0.1时，空间分辨率为22.6 lp/mm。Abstract: The Geant4 program was used to simulate the effect of micropore shape on the performance of CsI:Tl X-ray scintillation screen based on silicon microchannel array (SMA). The simulated scintillation screen performance parameters include: scintillation photons, bottom light output, transmission efficiency, percentage of n times total reflection, and modulation transfer function (MTF) versus spatial resolution. The shapes of the micropores were set to be square and circular during the simulation process, and the microchannel array period was the same for both hole shapes, which was 10 μm. The simulation results show that the number of scintillation photons in square micropores is better than that in circular micropores, and the number of fluorescent photons is directly proportional to the cross-sectional area of the micropores; while the thickness is less than 400 μm, the bottom light output of square micropores is better than that of circular micropores, when the thickness is greater than 400 μm, the situation is opposite; The transmission efficiency of circular micropores is better than that of square micropores; For the thickness of 40 and 200 μm, the spatial resolution of the square micropores scintillation screen is better than that of the circular micropores scintillation screen with the same thickness. A square microporous CsI: Tl scintillation screen sample was prepared, and the relationship between its MTF and spatial resolution was measured. When the MTF was 0.1, the spatial resolution was 22.6 lp/mm.
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Key words:
- Geant4 /
- scintillation screen /
- CsI:Tl /
- modulation transfer function /
- silicon microchannel array
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图 2 两种基于SMA的CsI:Tl闪烁屏结构示意图
Figure 2. Schematic structure of two silicon microchannel array (SMA) based CsI:Tl scintillation screens
图 3 基于SMA的CsI:Tl闪烁屏三维几何模型
Figure 3. SMA-based 3D geometric models of CsI:Tl scintillation screen
图 4 产生的闪烁光子数随闪烁屏厚度的变化
Figure 4. Variation of the number of generated scintillation photons with the thickness of the scintillation screen
图 5 闪烁光子数随X射线能量的变化
Figure 5. Variation of scintillation photon number with X-ray energy
图 6 BLO与闪烁屏厚度的关系
Figure 6. Relationship between BLO and thickness of scintillation screen
图 7 传输效率与闪烁屏厚度的关系
Figure 7. Transmission efficiency versus scintillation screen thickness
图 8 经n次全反射的闪烁光子数占闪烁光子总数的比例
Figure 8. Number of scintillating photons subjected to n total reflections as a proportion of the total number of scintillating photons
图 9 CsI:Tl闪烁屏的MTF与空间分辨率的关系
Figure 9. MTF versus spatial resolution for CsI:Tl flicker screens
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