Virtual point source efficiency calibration technology based on virtual point detector
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摘要: 主要针对尺寸为ϕ75 mm×25 mm的241Am标准体源HPGe探测器探测效率展开研究，通过LabSOCS软件模拟及蒙卡计算研究发现，使用同一种结构类型的探测器测量特定形状的体源，其虚拟点探测器位置与虚拟点源位置满足线性、二次函数、指数等关系。针对确定的探测器，通过点源在对称轴线上不同高度位置实验就可以标定出虚拟点探测器位置，再结合它们的线性函数进一步计算出虚拟点源位置，最后将点源放置于虚拟点位置刻度即可得到体源的探测效率。因此，该技术方法首次提出通过虚拟点探测器位置找到了虚拟点源的位置，是一种全新的刻度方法，已达到实际应用的程度，可以大面积推广应用该技术成果。Abstract: The detection efficiency of ϕ75 mm×25 mm of 241Am standard samples were studied by using laboratory HPGe detection. When we used detectors with the same type of structure to measure a given volume source, the linearity function between the virtual point source and the virtual point detector was established by using LabSOCS software and Monte Carlo method. For a detector, the position of virtual point detector can be fixed by a point source placed at different height, and then, the position of virtual point source can be fixed by using their linearity function. The real calibration process will be carried out by placing a point source at its virtual position, namely, the volume source is replaced with the point source. In conclusion, the position of virtual point source can be obtained through the virtual point detector. This is a completely new technology method, which will be widely applied in radioactive measurement.
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图 2 平板型HPGe探测器虚拟点探测器和虚拟点源函数关系
Figure 2. Function curve of virtual point detector and its virtual point location for planar HPGe detector
图 3 同轴型HPGe探测器虚拟点探测器和虚拟点源函数关系
Figure 3. Function curve of virtual point detector and its virtual point location for coaxial HPGe detector
图 5 宽能型探测器不同厚度虚拟点探测器和虚拟点源函数关系
Figure 5. Function curve of virtual point detector and its virtual point location for BEGe detector
图 6 不同半径宽能型探测器虚拟点探测器和虚拟点源函数关系
Figure 6. Function curve of virtual point detector and its virtual point location for BEGe detector of different radius
表 1 平板型HPGe探测器体源点源探测效率及虚拟点探测器和虚拟点源位置
Table 1. Position of virtual point detector and virtual point source, and efficiency of volume and point source for planar HPGe detector
type of detector diameter of crystal /mm diameter of detector /mm thickness of detector /mm efficiency of volume source distance between point source and detector/mm efficiency of point source position of virtual point detector /mm position of virtual point /mm planar 60 76.2 133.4 8.21×10-2 40
35
33
306.75×10-2
7.98×10-2
8.56×10-2
9.55×10-222.8 34.3 70 88.9 133.4 1.11×10-1 40
35
33
309.11×10-2
1.07×10-1
1.14×10-1
1.26×10-126.2 33.9 80 101.6 133.4 1.23×10-1 40
35
33
301.01×10-1
1.16×10-1
1.24×10-1
1.35×10-133.1 33.3 example_ BEGE / 101.6 133.4 1.23×10-1 40
35
33
301.01×10-1
1.16×10-1
1.24×10-1
1.35×10-133.1 33.2 8053 70 89 133.4 1.03×10-1 40
35
33
308.42×10-2
9.86×10-2
1.05×10-1
1.16×10-127.7 33.7 
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表 2 同轴型HPGe探测器体源点源探测效率及虚拟点探测器和虚拟点源位置
Table 2. Position of virtual point detector and virtual point source, and efficiency of volume and point source for coaxial HPGe detector
diameter of crystal /mm diameter of detector /mm thickness of detector /mm efficiency of volume source distance between point source and detector/mm efficiency of point source position of virtual point detector /mm position of virtual point /mm 45 76.2 133.4 2.47×10-2 40
38
35
302.37×10-2
2.55×10-2
2.85×10-2
3.48×10-216.9 38.8 65 76.2 133.4 3.69×10-2 45
40
38
353.15×10-2
3.68×10-2
3.91×10-2
4.32×10-223.7 40.0 70 88.9 133.4 2.76×10-2 45
43
41
402.57×10-2
2.71×10-2
2.86×10-2
2.94×10-231.5 42.3 75 95.26 133.4 3.57×10-2 45
43
41
403.31×10-2
3.49×10-2
3.67×10-2
3.77×10-233.6 42.1 80 101.6 133.4 2.34×10-2 46
45
43
402.29×10-2
2.35×10-2
2.46×10-2
2.63×10-243.1 45.1 90 101.6 160.3 2.61×10-2 46
45
43
402.60×10-2
2.65×10-2
2.76×10-2
2.95×10-252.7 47.8
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表 3 8062宽能型HPGe探测器(晶体直径70.0 mm)体源点源探测效率及虚拟点探测器和虚拟点源位置
Table 3. Position of virtual point detector and virtual point source, and efficiency of volume and point source for 8062 BEGe detector, diameter of crystal is 70.0 mm
thickness of detector/mm efficiency of volume source distance between point source and detector/mm efficiency of point source position of virtual point detector/mm position of virtual point/mm 40 1.09×10-2 37 1.22×10-2 0.1 1.33×10-2 35 1.33×10-2 15.5 35.2 25 2.06×10-2 22 2.39×10-2 40 3.00×10-2 37 3.36×10-2 0.3 3.49×10-2 35 3.64×10-2 16.8 36.3 25 5.59×10-2 22 6.44×10-2 40 4.55×10-2 37 5.09×10-2 0.5 5.08×10-2 35 5.50×10-2 17.9 37.1 25 8.36×10-2 22 9.58×10-2 40 7.21×10-2 37 8.03×10-2 1.0 7.51×10-2 35 8.65×10-2 20.2 38.8 25 1.29×10-1 22 1.47×10-1 45 9.12×10-2 40 1.07×10-1 5.0 1.01×10-1 37 1.18×10-1 24.2 41.8 35 1.27×10-1 25 1.82×10-1 45 9.16×10-2 40 1.08×10-1 10 1.02×10-1 37 1.19×10-1 23.3 41.5 35 1.27×10-1 25 1.83×10-1 45 9.16×10-2 40 1.08×10-1 20 1.02×10-1 37 1.19×10-1 23.3 41.5 35 1.27×10-1 25 1.83×10-1 45 9.16×10-2 40 1.08×10-1 30 1.02×10-1 37 1.19×10-1 23.3 41.5 35 1.27×10-1 25 1.83×10-1 45 9.16×10-2 40 1.08×10-1 45 1.02×10-1 37 1.19×10-1 23.3 41.5 35 1.27×10-1 25 1.83×10-1 45 9.16×10-2 40 1.08×10-1 60 1.02×10-1 37 1.19×10-1 23.3 41.5 35 1.27×10-1 25 1.83×10-1
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表 4 8062宽能型HPGe探测器(晶体厚度30.0 mm)体源点源探测效率及虚拟点探测器和虚拟点源位置
Table 4. Position of virtual point detector and virtual point source, and efficiency of volume and point source for 8062 BEGe detector with different diameter, thickness of crystal is 30.0 mm
diameter of detector/mm efficiency of volume source distance between point source and detector/mm efficiency of point source position of virtual point detector/mm position of virtual point/mm 45 1.09×10-1 40 1.26×10-1 80 1.18×10-1 37 1.38×10-1 29.6 42.2 35 1.47×10-1 25 2.03×10-1 45 1.00×10-1 40 1.17×10-1 75 1.10×10-1 37 1.29×10-1 26.4 41.9 35 1.38×10-1 25 1.94×10-1 45 9.16×10-2 40 1.08×10-1 70 1.02×10-1 37 1.19×10-1 23.4 41.7 35 1.27×10-1 25 1.83×10-1 45 8.27×10-2 40 9.79×10-2 65 9.24×10-2 37 1.09×10-1 10.3 41.3 35 1.17×10-1 25 2.03×10-1 45 7.39×10-2 40 8.80×10-2 60 8.32×10-2 37 9.82×10-2 17.7 41.6 35 1.06×10-1 25 1.59×10-1
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