Effect of Germanium Dead Layer on Detection Efficiency of High-Purity Germanium Based on Monte Carlo Simulations

Haisheng Song; Rongni Pang; Xiao Cai

doi:10.3788/LOP223019

Laser & Optoelectronics Progress, Volume. 60, Issue 23, 2304001(2023)

Effect of Germanium Dead Layer on Detection Efficiency of High-Purity Germanium Based on Monte Carlo Simulations

Haisheng Song¹, Rongni Pang^1,2、*, and Xiao Cai²

Author Affiliations

¹School of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, Gansu, China

²State Key Laboratory of Nuclear Detectors and Nuclear Electronics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100043, China

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Figures & Tables(8)

Fig. 1. Corresponding irradiation structure diagram for measuring high-purity germanium (HPGe)

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Fig. 2. Function relationship between detector energy and channel address

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Fig. 3. Relationship between dead layer thickness and simulation efficiency of ²⁴¹Am point source. Black spot data comes from simulation efficiency, horizontal line comes from experimental data, and vertical line determines thickness of dead layer through experimental and simulation linear function calculation

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Fig. 4. Comparison of actual efficiencies and Monte Carlo simulation efficiencies of different dead layer thicknesses

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Table 1. Crystal size of germanium detector provided by manufacturer

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Table 1. Crystal size of germanium detector provided by manufacturer

Dimension parameters of various parts of germanium detector	Value /mm
Germanium crystal diameter	86.3
Crystal length	85.8
Distance between crystal surface and aluminum shell front window	4.89
Thickness of outer package aluminum shell	1.5
Dead layer thickness（front）	0.5
Thickness of side dead layer	0.5
Cold finger core diameter	18
Cold finger core depth	52

Table 2. Standard point source used in experiment

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Table 2. Standard point source used in experiment

Radioactive source	Energy /keV	Branching ratio	Half life /a	Correction activity /Bq
²⁴¹Am	59.54	0.3570	432.212	3.65 $\times$ 10⁵
¹³³Ba	81.06	0.3406	10.538	2.25 $\times$ 10⁵
	302.85	0.1833
	356.02	0.6205
¹⁵²Eu	121.78	0.2837	13.516	2.23 $\times$ 10⁵
	344.29	0.2658
	778.20	0.1296
	964.11	0.1462
	1112.08	0.1350
	1408.00	0.2085

Table 3. Experimental and simulated detection efficiency results for different dead layer thicknesses

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Table 3. Experimental and simulated detection efficiency results for different dead layer thicknesses

Dead layer thickness		0.6	1.0	1.2	1.4	1.6	1.8	2.0
Dead layer thickness	$ε_{e x p}$				$ε_{s i m}$
59.54 keV	0.0012	0.0032	0.0020	0.0016	0.0013	0.0011	0.0008	0.0006
$δ$ /%	—	166.67	66.67	33.33	8.33	8.33	33.33	50.00
121.78 keV	0.0045	0.0053	0.0047	0.0045	0.0042	0.0041	0.0039	0.0039
$δ$ /%	—	17.78	4.44	0	6.67	8.89	15.38	15.38
344.29 keV	0.0032	0.0034	0.0035	0.0032	0.0032	0.0032	0.0031	0.0031
$δ$ /%	—	6.25	9.37	0	0	0	3.13	3.13

Table 4. Dead layer thickness of different characteristic rays
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Table 4. Dead layer thickness of different characteristic rays
Characteristic peak energy value /keV Thickness of outer dead layer /mm Error
59.54 1.50 0.02
121.78 1.41 0.03
344.29 1.30 0.03

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Haisheng Song, Rongni Pang, Xiao Cai. Effect of Germanium Dead Layer on Detection Efficiency of High-Purity Germanium Based on Monte Carlo Simulations[J]. Laser & Optoelectronics Progress, 2023, 60(23): 2304001

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