纯碘化铯(CsI)晶体的发光与光衰减特性研究

doi:10.15541/jim20160304

摘要/Abstract

摘要：

纯碘化铯晶体是一种具有快衰减闪烁特性的新型辐射探测材料, 在伽马射线、中子和其它辐射探测技术中有重要的应用前景。本研究以Bridgman法所生长的纯碘化铯为对象, 分别研究了该晶体的透射光谱以及在紫外光、连续X射线、脉冲X射线和宇宙射线激发下的发射光谱、时间响应特性和沿晶体生长方向不同部位的光输出分布特点。实验测得晶体的吸收边为240 nm, 激发和发射波长分别位于241 nm和318 nm, 发光衰减时间分别为2~3 ns和18~25 ns。以尺寸为30 mm×30 mm×200 mm的晶体籽晶端和尾端与PMT耦合所测得的光输出分别是143 p.e/MeV和127 p.e./MeV, 尽管晶体两端的光输出存在12.6%的差异, 但没有观察到衰减时间长于100 ns的慢分量。这些性能进一步证明纯碘化铯晶体具有作为快闪烁体的优势。

关键词: 纯碘化铯, 晶体, 透光性, 发光, 衰减时间, 光输出

Abstract:

Pure CsI crystal is a kind of fast scintillators which can be used to detect γ-rays, neutrons as well as other radiation. Optical transmission and luminescence properties of pure CsI crystal grown with Vertical Bridgman method were measured under the excitation of UV, continuous X-ray, pulse X-ray as well as cosmic rays at room temperature. Cut-off edge of the grown CsI crystal reaches 240 nm, which is the shortest among the literature reported previously. Excitation and emission wavelength are 241 nm and 318 nm, respectively. The decay times of the fast intrinsic luminescence can be fitted into two components, 2~3 nm and 18~25 nm under the excitation of X-ray or cosmic rays. The light outputs measured from the crystal with size of 30 mm×30 mm×200 mm are 143 p.e/MeV and 127 p.e./MeV as its seed end and tail end were coupled with PMT, respectively. Even though the non-uniformity (12.6%) exists along the growth direction of the crystal, no significant slow component longer than 100 ns are observed. All of these properties prove that the pure CsI crystal is a promising fast scintillator.

Key words: pure CsI, crystal, transmittance, luminescence, decay time, light output

中图分类号:

O734

任国浩, 宋朝晖, 张子川, 张侃, 杨帆, 李焕英, 陈晓峰. 纯碘化铯(CsI)晶体的发光与光衰减特性研究[J]. 无机材料学报, 2017, 32(2): 169-174.

REN Guo-Hao, SONG Zhao-Hui, ZHANG Zi-Chuan, ZHANG Kan, YANG Fan, LI Huan-Ying, CHEN Xiao-Feng. Luminescence and Decay Time Properties of Pure CsI Crystals[J]. Journal of Inorganic Materials, 2017, 32(2): 169-174.

图/表 11

图1 纯CsI晶体的照片(a)及其轴向与横向透射光谱图(b)

Fig. 1 Photo (a) and longitudinal and transversal transmittance (b) of pure CsI crystal

图2 纯CsI晶体的紫外激发发射光谱图

Fig. 2 Photoluminescence spectra of pure CsI crystal

图3 纯CsI晶体的X射线激发发射光谱图

Fig. 3 X-ray excited luminescence (XEL) spectra of pure CsI crystals

表1 8#CsI对脉冲X射线的时间响应参数

Table 1 Response of 8# CsI crystal to the pulse X-ray

Test No.	8#CsI			Reference
Test No.	Rise time/ns	Decaytime/ns	FWHM/ns	Rise time/ns	Decaytime/ns	FWHM/ns
1	1.07	37.31	5.29	1.85	7.96	4.79
2	1.16	39.88	5.36	1.86	7.85	4.97
3	1.17	44.96	5.50	1.95	8.40	4.90
4	1.10	40.88	5.49	1.85	7.25	4.80
mean	1.13	40.76	5.41	1.88	7.87	4.87

图4 8#CsI晶体对脉冲X射线的响应波形

Fig. 4 Response of pure CsI crystal to the pulse X-ray

图5 脉冲X射线激发下8#CsI晶体的下降沿波形拟合

Fig. 5 Decay curve and its fitted line of 8# CsI crystal excited by pulse X-ray

图6 8#CsI晶体对宇宙射线的响应波形

Fig. 6 Response of 8# CsI crystal to the cosmic ray

表2 CsI(pure)晶体对宇宙射线的时间响应

Table 2 Response of 8# pure CsI crystal to the cosmic ray

Sample	Rise time /ns	Decay time/ns	FWHM/ns
8#CsI(pure)	3.678	25.509	8.003

图 7 宇宙射线激发下从信道1(a) 和信道2(b) 所测得的CsI晶体下降沿的波形及其拟合曲线

Fig. 7 Decay curves and their fitted lines from channel 1 and channel 2 of pure CsI crystal excited with cosmic ray

表3 本文所测试的纯CsI衰减时间与以往文献报道值的对比

Table 3 Comparison of decay times of pure CsI reported previously and those tested in this work

	Kubota	Woody	Schotanus	Amsler	Belsky	This work
τ₁ / ns	10	7	2	6±1	5-9	2-3
τ₂/ ns	36	29	22	28±2	10-25	18-25
Reference	[6]	[13]	[9]	[12]	[16]

图8 CsI晶体分别用A端(上)、B两端(下)耦合时在不同时间门宽下所测得的光输出

Fig. 8 Light outputs of CsI crystal when it is coupled by A (top) and B (bottom) ends and integrated from different time gate

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