正电子湮没寿命测量统计精度研究

李楠; 祁宁; 陈志权; 王波

doi:10.11889/j.0253-3219.2018.hjs.41.010201

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正电子湮没寿命测量统计精度研究

低能加速器技术、射线技术及应用 | 更新时间：2021-05-19

- 正电子湮没寿命测量统计精度研究
- Study on the precision of positron lifetime measurements
- 核技术 2018年41卷第1期文章编号：010201
- 作者机构：
  
  武汉大学物理科学与技术学院核固体物理湖北省重点实验室武汉 430072
- 作者简介：
  
  [ "李楠, 女, 1993年出生, 2015年毕业于洛阳师范学院, 现为硕士研究生, 研究领域为材料微结构", "LI Nan, female, born in 1993, graduated from Luoyang Normal University in 2015, master student, focusing on material microstructure" ]
  祁宁, E-mail:ningqi@whu.edu.cn QI Ning, E-mail: ningqi@whu.edu.cn
- 基金信息：
  
  国家自然科学基金(11475130);国家自然科学基金(11575131)
- DOI：10.11889/j.0253-3219.2018.hjs.41.010201
  中图分类号： TL817.9
- 收稿日期：2017-03-31，
  
  修回日期：2017-06-05，
  
  纸质出版日期：2018-01-10
- 稿件说明：
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李楠, 祁宁, 陈志权, 等. 正电子湮没寿命测量统计精度研究[J]. 核技术, 2018,41(1):010201

Nan LI, Ning QI, Zhiquan CHEN, et al. Study on the precision of positron lifetime measurements[J]. Nuclear techniques, 2018, 41(1): 010201
李楠, 祁宁, 陈志权, 等. 正电子湮没寿命测量统计精度研究[J]. 核技术, 2018,41(1):010201 DOI： 10.11889/j.0253-3219.2018.hjs.41.010201.

Nan LI, Ning QI, Zhiquan CHEN, et al. Study on the precision of positron lifetime measurements[J]. Nuclear techniques, 2018, 41(1): 010201 DOI： 10.11889/j.0253-3219.2018.hjs.41.010201.

摘要

正电子湮没寿命与正电子所在位置的电子密度密切相关，因此能反映材料内部原子尺度的微观结构信息，是研究材料缺陷的灵敏探针。正电子湮没寿命可利用时间符合谱仪进行测量，而寿命谱仪的时间分辨函数一般在200-300 ps之间，因此在实际测量中得到的正电子寿命的精确程度是人们广泛关注的问题。本文通过对几种典型样品进行长时间重复测量，并通过改变谱仪的工作状态，研究了各种因素如谱仪的分辨函数、寿命谱总计数、样品中寿命成分个数及各寿命之间的间隔对所分析出的正电子寿命值的影响。研究发现，在谱仪保持状态稳定的情况下，寿命谱的统计测量计数为100万左右时，对于单晶Si中的单个正电子寿命（218ps），经过重复测量得到的标准偏差小于0.5 ps。对于存在三个寿命分量的高分子材料聚甲基丙烯酸甲酯（Poly（methyl methacrylate），PMMA）中，其平均寿命的标准偏差也小于1 ps，其中长寿命成分

（1.83 ns）的标准偏差仅为0.016 ns。研究还表明，谱仪时间分辩函数的大小对正电子寿命测量值的影响很小。我们的结果证明正电子寿命测量具有较高的统计精度，能准确反映材料中微观结构细小的变化。

Abstract

Background

The precision of positron lifetime measured in the experiment is of great concern.

Purpose

Some typical materials were chosen to repeat the positron lifetime measurements over a long time to assure the precision.

Methods

By adjusting the working conditions of the spectrometer

we studied the factors affecting the precision of the measured positron lifetime

such as the time resolution

total count of the lifetime spectrum

number of lifetime components in the sample and also the interval between each lifetime components.

Results

It was found that with stable working condition of the spectrometer and a total count of 1 million for each spectrum

the positron bulk lifetime in Si single crystal is about 218 ps

and the standard deviation is only 0.5 ps after several repeated measurements. In poly(methyl methacrylate) (PMMA)

where positrons have three lifetime components

the standard deviation of the average lifetime is also only 1 ps

and the standard deviation of the longest lifetime

(1.83 ns) is 0.016 ns. Our experiment also shows that the time resolution of the spectrometer has little effect on the measure of positron lifetime.

Conclusion

The results indicate the positron lifetime measurement has high precision

and is a reliable tool to detect the change of the microstructure of materials.

关键词

Keywords

references

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