Method of positron annihilation lifetime measurement triggered by start-signal

Zhenjie HAN; Fuyan LIU; Peng ZHANG; Baoyi WANG; Xingzhong CAO; Yuxiao LI; Long WEI

doi:10.11889/j.0253-3219.2018.hjs.41.060402

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Method of positron annihilation lifetime measurement triggered by start-signal

NUCLEAR ELECTRONICS AND INSTRUMENTATION | 更新时间：2021-05-19

- Method of positron annihilation lifetime measurement triggered by start-signal
- NUCLEAR TECHNIQUES Vol. 41, Issue 6, Article number: 060402(2018)
- 作者机构：
  
  1.郑州大学物理工程学院郑州 450001
  2.中国科学院高能物理研究所多学科研究中心北京 100049
- 作者简介：
- 基金信息：
  
  National Natural Science Foundation of China;National Natural Science Foundation of China
- DOI：10.11889/j.0253-3219.2018.hjs.41.060402
  CLC： TL817.9
- Received：29 December 2017，
  
  Revised：16 March 2018，
  
  Published：10 June 2018
- 稿件说明：
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Zhenjie HAN, Fuyan LIU, Peng ZHANG, et al. Method of positron annihilation lifetime measurement triggered by start-signal[J]. Nuclear techniques, 2018, 41(6): 060402
DOI：

Zhenjie HAN, Fuyan LIU, Peng ZHANG, et al. Method of positron annihilation lifetime measurement triggered by start-signal[J]. Nuclear techniques, 2018, 41(6): 060402 DOI： 10.11889/j.0253-3219.2018.hjs.41.060402.

摘要

正电子湮没寿命测量作为一种典型的核物理时间测量方法，其最为关键的两个性能参数是时间分辨率和符合计数率。决定时间分辨率的主要因素是探测器中闪烁晶体及光电转换器件的时间响应，而符合计数率不仅取决于探测器的探测效率，还取决于电子学系统对时间信号的判选方法。本文提出并设计了一种能够有效提高正电子湮没寿命符合测量计数率的方法。该方法通过对两探测器信号中的起始信号成分进行逻辑"或"运算产生外触发信号，利用高速数字化采集设备在此触发信号的触发下实现对有效事例的高效判选。其中任意一个探测器既可作为起始探测器也可作为终止探测器，有效提高了谱仪对探测器信号的利用率。实验表明：该方法在不影响时间分辨率和正电子湮没寿命谱与其峰谷比前提下，可获得更高效的符合计数率。

Abstract

Background

Positron annihilation lifetime measurement as a typical time measuring method of nuclear physics

its time resolution and coincidence count rate are the most important performance parameters. The main factors that determine the time resolution of the spectrometer are the time response of the scintillation crystal and the photoelectric conversion device of the detector

and the coincidence count rate depends not only on the detection efficiency of the detector but also on the judgment method of the time signals by the electronic system.

Purpose

This paper aims to find a novel method for improving the utilization rate of detector signals and the coincidence count rate of positron annihilation lifetime measurement effectively.

Methods

The detector signals were divided into two same parts by splitters. One part of the signals was applied to generate an external triggering signal by performing a logic disjunction (OR) operation on the start-signal components to trigger the digitizer for acquiring the other part of signals. Two time interval measurement units which are used for timing

time interval calculation and data statistics were set. To verify the feasibility of this method

the digital storage oscilloscope was used.

Results

Measurement results showed that

the timing resolution of this testing system is 222 ps. Positron annihilation short lifetime

for sample pure Fe is about 108 ps and the long lifetime

for HDPE is about 2.4 ns. And compared with the conventional measurement

this method gave double the coincidence count rate approximately.

Conclusions

In the conventional measurement

regardless of which detector is used as start-detector or stop-detector

it doesn't influence the measured positron annihilation lifetime spectrum. By using the logic OR operation on the start-signal components of two detectors for triggering

the coincidence count rate will be improved effectively

however

the time resolution and positron annihilation lifetime spectrum or its peak-to-valley are uninfluenced. And each detector can be regarded as a start-detector and the stop-detector.

关键词

Keywords

references

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