Nuclear Techniques ›› 2019, Vol. 42 ›› Issue (9): 90202-090202.doi: 10.11889/j.0253-3219.2019.hjs.42.090202

• ACCELERATOR, RAY TECHNOLOGY AND APPLICATIONS • Previous Articles     Next Articles

Simulating the effect of Prebuncher-Chopper on pulsing slow positron beam

Longpeng LIU1,2,Fuyan LIU2,Shilun PEI3,Peng KUANG2,Baoyi WANG2(),Peng ZHANG2,Huaiqiang ZHANG1(),Xingzhong CAO2   

  1. 1. School of Nuclear Science and Engineering, East China University of Technology, Nanchang 330013, China
    2. Multi-discipline Research Center, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
    3. China Institute of Atomic Energy, Cyclotron Research and Design Center, Beijing 102413, China
  • Received:2019-05-06 Revised:2019-07-05 Online:2019-09-10 Published:2019-09-18
  • Contact: Baoyi WANG,Huaiqiang ZHANG E-mail:wangboy@ihep.ac.cn;zhanghq821@163.com
  • About author:LIU Longpeng, male, born in 1992, graduated from North China University of Water Resources and Electric Power in 2017, master student, focusing on study of positron annihilation spectroscopy technology
  • Supported by:
    National Natural Science Foundation of China(11575205);the Scientific Instrument Developing Project of Chinese Academy of Sciences(YJKYYQ20180007)

Abstract: Background

Slow positron annihilation lifetime spectrum measurement is an important analytical method for high sensitivity and non-destructive detection of material micro-defects. Pulsed positron system is the core component of this technology.

Purpose

This study aims to obtain periodic positron pulses with high time resolution for lifetime measurement and to provide a signal marking the time of positron generation.

Methods

In this paper, the Parmela program was applied to simulate and calculate the effect of different beam parameters on positrons bunching based on the “Prebuncher-Chopper” pulsed system. Effect of different beam parameters on 150 ps (half-width) bunching was simulated and compared with calculation results of “Prebuncher-Chopper” bunching system.

Results

The results show that increasing beam energy, reducing beam energy spread and reducing beam spot size are beneficial to improve pulse efficiency. Moreover, when the positron beam energy is greater than 500 eV, the energy spread is less than 5 eV and the beam spot is less than 12 mm, the positron utilization ratio is more than 20% and the bunching efficiency is more than 85% using “Prebuncher-Chopper” pulsed system.

Conclusion

In contrast to the “Chopper-Prebuncher” system, “Prebuncher-Chopper” pulsed system can provide a higher positron utilization rate under the same beam parameters. Meanwhile, the time resolution (≤150 ps) and the bunching efficiency (≤85%) meet the measurement requirement.

Key words: Slow positron beam, Pulsed system, Positron utilization ratio, Bunching efficiency, Parmela

CLC Number: 

  • TL824