Nuclear Techniques ›› 2020, Vol. 43 ›› Issue (9): 90102-090102.doi: 10.11889/j.0253-3219.2020.hjs.43.090102

• SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS • Previous Articles     Next Articles

Design of gas bremsstrahlung absorber at high energy photon source beamlines

Pingcheng LIU1,2,3,Qiongyao LIU3,Zhongjian MA1,Huijie ZHANG1,Mingyang YAN1,Qingbin WANG1,2()   

  1. 1.Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
    2.Spallation Neutron Source Science Center, Dongguan 523803, China
    3.University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2020-03-31 Revised:2020-06-19 Online:2020-09-15 Published:2020-09-09
  • Contact: Qingbin WANG E-mail:qbwang@ihep.ac.cn
  • About author:LIU Pingcheng, male, born in 1993, graduated from Harbin Institute of Technology in 2015, doctoral student, focusing on nuclear technology application
  • Supported by:
    National Key Scientific Instrument and Equipment Development Project(2011YQ120096)

Abstract: Background

The high energy photon source (HEPS) currently under construction in Beijing will be the brightest synchrotron radiation facilities in the world. The high energy electrons which generate the desired synchrotron radiation interact with matter (for example, residual gas molecules in the vacuum chamber), to produce a spectrum of bremsstrahlung photons with energies up to the electron energy – in HEPS 6 GeV. The bremsstrahlung is highly penetrating, and it can produce exotic reactions in any material that it strikes, leading to the production of other radiations, especially photoneutrons. The beam stops are made of either lead or tungsten of rectangular shape in order to prevent the gas bremsstrahlung when transmitting through beamline to an experimental enclosure.

Purpose

This study aims to design a new gas bremsstrahlung absorber to reduce the dose equivalent rate by simulation calculation based on the spectrum of scattered photons and photoneutrons for HEPS beamlines.

Methods

Based on the technical specification, layout and related parameters of HEPS and the first optical enclosure (FOE), Monte Carlo simulation software FLUKA was mainly utilized to investigate the gas bremsstrahlung production in HEPS straight sections. A complete treatment of electron, positron and photon interactions at energies above 100 eV were calculated for the gas bremsstrahlung generated in the HEPS storage ring straight section and the gas bremsstrahlung transmitted through the beamline and scatters from components and the radiation emanating through the hutch wall.

Results

The results show that the beam stop is effective in shielding photons, but the photoneutrons in HEPS beamlines is inevitable. The equivalent rate of neutrons outside the shield wall is still high. The maximum energy of neutrons in photonuclear reaction reaches upto 300 MeV. Giant resonance neutrons (0.1~5 MeV) account for 91% of the total flux of photoneutrons. Using polyethylene as local shield is a very effective method.

Conclusions

The combined shielding of lead and boron containing polyethylene can effectively reduce the neutron dose equivalent rate inside and outside FOE of HEPS beamlines.

Key words: Monte Carlo, Radiation shielding, Gas bremsstrahlung, HEPS

CLC Number: 

  • TL71