Physical Study Of The Back-streaming White Neutron Beam For Irradiation Effects

The China Spallation Neutron Source(CSNS),located in Dongguan City,Guangdong Province,is a large scientific facility amid the national "The Eleventh Five-Year Plan".It is the world's fourth-largest spallation neutron source after the Spallation Neutron Source(SNS),the Japan Proton Accelerator Research Complex(J-PARC),and ISIS.A large number of neutrons are produced by the spallation reaction of bombarding a tungsten target with high-energy proton beams.In the back-streaming direction,there are also many neutrons emitted from the target.A white neutron beamline exploiting these back-streaming neutrons,is named Back-n and has a continued and wide neutron energy spectrum.Back-n is the first white neutron source for nuclear data measurement in China.The Back-n neutron beam also has a good application in neutron radiography,material radiation test,and atmospheric neutron irradiation experiments,etc.With an increase in the application of high-integrated chips and circuits,there is a strong demand for neutron irradiation test of electronic devices both domestically and internationally in recent years,and Back-n supplies the test condition for atmospheric neutron irradiation experiments in China.In this paper,a deep research on the beam physics of Back-n is carried out,mainly including finding optimal parametric method for the experimentally measured proton distribution,simulating the characteristics of Back-n beam with a more real distribution,analyzing the influence of the proton beam distribution on the spectrum and fluence of Back-n endstations.The spectra and fluences for different aperture combinations of the three collimators are analyzed,which creates more beam modes available and helps to meet more experimental requirements.According to requirements of high-flux irradiation,the beam characteristics at the front of Back-n beamline are analyzed in detail in this paper.And the physical design is given.At the same time,the influence of back-scattered neutrons on the irradiation experiment on the irradiation platform is also calculated.Based on this research,the construction of the irradiation platform has been completed,and it has begun to provide users with experimental beam on irradiation applications.