The Neutron Detector Based On Boron-containing Plastic Scintillator And Cherenkov Detector

Neutrons are electrically neutral,and are almost unaffected by coulomb forces when interacting with nuclei.In practical applications,neutrons are widely used,such as neutron logging,boron neutron therapy,nuclear energy and other applications have important significance.The acquisition of neutrons,the study of neutron characteristics and the technical application of neutrons are inseparable from the detection of neutron flux and energy.Therefore,neutron detection technology has received extensive attention.The neutron field is usually accompanied by gamma rays,which interfere with neutron measurements.Therefore,it is of practical value to develop a detector that can simultaneously measure the thermal and fast neutron fluxes in the neutron/gamma mixed field and has a certain resolution of neutron energy.In this paper,a neutron detector is designed to study the neutron/gamma hybrid field.It can measure the flux of thermal neutrons and fast neutrons in the neutron/gamma hybrid field,and it also can distinguish the neutron energy in the range of 1-7MeV.In this paper,Geant4 monte carlo simulation software was used to optimize and select the structure and materials of the neutron detector,and the performance of the detector after processing and manufacturing was tested.The main contents are as follows:(1)A wide-energy neutron flux detector designed for thermal neutrons in the energy range of 0-0.1ev,fast neutrons in the energy range of 1-14 mev,and gamma fields within 10 MeV.The detector is based on a laminated composite structure of plastic scintillation containing boron and Cherenkov radiator made of silica.Boron,which is sensitive to thermal neutrons,is doped in the plastic scintillator,which is already capable of detecting fast neutrons and gamma rays,increasing its response to thermal neutron energy.Cherenkov radiator can be used to detect the total gamma signal of neutron/gamma mixed field according to its characteristics of generating cherenkov light.The neutron and gamma counts recorded by the boron-containing plastic scintillator were divided into light intensity partitions,and the corresponding gamma counts of cherenkov detector were divided into light intensity partitions.The neutron flux and energy resolution information can be obtained by dividing the above two kinds of counts by a certain ratio.(2)Geant4 monte carlo simulation software was used to optimize the structure design of the detector and the selection of thermal neutron sensitive materials.The simulation results of B and Li F were compared,and B was finally selected as the added material.The optimal thickness of plastic scintillator was 3cm and that of cherenkov radiator was 2cm.By simulating the detector’s response to1-14 MeV monoenergetic neutrons,the relative error of the detector’s detection of neutrons is analyzed.The neutron detection error above 7MeV energy is more than 10%.To avoid large errors,neutron energy ranges suitable for the detector were set as 1-7MeV and 0-0.1eV.Through simulation,the light intensity range of the boron-plastic flash in response to the energy of each neutron and the light intensity range of the cerenkov detector should be deducted from the gamma ray background count are obtained.Then through the gain parameters of the photomultiplier tube and the preamplifier,the light intensity interval is converted into the voltage signal interval output by the detector.Different signal interval counts of boron-containing plastic scintillators are subtracted from the corresponding cerenkov detector signal interval counts of a certain proportion,so that the flux of neutrons with different energies can be detected.(3)Manufacture the detector according to the optimized structure obtained by simulation,and complete the prototype of the detector.The response of the designed detector to the shielded Am Be source device was studied by experiment and simulation.The results show that the data obtained by the detector are in good agreement with the data obtained by the simulation,which verifies that it can be used for neutron flux measurement and has a certain energy resolution ability.