Study And Design On The Two-Dimensional Fast Neutron Imaging Detector Based On Miro-channel

A new fast neutron imaging detector, which consist of a polyethylene(PE) converter and a micro-channel plate(MCP), is proposed for fast neutron radiography.The yields of the recoil proton produced by 14.5MeV fast neutron on the eight kinds of hydrogen-rich material are simulated using MCNPX code. Polyethylene is chosen as the fast neutron-proton converter according to the results.The yields,the energy, spectraangular distribution and the energy spectra from different angles of the recoil proton produced by 14.5MeV or 2.5MeV fast neutron on the PE converter are simulated using MCNPX code and Geant4 code. Finally,through the analysis of the data,it is determined that 2.5mm is the best thickness of PE for 14.5MeV fast neutron and 85-100um is the best for 2.5MeV fast neutron.The property of the secondary electron produced by proton or electron on MCP material are simulated using Geant4 code. The results show that the smaller the incident angle is,the greater the electron yield will be.Under 14.5MeV or 2.5MeV fast neutron incident, the proton transportation process in PE and the electronic gain process in one MCP are simulated using Geant4 code, the electron beam spot images are recorded after MCP. The simulation results show that the electron beam spot diameter is slightly bigger than MCP aperture. It can be predicted that the spatial resolution of the detector close to MCP aperture. The neutron-electron Conversion efficiency of this detector is 10%.Under 14.5MeV or 2.5MeV fast neutron incident, the proton transportation process in PE and the electronic gain process in two V-shape MCP is simulated using Geant4 code, the electron beam spot images are recorded after MCP. The simulation results show that the electron beam spot diameter is slightly bigger than MCP aperture. It can be predicted that the spatial resolution of the detector close to MCP aperture. The neutron-electron conversion efficiency of this detector for 14.5MeV and 2.5MeV are 3500% and 1200%,which are much bigger than the conversion efficiency of the detector with one MCP,Under 14.5MeV or 2.5MeV fast neutron incident, the electronic gain process caused by alpha particles and proton,which were produced in MCP, is simulated using Geant4 code, The result shows that the enhancement of this process is about 10%. the influence on fast neutron imaging caused by gamma ray, which were produced in PE, is simulated using Geant4 code.The result shows that MCP is not sensitive to gamma ray.