Study On The 14MeV Fast Neutron Imaging And 3D Image Reconstruction Method With Geant4

This paper mainly use the 14MeV fast neutron active method for detecting and imaging the shielded highly enriched uranium based on the Geat4 toolkits within Monte Carlo and use ROOT toolkit analysis the simulation data in detail. The work content and results are the following four aspects:the first, this work use the difference of time of flight to discriminate the different particles, which are gamma-rays, fission neutrons, incident neutrons and scattered neutrons. The gamma-ray which is before the 58ns is one hundred percent,90% of the 60-100ns includes the incident neutrons and scattered neutrons,100ns after 95% is the fission neutrons and multi-body scattered neutrons with low energy. Secondly, the use of the simulation prompt gamma rays data, gamma-rays location and time on the detection of the objects which they are pieces of the highly enriched uranium, lead, iron and polyethylene blocks, etc., and initialization vector of incident neutrons, reconstructed three-dimensional image. The reconstructed image in the vertical direction of incident neutron beam has a good agreement between reconstructed locations with the detected objects; the location deviation is not big than 1%. But along the incoming neutron beam direction position deviation should be slightly worse. Main feature are the low reconstruction counts intensity which is closer the neutron source and the tailing which is far the neutron source. This work analyses the causes and gives some accounts, for detail see chapter 3.2.5. Thirdly, the transmission image shows a clear density distribution of the detection objects based on incident 14MeV neutrons. Fourthly, the simulation data about prompt gamma rays has a good agreement between with the experimental data by the IAEA in 1998.