| Neutron flux and neutron spectrum have important influences on the detection precision of online detection instrument which is based on prompt gamma-ray neutron activation analysis(PGNAA)technique.When detecting the sample element contents by PGNAA technique,the neutron flux and neutron spectrum have a significant effect on the spectrum of gamma rays that emit from the samples.So it is significant to design neutron moderator and reflector for online detection instrument based on PGNAA technique.The thesis investigates the neutron moderator and reflector.Furthermore,absolute neutron flux measurement by foil-activation technique is carried out on the simulation platform and compared with the simulation results.The main contents of the paper are as follows:1)The materials and structures of moderator and reflector are optimized by Monte Carlo method for the neutron point sources which energy level are at 2.5MeV and 14 MeV.2)A PGNAA online detection instrument simulation platform is designed by MCNP.And the Neutron flux and its spatial distribution on the upper surface of the belt in the simulation platform are measured by foil-activation technique with the purpose of offering a measuring method for PGNAA online detection instrument.3)The further optimization design of the whole structure is studied by MCNP for the cement and ore online detection instrument,which ues DD or DT neutron generator.Besides,the coal detection instrument based on DT neutron generator,is also carried out. |
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