Neutron direct-radiation response of medium-type fast-neutron detector

The medium-type fast-neutron detector responds to direct neutron irradiation and it has an extreme effect on its design and practical applications. Monte-Carlo simulation programs based on Geant4 toolkit are developed to study the neutron direct radiation response sensitivity of the medium-type fast-neutron detector. The emission of the charged heavy particles of commonly used materials of detector's sensitive unit due to neutron incidence is simulated. The result shows that the selection of the materials of the charge collector, the threshold absorber and the rear isolator directly affect on the response sensitivity of neutron direct radiation. The response sensitivity of neutron direct radiation contributes about 6% to the total neutron sensitivity in the present sensitive unit which uses a graphite sensitive collector and Teflon threshold absorber and rear isolator. An improved structure of sensitive unit using high resistance graphite as the material of the threshold absorber and a rear isolator instead of Teflon is discussed, which can effectively reduce the response sensitivity of neutron direct radiation.