Removal of scattered neutrons in thermal neutron radiography using a multichannel collimator

The present paper proposes and examines an experimental procedure for removing the influences of scattered neutrons and gamma-rays on thermal neutron radiography (TNR). A multichannel collimator coated with a neutron-absorbing compound eliminates scattered neutrons that fall on an imaging device. In order to measure contamination of the gamma-rays, a supplementary detector is used. By evaluating neutron transmittance of several objects, the procedure is confirmed to effectively remove scattered neutrons and gamma-rays within the detectable transmittance range of conventional TNR. In addition, the effect of changing the beam spectrum with penetrating lead on the relationship between neutron transmittance and thickness is determined.