Analysis of background component introduced by mirror in neutron radiography CCD image system

In a CCD based neutron radiography system, some fluorescent light will be reflected back to the scintillator by the mirror if the mirror is too close to the scintillator. Some of the incoming neutrons may also be scattered back to the scintillator. These two factors form a strong background that cannot be neglected. This background is harmful to quantitative analysis and CT reconstruction. The analytic calculation of the reflection component as the well as Monte Carlo simulation of the back-scattering component has been carried out, the result of which agrees well with the background measurements. The background component introduced by mirror accounts for more than 10% of the whole background in a typical detection system configuration.