Scintillator screen development for fast neutron radiography and tomography and its application at the beamline of the 10?MW BNC research reactor

摘要

Simple and inexpensive ZnS-based fast neutron imaging screens have been developed and their performance has been tested and compared to a commercially available one using the RAD beamline of the 10?MW research reactor of the Budapest Neutron Centre (BNC), Hungary. ZnS(Ag) and ZnS(Cu) powders have been mixed with optical epoxy, deaerated and casted into sheet form using an aluminum frame. The ZnS concentration and the screen thickness have been optimised using sample screen pieces. The in-house screens have been tested in camera-based neutron imaging detectors in a reactor beamline and compared with a commercially available polypropylene/ZnS(Cu) fast neutron imaging screen and with a BC400 plastic scintillator slab screen. It has been found that the in-house screen produces only about60%of light intensity of the commercial polypropylene/ZnS screen, which is mainly due to the lower hydrogen density of the optical epoxy compared to polypropylene by the same amount. The BC400 performs inferior compared to any ZnS-based scintillator tested here. Fast neutron tomography has been performed with both the commercial and the in-house screens on the reactor beamline. A spatial resolution of around1.6mm has been achieved. Typically 10–15?min exposures were needed to obtain good quality radiographic images, whereas several hours of acquisition were needed to obtain the full tomographic set images. High quality imaging results have been obtained on large (150?mm in diameter) and dense objects (hydraulic couplings) proving the feasibility and utility of fast neutron imaging for such samples.