Multi-dimensional neutron computed tomography using cooled charge-coupled devices

A prototype position-sensitive neutron detector was designed and built for two- and three-dimensional tomographic imaging of materials and complex assemblies. The detector system consists of an LiF-ZnS scintillator screen optically coupled to a cooled charge-coupled device (CCD). Practical resolution limits of the single-screen system were calculated to be approximately 100 μm, determined by the neutron-beam divergence and the resolution of the scintillator screen. Contrast resolution in a (200-μm)³ volume element was calculated to be 1% of the cross section in small samples. The system included the MIT Research Reactor as a thermal neutron source (nominal flux approximately 2.4×10⁸ n°/cm-²s), a rotating sample holder, and the two-dimensional position-sensitive detector. The effects of scatter were estimated and compared to data. Two- and three-dimensional tomograms of phantoms and several demonstration objects, including a control valve and an oil well dolomite core sample, were obtained