Having formed a neutron image, it is necessary to find a way to visualize it. In the MIT microscope, the neutron flux at the imaging focal plane was measured by a CCD imaging array with a neutron scintillation screen placed in front of it. The scintillation screen is made of zinc sulfide (a traditional fluorescent compound) laced with lithium. When a thermal neutron is absorbed by a lithium-6 nucleus, it causes a fission reaction that produces helium, tritium, and a lot of excess energy. These fission products cause the ZnS phosphor to light up like a Christmas tree, producing an image in light that can be captured with the CCD array.