Unlike pure Gd, gadolinium fluoride and gadolinium
oxide, while being highly sensitive to neutrons, are optically
transparent and thus, allow the transmission of scintillation
light to the photodetector, as shown in Fig. 1. An
additional benefit of this approach is that the screen can
be fabricated not only on a transparent fiberoptic substrate,
but also on non-transparent substrates such as aluminum
for reversed coupling, as shown in Fig. 1. This
allows production of larger area, rugged sensors. Furthermore,
the CsI(Tl) sensor is finely pixelated to achieve two
important effects. One, it increases the total surface area
of the scintillator by fivefold (each three-dimensional pixel
has five open surfaces), allowing a conformal layer of the
Gd2O3 converter, thus improving detection efficiency.
And second, it further limits the lateral spread of scintillation
light, improving image contrast. It has been shown
previously that pixelation of CsI(Tl) scintillator screens
can improve the detective quantum efficiency (DQE) of
an X-ray system by a significant amount as compared to
non-pixelated screens [20].
2. Scintillator screen fabrication