Fig. 7 also suggests that the thickness of CsI(Tl) in the sample on the top is somewhat higher
than optimal making the screen slightly sensitive to gammas.
This is evident from the faint presence of Pb disks seen in the top ASTM image.
The second image (on the bottom), obtained with the thinner CsI layer shows almost no sensitivity to the gammas.
The cadmium phantoms as well as the boron nitride and cadmium discs in the ASTM phantoms are all very sharply
defined in both the images. These data show that both the screens have a high level of radiographic sensitivity with
respect to the step block materials. The noise level in the figure on the top is higher than that in the figure on the
right due to lower scintillation efficiency of CsI layer in that sensor. Scintillation efficiency is influenced by the deposition
parameters and can vary. Further investigation is being conducted.