in the material thicknesses and also all the stringer-skin-riveted
joints of 4 mm diameter along the stringer columns can be seen in
the X-ray backscatter image (see indication ‘1’ in Fig. 8(a)). Interest-
ingly, the scattered radiation from the steel (Fe) mounting table is
also evident in the backscatter image (see indication ‘2’ in Fig. 8(a)).
The measured back-scattered intensity profiles along the two
columns of the stringer component, represented as locations ‘A’
and ‘B’ in Fig. 8(a), are shown in Fig. 8(b). A good contrast between
background and skin-joint materials can be noticed in the intensity
profiles. Additionally, depending on the distance between object and
slit camera (OSD) and the angle between incident and scattered
radiation ðθÞ, the differences in the backscattered signal intensities
are observed.