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![[Figure 12]](ge5117fig12mag.jpg)
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Figure 12
Composite plot of the measured specular reflectivites as a function of beam angular divergence for the 10 + 10 = 20 µm patterned film structure with the mean beam wavevector perpendicular to the grating bars. The values of the angular beam divergence and the corresponding aperture widths are given in Table 4 ![[link]](../../../../../../logos/arrows/j_arr.gif){kind=small} . Geometrical beam footprint corrections have not been made and the effect of non-specular scattering and other details are discussed in the main text. Also, for clarity, error bars have not been plotted: however, for the data collected at the three coarser values of angular divergence, the uncertainty is approximately three times the size of the symbols, whereas the uncertainty in the data corresponding to the three finer divergences is about six times the symbol size. Although the angular divergence of the incident beam was varied by more than a factor of 40, the individual neutron wave packets in each of the different beams had a transverse extent sufficient to effectively average over a significant number of Ni stripes and intervening troughs, thereby resulting in a single critical value of Qc corresponding to the mean value of SLD. Note that, because of the rounding of the critical edge due to beam angular divergence, a single common value of Qc is best shown by the nearly identical intersection of all of the separate data sets at approximately a value of half the maximum measured specular reflectivity. |
![[Figure 12]](ge5117fig12.jpg)
 | JOURNAL OF APPLIED CRYSTALLOGRAPHY |
ISSN: 1600-5767
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