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Figure 5
(a) Histogram (in black) of counts in a region of the pattern shown in Fig. 4[link](a), but prior to polarization correction, at a radius of approximately 260 pixels. The region was obtained by contouring the polarization-uncorrected radial average [see equation (8)[link]]. A fit of pNW(I; 4) is shown in blue, yielding a value of μ = 532 adu = 18.6 photons, as indicated by the blue dashed line, and Σ = 269 adu = 9.4 photons. The discrete noisy Wilson distribution obtained by applying equations (14) is shown in sky blue and gives a higher estimate of the background with μ = 23 photons and Σ = 8 photons. (b) Histogram of counts in a region of the crystal-free pattern of Fig. 4[link](b), with a fit of a Poisson distribution (sky blue) with a mean of 18 photons. The dash–dotted grey lines indicate Gaussian fits, shown to emphasize the skewness of the distributions.

Journal logoJOURNAL OF
APPLIED
CRYSTALLOGRAPHY
ISSN: 1600-5767
Volume 50| Part 4| August 2017| Pages 1084-1103
https://doi.org/10.1107/S160057671700749X
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