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Figure 9
Calculating the average phase gradient of a sphere. Arrow A depicts an X-ray passing through a sample sphere of thickness T. Arrow B depicts an X-ray passing through a vacuum on the edge of the sphere. The phase gradient of the curve connecting points A and C is approximated by the gradient of the dotted line. The distance between A and B along the x-axis can be described as the change in distance between A and B, which is equal to T/2. This distance is equal to distance BC. The change in phase between points A and B is described as [\Delta\varphi]. The phase change incurred by the sample by point A = [-k\delta T] where δ is the refractive index decrement corresponding to the refractive index n = 1 − δ. The phase change incurred by the sample by point B = 0. The phase difference, [\Delta\varphi], between A and B is [-Tk\delta].

Journal logoJOURNAL OF
SYNCHROTRON
RADIATION
ISSN: 1600-5775
Volume 22| Part 5| September 2015| Pages 1279-1288
https://doi.org/10.1107/S1600577515011406
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