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![[Figure 1]](pp5016fig1mag.jpg)
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Figure 1
(a) The Rowland circle geometry for flat analyser crystals. A crystal placed horizontally through the point P, at the top of the Rowland circle, reflects rays from the source S at Bragg angle θ to the point E(θ). A flat crystal passing through point X, where the radius CX is at an angle 2β from the vertical, must be tilted by β to reflect at the same Bragg angle. It follows that the crystal lies along the line PX. (b) From the observation that appropriately tilted crystals lie on lines passing through P, it is possible to show that the virtual source for reflection from any such crystal lies on a circle of radius 2Rsinθ centered at P. Given a range of Bragg angles, there is an arc on this circle that spatially selects rays reflected in this range from any crystal placed on the Rowland circle. |
![[Figure 1]](pp5016fig1.jpg)
 | JOURNAL OF SYNCHROTRON RADIATION |
ISSN: 1600-5775
