Jong-Boumann and Precession Camera

It has been said that the Precision camera records the undistorted reciprocal lattice. There are two t3rpes of Precision cameras. The one is due to de Jong and Boumann and the other is due to Buerger. The Precession camera developed by Buerger is quite different and difficult to visualize and so, the Boumann method is first described here. 

The layer screen used in this method is annular opening in which the central opaque part is supported to the outer part, leaving the desired annular opening by cellophane paper which is transparent to X-ray (Fig. 7.11). In de Jong and Boumann method, like Weissenberg, the diffraction data are spread out over the flat film by rotating it (Figs. 7.12 and 7.13). 

If /X and V are the angles, respectively, between the X-ray incident direction and crystal axis and semiapex angle of the diffraction cone as shown in the following figure. 

the distance through which the film is to be moved back and the formulae relating to the recording of upper layer are given as For zero layer arrangement jj, = u = 45°, layer screen subtends 90° cone at the crystal, and this is to be kept constant. The upper layer is to be recorded by changing /i. 

Precession camera. It has been stated that the visualization of Precession camera is rather difficult compared with de Jong-Boumann camera. Therefore, only zero layer Precision setup is described in brief. The detailed information is available in more specialized books given in the references for further reading [2]. 

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