Cameras Buerger precession

Staudenmann, J.-L., Horning, R. D., and Knox, R. D. Buerger precession camera and overall characterization of thin films and flat-plate crystals. J. Appl. Cryst. 20, 210-221 (1987). 

Buerger (1944) developed a very ingenious variant of the same basic idea in his precession camera. In this camera, the crystal does not rotate instead, its axis performs a precessing movement (Fig. 106). 

Fig. 106. Principle of Buerger s precession camera. The crystal does not rotate its axis processes. The lower diagram shows the situation 90° after the upper diagram.

Of the many types of X-ray cameras, only two are still in even occasional use in protein crystallography — the Buerger or precession camera and the rotation/oscillation camera. The precession camera is used primarily in... 

The Laue method involves a stationary crystal and polychromatic ( white ) X rays. In the other camera methods, monochromatic radiation is used. In these cases the crystal may be oscillated over a small angular range (oscillation method) or rotated 360° about an axis (rotation method). The layer lines so formed may be selected individually. In the Weissenberg method, the oscillation of the crystal is coupled with a movement of the photographic film. The Buerger precession method, by a more complex motion of the instrument, produces an undistorted and magnified picture of the reciprocal lattice. 

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. 

Precession (Buerger) Camera. In contrast to the Weissenberg camera, the crystal carrier is now coupled to the film cassette so that both move in exactly the same way while the pattern is being recorded (Fig. 23). A direction in the crystal pre-cesses (precession angle /<) about the incident X-ray beam, so that reciprocal lattice points lying in a plane perpendicular to this crystal direction cut the reflection sphere. A precession pattern represents the reciprocal lattice in undistorted form... 

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