Borrmann fan

Figure 4.10 The diffraction and rediffraction of an X-ray beam from a set of reflecting planes. The triangle bounded by the incident beam and the diffracted beam from the entry surface is called the Borrmann fan...

Figure 4.18 The effect of spherical incident waves on the excitation of Bloch waves, (a) Reciprocal space the divergent incident beam has wavevectors ranging from P j O to P 2 O. (b) Real space energy is distributed throughout the Borrmann fan ABC. The beams generated outside the crystal are indicated...

We see that very close to the Bragg condition, where the dispersion strrface is highly cttrved, R K and the crystal acts as a powerful angrtlar amplifier. A reaches 3.5xl0 in the centre of the dispersion surface for sihcon in the 220 reflection with MoK radiation. Far from the centre, the dispersion strrface becomes asymptotic to the spheres about the reciprocal lattice points and A approaches unity. Thus when the whole of the dispersion strrface is excited by a spherical wave, owing to the amplification close to the Bragg condition, the density of wavelields will be veiy low in the centre of the Borrmann fan and... 

Figure 8.12 Grid filling the inverted Borrmann fan over which numerical integration of Takagi s equations can be accomplished...

Figure 8.16 Section topograph of a dislocation in silicon. The dislocation cuts the Borrmann fan obliquely, resulting in displacement of the direct, intermediary and dynamical images. We note that the dynamical image, unlike the direct image, is not localised. 1, direct image 2, intermediary image 3, dynamical image...

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