Brilliance and flux reduction in imperfect inclined crystals

The inclined crystal geometry has been suggested as a method of reducing the surface absorbed power density of high-heat-load monochromators for third-generation synchrotron radiation sources. Computer simulations have shown that if the crystals are perfectly aligned and have no strains then the diffraction properties of a pair of inclined crystals are very similar to a pair of conventional flat crystals with only subtle effects differentiating the two configurations. However, if the crystals are strained, these subtle differences in the behavior of inclined crystals can result in large beam divergences causing brilliance and flux losses. This manuscript elaborates on these issues and estimates potential brilliance and flux losses from strained inclined crystals at the APS

X-ray diffraction study of GaSb/AlSb strained-layer-superlattices grown on miscut (100) substrates

A series of superlattices were grown by molecular beam epitaxy on (100) GaSb substrates which had been miscut by 2, 3, and 4 degrees toward the direction. These superlattices were then studied by scanning all possible (444) or (511) (asymmetric) reflections with high resolution multiple-crystal x-ray diffractometry. In addition, the (400) (quasi-symmetric) reflection was scanned. From peak splittings we extracted mismatch and tilt parameters for the epitaxial unit cell. We compared our results for the non-tetragonal component of the distortion ot calculations based on the coherent strain model of Hornstra and Bartels (J. Cryst. Growth 44,513 (1978)). We find that this model which was developed for epitaxial growth on a general (hkl) plane also describes our results for growth on vicinal (100) planes. The resolution of our data is sufficient to establish that the distortion was not purely tetragonal. A monoclinic unit cell symmetry adequately describes our results