Laue-Transmission Integrated Reflectivities for 'Thin' Crystal Diamond, Si and Ge X-Ray Monochromators

Optimised theoretical 〈111〉 and 〈220〉 Laue-diffracted integrated reflectivities vs. crystal thickness (0 to 100 μm) are determined for perfect diamond, silicon and germanium monochromator crystals in which both symmetric and asymmetric Laue modes are compared. Oscillations in transmitted integrated reflectivity vs. crystal thickness are shown to fluctuate between ≈10 to 40% for crystals ≥50 μm thick which demands an accuracy of a few μm in parallelism between entrance and exit surfaces to achieve optimum efficiency. The special case for diamond, when used as a first white synchroton radiation (WSR) Laue monochromator is also discussed. Less perfect diamonds with higher point defect concentration are simulated by decreasing the static Debye-Waller factor