Figure 1
The geometric parameters of the LogSpiral curved MAD system are determined by the energy range used; the corresponding values of angles ΘA and 2ΘA for a Si(111) analyser and the detector determine the length and separation of the analyser crystals. (a) Using ∼5 keV X-rays, the gap between analyser crystals must be large enough (interval 8 mm, thickness 3 mm → gap 5 mm) and their length small enough to allow the passage of adjacent beams; at low energy, filtered beams are more easily partially cut by adjacent analyser crystals. (b) Using 9.5 keV X-rays, a crystal length of 26 mm allows filtering of 4.6 mm-wide beams. (c) Using ∼40 keV X-rays, a crystal length of 26 mm allows filtering of 1.6 mm-wide beams; the length of the analyser crystals should be longer (e.g. 80 mm) to allow filtering of a reasonable beam width (e.g. 4.6 mm). |