Diffractometers and Reflectometers
In the previous chapter we described the basic elements of x-ray equipment, namely, x-ray sources, optical elements to define the beam pass and a proper band pass of energy, and various recording units to detect the x-rays. In this chapter we deal with the experimental arrangement as a whole. There are general aspects to consider in setting-up an x-ray experiment: The sample is illuminated by an incident beam striking the sample surface under a definite angle of incidence α i . The incident beam may be characterized by its incident divergence ∆α i , and its energy spread ∆λ. After interaction of the beam with the sample, the scattering intensity escaping from the surface at a takeoff angle α f has to be recorded. Owing to the finite size of the detector window, all the photons leaving the sample surface in a take-off angle range (α f −∆α f /2, α f +∆ α f /2) are registered by the detector simultaneously. The plane containing the source and the surface normal of the sample is called the scattering plane. Since the scattering happens within the scattering plane, the scattering geometry is called coplanar. In the so-called not coplanar or off-plane scattering geometry (Sect. 4.3), the directions of the incident and the scattered beams are also characterized by the azimuthal angles θ i and θ f and by the widths of the corresponding angular intervals ∆θ i , and ∆θ f .
KeywordsIncident Beam Angular Resolution Powder Diffractometer Exit Angle Diffraction Curve
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