Goniostats with point detectors

The second slit box is located on the detector arm between the sample and the detector. The slit nearest to the sample serves as a scatter slit. It is followed by another Soller slit and a receiving slit positioned just before the detector. The detector in this case is a solid-state detector, which is cooled by a built-in Peltier refrigerator enabling to adjust and maintain the detector sensitivity at extremely narrow width to allow only x-ray photons of specific energy to be registered. Monochromatization of the diffracted x-ray beam is, therefore, achieved electronically rather than by physical means (e.g. by a P-filter or a crystal monochromator), which increases the registered diffracted intensity by eliminating losses in the filter or in the monochromator. 

Overall, powder diffractometers equipped with point detectors offer the best resolution of the resulting powder diffraction data. While the instrumental resolution increases with the increasing goniometer radius, the intensity of the diffracted beam unfortunately decreases because the incident beam produced by an analytical x-ray tube is always divergent. Therefore, typical goniometer radii vary between 150 and -300 mm. 

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