Goniometer horizontal axis

Figure 3.11. The schematic of the goniostat of a Scintag XDS2000 powder diffractometer with the horizontal axis and synchronized rotations of both the source and detector arms. This goniometer is equipped with a liquid nitrogen-cooled solid-state detector, which enables monochromatization of the diffracted beam by selecting a narrow energy window, thus registering only characteristic energy photons. R - is the radius of the goniometer.

The orientation of both the goniometer axis and specimen surface (or specimen axis) with respect to the horizon, i.e. they may be located in a vertical or horizontal plane. 

Figure 3.7. Horizontal (left) and vertical (right) orientations of a flat sample. The location of the goniometer axis is shown using a dash-double dotted line with small filled circles at the ends. The dashed line indicates the location of the optical axis, which is the line connecting the focus of the x-ray tube, the receiving slit and the sample surface in the reflection geometry, or the sample center in the transmission geometry at 0 = 20 = 0°.

The orientation of the sample usually establishes the orientation of the goniometer axis, i.e. the axis around which both the detector and sample (or both the detector and x-ray source) rotate in a synchronized fashion during 0-20 or 0-0 data collection. A horizontal sample orientation implies that the goniometer axis is located in the horizontal plane, and a vertical sample orientation makes the goniometer axis vertical, as depicted in Figure 3.7. 

A different goniostat with the horizontal orientation of the specimen and Bragg-Brentano geometry is shown in Figure 3.13. The x-ray tube housing is mounted on the movable arm, and both the x-ray source and the detector can be rotated in a synchronized fashion about the common horizontal goniometer axis (also see the schematic in Figure 3.10, middle). 

When you called the person in charge of the diffractometer D (see problem 4) she told you that the goniometer axis is horizontal and that the x-ray source arm is stationary. Do you need to worry about mixing your powder with a binder ... 

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