In wide angle mode we assume that the detector is mounted on a 2theta arm which has been rotated away from the primary beam. The Detector Azimuth establishes the direction that the 2theta arm has been rotated. An azimuth of zero corresponds to a rotation in the horizontal plane (common to laboratory tabletop units). In this case the beam zero will be to the right or left of the center of the detector. An azimuth of 90 corresponds to a rotation in the vertical plan (often used in synchrotron diffraction systems). In this case the beam zero will be above or below the center of the detector. In either case it is likely that the beam zero position itself is not on the detector, but the instrument user should know where it is. |