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Figure 7
The geometry of the spectrometer in the vertical (dispersive) plane, showing the principle of operation for choosing the photon energy range (not to scale, for clarity). Setting a particular incidence angle is done by horizontal movement and rotation of the grating cradle. Since the horizontal grating movement rotates the Rowland circle around the source, the detector needs to be correspondingly shifted vertically and rotated to maintain its tangential orientation to the Rowland circle for a given grating cradle setting. |