Optic Alignment Made Easy

Spherically bent crystal analyzers (SBCAs) are important components for Rowland circle x-ray spectrometers in both our lab-based x-ray absorption/emission spectrometers and also in many synchrotron-based emission instruments. As with all focusing optics, an SBCA must be properly aligned to ensure best instrument performance. This procedure is complicated by so-called “wafer miscut”, the angular deviation between the wafer surface and underlying crystal planes. Wafer miscut introduces an ambiguous error in the refocusing position.

Typically, refocusing of an optical-wavelength laser is used for initial alignment and then corrections are applied by using a two-axis tilt for fine adjustment of the SBCA orientation with iterative optimization scans. While effective, the inclusion of a motorized two-axis tilt imposes additional cost and complexity for each of instrument construction, maintenance, and operation. Additionally, non-experts often find the technique to be tedious and time-intensive.

Using the patent pending “Clock Angle Protocol”, first reported in our joint publication with the University of Washington, easyXAFS greatly simplifies SBCA alignment while eliminating the need for fine-tilt adjustment, see Fig. 1. This result allows for optic pre-alignment. Once aligned, an optic can be rapidly and reproducibly re-installed. Put in the SBCA, do one quick scan of the detector position, and get started on your science.

Figure 1. Using the “Clock Angle Protocol” for pre-alignment, crystal optics can be readily and reproducibly re-installed without degradation of instrument performance. Shown above are two emission scans where the optic has been removed and subsequently reinstalled without re-optimization.

This improvement has been integrated into our full line of hard x-ray spectrometers (see Fig. 2), saving you money and time by simplifying operations and also simplifying your user training and support. We would be happy to tell you more about this and other streamlined user operations at

Figure 2. Integration of the “Clock Angle” correction allows for a simple cartridge loading of SBCAs.

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