As a rule, we try to stay at the same energy for all measurement of a single sample – changing camera length rather than beam wavelength to access different q-ranges. When doing anomalous studies around an element edge or increasing the x-ray energy to access the high-q WAXS regime changing energy is unavoidable.

The x-ray mirrors in the front optics enclosure need to be set to allow harmonic rejection. If we are lucky we can get away with a simple lateral translation of the mirror (to change coating stripes) rather than a change in incident angle. The latter requires re-alignment of all down-stream components – including the SAXS camera.

The 15-ID mirrors have a choice of 3 different coatings (Si, Rh, Pt). This calculator aids in choosing the optimum mirror angles - low enough to allow good beam throughput and high enough to reject higher order harmonics.

Note: for energies greater than 12 keV, the third harmonic of the undulator will usually be used.