Three interchangeable devices are used to monochromate the source:

1. Mechanical Velocity Selector: Helical path selects triangular wavelength distribution having fwhm of 12%. Changing rotation speed allows range in mean wavelength: 4.5 Å < λ < 12.0 Å
2. Double reflection Pyrolytic Graphite monochromator provides higher resolution: 1% fwhm, range: 4.0 Å < λ < 6.0 Å
3. Beryllium filter cuts λ < 4.0 Å, mirror cuts λ > 8.0 Å, providing lower resolution but factor of five flux gain.