X-Ray Beam Modes and Properties
The following information will be updated later in the APS Upgrade/commissioning period in 2024.
The Insertion Device (ID) for the DCS is a Revolver Undulator that can be switched between two sets of magnets with periods of 27 mm or 17.2 mm (U27 and U17.2) to provide spectral tuning in energy from 7 to 100 keV.
The beamline optics are designed to deliver both unfocused (White) and focused (Pink) x-ray beam modes that can be fine-tuned in energy, beam-size, bandwidth, and flux to deliver an appropriately conditioned beam for each experiment. The three standard beam modes used at DCS are as follows:
- ‘White beam’ refers to the broad-band x-rays directly from the undulator, unfocused and containing all harmonics. The white beam from the U17 is typically used for phase contrast imaging (PCI).
- ‘Pink beam’ is focused by reflecting from dynamically-figured Kirkpatrick-Baez mirrors. The mirrors act as an energy filter on the undulator output, leaving only the lowest energy harmonics. The broad bandwidth (3.5-5.5% BW) beam can be used for x-ray diffraction (XRD), small-angle x-ray scattering (SAXS), or extended x-ray absorption fine structure (EXAFS). Additionally, a very broad pink beam for Laue diffraction can be generated by tapering the magnet gap in the U27.
- ‘Mono’ – The single multilayer monochromator (SMM) in each station can be used for XRD experiments with nearly the same peak spectral flux and narrower bandwidth (1.5% BW).
X-Ray Characterization
Complete set of x-ray diagnostics in each station for precise alignment, focus, and characterization of x-rays for each experimental setup
- Laser aligned to x-rays beams provides visible beam path for initial alignment
- GigE camera coupled to YAG crystal with microscope objective for precisely focusing and shaping x-ray beam
- Spectral flux characterization using Si(220) monochromator on precision rotation stage
