High Energy Wiggler Beamline (20-94 keV)
The high energy X-rays coming from the central portion of the wiggler radiation fan are reflected inboard by a Si (111), (422), or (533) single crystal monochromator in Laue mode. The monochromator also provides excellent vetical focusing and some horizontal focusing.
Flux ranges from about 5x109 to 2x1013 depending on the energy. Vertical focal size is about 100 μm whle horizontal focus is a about 2 mm but is usually slitted down to be close to the size of the vertical foucs.
The high energy beamline generally operates with a Perkin Elmer area detector mounted on a translation table which moves to follow the Bragg angle of the monochromator as the energy is changed. This flexible setup allows essentially any energy within the beamlines range to be easily accessed. The ability to choose the energy and to collect and integrate the entire diffraction rings enables the following abilities.
Pair Distribution Functions: The PDF gives the distribution of inter-atomic distances in a material and is an excellent probe of the local and medium range structure. The use of high energy X-rays allows high resolution PDFs to be generated by collecting data up to high Qmax values. Typical usable Qmax values can range anywhere from 22 - 32 A-1 depending on the energy chosen. Even higher values can be obtained by raising and tilting the detector. The ablity to choose the wavelength allows one to optimize between photon flux, Qmax, and instrumental dampening to suit the needs of a particular problem.
Rapid Powder Diffraction Data Collection: The use of an area detector allows rapid collection of powder diffraction data with very high counting statisitics. Patterns can ususally be collected in under a minute and often in just a few seconds. This can be very useful for making measurements as a function of temperature, in-situ reactions, studying large numbers of samples, and many other purposes.
Penetration of Samples: By using high energy X-rays powder diffraction data can be collected on thick samples, such as batteries and other devices that benefit from being examined in-operando.
High Pressure Studies: This beamline has the ideal energy range for high pressure expeirments using a diamond anvil cell (DAC). Users must supply their own DAC.