• 4-ID-D overview
• 6 circles Huber diffractometer.
• Polarization analysis available for various energies. Please contact your local contact ahead of time (at least a month) to check if we have the correct analyzer for your experiment.
• Temperature range (closed cycle helium cryostat): 5-300 K.
• Measurement is performed in Laue geometry.
• Setup is optimized of measurements on and off resonance using x-ray energies between 10 and 23 keV.
• Focused x-ray beam on sample position is ~100x250 microns. Smaller beams are achieved using a slit.
• Diffraction detectors:
  • Oxford Cyberstar (NaI and YAP) - Large dynamical range (~ 500K counts).
  • Vortex Si-drift detector - Energy discrimination (~ 150 eV resolution).
  • Pilatus (loan from detector pool) - Area detector.

Designed and machined at University of Chicago.

• Cell material: Brass.
• Type of diamond anvils: Boehler-Almax.
• Available culet diameters: 800 and 500 microns, that can reach ~ 15 and 40 GPa, respectively.
• Diffraction is measured in Laue geometry through the pressure cell ~ 70 degrees opening. See below for further details on how to check if a Bragg peak is accessible.
• Diffraction from gold or silver is used for in-situ pressure calibration. See reference: Holzapfel et al., J. Phys. Chem Ref. Data 30, 515 (2001) [there is a typo in equation 13, it should be p = 3.K₀.(1-x)/(x⁵).exp(c₀.(1-x)].(1+c₂.x.(1-x))]
• Pressure is applid in-situ with a helium gas membrane.

The size of the strain acting on a single crystal at high pressure does not solely depend on the hydrostaticity of the pressure media, but also on the ratio between sample and pressure media volumes. X-ray diffraction is highly sensitive to such strain, thus the sample size and pressure media need to be carefully chosen.

Information:

• Sample chamber size (before loading the pressure media) varies with the type of gasket used, but it is normally a cylinder with ~ 400 x 100 microns (diameter x depth) and ~ 250 x 80 microns for diamond culets of 800 and 500 microns, respectively.
• Available pressure media: silicon oil, 4:1 methanol:ethanol, neon and helium. Useful references for their hydrostaticity:
  • ​Klotz et al., J. Phys. D: Appl. Phys. 42, 075413 (2009).
  • Feng et al., Rev. Sci. Instrum. 81, 041301 (2010).​

Experiments using diamonds with 800 microns diameter (< 15 GPa)

For measurements below 10 GPa we recommend using 4:1 methanol:ethanol pressure media and a sample size of ~ 50x50 microns lateral size (see figure below). The thickness is mostly determined by the sample- and energy- specific x-ray transmission, but it typically is ~30-40 microns. Above 10 GPa the hydrostaticity of the 4:1 methanol:ethanol mixture deteriorates, and neon or helium may be preferable.

Experiments using diamonds with 500 microns diameter (< 40 GPa)

Helium pressure media is recomended for this pressure range. However, the He gas loading process typically reduces the sample chamber diameter to about 120 microns. Therefore we recommend to use samples of ~30x30 microns lateral size, and usually ~20 microns thickness.

The pressure cell angular aperture and the sample geometry determines the accessible Bragg peaks. In the usual operational mode, we mantain phi fixed and use theta, two theta and chi to move in reciprocal space (see figure below). In this case, the rules that a Bragg peak needs to obey are:

• theta < 35 degrees (note that theta is the motor angle, which may not be the same as the Bragg angle)
• two theta - theta  < 70 degrees
• -110 degrees < chi < 90 degrees (this is a wide range, so this is usually not a problem)