ALS beamline 12.2.2

Synchrotron X-ray diffraction under non-ambient conditions

Beamline 12.2.2 at the Advanced Light Source is a synchrotron X-ray diffraction beamline for samples at non ambient conditions of pressure, temperature and atmospheric conditions.

The beamline photon energy range is 6-35keV with a minimal x-ray spot size of 5x5 um.

The beamline offers mainly three areas of expertise:

- High-pressure X-ray powder diffraction through diamond anvil cells in axial or radial diffraction. Both geometries can be combined with double-sided laser heating.

- Ambient pressure X-ray powder diffraction at temperatures up to ~ 1000 C and simultaneous controlled atmosphere.

- High-pressure X-ray single crystal diffraction allowing for large DAC's (BX90, symmetric cells). This capability is currently available in a single axis configuration. A 4-circle goniometer is being commissioned on endstation 1.

Earth is considered a watery planet, simply by virtue of the fact that 71% of its surface is covered by oceans. But researchers have discovered that, in the massive volume of material in Earth’s interior, minerals can serve as an important water reservoir, providing a new perspective on our planet’s water budget.

Minerals in the transition zone between the upper and lower mantles (between 400 and 670 km deep) can store up to one percent of their weight in water. Given the volume of this layer, that could add up to an ocean’s worth of water. However, the amount of water that might be stored in the lower mantle—representing 55% of the Earth’s volume—is unknown.

Despite some controversy, the current consensus is that the two most abundant minerals in the lower mantle have little capacity for water storage. In this work, researchers studied the third most abundant mineral, CaSiO3-perovskite (Ca-Pv).

At the Advanced Light Source (ALS), the researchers were able to conduct both infrared and x-ray experiments on the same samples at the same high pressures. Infrared spectroscopy at Beamline 1.4 revealed whether Ca-Pv can incorporate water in its crystal structure, and x-ray diffraction at Beamline 12.2.2 elucidated how water might alter the crystal structure.

The results showed that Ca-Pv can store up to 1% of its weight in water—representing about half an ocean of water. Furthermore, since Ca-Pv is the dominant mineral in the subducting oceanic crust, the study opens up the possibility that Ca-Pv could be an important factor in water circulation between the surface and deep interior of Earth.

Beamline acknowledgement policy:

  • Any publication connected to work on beamline 12.2.2 or the high-pressure lab (6-2241) must be acknowledged in the following manner:

Beamline 12.2.2 at the Advanced Light Source is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231.

  • Any publication benefiting from the use of the 12.2.2 laser mill in the preparation lab 6-2241 must be acknowledged in the following manner:

This research was partially supported by COMPRES, the Consortium for Materials Properties Research in Earth Sciences under NSF Cooperative Agreement EAR 1606856

Please note that failure to include these acknowledgment may jeopardize future access to beamline 12.2.2 and/or its support facilities.

Financial Support

U.S. Department of Energy - The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

COMPRES - Beamline 12.2.2 is partially supported by COMPRES, the Consortium for Materials Properties Research in Earth Sciences under NSF Cooperative Agreement EAR 1606856"