X-ray Facility to Investigate Earth’s Core

ID24, a new x-ray beamline developed at the European Synchrotron Radiation Facility (ESRF), will explore the last white spot on our globe: the center of Earth.

This computer-generated image shows the layers of the Earth: the outer solid crust, the viscous upper and lower mantle, the liquid outer core and the solid inner core. (Credit: ESRF)

The device soon could explore matter at temperatures and pressures so extreme they can be produced for only microseconds using powerful pulsed lasers. Matter in such states is present in the Earth’s liquid iron core, 2500 km beneath the surface, and also in elusive "warm dense matter" inside large planets such as Jupiter.

The ID24 beamline works like an active probe rather than a passive detector, firing an intense beam of x-rays at a sample using the absorption spectroscopy technique. Not only can the abundance of an element be deducted, but also its chemical states, other atoms, or elements, that are in their immediate neighborhood, and their distance. A complete picture at the atomic scale of the sample studied is obtained, the researchers say.

A diamond anvil cell allows microscopic pieces of material to compress to pressures of 3 Mbar and more. Laser pulses (black arrows) then heat the sample and an x-ray beam (orange) passes through the cell to probe the states of matter at these extreme conditions. (Credit: ESRF/Format Editions)

ID24 can observe – such as in a time-lapse film sequence – many rapid processes, including laser heating of iron to 10,000°, charge reactions in new batteries or catalysts cleaning pollutants. It is the first of eight new beamlines built within the ESRF Upgrade Programme and extends ESRF’s capabilities in x-ray absorption spectroscopy to sample volumes 20 times smaller and time resolutions 1000 times better than in the past.

This image shows the heating of a catalyst sample in an "in situ" cell at actual operating conditions. The catalyst is studied using time-resolved x-ray absorption spectroscopy. At ID24, the time resolution can be as short as a few microseconds. (Credit: ESRF)

Germanium microstrip detectors enable measurements to be made sequentially and rapidly (a million in 1 s), so as not to miss any detail. A stable, microscopic x-ray beam means that they also can be made in two dimensions by scanning across a sample to obtain a map instead of a measurement only at a single point. A powerful infrared spectrometer complements the x-ray detectors for the study of chemical reactions under industrial processing conditions.

"Scientists can use several other synchrotrons, notably in Japan and the US, for fast x-ray absorption spectroscopy, but it is the microsecond time resolution for single-shot acquisition (or experiments) coupled to the micron-size spot that makes ID24 unique worldwide," said Sakura Pascarelli, the scientist responsible for ID24.

Because of new technologies used at ID24, scientists can study what happens at extreme conditions; for example, when materials undergo a fast chemical reaction or the temperature at which a mineral melts in the interior of a planet.

ID24 has been tested with x-ray beams and is expected to be open for users worldwide in May 2012.

For more information, visit: www.esrf.eu