Science & Environment

X-ray facility to study conditions at Earth's core

X-ray absorption spectroscopy setup (ESRF)
Image caption Materials are heated to searing temperatures before being probed with a spray of intense X-rays

An experiment to recreate the extreme conditions of the centre of the Earth was officially opened on Thursday.

The ID24 beam line at the European Synchrotron Radiation Facility (ESRF) will use X-ray beams to subject iron and other materials to extraordinary temperatures and pressures.

How the X-rays are absorbed should give insight into the mysterious processes going on at and near the Earth's core.

For example, the work could unravel why the Earth's magnetic field can "flip".

The Earth's core, some 3,000km (1,900 miles) below sea level, will never be reached directly by scientists. In fact, research continues in an attempt to drill through the Earth's outermost layer, the crust. At its thinnest, beneath the oceans, the crust is just 10km thick.

So it is left to laboratory experiments to attempt to recreate the conditions at the core, to investigate how the Earth's magnetic field comes about, why it changes, and how shock waves from earthquakes propagate through it.

Diamonds are for pressure

At the heart of the experiments to be carried out at ID24 is what is known as a diamond anvil cell - an established and remarkably simple means to create high pressures by confining tiny samples between the points of two carefully cut diamonds.

The samples are compressed at a pressure millions of times higher than that on the Earth's surface.

Image caption The inner and outer core of the Earth give rise to its magnetic field, but mysteries remain as to how

High-power lasers are then fired through the diamonds at the samples, heating them to higher than 10,000C. Then X-rays are used as a probe to determine the precise composition and chemistry of samples.

The newly upgraded ID24 makes it possible to focus the X-rays to a much smaller spot than existing facilities - just millionths of a metre.

What is more, the reactions that go on as matter is heated and squeezed can be monitored with a resolution hundreds of times higher, with "snapshots" occurring every millionth of a second.

"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... coupled to the micron-sized spot that makes ID24 unique worldwide," said Sakura Pascarelli, the chief scientist on the ID24 beam line.

"The rebuilt ID24 sets the ESRF apart, and even before the first users have arrived, I am asked to share our technology."

ID24 is the first of eight beam lines at the ESRF, located in Grenoble, France, that will be radically overhauled as part of the eight-year, 180m euro (£154m) ESRF Upgrade Programme.

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