How Science Works: XFEL

LCLS Undulator Hall.

The Undulator Hall at the Linear Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory (SLAC), USA. Courtesy of SLAC.

If you’ve never heard of XFELs then get ready for that to change. X-ray Free Electron Lasers – to use their full name – are the next big thing in scientific technology and they are reshaping the way we approach some of the world’s most challenging experiments.

XFELs are like a cross between an X-ray microscope and a laser. They work by producing very intense pulses of light at an astonishingly fast rate – we’re talking between hundreds and tens of thousands of light pulses each second.

This allows scientists to study matter in intense detail and observe reactions that take place in just a fraction of a second, opening up a whole new world of atomic-level exploration.

With this sort of technology, we can create better medicines, technology and engineering: and it all starts with unpicking the complexity of the atomic and molecular world.

What is it?

XFELs are used to study some of the most challenging and complex matter there is. This means viruses, smart materials, electronics and biomolecules that have been virtually impossible to fully study in the past.

XFELs produce extremely bright light, which allows scientists to explore matter that often can’t be studied in traditional ways. And they create this light using our old friends, electrons.

Electrons are generated and accelerated to increase their energy. They are shot in a line, down a long tunnel – a very, very long tunnel. In fact, the European XFEL is over 3 kilometres, stretching from Hamburg to the neighbouring town of Schenefeld.

The electrons are clustered into ‘microbunches’: short, powerful pulses of energy. They then emit X-rays, which hit the target sample hundreds or thousands of times a second. This allows us to see the very quick movements of atoms and molecules, viewing lightning-fast processes like a sub-microscopic movie.

Blog - XFEL

Accelerator tunnel at the European XFEL (Courtesy of EU-XFEL)

The History

The first Free Electron Lasers were built in the 1970s. They worked in a similar way to XFELs but with one major difference: they couldn’t produce X-ray light. Limited to infrared, visible and ultraviolet, these lasers just couldn’t achieve the same level of atomic detail that we see on XFELs today.

For years, a functional X-ray laser was all but a dream. But that all changed in the early 21st century. In 2009, the world’s first XFEL came online in Stanford, USA. Right up until the day it was completed, people weren’t entirely sure it would work.

But as history would have it, the XFEL was a huge success, delivering unprecedented detail and insights into reactions on the atomic scale. In 2011, Japan completed its own machine and the European XFEL is soon to come online. Korea and Switzerland have a further two currently in construction.

This rapid growth in popularity demonstrates how far XFEL technology has pushed the frontiers of scientific enquiry – as a result, scientists around the world are clamouring to exploit its capabilities.



A version of this article was originally published in Inside Diamond Magazine


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