Green light for flash fantastic
By Jonathan Amos
Science reporter, BBC News
A major new particle accelerator is to be built at Hamburg, Germany, that is capable of producing super-brilliant, ultra-short flashes of X-ray light.
The intense beam made in the 3.4km-long (2.1 miles) machine will probe how matter is pieced together atom by atom.
The properties of the X-ray Free-Electron Laser (XFEL) should make it possible, for example, to film the very moment a chemical reaction occurs.
Construction of the 986m euro (£668m) facility will begin later this year.
It will be placed underground. The XFEL will begin on the DESY (Deutsches Elektronen-Synchrotron) site in Hamburg and then run north-west, fanning out to experimental stations beneath the neighbouring town of Schenefeld.
Electron wiggle
Scientists from academia and industry across the world are expected to apply for time on the facility when it becomes operational in 2013.
The insights they gain are expected to lead to a raft of discoveries across biology, chemistry, physics and Earth sciences.
"This will be a fundamental research tool that is needed, for example, to make advances in the pharmaceutical industry and in the domain of new materials, in particular nano-materials," explained Professor Massimo Altarelli, the XFEL project team leader.
"It will also lead to a lot of advances in plasma physics, in high-energy density matter because its pulses generate plasmas in conditions that you cannot generate any other way. This is relevant for astrophysics and for understanding fusion for energy production," he told BBC News.
See how the XFEL will work
The first part of the XFEL consists of a particle accelerator in which bunches of electrons are taken to almost the speed of light, before being thrown down a slalom course controlled by a long system of magnets known as undulators.
As the electrons bend and turn, they emit flashes of X-rays; and as the particles interact with the radiation, they also bunch even tighter.
Their compact configuration not only intensifies their light emission but gives it coherence as well. In essence, the X-rays are "in sync" and have the properties of laser light.
Getting depth
The peak brilliance of the linear XFEL should be a billion times greater than current X-ray light sources that use a ring configuration - such as the European Synchrotron Radiation Facility (ESRF) at Grenoble, France; or the recently opened Diamond Light Source at Harwell, UK.
The principles of investigation, though, are much the same. As the X-rays pass through matter, their paths change and this gives clues to the atomic arrangement of the material under study.
The XFEL should produce flashes of light that last less than 100 quadrillionths of a second (100 femtoseconds). This is the timescale of molecular movement, which will make it possible to film chemical reactions without any blurring of the image.
In addition, because the flashes have the properties of laser light, it should be possible to do holography - to capture three-dimensional images of molecules.
"The brilliance of the free-electron laser gives us the hope that we will be able to get an X-ray diffraction pattern for a single macromolecule like a protein, so that you don't need to crystallise the protein to deduce its atomic structure," said Professor Altarelli...
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