One of the most powerful X-ray machines ever built has officially opened in the German city of Hamburg.
The
facility, which has cost more than a billion euros to build, will be
used to study the detailed structure of matter, atom by atom.
It is called the European X-ray Free Electron Laser (XFEL).
Scientists
say the way it shines light on targets will permit, for example,
chemical bonds to be filmed in the instant that they are made or broken.
The researchers anticipate fundamental discoveries that lead to new
medical treatments and novel materials, to name just two possibilities.
The XFEL will begin operations with 11 nations as members of its consortium
Prof Robert Feidenhans'l is the MD of the non-profit company established to run the facility.
"It's a fantastic and exciting day for us to open the European XFEL for operation after more than eight years of construction,"
"I now declare we are ready to take data; we are ready to meet the challenge of getting groundbreaking results."
The
machine is a superconducting linear accelerator that is housed in a
3.4km-long tunnel complex some 40m beneath Hamburg and the nearby town
of Schenefeld.
It works by accelerating bunches of electrons to almost light-speed,
before then throwing them down a slalom course controlled by a system of
magnets, known as undulators.
As the electrons bend and turn,
they emit flashes of X-rays; and as the particles interact with this
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.
The beam will penetrate and detail at the atomic scale whatever is put in its path.
This could be the protein molecules that drive our bodies or the catalyst materials used to produce industrial chemicals.
How to produce super-bright flashes
- At the head of the XFEL, bunches of electrons are first sped up to near-light-speed in a super-cold, evacuated accelerator
- The particles are directed down long undulators - magnetic systems that produce a slalom course for the electrons
- As they wiggle back and forth in the undulators, the fast-moving electrons emit very bright X-ray flashes
- The particles interact with this great sea of X-rays and begin to organise themselves into even tighter groupings
- This intensifies the brilliance of their emission and gives it coherence - the X-rays are "in sync" and laser-like
- Having done their job, the electrons are siphoned off, leaving the X-ray flashes to hit their experimental targets
Many nations around the world use circular machines called synchrotrons that do a very similar job.
But
the light generated by the XFEL is about a billion times brighter than
those facilities. What also sets the XFEL apart is the super-fast time
structure in its flashes.
The machine will deliver
trillions (1,000,000,000,000) of X-ray photons in a pulse lasting just
50 femtoseconds (0.000,000,000,000,05 sec), and it can repeat this
27,000 times a second.
It allows for time-resolved investigations
that are beyond what is possible in standard synchrotrons. For example,
scientists will use a jet to stream their samples in front of the beam,
priming them with another laser so that chemical reactions are triggered
at just the right moment to be caught by the pulses.
The conventional X-ray light sources also use pure
crystals of the biological molecules they want to study. These can be
very difficult to make - impossible in some cases.
"The huge
hope for XFEL is that we will be able to do single particle imaging. So,
you just put a stream of your protein complex or virus into the beam
and you'd have enough photons that an individual biological entity would
scatter those photons for you to get the shape of it," explained Oxford
University's Prof Elspeth Garman, who sits on the committee that will
allocate scientists experimental time in Hamburg.
Prof Garman already fulfils this role for the American machine at the National Accelerator Laboratory in Stanford University, California.
This facility is now heavily oversubscribed and so the addition of the
European option - which is also a step on in capability - will be most
welcome, she says.
When the project was green-lit in 2007, the UK
looked certain to become a consortium member, but then stepped away from
participation after the financial crash.
This situation has now
changed again and following a brief discussion about whether it should
build its own machine, Britain is expected to formally climb aboard the
German-led project in the coming weeks.
The in-out uncertainty, however, has not stopped UK technical contributions.
British
engineers have made an advanced camera called the Large Pixel Detector
which has been installed in Hamburg ready for the first raft of
experiments. It operates at a frame rate of 4.5MHz - 4.5 million
pictures per second.
Matthew Hart was the lead engineer on the LPD at the Science and Technology Facilities Council's (STFC) Rutherford Appleton Laboratory (RAL) near Oxford.
"The
LPD captures the pattern of the X-rays after they've scattered through
whatever it is the scientists have put in the beam. Its imaging surface
is about half a metre by half a metre," he told BBC News.
"It's
something we've been working on for 10 years, and it's incredibly
bespoke. It has to run really fast, handle really intense levels of
X-rays but at the same time capture very small signals as well; and have
very low noise."
The laboratory is currently making a second detector, or at least the replacement parts for one.
The
XFEL's high-energy beam is so intense it actually destroys samples as
it probes them, and it is expected the cameras that record the action
will also become degraded over time.
Japan, too, operates a free
electron laser, although its flash rate is not as high as the Stanford
machine and a long way short of the Hamburg capability.
The
European XFEL is not an EU institution. However, many of the scientists
who come through the complex will be in receipt of EU grants dispersed
under the bloc's research budget, Horizon 2020.
