Scientific vandalism helps ITER

  Physicist Gilles Arnoux keeps a close eye on the JET fusion energy experiment. Scientists at JET, the world’s largest fusion energy research facility, have been deliberately melting parts of their own machine as they test materials for the fusion…

 

Physicist Gilles Arnoux keeps a close eye on the JET fusion energy experiment.

Scientists at JET, the world’s largest fusion energy research facility, have been deliberately melting parts of their own machine as they test materials for the fusion reactors of the future. These apparent acts of scientific vandalism are actually courageous experiments which have yielded valuable information for JET’s successor – the huge international ITER project being built in the south of France.

The experiments were requested by ITER, which is currently assessing what material should be used for its plasma-facing wall. To achieve fusion, gas is heated to over one hundred million degrees, at which temperature it becomes a plasma, similar to the sun. Plasma is held inside a magnetic chamber known as a tokamak. Of particular concern to researchers are bursts of turbulence on the edge of the plasma similar to solar flares, which can momentarily inflict on to small areas of the tokamak wall heat loads far greater than a blow torch.

JET scientists have been astonished by the machine’s faultless performance during the recent tests.
“There was a slight worry we would see uncontrolled, firework-like splashes of molten metal,” said Dr Gilles Arnoux, one of the scientific coordinators of the experiment, “and that might affect subsequent experiments. But it was a smooth melt; the plasma didn’t seem to notice. I was surprised at how little impact it had.”
The tests at JET involved subjecting a small area of deliberately misaligned tungsten wall tile to regulated bursts of turbulent events. The peak temperature of the tile during the transient bursts was slowly increased until it exceeded tungsten’s melting point, 3422 degrees Celsius, to assess what effect molten tungsten might have on the operation of the plasma. In particular, it was feared that a melt event might contaminate the hydrogen-based plasma with tungsten and lead to a disruption – an uncontrolled energy dump from the plasma – which could lead to further surface melting in a fusion experiment as large as ITER.

Enlarge

JET’s experiments of a tungsten wall tile help ITER to decide on the material for the plasma-facing wall.
Instead, as shown in the picture, the molten tungsten moved smoothly to one end of the tile and formed a droplet, that grew with each additional plasma pulse. Curiously the molten metal did not run downwards – a result of the magnetic forces inside the tokamak – and, to the scientists’ relief, moved away from the hottest part of the plasma rather than being swept back into the exposed area. Subsequent experiments were performed without any interruption to proceedings.

Joining the JET team in the control room was the leader of ITER’s Divertor and Plasma Wall Interactions section, Dr Richard Pitts, who has been involved throughout the planning of the experiment.
Dr Pitts said: “It has been a great success and has achieved what it set out to do: to demonstrate that repetitive, fast transient heat pulses pushing tungsten over the melt threshold for just a millisecond or two each time, do not drive melt splashing nor do they appear to have any observable effect on the core plasma. It seems that we can broadly understand what we have seen on the basis of complex computer simulations describing the melt dynamics and thus our confidence is increased in the extrapolations we make for the behaviour to expect on ITER, which use the same computer codes. These results are extremely significant for the choice which ITER is preparing to make regarding the use of tungsten.”
Despite the early optimism much analysis remains to be done. The full story will not be known until mid 2014, when JET’s current run of experiments concludes and the melted tile can be removed and analysed.

Explore further:

New jet results tick all the boxes for ITER

Provided by European Fusion Development Agreement

view popular

4.9 /5 (13 votes)

Related Stories

New jet results tick all the boxes for ITER

Oct 08, 2012

Latest results from the Joint European Torus (JET) fusion device are giving researchers increasing confidence in prospects for the next-generation ITER project, the international experiment that is expected …

Disruption mitigation researchers investigate design options

Jan 21, 2013

ITER, the world’s first reactor-scale fusion machine, will have a plasma volume more than 10 times that of the next largest tokamak, JET. Plasma disruptions that can occur in a tokamak when the plasma be …

World’s largest fusion device goes back to work

Sep 05, 2011

September is commonly the month where things begin to gather pace again, and in the world of fusion energy research, things are no different. European scientists working on the Joint European Torus (JET), …

I-mode powers up on alcator C-mod tokamak

Nov 10, 2011

A key challenge in producing fusion energy is confining the plasma long enough for the ionized hydrogen to fuse and produce net power. Suppressing plasma turbulence is one approach to this, but the resulting …

ELISE investigating new type of heating for ITER

Nov 29, 2012

(Phys.org)—Tests for the heating that is to bring the plasma of the ITER international fusion test reactor to a temperature of many million degrees can go ahead from today: After three years of construction, …

New imaging technique provides improved insight into controlling the plasma in fusion experiments

Jul 10, 2013

A key issue for the development of fusion energy to generate electricity is the ability to confine the superhot, charged plasma gas that fuels fusion reactions in magnetic devices called tokamaks. This gas …

Recommended for you

Existence of new element confirmed

3 hours ago

Remember the periodic table from chemistry class in school? Researchers from Lund University in Sweden have presented fresh evidence that confirms the existence of a previously unknown chemical element. The …

Physicist finds that E. coli replicate close to thermodynamic limits of efficiency

4 hours ago

All living things must obey the laws of physics—including the second law of thermodynamics, which states that the universe’s disorder, or entropy, can only grow. Highly ordered cells and organisms appear …

Laser fusion experiment yields record energy

4 hours ago

(Phys.org) —In the early morning hours of Aug.13, Lawrence Livermore’s National Ignition Facility (NIF) focused all 192 of its ultra-powerful laser beams on a tiny deuterium-tritium filled capsule. In …

Overhead costs of fusion power plants can be reduced by planning reactor maintenance and structure together

4 hours ago

VTT Technical Research Centre of Finland’s research results indicate that joint planning of the reactor structure and remote maintenance system can significantly improve the utilisation rates of future fusion power plants. …

Sonata in LHCb: The sound of antimatter (w/ Video)

5 hours ago

In a recent paper the LHCb collaboration at CERN observed two particles changing from matter into antimatter and back again. Now the collaboration has turned that data into sound, so that you can listen to the music of antimatter.

How does complex behavior spontaneously emerge in the brain?

23 hours ago

(Phys.org) —The idea of emergence, in which complex behavior spontaneously emerges out of simple interactions, exists in a wide variety of areas, such as economics, the Internet, and urban development. …

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

More news stories

Quantum measurement carries information even when the measurement outcome is unread

(Phys.org) —Some tasks that are impossible in classical systems can be realized in quantum systems. This fact is exemplified by a new protocol that highlights an important difference between classical and …

Laser fusion experiment yields record energy

(Phys.org) —In the early morning hours of Aug.13, Lawrence Livermore’s National Ignition Facility (NIF) focused all 192 of its ultra-powerful laser beams on a tiny deuterium-tritium filled capsule. In …

How does complex behavior spontaneously emerge in the brain?

(Phys.org) —The idea of emergence, in which complex behavior spontaneously emerges out of simple interactions, exists in a wide variety of areas, such as economics, the Internet, and urban development. …

Physicist finds that E. coli replicate close to thermodynamic limits of efficiency

All living things must obey the laws of physics—including the second law of thermodynamics, which states that the universe’s disorder, or entropy, can only grow. Highly ordered cells and organisms appear …

Physicist disentangles ‘Schrodinger’s cat’ debate

Physicist Art Hobson has offered a solution, within the framework of standard quantum physics, to the long-running debate about the nature of quantum measurement.

Facebook says governments demanded data on 38K users (Update)

Government agents in 74 countries demanded information on about 38,000 Facebook users in the first half of this year, with about half the orders coming from authorities in the United States, the company said …

Earthquakes and tectonics in Pamir Tien Shan

Real time analysis of shear waves as a means of earth quake hazard mitigation. First time observed continental subduction in a continent-continent collision.

Supervolcanic ash can turn to lava miles from eruption, scientists find

Supervolcanoes, such as the one sitting dormant under Yellowstone National Park, are capable of producing eruptions thousands of times more powerful than normal volcanic eruptions. While they only happen …

Exploring Google Glass through eyes of early users

Geeks aren’t the only people wearing Google Glass. Among the people testing Google Inc.’s wearable computer are teachers, dentists, doctors, hair stylists, architects, athletes and even a zookeeper.

European hunter-gatherers owned pigs as early as 4600BC

European hunter-gatherers acquired domesticated pigs from nearby farmers as early as 4600BC, according to new evidence.