14 Dec (NucNet): Scientists at the Max Planck Institute for Plasma Physics (IPP) in Germany say they have reached a milestone in a quest to derive energy from nuclear fusion by starting up one of the world’s largest nuclear fusion machines for the first time and briefly generating a super-heated helium plasma inside a vessel – a key point in the experimental process.
The 16-metre-wide machine is the Wendelstein 7-X, a type of nuclear fusion device called a stellarator.
Scientists have been talking about the enormous potential of stellarators for decades, but this is the first time a team has shown that it can produce and control plasma.
IPP said in a statement that after over a year of technical preparation and tests, experimental operation of the Wendelstein 7-X, at Greifswald in northern Germany, has now commenced “according to plan”.
“With the Wendelstein 7-X, the world’s largest stellarator-type fusion device, the researchers would like to prove that this type of device is suitable for use as a power station,” the statement said.
The first plasma in the machine lasted one tenth of a second and reached a temperature of around one million kelvins. “We’re very satisfied,” said Hans-Stephan Bosch, whose division is responsible for the operation of the Wendelstein 7-X. “Everything went according to plan.”
IPP said investment costs of the Wendelstein 7-X totalled €370m ($405m) and were provided by the German federal and state governments and the European Union. The components were manufactured by companies throughout Europe. Orders in excess of €70m were placed with companies in the region.
In the next stages of the experiment, the researchers want to extend the duration of the plasma discharges and to investigate the best method for producing and heating helium plasmas using microwaves.
After a break for New Year, confinement studies will resume in January 2016 when the scientist will test, among other things, how well the helium plasma is confined in the magnetic field. With these tests, the scientists will prepare the way for the first experiments with hydrogen plasma, which is ultimately intended to be fused into helium in the fusion experiments.
IPP said the objective of fusion research is to develop “a climate- and environmentally-friendly power plant”, which, like the sun, harvests energy from the fusion of atomic nuclei. As the fusion fire only ignites at temperatures in excess of 100 million kelvins, the fuel – a thin plasma consisting of hydrogen – must not come into contact with vessel walls. Confined by magnetic fields, it floats almost entirely contact-free in the interior of a vacuum chamber.
Two different designs for the magnetic cage have become established – the tokamak and the stellarator. Both types of system are being tested at the IPP. The Tokamak Asdex Upgrade is in operation at Garching and the Wendelstein 7-X stellarator is now operational at Greifswald.
IPP said many scientists currently believe that a tokamak – the international test reactor International Thermonuclear Experimental Reactor (Iter), which is being constructed at Cadarache in France as part of a worldwide collaborative project – is the only system capable of producing an energy-supplying plasma. The Wendelstein 7-X, the world’s largest stellarator-type fusion device, will not produce energy. Nevertheless, it should demonstrate that stellarators are also suitable for use as power plants, IPP said.
Stellarator machines have a complex geometry designed to enable continuous fusion energy production, whereas tokamaks have a simpler torus or donut-shaped geometry, which allows only pulsed operation.
