The first test of the Wendelstein 7-X fusion reactor has produced helium plasma, with plans now under way for hydrogen plasma tests in 2016 to determine the suitability of such a reactor for electric power production.

After nine years of construction and more than a million hours of assembly, scientists at the Max Planck Institute of Plasma Physics operated the stellerator-type fusion device for the first time on December 10. Operators at the Greifswald facility started up the magnetic field and initiated the computer-operated experiment control system to feed around one milligram of helium gas into the evacuated plasma vessel, switched on the microwave heating for a brief 1.3-megawatt pulse and the first plasma was observed by the installed cameras and measuring devices.

Wendelstein 7-X is the world's largest stellerator-type fusion device. Image credit: IPP/Thorsten Bräuer.“We’re starting with a plasma produced from the noble gas helium. We’re not changing over to the actual investigation object, a hydrogen plasma, until (2016),” says project leader Thomas Klinger. “This is because it’s easier to achieve the plasma state with helium. In addition, we can clean the surface of the plasma vessel with helium plasmas.”

The first plasma in the machine had a duration of 1/10th of a second and achieved a temperature of around 1 million degrees.

“Everything went according to plan," says Dr. Hans-Stephan Bosch, whose division is responsible for the operation of the Wendelstein 7-X.

The next task will be to extend the duration of the plasma discharges and to investigate the best method of producing and heating helium plasmas using microwaves. Confinement studies were set to continue in January, which will prepare the way for producing the first plasma from hydrogen.

The objective of fusion research is to develop a power source that is friendly to the climate and, similar to the sun, harvests energy from the fusion of atomic nuclei. As the fusion fire only ignites at temperatures of more than 100 million degrees, the fuel—a thin hydrogen plasma—cannot come into contact with cold vessel walls. Confined by magnetic fields, it floats virtually free from contact within the interior of a vacuum chamber.

For the magnetic cage, the IPP is considering two different designs: the stellerator and the tokamak. Currently, only tokamaks are thought to be capable of producing an energy-supplying plasma.

While the Wendelstein 7-X will not produce energy, it is intended to demonstrate that stellarators are also suitable as a power plant. And with discharges lasting 30 minutes, the stellarator should demonstrate its fundamental advantage over tokamaks—the ability to operate continuously. In contrast, tokamaks can operate only in pulses without auxiliary equipment.