Hydrogen plasma created in stellerator Thursday, 04 February 2016

Last night, the Wendelstein 7-X fusion device at the Max Planck Institute for Plasma Physics (IPP) in Germany, successfully produced its first hydrogen plasma. Supporters of this type of nuclear technology are hopeful that it will ultimately demonstrate the viability of a continuously operating nuclear fusion reactor.

German Chancellor Angela Merkel was on hand to press the switch which sent a 2 MW pulse of microwave heating into a small quantity of hydrogen gas, converting the gas into an extremely hot low-density hydrogen plasma.

“With a temperature of 80 million degrees and a lifetime of a quarter of a second, the device’s first hydrogen plasma has completely lived up to our expectations”, said IPP's Dr. Hans-Stephan Bosch.

Since first creating a helium plasma in December last year, the reactor has produced more than 300 helium discharges, designed to clean the plasma vessel so it was capable of reaching the plasma temperatures necessary for the hydrogen test.

The Wendelstein 7-X is a stellarator type fusion device. Its core is a ring of 50 superconducting coils, each around 3.5 m tall. They are threaded onto a ring-shaped steel plasma vessel and encased by a steel shell.

In the vacuum generated inside the shell, the coils are cooled down to superconduction temperature close to absolute zero using liquid helium. Once switched on, they consume hardly any energy.

The magnetic cage they create keeps the 30 cubic metres of ultra-thin plasma – the test object – suspended inside the plasma vessel. As the fusion fire only ignites at temperatures in excess of 100 million degrees, the fuel must not come into contact with cold vessel walls. Confined by magnetic fields, it floats almost entirely contact-free in the interior of a vacuum chamber.

There are two different designs for the magnetic cage in nuclear reactors, the tokamak and the stellarator. An experimental tokamak reactor is currently under construction at Cadarache in southern France, however, the German researchers feel that if they can prove the viability of stellarators, they will have a significant advantage over tokamaks in being able to operate continuously.

 

The first hydrogen plasma lights up the inside of the Wendelstein stellarator. Image: IPP