Scientists start Wendelstein 7-X fusion reactor for the first time

The Wendelstein 7-X stellarator is turned on for the first time. The German fusion reactor was able to produce a helium plasma for the first time on December 10. This marks a new phase after almost twenty years of designing and building the fusion reactor.

This is reported by the Max-Planck-Institut für Plasmaphysik in Greifswald, Germany. The Wendelstein 7-X is the largest stellarator fusion reactor in the world. With the wokkel-shaped device, research is being conducted into the usefulness of such reactors for possible future power plants. A short pulse of microwaves of 1.8 megawatts created the first plasma with one milligram of helium gas. Several measuring instruments and cameras in the device detected the plasma. Only next year will experiments start with hydrogen to form a plasma. This is because it is easier to get a stable plasma with helium. The plasma existed for a tenth of a second and reached a temperature of more than one million degrees Celsius.

The Wendelstein 7-X without plasma and with plasma. The color photo is a colored black and white photo.

The purpose of this reactor is to conduct research into nuclear fusion in a stellarator and to learn whether it is actually possible to produce energy with a stellarator reactor. The Wendelstein 7-X should clarify whether a stellarator is indeed better at balancing the plasma than a tokamak reactor. The latter is better known as a fusion reactor and has a donut shape. The problem with a tokamak is that it cannot hold plasma for long periods of time, because the plasma has to be kept in the donut shape with great effort by an enormous amount of current. Therefore, a tokamak pulses and continuous plasma cannot exist.

A stellarator does not have this problem, because the shape of a stellarator is designed in such a way that the plasma can take its natural shape, a kind of twisted wok. No electrical current is then needed to pass through the plasma to keep it in the right place, although a lot of current is still needed to make everything function. In order for a stellarator to work, a plasma of more than 100 million degrees Celsius must first be formed, about seven times the temperature of the sun’s core. This makes it impossible to handle the gas in a normal vessel. The plasma is held in place by magnetism. Very strong electromagnets form a cage around the plasma, as it were, and ensure that the reactor wall is not hit. In a tokamak there is an imbalance, which means that the particles want to go to the wall. To prevent that, the stellarator’s shape has been twisted so bizarrely and the electromagnets have been placed at all sorts of odd angles.

Wendelstein 7-X: location of electromagnets, location of plasma within electromagnets, human-sized design, photo outside and inside. Source: IPP

The Wendelstein 7-X is not the first stellarator, but it is the largest. The vessel has an outer diameter of eleven meters and could not have been conceived without the help of supercomputers. The computers needed for this only became available in the 1980s. All components must be made and assembled with extreme precision. The actual construction of the Wendelstein 7-X started in April 2005 after the financing and construction of the superconducting magnets had already arisen. Actually, the device should have been finished in 2006 and it should have cost about 550 million euros. That was ten years later and the costs are estimated at 1.06 billion euros.

The whole consists of a ring of fifty superconducting magnets and twenty magnets for fine adjustment. The magnets, some 3.5 meters high, sit in a vacuum and are cooled with liquid helium to near absolute zero and sit as close to the plasma as possible. The whole is surrounded by a steel outer wall. The plasma that is held in check has a volume of thirty cubic meters. There are 254 access holes on the outside for maintenance and diagnostics.

Another major nuclear fusion project in Europe is ITER. This reactor is a global collaborative project and uses a tokamak. Originally it should have been running in 2016. This has been delayed for years. Currently, the project appears to be increasingly collapsing under bureaucratic pressure. The target is now for the first plasma in 2020 and the first experiments in 2027.