Nuclear fusion is the opposite to nuclear fission: While heavy elements release energy when they're split, light elements like hydrogen or helium release energy when their nuclei are fused. One advantage of the latter is the absence of long-term radioactive waste. But nuclear fusions only work under extreme temperatures, measured in millions of degrees centigrate – far too hot for any material vessel. This is why the hot plasma is enclosed by magnetic fields, a fact that makes the construction of fusion facilities not easier but more complicated.
Over the past decades, two main designs have emerged: tokamaks and stellarators. Both designs are donut-shaped, but in the stellarator Wendelstein 7-X, an innovative construction design allows for a (theoretically) continuous plasma containment within a magnetic field. Worldwide, more tokamaks are running or being built than stellarators. Here, plasma containment is facilitated by an electric current that runs through the plasma itself – but this current causes side effects that make a continuous operation even more intricate in tokamaks. Prof. Günter is an expert for both designs, for many years she was head of the research department Tokamak Theory at the IPP.