As the dynamics inside a fusion reactor are very complex, the walls melt.

Image credit: Max Planck Insтιтute of Plasma physics. Cutaway of a Fusion Reactor

A team of researchers from the Max Planck Insтιтute for Plasma Physics (IPP) and the Vienna University of Technology (TU Wein) have discovered a way to control Type-I ELM plasma instabilities, that melt the walls of fusion devices. The study is published in the journal Physical Review Letters.

There is no doubt that the day will come when fusion power plants can provide sustainable energy and solve our persistent energy problems. It is the main reason why so many scientists around the world are working on this power source. Power generation in this way actually mimics the sun.

For the method to work, the plasmas must be heated to 100 million degrees Celsius inside the reactors. A Magnetic fields surrounds the plasma keep the walls of the reactor from melting. The shell that forms around the plasma can  work only because the outermost few centimeters of the edge of that shell, called the magnetically formed plasma edge, is very  well insulated.

However, there is a drawback to this method of keeping the plasma’s solar-level heat within. In that edge region, which are plasma instabilities, exist there (ELMs). ELMs typically happen during fusion reactions. In the course of an ELM, intense plasma particles may strike the reactor’s wall and cause possible damage.

The researchers returned to a technique of operation that had been previously abandoned, in a move that would remind anybody of presenting an original of anything after numerous trials of other approaches just to discover that the original is the correct one.

Instead of possibly harming the reactor’s walls, very destructive instabilities. Numerous minor instabilities are possible, but none of them pose a threat to the walls of the reactor.

Elisabeth Wolfrum, research group head at IPP in Garching, Germany, and professor at TU Wien, states that “Our discovery marks a breakthrough in understanding the occurrence and prevention of mᴀssive Type I ELMs.” The operating regime we provide is most likely the most optimistic case for fusion power plant plasmas in the future. Now, the findings have been released in the publication Physical Review Letters.

Toroidal tokamak fusion reactor is the name of the reactor. Extremely H๏τ plasma particles travel quickly within this reactor. Strong magnetic coils make sure that the particles stay contained rather than destroying the reactor’s walls by striking them.

How a fusion reactor works is complex, and the dynamics inside are also complex. The motion of the particles depends on the plasma density, temperature and magnetic field. The reactor’s operation is determined by the selection of these parameters. When the smaller particles of plasma strike the walls or the reactor, instead of a round shape, the reactor takes on a triangular shape with rounded corners, however this shape is far less damaged than that caused by a big ELM. 

The primary author of the study, Georg Harrer, compares it to a cooking pot with a cover where water is beginning to boil. “If the pressure increases more, the lid will raise and shake violently as the steam escapes. However, if you tilt the lid just a little bit, steam may constantly escape while the top stays put and doesn’t rattle.”

The possibility for a continuous fusion process with enormous energy is greatly increased by this. A perpetual energy source.

Reference(s): Physical Review Letters