As the dynamics inside a fusion reactor are very complex, the walls melt.
Image credit: Max Planck Institute of Plasma physics.
Cutaway of a Fusion Reactor |
A team of researchers from the Max Planck Institute 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 massive 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 hot 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