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The basic design of fusion tokamaks was largely developed in the the Soviet union in the 1960’s. In the 1970’s there was a lot of optimism that a practically endless source of energy was being developed, and several Tokamaks were built and operated around the world.

However, operational problems soon emerged and it became evident that more advanced and larger designs were needed in order to overcome them. Already in the mid 1980’s an agreement was made between Reagan and Gorbachev to build the International Thermonuclear Experimental Reactor or ITER, but Soviet Union collapsed and the Reagan administration cut public spending. Only now is ITER being built, in Cadarache in France. Construction started in 2010, and it is planned to become operational in 2025.

For a Tokamak to function, the fusion fuel is heated by an external source to reach over 150 million degrees, which is about 10 times higher than the core temperature of the sun. At such a high energy the hydrogen isotopes deuterium and tritium, that will be used in ITER, separates into electrons and nuclei, or a so called plasma. The charged particles move with extreme velocity (~1000km/sec for nuclei) and are confined to the center of a vacuum chamber by a magnetic field. When deuterium and tritium nuclei collide the may fuse to form Helium, free neutrons and energy. When this process begin to produce enough energy so that the useful output is larger than the input energy, the reactor can be used as a power-plant.

To be honest, all this sounds like the crazy ideas of a mad scientist. How can a fusion reactor operate at at 150 million degrees and not immediately be destroyed? At the core of the explation for this is the difference between temperature and heat energy density.

In outer space for example, solar wind particles, which is a very dilute plasma, have a temperature of about 150,000 degrees, but space is still really ‘cold’, because there are so few particles. In ITER only a few grams of fuel will be present at any time in the huge reactor chamber and the charged particles of the plasma are kept insulated from the walls by a magnetic field.However, the radiation damage of the plasma may still be severe. This is also one of the core questions of fusion reactor construction – will the reactor material withstand the radiation damage long enough for fusion to be useful as an energy producer? Another risk with radiation damage is that the plasma easily become contaminated by damage-debris from reactor walls and therefore lose its energy production capability.

The E-TASC Hel is a project that will contribute to the search for solutions to questions of this kind by enabling numerical computer models and optimising them for the most modern super-computers available. One such super-computer is currently being set up in an old paper-mill building in Kajaani in Finland. The Kajaani computer, LUMI, is based on general-purpose Graphics Processing Units, or GPUs for short, and has an immense compute power. The downside is that the computer is complex and the fusion modelling compute-codes has to be modified to be able to utilize LUMIs compute power.

This is the main task of E-TASC Hel – we have to model the dynamics of ITER and DEMO to the best of our ability in order to give the reactors the best possible chance of being functional. There is really no way to overstimate the importance and impact a functioning and efficient fusion energy production would have for mankind – enormous amount of energy in form of electricity without burning of fossil fuel. Electricity that can run industries, charge batteries and produce renewable fuels – the holy grail of climate problem solutions.

When I indicate that a lot of mankinds future depend on projects like this, I am not exaggerating that much. It is truly humbling to be a part of this – maybe not as melodramatic, but still a bit like taking part in an apocalyptic sci-fi movie: a bunch of scientists working seemingly against all odds to save mankind.

Jan Åström
The writer is Fil. Dr. in Theoretical physics from Åbo Akademi University and a developer of scientific code at CSC.

Read more:

  • Three million euros in EU funding for Finnish research into fusion energy and artificial intelligence