Code breakthrough could greatly improve design of nuclear fusion reactors

The XGC-S code is opening ‘a big window’ for nuclear fusion research by helping train simulators.

Researchers from the US Department of Energy (DoE) and the Princeton Plasma Physics Laboratory (PPPL) have demonstrated that an advanced computer code could help design much more efficient and better nuclear fusion reactors.

Nuclear fusion is an attempt to harness the power of the sun in a reactor, potentially providing near limitless, cheap and clean energy. It is often described as the ‘holy grail’ of physics.

Now, writing in Physics of Plasmas, the PPPL and DoE researchers said that this code, dubbed XGC-S, will greatly benefit the design of stellarators – one of a fusion reactor’s key components.

This twisting magnetic coil is essential to trapping hot, charged plasma gas, but it must be precisely engineered to prevent heat from escaping the plasma core where it stokes the fusion reactions.

“The main result of our research is that we can use the code to simulate both the early, or linear, and turbulent plasma behaviour in stellarators,” said Michael Cole, lead author of the paper.

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“This means that we can start to determine which stellarator shape contains heat best and most efficiently maintains conditions for fusion.”

‘A really important development’

In testing, the researchers simulated the behaviour of plasma inside fusion machines shaped like doughnuts, but with pinches and deformations that make the device more efficient, a kind of shape known as quasi-axisymmetric.

By using XGC-S, the simulations showed that a type of disturbance limited to a small area can become complex and expand to fill a larger space within the plasma. This makes the new code substantially more accurate than what was previously possible.

David Gates, head of the Department of Advanced Projects at PPPL, said: “I think this is the beginning of a really important development in the study of turbulence in stellarators. It opens up a big window for getting new results.”

They now plan to modify XGC-S further to create an even clearer picture of how turbulence affects heat leakage in a reactor.

Cole added: “Once you have an accurate code and a powerful computer, changing the stellarator design you are simulating is easy.”

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