Nuclear fusion made more stable thanks to a rather simple solution

21 Aug 2017

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Bringing us yet another step closer to harnessed nuclear fusion energy, a team of researchers has found a simple way to make it more stable.

There are numerous challenges to harnessing a nuclear fusion reaction with the potential to have a near-limitless, clean and cheap power source, and one of them is creating stable plasma.

One of the most common instabilities found during the latest research is called a global Alfven eigenmode (GAE), a wave-like disturbance that can cause fusion reactions to fizzle out, which, unsurprisingly, is not good.

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However, in a paper published to Physical Review Letters, a team from Princeton University has found a remarkably simple way to suppress GAE in its own experimental reactor known as the National Spherical Torus Experiment Upgrade (NSTX-U).

Like a snake trying to eat its tail

The GAE instability is sometimes compared to a snake trying to eat its own tail, in that the same neutral beam particles instrumental to the process that heat the plasma are ionised inside the gas.

Once triggered by these fast ions, the GAEs can rise up and drive them out, cooling the plasma and halting fusion reactions.

However, to help stop this, the Princeton researchers simply installed a second beam injector.

Once switched on, the beam flows through the plasma at a higher pitch-angle, in a direction roughly parallel to the magnetic field that confines the hot gas, resulting in the GAEs being suppressed in a matter of milliseconds.

Fast ions from the beam combined with those from the original beam to increase the density of the ions and alter their distribution in the plasma.

‘A welcome discovery’

All of this is good news for nuclear fusion development, as NSTX-U’s head of research, Jonathan Menard, explained.

“Normally, when you inject energetic particles, you drive up instabilities,” he said.

“The fact that the second neutral beam was able to turn them off by varying the fast-ion distribution with a small amount of particles provides our research with flexibility and is a welcome discovery.”

Earlier this year, a team from Chalmers University of Technology in Sweden managed to achieve another major breakthrough in stability within nuclear fusion, specifically with preventing reactors from blowing up under the intense pressure during a reaction.

Colm Gorey was a senior journalist with Silicon Republic