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Physicists overcome two key operating hurdles in fusion reactions

Physicists overcome two key operating hurdles in fusion reactions
Database of H98y2 and fGr for DIII-D discharges. More than 3,600 discharges are included. Violet diamonds show high-βP experiments performed in 2019 with impurity injection. Blue squares are the new high-βP experiments performed in 2022 without impurity injection. Yellow circles represent all other experiments performed in 2019–2022. The area shaded in orange indicates the parameter space for attractive FPP designs. Vertical and horizontal dashed lines show fGr = 1.0 and H98y2 = 1.0, respectively. Credit: Nature (2024). DOI: 10.1038/s41586-024-07313-3

A team of physicists from several institutions across the U.S. working with a colleague from China, at the DIII-D National Fusion Facility, in San Diego, California, has devised a way to overcome two key hurdles standing in the way of using fusion as a general power source.

In their paper published in the journal Nature, the group describes how they devised a way to raise the density of the plasma in their reactor while also keeping it stable.

Scientists at various sites around the world have been working for several years to figure out how to use to create electricity for general use—thereby freeing the world from using coal and gas fired that spew into the atmosphere. But it has been a long and difficult road.

It was just in the past couple of years that researchers were able to show that a fusion reaction could be made to sustain itself, and that more power could be produced than was input into such a system.

The next two hurdles to overcome are increasing the density of the plasma in the reactor and then containing it for extended periods of time—long enough for it to be useful for producing electricity. In this new study, the research team has devised a way to do both in a tokamak chamber.

To contain the plasma as its density was increased, the team used additional magnets and bursts of deuterium where needed. They also allowed for higher densities at the core than near the edges, helping to ensure the plasma could not escape. They held it in that state for 2.2 seconds, long enough to prove that it could be done.

They also found that during that short time span, the average in the reactor was 20% over the Greenwald limit—a theoretical barrier that had been predicted to mark the point at which adding pressure would escape the holding the plasma in place.

They also found that the stability of the was H98y2 above 1, which means that the experiment was successful.

The research team acknowledges that their experiment was done in a very small reactor—one with a diameter of just 1.6 meters. For such an achievement to be considered fully successful, it will have to be done in a much larger reactor, such as the one currently under construction in France, which will have a diameter of 6.2 meters.

More information: S. Ding et al, A high-density and high-confinement tokamak plasma regime for fusion energy, Nature (2024). DOI: 10.1038/s41586-024-07313-3

Journal information: Nature

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Citation: Physicists overcome two key operating hurdles in fusion reactions (2024, April 29) retrieved 18 May 2024 from
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