Fusion Physicists Found a Way Around a Long-Standing Density Limit (sciencealert.com)
(Friday January 09, 2026 @05:00AM (BeauHD)
from the impressive-feats dept.)
- Reference: 0180551693
- News link: https://science.slashdot.org/story/26/01/09/0319216/fusion-physicists-found-a-way-around-a-long-standing-density-limit
- Source link: https://www.sciencealert.com/fusion-physicists-found-a-way-around-a-long-standing-density-limit
[1]alternative_right shares a report from ScienceAlert:
> At the Experimental Advanced Superconducting Tokamak (EAST), physicists [2]successfully exceeded what is known as the Greenwald limit , a practical density boundary beyond which plasmas tend to violently destabilize, often damaging reactor components. For a long time, the [3]Greenwald limit was accepted as a given and incorporated [4]into fusion reactor engineering . The new work shows that precise control over how the plasma is created and interacts with the reactor walls can push it beyond this limit into what physicists call a 'density-free' regime.
>
> [...] A team led by physicists Ping Zhu of Huazhong University of Science and Technology and Ning Yan of the Chinese Academy of Sciences designed an experiment to take this theory further, based on a simple premise: that the density limit is strongly influenced by the initial plasma-wall interactions as the reactor starts up. In their experiment, the researchers wanted to see if they could deliberately steer the outcome of this interaction. They carefully controlled the pressure of the fuel gas during tokamak startup and added a burst of heating called electron cyclotron resonance heating.
>
> These changes altered how the plasma interacts with the tokamak walls through a cooler plasma boundary, which dramatically reduced the degree to which wall impurities entered the plasma. Under this regime, the researchers were able to reach densities up to about 65 percent higher than the tokamak's Greenwald limit. This doesn't mean that magnetically confined plasmas can now operate with no density limits whatsoever. However, it does show that the Greenwald limit is not a fundamental barrier and that tweaking operational processes could lead to more effective fusion reactors.
The findings have been [5]published in Science Advances .
[1] https://slashdot.org/~alternative_right
[2] https://www.sciencealert.com/fusion-physicists-found-a-way-around-a-long-standing-density-limit
[3] https://wiki.fusion.ciemat.es/wiki/Greenwald_limit
[4] https://doi.org/10.1103/PhysRevLett.128.185003
[5] https://doi.org/10.1126/sciadv.adz3040
> At the Experimental Advanced Superconducting Tokamak (EAST), physicists [2]successfully exceeded what is known as the Greenwald limit , a practical density boundary beyond which plasmas tend to violently destabilize, often damaging reactor components. For a long time, the [3]Greenwald limit was accepted as a given and incorporated [4]into fusion reactor engineering . The new work shows that precise control over how the plasma is created and interacts with the reactor walls can push it beyond this limit into what physicists call a 'density-free' regime.
>
> [...] A team led by physicists Ping Zhu of Huazhong University of Science and Technology and Ning Yan of the Chinese Academy of Sciences designed an experiment to take this theory further, based on a simple premise: that the density limit is strongly influenced by the initial plasma-wall interactions as the reactor starts up. In their experiment, the researchers wanted to see if they could deliberately steer the outcome of this interaction. They carefully controlled the pressure of the fuel gas during tokamak startup and added a burst of heating called electron cyclotron resonance heating.
>
> These changes altered how the plasma interacts with the tokamak walls through a cooler plasma boundary, which dramatically reduced the degree to which wall impurities entered the plasma. Under this regime, the researchers were able to reach densities up to about 65 percent higher than the tokamak's Greenwald limit. This doesn't mean that magnetically confined plasmas can now operate with no density limits whatsoever. However, it does show that the Greenwald limit is not a fundamental barrier and that tweaking operational processes could lead to more effective fusion reactors.
The findings have been [5]published in Science Advances .
[1] https://slashdot.org/~alternative_right
[2] https://www.sciencealert.com/fusion-physicists-found-a-way-around-a-long-standing-density-limit
[3] https://wiki.fusion.ciemat.es/wiki/Greenwald_limit
[4] https://doi.org/10.1103/PhysRevLett.128.185003
[5] https://doi.org/10.1126/sciadv.adz3040