Fusion research is heating up as different laboratories explore combining techniques to control instability in plasmas.
Researchers at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) have successfully simulated a new combination method for managing fusion plasma. They were able to show how the two united methods offer more flexibility and stability.
The two processes used are electron cyclotron current drive (ECCD) and applying resonant magnetic perturbations (RMP). ECCD is used in magnetic confinement fusion experiments to control and sustain the plasma current. The application of resonant magnetic perturbations (RMPs) includes introducing small, controlled magnetic disturbances into the plasma.
Qiming Hu is the lead author of the study. In an official statement, he said, “This is kind of a new idea.” The study was published in Nuclear Fusion. It indicates that even though the work showed a lot of promise, there are serious challenges. One problem is perfecting the methods for minimizing bursts of particles known as edge-localized modes (ELMs) from the plasma, which can be dangerous.
A fusion reactor known as a tokamak uses magnetic fields to contain the plasma in a donut shape. However, the ELMs can lead to the end of the reaction. They can potentially damage the device in the process. Alessandro Bortolon said, “The best way we’ve found to avoid them is by applying RMPs.
The magnetic fields initially applied by the tokamak travel around the torus-shaped plasma like a rope. The magnetic fields created by the RMPs weave in and out. They produce fields known as magnetic islands due to their oval shape.
Magnetic islands in plasma are generally unwanted. If they are too big, the plasma itself can be disrupted. However, in experimental conditions, they can be beneficial.
Creating RMPs big enough to develop the desired magnetic islands in the plasma is a challenge. This is where the ECCD generates microwave beams. They act as a special component that lowers the current needed to generate the RMPs necessary to make the islands. They make the process more controllable and also perfect the size of the islands for maximum plasma edge stability.
When the ECCD was aimed in the same direction as the current, the width of the island decreased. When the ECCD was aimed opposite to the current, the pedestal pressure increased. Hu said, “Applying the ECCD in the opposite direction produced opposite results.”
Hu added that “People think applying localized ECCD at the plasma edge is risky because the microwaves may damage in-vessel components. We’ve shown that it’s doable, and we’ve demonstrated the flexibility of the approach. This might open new avenues for designing future devices.”
The combination of these two methods improves stability and control. This is essential for energy production via fusion reactions.
This could mean a reduction in the cost of fusion energy production in commercial-scale fusion devices of the future. Hopefully, it will lead us to reduce our reliance on fossil fuels and mitigate the impacts of climate change. This can be a step toward a more sustainable future.