PPPL physicist Robert Lunsford, clockwise from the upper left corner, is a schematic diagram of the powder device, a computer rendering of the Wendelstein 7-X fusion facility, an image of the plasma in the facility, and a picture of the powder entering the plasma.
Newswise — When trying a new device that injects powder to clean the walls of the world’s largest stellar simulator, scientists were pleased to discover that these fragments are located in Greifswald, Germany, named Wendelstein 7-X (W7-X ) After each injection of the twisted fusion device, the atoms confined by the magnetic field in the device will temporarily heat up. Researchers led by scientists from the Princeton Plasma Physics Laboratory (PPPL) of the U.S. Department of Energy (DOE) and the Max Planck Institute for Plasma Physics (IPP) in Germany discovered that pulsed injection of boron carbide (a component in sandpaper) Increase the density and temperature of superheated atomic fragments or plasma, thereby improving fusion performance.
Fusion is the driving force that drives the sun and stars. It combines light elements in the form of plasma-the state of hot electric matter composed of free electrons and atomic nuclei or ions-which accounts for 99% of the visible universe. Scientists all over the world are seeking to replicate the reaction on Earth to generate large amounts of energy.
Boron coatings are widely used to cover the interior of tokamaks, which are doughnut-shaped fusion devices operating around the world, and star simulators, their twisting cousins. This coating prevents metals and other heavy elements from leaching into the plasma from the wall, thereby reducing the efficiency of the fusion reaction. It also traps hydrogen escaping from the main plasma, preventing it from returning to the plasma and cooling the reaction.
However, these coatings wear out over time, and many of the technologies used today can only be reapplied when the high-energy fusion plasma device is turned off. Although this is not a problem for today's experiments, shutting down future facilities will not be so easy, as they will have to operate continuously for several weeks. "Finding a way to repair the wall coating while the fusion reaction is in progress is an important part of our research," said Robert Lunsford, a PPPL physicist who is the first author of a paper reporting the results of plasma physics.
In other fusion research facilities around the world, PPPL scientists installed a three-foot-tall impurity powder dropper that can distribute a controlled amount of powder directly to the top of the plasma, like salt in a vibrating screen. This technology is difficult to install on the W7-X in the available installation time, but it may be integrated into the device in the future.
Lunsford said: "Instead, we had to give up everything and shrink a powder dropper to the size of a loaf of bread so that it can be mounted on a robotic arm that reaches the inside of the plasma." "For the prototype, it It runs very well."
What excites the researchers is to see the temperature rise after the injection. The plasma physics paper reports that the injected boron carbide appears to cool the edges of the plasma and increase the density gradient. "This means that as you move from the edge to the core, the plasma edge becomes denser faster," Lunsford said. "This in turn reduces turbulence, the complex vortex that takes heat away from the plasma." As the turbulence is reduced, the plasma retains more heat and makes the fusion reaction more efficient.
"These results are very exciting," said Novimir Pablant, a PPPL physicist, one of the paper's co-authors. "There are only a few ways to heat the ions, so any new tool helps a lot. Now we hope to use this technique to better control the shape of the plasma."
The researchers plan to conduct more experiments to confirm this discovery. They will also work with W7-X scientists, who have discovered other ways to change the shape of the plasma through techniques such as launching hydrogen particles into the plasma core at high speeds. Physicists say that these contour shaping tools are an important step in advancing fusion research.
The collaborators in this research include scientists from the Max Planck Institute for Plasma Physics in Germany and the Jülich Research Center, the Hungarian Energy Research Center and the Spanish National Laboratory for Fusion. The research was supported by the U.S. Department of Energy's Office of Science (Fusion Energy Science) and the European Atomic Energy Consortium Research and Training Program.
Located at the Forestal campus of Princeton University in Princeboro, New Jersey, PPPL is committed to creating new knowledge about plasma physics-superheated charged gases-and developing practical solutions for the generation of fusion energy. The laboratory is managed by the Office of University Science of the US Department of Energy, which is the largest supporter of basic research in the physical sciences of the United States and is dedicated to solving some of the most pressing challenges of our time. For more information, please visit https://energy.gov/science
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