New Discoveries About the Nature of Light Could Improve Methods for Heating Fusion Plasma

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Rendition of light particles (enlarged) being emitted by a lighthouse
Source: Kyle Palmer/PPPL Communications Department

June 11, 2024 | Originally published by Princeton Plasma Physics Laboratory on May 23, 2024

Both literally and figuratively, light pervades the world. It banishes darkness, conveys telecommunications signals between continents, and makes visible the invisible, from faraway galaxies to the smallest bacterium. Light can also help heat the plasma within ring-shaped devices known as tokamaks as scientists worldwide strive to harness the fusion process to generate green electricity.

Now, scientists have made discoveries about light particles known as photons that could aid the quest for fusion energy. By performing a series of mathematical calculations, the researchers found that one of a photon’s basic properties is topological, meaning that it doesn’t change even as the photon moves through different materials and environments.

This property is polarization, the direction — left or right — that electric fields take as they move around a photon. Because of basic physical laws, a photon’s polarization helps determine the direction the photon travels and limits its movement. Therefore, a beam of light made up of only photons with one type of polarization cannot spread into every part of a given space. These findings demonstrate the Princeton Plasma Physics Laboratory’s (PPPL’s) strengths in theoretical physics and fusion research.

“Having a more accurate understanding of the fundamental nature of photons could lead to scientists designing better light beams for heating and measuring plasma,” said Hong Qin, a principal research physicist at the U.S. Department of Energy’s (DOE’s) PPPL and coauthor of a paper reporting the results in Physical Review D.

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