Scientists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have furthered understanding of a barrier that can prevent doughnut-shaped fusion facilities known as tokamaks from operating at high efficiency by causing vital heat to be lost from them.
Led by PPPL physicist Roscoe White, the research team used computers to simulate a type of plasma movement that can bump highly energetic particles from the core to the edge, a phenomenon that could occur in ITER, the multinational tokamak being built in France to demonstrate the feasibility of fusion as an energy source.
“For any fusion device to work, you need to make sure that the highly energetic particles within it are very well confined within the plasma core,” said PPPL physicist Vinícius Duarte, a member of the research team that reported the results in Physics of Plasmas. “If those particles drift to the edge of the plasma, you can’t sustain the steady-state burning plasma needed to make fusion-powered electricity a reality.”
Duarte refers to a phenomenon called “chirping” that occurs when the frequency of the waves of plasma that interact with highly energetic particles changes suddenly, ultimately causing energy to escape from the plasma core and produce rapidly changing tones. The new findings, which elucidate aspects of how chirping forms in a tokamak, could help researchers figure out how to thwart the chirps and keep in the vital heat. Preventing the sudden frequency changes could also protect the tokamak walls from the sudden release of concentrated and damaging bursts of energy.
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