(June 30, 2015) Researchers
at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory
(PPPL) have developed a detailed model of the source of a puzzling limitation
on fusion reactions. The findings, published this month in Physics of Plasmas,
complete and confirm previous PPPL research and could lead to steps to overcome
the barrier if the model proves consistent with experimental data. “We used to
have correlation,” said physicist David Gates, first author of the paper. “Now
we believe we have causation.” This work was supported by the DOE Office of
Science.
At issue is a problem known as the “density limit” that
keeps donut-shaped fusion facilities called tokamaks from operating at peak
efficiency. This limit occurs when the superhot, charged plasma gas that fuels
fusion reactions reaches a certain density and spirals apart in a flash of
light, shutting down the reaction. Overcoming the limit could facilitate the
development of fusion as a safe, clean and abundant source of energy for
generating electricity.