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Physicists improve the understanding of heat and particle flow at the edge of a fusion device

Physicists improve the understanding of heat and particle flow at the edge of a fusion device

The physical PPPL C.S. Chang. Credit: Elle Starkman

The physicists of the Princeton Plasma Physics Laboratory (PPPL) of the Department of Energy of the United States (DOE) have discovered valuable information about how the electrically charged gas known as "plasma" flows at the edge inside the fusion devices in the form of donuts called "tokamaks". The results mark an encouraging sign for the development of machines to produce fusion energy to generate electricity without generating long-term hazardous waste.

The result partially corroborates the findings of the PPPL that the width of the heat escape produced by the fusion reactions could be six times larger and, therefore, less narrow, concentrated and damaging, than had been thought. "These findings are good news for ITER," said the PPPL physicist C.S. Chang, lead author of a description of the research in Physics of plasmas, referring to the international fusion experiment under construction in France. "The findings show that heat escaping in ITER will have a lower chance of damaging the machine," Chang said.

The fusion, the power that drives the sun and stars, is the fusion of light elements in the form of plasma, the hot state and charged with matter composed of free electrons and atomic nuclei, which produces energy. Scientists around the world are trying to replicate the fusion on Earth to obtain a virtually inexhaustible energy supply to generate electricity.

The superhot plasma within the tokamaks, which can reach hundreds of millions of degrees, is confined by magnetic fields that hold the plasma of the walls of the machines. However, particles and heat can escape from confinement fields in the "magnetic separator", the boundary between magnetically confined and unconfined plasmas. At this limit, the field lines intersect at the so-called point X, the place where the waste heat and particles escape and hit a target called the "deviator plate".

The new findings reveal the striking effect of point X in the escape by showing that an electric charge shock similar to a hill occurs at point X. This electrical hill causes the plasma to circulate around it, which prevents the particles from of plasma travel between the upstream and downstream areas of the field lines in a straight path. Instead, like the cars that maneuver around a construction site, the plasma-charged particles deviate around the hill.

The researchers produced these findings with XGC, an advanced computer code developed with external collaborators in PPPL that models the plasma as a collection of individual particles rather than as a single fluid. The model, which showed that the connection between the upstream plasma located on point X and the plasma downstream below point X formed in a way not predicted by simpler codes, could lead to more accurate predictions about the leak and cause the future is great. – Facilities of scale less vulnerable to internal damages.

"This result shows that the previous model of field lines involving flow tubes is incomplete," Chang said, referring to the tubular areas surrounding the magnetic flux regions, "and that the current understanding of the interaction between plasmas In the ascending and descending sense, it is not our next step to discover a more precise relationship between ascending and descending flow plasmas using a code like ours, that knowledge will help us to develop more precise equations and improved reduced models, which in fact are already in progress ".

The team gains the most time from supercomputers to study the edge of fusion plasmas

More information:
C. Chang et al., Physics of the ion orbit of point X in the scraping layer and generation of an electrostatic potential perturbation located around point X, Physics of plasmas (2019). DOI: 10.1063 / 1.5072795

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Princeton Plasma Physics Laboratory

Physicists improve understanding of heat and particle flow at the edge of a fusion device (2019, April 15)
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