New Research Enables Investigations of Zonal Flows in Fusion Reaction

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Researchers from Hefei University of Technology detected geodesic acoustic mode at two different points simultaneously within a fusion reactor

Fusion reaction is a source of abundant clean energy, where isotopes of hydrogen combine to form helium with release of large amounts of energy in the process. However, fusion power plants require to trigger low-to-high confinement transition (L-H transition) to be effective. Plasma temperature and density in the reaction increase after an L-H transition, which in turn produces more power. L-H transition is associated with zonal flows of plasma. In theory, zonal flows in a plasma consist of both a stationary flow with a near-zero frequency and geodesic acoustic mode (GAM), which oscillates at a higher frequency. Now, researchers from Hefei University of Technology detected GAM at two different points simultaneously within the fusion reactor. The new experimental setup is expected to be a beneficial diagnostic tool that helps to investigate the physics of zonal flows and their role in L-H transition. The research was published in the journal Physics of Plasmas on September 11, 2018.

Zonal flows are evident in places with turbulence such as inside a fusion device, a planet’s atmosphere, and Jovian belts and zones of the planet Jupiter. Zonal flows in fusion plasmas are necessary for regulating turbulence and particle transport within the reactor. The researchers used the Experimental Advanced Superconducting Tokamak (EAST), which is a magnetic fusion energy reactor in Hefei, China. To detect fluctuations in turbulence and plasma density with high precision, two Doppler reflectometers were installed on different sides of EAST. The detected GAM had a pitch of F, five octaves above middle C. The measurements taken at the two points showed that each reflectometer also picked up information from nonzonal flows. However, accurate zonal flows information is required from multipoint measurement. Both measurements revealed that GAM interacted with the ambient turbulence. The researchers are focused on further investigating the role of zonal flows in turbulence and turbulent transport within EAST.

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