Suppressed ion-scale turbulence in a hot high-β plasma

• Published in: Nature communications 2016-12, Vol.7 (1), p.13860-13860, Article 13860
• Main Authors: Schmitz, L., Fulton, D. P., Ruskov, E., Lau, C., Deng, B. H., Tajima, T., Binderbauer, M. W., Holod, I., Lin, Z., Gota, H., Tuszewski, M., Dettrick, S. A., Steinhauer, L. C.
• Format: Article
• Language: English
• Subjects: 639/766/1960/1136; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms13860

An economic magnetic fusion reactor favours a high ratio of plasma kinetic pressure to magnetic pressure in a well-confined, hot plasma with low thermal losses across the confining magnetic field. Field-reversed configuration (FRC) plasmas are potentially attractive as a reactor concept, achieving high plasma pressure in a simple axisymmetric geometry. Here, we show that FRC plasmas have unique, beneficial microstability properties that differ from typical regimes in toroidal confinement devices. Ion-scale fluctuations are found to be absent or strongly suppressed in the plasma core, mainly due to the large FRC ion orbits, resulting in near-classical thermal ion confinement. In the surrounding boundary layer plasma, ion- and electron-scale turbulence is observed once a critical pressure gradient is exceeded. The critical gradient increases in the presence of sheared plasma flow induced via electrostatic biasing, opening the prospect of active boundary and transport control in view of reactor requirements. Magnetic fusion reactors with higher ratio of plasma kinetic pressure to magnetic pressure are economically desirable. The authors demonstrate a path to such a reactor in a field reversed configuration that can attain microstability and reduced particle and thermal fluxes by manipulating the shear flow.