A long-pulse high-confinement plasma regime in the Experimental Advanced Superconducting Tokamak

• Published in: Nature physics Vol. 9; no. 12; pp. 817 - 821
• Main Authors: Li, J., Guo, H. Y., Wan, B. N., Gong, X. Z., Liang, Y. F., Xu, G. S., Gan, K. F., Hu, J. S., Wang, H. Q., Wang, L., Zeng, L., Zhao, Y. P., Denner, P., Jackson, G. L., Loarte, A., Maingi, R., Menard, J. E., Rack, M., Zou, X. L.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.12.2013; Nature Publishing Group
• Subjects: 639/766/1960/1136; Atomic; Boundary control; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Deposition; Footprints; Heat transport; Lithium; Mathematical and Computational Physics; Molecular; Optical and Plasma Physics; Physics; Plasma; Plasma (physics); Superconductivity; Theoretical; Tokamak devices; Walls
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys2795

High-performance and long-pulse operation is a crucial goal of current magnetic fusion research. Here, we demonstrate a high-confinement plasma regime known as an H-mode with a record pulse length of over 30 s in the Experimental Advanced Superconducting Tokamak sustained by lower hybrid wave current drive (LHCD) with advanced lithium wall conditioning. We find that LHCD provides a flexible boundary control for a ubiquitous edge instability in H-mode plasmas known as an edge-localized mode, which leads to a marked reduction in the heat load on the vessel wall compared with standard edge-localized modes. LHCD also induces edge plasma ergodization that broadens the heat deposition footprint. The heat transport caused by this ergodization can be actively controlled by regulating the edge plasma conditions. This potentially offers a new means for heat-flux control, which is a key issue for next-step fusion development. A high-confinement plasma that is potentially useful for controlled fusion has now been sustained for over 30 s. The Experimental Advanced Superconducting Tokamak in Hefei, China, achieved this record pulse length by first confining the plasma using lithium-treated vessel walls, and then maintaining it with a so-called lower hybrid current drive.