Configuration and Heating Power Dependence of Edge Parameters and H-mode Dynamics in National Spherical Torus Experiment (NSTX)

Bush, C.E. ; Bell, M.G. ; Bell, R.E. ; Boedo, J. ; Fredrickson, E.D. ; Kaye, S.M. ; Kubota, S. ; LeBlanc, B.P. ; Maingi, R. ; Maqueda, R.J. ; Sabbagh, S.A. ; Soukhanovskii, V.A. ; Stutman, D. ; Swain, D.W. ; Wilgen, J.B. ; Zweben, S.J. ; Davis, W.M. ; Gates, D.A. ; Johnson, D.W. ; Kaita, R. ; Kugel, H.W. ; Mastrovito, D. ; Medley, S. ; Menard, J.E. ; Mueller, D. ; Ono, M. ; Paoletti, F. ; Paul, S.J. ; Peng, Y-K.M. ; Raman, R. ; Roney, P.G. ; Roquemore, A.L. ; Skinner, C.H. ; Synakowski, E.J. ; Taylor, G. ; Team, the NSTX

Princeton University. Plasma Physics Laboratory.

关键词: Nstx Tokamak;    Heating;    70 Plasma Physics And Fusion Technology;    Experimental Reactors;    Confinement Time;   

DOI  :  10.2172/809958
RP-ID  :  PPPL-3764
RP-ID  :  AC02-76CH03073
RP-ID  :  809958

美国|英语

来源: UNT Digital Library

【 摘 要 】

Edge parameters play a critical role in H-mode (high-confinement mode) access, which is a key component of plasma discharge optimization in present-day toroidal confinement experiments and the design of next-generation devices. Because the edge magnetic topology of a spherical torus (ST) differs from a conventional aspect ratio tokamak, H-modes in STs exhibit important differences compared with tokamaks. The dependence of the NSTX (National Spherical Torus Experiment) edge plasma on heating power, including the L-H transition requirements and the occurrence of edge-localized modes (ELMs), and on divertor configuration is quantified. Comparisons between good L-modes (low-confinement modes) and H-modes show greater differences in the ion channel than the electron channel. The threshold power for the H-mode transition in NSTX is generally above the predictions of a recent ITER (International Thermonuclear Experimental Reactor) scaling. Correlations of transition and ELM phenomena with turbulent fluctuations revealed by Gas Puff Imaging (GPI) and reflectometry are observed. In both single-null and double-null divertor discharges, the density peaks off-axis, sometimes developing prominent ''ears'' which can be sustained for many energy confinement times, tau subscript ''E'', in the absence of ELMs. A wide variety of ELM behavior is observed, and ELM characteristics depend on configuration and fueling.