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

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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 ... continued below

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2.6 Megabytes pages

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Bush, C.E.; Bell, M.G.; Bell, R.E.; Boedo, J.; Fredrickson, E.D.; Kaye, S.M. et al. January 9, 2003.

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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.

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2.6 Megabytes pages

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INIS; OSTI as DE00809958

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  • Other Information: PBD: 9 Jan 2003

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  • Report No.: PPPL-3764
  • Grant Number: AC02-76CH03073
  • DOI: 10.2172/809958 | External Link
  • Office of Scientific & Technical Information Report Number: 809958
  • Archival Resource Key: ark:/67531/metadc733696

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  • January 9, 2003

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  • Oct. 18, 2015, 6:40 p.m.

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  • April 15, 2016, 8:34 p.m.

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Bush, C.E.; Bell, M.G.; Bell, R.E.; Boedo, J.; Fredrickson, E.D.; Kaye, S.M. et al. Configuration and Heating Power Dependence of Edge Parameters and H-mode Dynamics in National Spherical Torus Experiment (NSTX), report, January 9, 2003; Princeton, New Jersey. (digital.library.unt.edu/ark:/67531/metadc733696/: accessed September 22, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.