Dynamical Evolution of Pedestal Parameters in ELMy H-mode in the National Spherical Torus Experiment

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Characterizations of the pedestal parameter dynamics throughout the edge localized modes(ELM) cycles are performed on the National Spherical Torus Experiment (NSTX, [M. Ono et al., Nucl. Fusion 40, 557 (2000)]). A clear buildup of the pedestal height is observed between ELMs for three di erent plasma currents, which tends to saturate prior to the onset of ELM at low and medium plasma current. Similarly, the pedestal width increases with no clear evidence of saturation during an ELM cycle. The maximum pedestal gradient increases as a function of plasma current, reaches a nominal value after the ELM crash, and remains constant ... continued below

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Diallo, A; Kubota, S; Sontag, A; Osborne, T; Podesta, M; Bell, R E et al. July 27, 2011.

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Description

Characterizations of the pedestal parameter dynamics throughout the edge localized modes(ELM) cycles are performed on the National Spherical Torus Experiment (NSTX, [M. Ono et al., Nucl. Fusion 40, 557 (2000)]). A clear buildup of the pedestal height is observed between ELMs for three di erent plasma currents, which tends to saturate prior to the onset of ELM at low and medium plasma current. Similarly, the pedestal width increases with no clear evidence of saturation during an ELM cycle. The maximum pedestal gradient increases as a function of plasma current, reaches a nominal value after the ELM crash, and remains constant until the end of the ELM cycle. The pedestal height just prior to the onset of ELM is shown to increase quadratically with plasma current. The pedestal width Δ is proportional to the square-root of the poloidal Β at the top of the pedestal. Coherent density uctuations strongly increasing at the plasma edge are observed to be maximum after the ELM crash and to decay during the rest of the ELM cycle. Finally, the pedestal parameters evolution during the ELM cycle as well as the scaling with Ip of the pedestal pressure prior to the onset ELM are found to be qualitatively consistent with the peeling ballooning theory.

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  • Nuclear Fusion (July 2011)

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  • Report No.: PPPL-4645
  • Grant Number: DE-ACO2-09CH11466
  • DOI: 10.2172/1062583 | External Link
  • Office of Scientific & Technical Information Report Number: 1062583
  • Archival Resource Key: ark:/67531/metadc837217

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  • July 27, 2011

Added to The UNT Digital Library

  • May 19, 2016, 9:45 a.m.

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  • July 18, 2016, 5:24 p.m.

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Diallo, A; Kubota, S; Sontag, A; Osborne, T; Podesta, M; Bell, R E et al. Dynamical Evolution of Pedestal Parameters in ELMy H-mode in the National Spherical Torus Experiment, report, July 27, 2011; Princeton, New Jersey. (digital.library.unt.edu/ark:/67531/metadc837217/: accessed April 24, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.