Effects of divertor geometry on H-mode pedestal structure in attached and detached plasmas in the DIII-D tokamak [Effects of divertor geometry on H-mode pedestal structure near divertor detachment in the DIII-D tokamak]

Wang, H. Q.; Guo, H. Y.; Leonard, A. W.; Moser, A. L.; Osborne, T. H.; Snyder, P. B.; Belli, E.; Groebner, R. J.; Thomas, D. M.; Watkins, J. G.; Yan, Z.

doi:10.1088/1741-4326/aacbde

Effects of divertor geometry on H-mode pedestal structure in attached and detached plasmas in the DIII-D tokamak [Effects of divertor geometry on H-mode pedestal structure near divertor detachment in the DIII-D tokamak]

Journal Article · Thu Jul 05 00:00:00 EDT 2018 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/aacbde· OSTI ID:1461182

Wang, H. Q. ^[1]; Guo, H. Y. ^[2]; ^[2]; Moser, A. L. ^[2]; Osborne, T. H. ^[2]; Snyder, P. B. ^[2]; Belli, E. ^[2]; Groebner, R. J. ^[2]; Thomas, D. M. ^[2]; Watkins, J. G. ^[3]; Yan, Z. ^[4]

Oak Ridge Associated Univ., Oak Ridge, TN (United States); General Atomics
General Atomics, San Diego, CA (United States)
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Univ. of Wisconsin-Madison, Madison, WI (United States)

Dedicated experiments have been performed in the DIII-D tokamak to assess the influence of divertor geometry on the H-mode pedestal structure. It has been found that in both attached and detached plasmas, compared to the open divertor, the more closed divertor traps more neutrals in the divertor region, leading to lower pedestal fueling and thus results in lower density and higher temperature at the pedestal top. In addition, approaching divertor detachment by increasing the gas-puffing rate, for different divertor geometries, the pedestal width exhibits different trends. In the attached plasma, the pedestal width agrees well with the theoretical and empirical pedestal-poloidal-beta scaling. However, during divertor detachment, in the open divertor the pedestal width is significantly reduced. In contrast, for detached plasmas with the more closed divertor, the pedestal is significantly wider, by up to 50% compared to the theoretical scaling. Moreover, near divertor detachment, the open diverted plasma exhibits a more aligned density and temperature pedestal profile, while in the closed divertor the detachment results in a relative shift (up to 50% of the pedestal width) between the density and temperature pedestal profiles. Such changes in the pedestal structure, coupled with reduced pedestal fueling, allow for the achievement of divertor detachment while retaining high pedestal performance with the more closed divertor.

View Accepted Manuscript (DOE)

Research Organization:: General Atomics, San Diego, CA (United States)

Sponsoring Organization:: USDOE Office of Nuclear Energy (NE)

Contributing Organization:: The DIII-D group

Grant/Contract Number:: FC02-04ER54698

OSTI ID:: 1461182

Alternate ID(s):: OSTI ID: 22929477

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 9 Vol. 58; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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Effects of divertor geometry on H-mode pedestal structure in attached and detached plasmas in the DIII-D tokamak [Effects of divertor geometry on H-mode pedestal structure near divertor detachment in the DIII-D tokamak]

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