Helium transport in enhanced confinement regimes on the TEXTOR and DIII-D tokamaks

  • D. L. Hillis
  • , J. T. Hogan
  • , K. H. Finken
  • , W. P. West
  • , R. R. Weynants
  • , M. R. Wade
  • , K. Akaishi
  • , W. Y. Baek
  • , J. Boedo
  • , K. H. Burrell
  • , R. W. Conn
  • , K. H. Dippel
  • , R. Doerner
  • , H. Euringer
  • , D. Finkenthal
  • , D. S. Gray
  • , C. M. Greenfield
  • , P. Gohil
  • , R. J. Groebner
  • , J. Kim
  • C. C. Klepper, A. M. Messiaen, P. K. Mioduszewski, A. Miyahara, R. Moyer, G. Van Oost, A. Pospieszcyk, D. Reiter, D. Rusbüldt, R. P. Seraydarian, R. Van Nieuwenhove, G. H. Wolf

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

Comparisons of helium (He) transport and exhaust in L-mode and in an enhanced confinement regime (H-mode), which is induced by a polarizing electrode, have been made for the TEXTOR tokamak. The results show an increased tendency for He accumulation when bulk plasma energy and particle confinement are improved during the polarization-induced H-mode. Since these results imply that a high He pumping efficency may be necessary for H-mode burning plasmas, we have begun exploring He transport in a divertor H-mode, similar to that proposed for the international thermonuclear experimental reactor (ITER). A collaborative program has been initiated to measure He transport and scaling on DIII-D during L-mode, H-mode, and ELMing H-mode plasma conditions. To simulate the presence of He ash in DIII-D, a 25 ms He puff is injected into a DIII-D plasma, resulting in a He concentration of ≈5%. The time dependence of the He2+ density profiles in the plasma core is measured by charge-exchange recombination spectroscopy at 11 radial locations.

Original languageEnglish
Pages (from-to)35-44
Number of pages10
JournalJournal of Nuclear Materials
Volume196-198
Issue numberC
DOIs
StatePublished - Dec 1 1992

Funding

For future steady-state tokamaks, such as the international thermonuclear experimental reactor (ITER), continuous purging of the helium (He) ash is essential. Estimates [1]s how that newly created He ions must be removed within 7 to 15 energy confinement times to maintain continuous reactor operation (r~e/r E < 7- 15). Recent measurements [2-6] on TEXTOR and other tokamaks demonstrate that He can be readily transported from the plasma core during L-mode plasma discharges. TEXTOR experiments use the advanced limiter test-II (ALT-II) system, a toroidal belt * Research sponsored in part by the Office of Fusion Energy, US Department of Energy, under contract DE-AC06-84OR21400 with Martin Marietta Energy Systems, Inc., and by the US Department of Energy under contract DE-AC03-89ER51114.

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