Developing snowflake divertor physics basis in the DIII-D, NSTX and NSTX-U tokamaks aimed at the divertor power exhaust solution.

V. A. Soukhanovskii, S. L. Allen, M. E. Fenstermacher, C. J. Lasnier, M. A. Makowski, A. G. McLean, E. T. Meier, W. H. Meyer, T. D. Rognlien, D. D. Ryutov, F. Scotti, E. Kolemen, R. E. Bell, A. Diallo, S. Gerhardt, R. Kaita, S. Kaye, B. P. Leblanc, R. Maingi, J. E. MenardM. Podesta, A. L. Roquemore, R. J. Groebner, A. W. Hyatt, A. W. Leonard, T. H. Osborne, T. W. Petrie, J. W. Ahn, R. Raman, J. G. Watkins

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Experimental results from the National Spherical Torus Experiment (NSTX), a medium-size spherical tokamak with a compact divertor, and DIII-D, a large conventional aspect ratio tokamak, demonstrate that the snowflake (SF) divertor configuration (D.D. Ryutov, Phys. Plasmas, 14, 064502, 2007) may provide a promising solution for mitigating divertor heat loads and target plate erosion compatible with core H-mode confinement in future fusion devices, where the standard radiative divertor solution may be inadequate. In NSTX, where the initial high-power SF experiment were performed, the SF divertor was compatible with H-mode confinement, and led to the destabilization of large ELMs. However, a stable partial detachment of the outer strike point was also achieved where inter-ELM peak heat flux was reduced by factors 3-5, and peak ELM heat flux was reduced by up to 80% (cf. standard divertor). The DIII-D studies show the SF divertor enables significant power spreading in attached and radiative divertor conditions. Results include: compatibility with the core and pedestal, peak inter-ELM divertor heat flux reduction due to geometry at lower ne, and ELM energy and divertor peak heat flux reduction, especially prominent in radiative D2-seeded SF divertor, and nearly complete power detachment and broader radiated power distribution in the radiative D2-seeded SF divertor at PSOL = 3-4 MW. A variety of SF configurations can be supported by the divertor coil set in NSTX Upgrade. Edge transport modeling with the multi-fluid edge transport code UEDGE shows that the radiative SF divertor can successfully reduce peak divertor heat flux for the projected PSOL ≃ 9 MW case. The radiative SF divertor with carbon impurity provides a wider ne operating window, 50% less argon is needed in the impurity-seeded SF configuration to achieve similar qpeak reduction factors (cf. standard divertor).

Original languageEnglish (US)
Title of host publication2015 IEEE 26th Symposium on Fusion Engineering, SOFE 2015
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Electronic)9781479982646
StatePublished - May 31 2016
Event26th IEEE Symposium on Fusion Engineering, SOFE 2015 - Austin, United States
Duration: May 31 2015Jun 4 2015

Publication series

NameProceedings - Symposium on Fusion Engineering


Other26th IEEE Symposium on Fusion Engineering, SOFE 2015
Country/TerritoryUnited States

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering


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