Developing snowflake divertor physics basis in the DIII-D, NSTX and NSTX-U tokamaks aimed at the divertor power exhaust solution [Snowflake divertor experiments in the DIII-D, NSTX and NSTX-U tokamaks aimed at the development of the divertor power exhaust solution]

Journal Article · Thu Jun 02 00:00:00 EDT 2016 · 2015 IEEE 26th Symposium on Fusion Engineering (SOFE)

DOI:https://doi.org/10.1109/SOFE.2015.7482263· OSTI ID:1373886

Soukhanovskii, V. A. ^[1]; Allen, S. L. ^[1]; Fenstermacher, M. E. ^[1]; Lasnier, C. J. ^[1]; Makowski, M. A. ^[1]; McLean, A. G. ^[1]; Meier, E. T. ^[2]; Meyer, W. H. ^[1]; Rognlien, T. D. ^[1]; Ryutov, D. D. ^[1]; Scotti, F. ^[1]; Kolemen, E. ^[3]; Bell, R. E. ^[3]; Diallo, A. ^[3]; Gerhardt, S. ^[3]; Kaita, R. ^[3]; Kaye, S. ^[3]; LeBlanc, B. P. ^[3]; Maingi, R. ^[3]; Menard, J. E. ^[3] ; Podesta, M. ^[3]; Roquemore, A. L. ^[3]; Groebner, R. J. ^[4]; Hyatt, A. W. ^[4]; Leonard, A. W. ^[4]; Osborne, T. H. ^[4]; Petrie, T. W. ^[4]; Ahn, J. -W. ^[5]; Raman, R. ^[6]; Watkins, J. G. ^[7]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); College of William and Mary, Williamsburg, VA (United States)
3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
4. General Atomics, San Diego, CA (United States)
5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
6. Univ. of Washington, Seattle, WA (United States)
7. Sandia National Lab. (SNL-CA), Livermore, CA (United States)

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 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 n_e, 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 P_SOL = 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 P_SOL ≃9 MW case. In conclusion, the radiative SF divertor with carbon impurity provides a wider n_e operating window, 50% less argon is needed in the impurity-seeded SF configuration to achieve similar q_peak reduction factors (cf. standard divertor).

• Research Organization: General Atomics, San Diego, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: FC02-04ER54698
• OSTI ID: 1373886
• Journal Information: 2015 IEEE 26th Symposium on Fusion Engineering (SOFE), Conference: 2015 IEEE 26. Symposium on Fusion Engineering (SOFE), Austin, TX (United States), 31 May-4 Jun 2015
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY