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Title: High fusion performance in Super H-mode experiments on Alcator C-Mod and DIII-D

Abstract

The “Super H-Mode” regime is predicted to enable pedestal height and fusion performance substantially higher than standard H-Mode operation. This regime exists due to a bifurcation of the pedestal pressure, as a function of density, that is predicted by the EPED model to occur in strongly shaped plasmas above a critical pedestal density. Experiments on Alcator C-Mod and DIII-D have achieved access to the Super H-Mode (and Near Super H) regime, and obtained very high pedestal pressure, including the highest achieved on a tokamak ( p ped ~80 kPa) in C-Mod experiments operating near the ITER magnetic field. DIII-D Super H experiments have demonstrated strong performance, including the highest stored energy in the present configuration of DIII-D ( W ~ 2.2-3.2MJ), while utilizing only about half of the available heating power ( P heat ~ 7-12 MW). These DIII-D experiments have obtained the highest value of peak fusion gain, Q DT, equiv ~ 0.5, achieved on a medium scale ( R < 2m) tokamak. Sustained high performance operation (β N ~ 2.9, H 98 ~ 1.6) has been achieved utilizing n = 3 magnetic perturbations for density and impurity control. Pedestal and global confinement have been maintained in the presencemore » of deuterium and nitrogen gas puffing, which enables a more radiative divertor condition. Here, a pair of simple performance metrics is developed to assess and compare regimes. Super H-Mode access is predicted for ITER and expected, based on both theoretical prediction and observed normalized performance, to allow ITER to achieve its goals (Q = 10) at I p < 15MA, and to potentially enable more compact, cost effective pilot plant and reactor designs.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [1]; ORCiD logo [1];  [1]; ORCiD logo [3]; ORCiD logo [1]; ORCiD logo [1];  [2]; ORCiD logo [3];  [1];  [2];  [3]; ORCiD logo [2]; ORCiD logo [3];  [1];  [4];  [1];  [3];  [1] more »; ORCiD logo [5];  [6] « less
  1. General Atomics, San Diego, CA (United States)
  2. MIT Plasma Science and Fusion Center, Cambridge, MA (United States)
  3. Princeton Univ., NJ (United States)
  4. College of William and Mary, Williamsburg, VA (United States)
  5. Univ. of York, York (United Kingdom of Great Britain and Northern Ireland); Culham Center for Fusion Energy, Oxon (United Kingdom of Great Britain and Northern Ireland)
  6. Univ. of California, Irvine, CA (United States)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1572159
Grant/Contract Number:  
[FG02-95ER54309]
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
[ Journal Volume: 59; Journal Issue: 8]; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; pedestal; tokamak; fusion gain; Super H Mode; EPED; DIII-D; Alcator C-Mod

Citation Formats

Snyder, P. B., Hughes, J. W., Osborne, T. H., Paz-Soldan, C., Solomon, W. M., Knolker, M., Eldon, D., Evans, T., Golfinopoulos, T., Grierson, B. A., Groebner, R. J., Hubbard, A. E., Kolemen, E., LaBombard, B., Laggner, F. M., Meneghini, O., Mordijck, S., Petrie, T., Scott, S., Wang, H. Q., Wilson, H. R., and Zhu, Y. B. High fusion performance in Super H-mode experiments on Alcator C-Mod and DIII-D. United States: N. p., 2019. Web. doi:10.1088/1741-4326/ab235b.
Snyder, P. B., Hughes, J. W., Osborne, T. H., Paz-Soldan, C., Solomon, W. M., Knolker, M., Eldon, D., Evans, T., Golfinopoulos, T., Grierson, B. A., Groebner, R. J., Hubbard, A. E., Kolemen, E., LaBombard, B., Laggner, F. M., Meneghini, O., Mordijck, S., Petrie, T., Scott, S., Wang, H. Q., Wilson, H. R., & Zhu, Y. B. High fusion performance in Super H-mode experiments on Alcator C-Mod and DIII-D. United States. doi:10.1088/1741-4326/ab235b.
Snyder, P. B., Hughes, J. W., Osborne, T. H., Paz-Soldan, C., Solomon, W. M., Knolker, M., Eldon, D., Evans, T., Golfinopoulos, T., Grierson, B. A., Groebner, R. J., Hubbard, A. E., Kolemen, E., LaBombard, B., Laggner, F. M., Meneghini, O., Mordijck, S., Petrie, T., Scott, S., Wang, H. Q., Wilson, H. R., and Zhu, Y. B. Mon . "High fusion performance in Super H-mode experiments on Alcator C-Mod and DIII-D". United States. doi:10.1088/1741-4326/ab235b. https://www.osti.gov/servlets/purl/1572159.
@article{osti_1572159,
title = {High fusion performance in Super H-mode experiments on Alcator C-Mod and DIII-D},
author = {Snyder, P. B. and Hughes, J. W. and Osborne, T. H. and Paz-Soldan, C. and Solomon, W. M. and Knolker, M. and Eldon, D. and Evans, T. and Golfinopoulos, T. and Grierson, B. A. and Groebner, R. J. and Hubbard, A. E. and Kolemen, E. and LaBombard, B. and Laggner, F. M. and Meneghini, O. and Mordijck, S. and Petrie, T. and Scott, S. and Wang, H. Q. and Wilson, H. R. and Zhu, Y. B.},
abstractNote = {The “Super H-Mode” regime is predicted to enable pedestal height and fusion performance substantially higher than standard H-Mode operation. This regime exists due to a bifurcation of the pedestal pressure, as a function of density, that is predicted by the EPED model to occur in strongly shaped plasmas above a critical pedestal density. Experiments on Alcator C-Mod and DIII-D have achieved access to the Super H-Mode (and Near Super H) regime, and obtained very high pedestal pressure, including the highest achieved on a tokamak (pped ~80 kPa) in C-Mod experiments operating near the ITER magnetic field. DIII-D Super H experiments have demonstrated strong performance, including the highest stored energy in the present configuration of DIII-D (W ~ 2.2-3.2MJ), while utilizing only about half of the available heating power (Pheat ~ 7-12 MW). These DIII-D experiments have obtained the highest value of peak fusion gain, Q DT, equiv ~ 0.5, achieved on a medium scale (R < 2m) tokamak. Sustained high performance operation (βN ~ 2.9, H98 ~ 1.6) has been achieved utilizing n = 3 magnetic perturbations for density and impurity control. Pedestal and global confinement have been maintained in the presence of deuterium and nitrogen gas puffing, which enables a more radiative divertor condition. Here, a pair of simple performance metrics is developed to assess and compare regimes. Super H-Mode access is predicted for ITER and expected, based on both theoretical prediction and observed normalized performance, to allow ITER to achieve its goals (Q = 10) at I p < 15MA, and to potentially enable more compact, cost effective pilot plant and reactor designs.},
doi = {10.1088/1741-4326/ab235b},
journal = {Nuclear Fusion},
number = [8],
volume = [59],
place = {United States},
year = {2019},
month = {6}
}

Journal Article:
Free Publicly Available Full Text
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Figures / Tables:

Figure 1 Figure 1: (a) Illustration of the $EPED$ model, which predicts pedestal height and width via calculated P-B (blue lines) and $KBM$ (green dashed line) constraints. Most commonly only a single solution (black circle) is found, but for strong shaping above a critical density, this solution bifurcates and two additional solutionsmore » (red circles), called “Super H mode” (SH) solutions are found. (b) $EPED$ predictions as a function of density indicate paths to Super H mode (arrows) via reaching sufficiently low pedestal density, and then increasing density over time. The green squares are measurements from DⅢ-D discharge 171322 at 1.6MA. Good agreement is found between the DⅢ-D observations and the $EPED$ predictions (thick red, blue and black lines), which indicate access to the Near Super H and Super H regime.« less

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