Ballooning instability preventing the H-mode access in plasmas with negative triangularity shape on the DIII-D tokamak

Saarelma, Samuli; Austin, Max E.; Knölker, M.; Marinoni, Alessandro; Paz-Soldan, Carlos; Schmitz, Lothar; Snyder, Philip B.

doi:10.1088/1361-6587/ac1ea4

Title: Ballooning instability preventing the H-mode access in plasmas with negative triangularity shape on the DIII-D tokamak

Journal Article · 07 September 2021 · Plasma Physics and Controlled Fusion

DOI: https://doi.org/10.1088/1361-6587/ac1ea4 · OSTI ID:1818123

^[1]; Austin, Max E. ^[2];

^[2]; Marinoni, Alessandro ^[3];

^[2];

^[4];

^[2]

Culham Centre for Fusion Energy, Oxon (United Kingdom); General Atomics
General Atomics, San Diego, CA (United States)
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Univ. of California, Los Angeles, CA (United States)

Infinite toroidal mode number (n=∞ ) ballooning mode analysis of negative triangularity discharges on DIII-D shows that the access to 2nd stability becomes strongly restricted when the top triangularity decreases even modestly from -0.18 to -0.36. This is observed in experiment to coincide with the suppression of the L-H-transition. Further theoretical analysis with ballooning mode limited pedestals shows that the threshold for opening the 2nd stability access rises from a pedestal temperature of 0.3 keV to 1 keV when the top triangularity is decreased from -0.18 to -0.36 indicating that to access the 2nd stability with the more negative triangular shape would require unrealistically high pedestal temperature. Furthermore, the pedestal predicted by the EPED code agrees with the experimental H-mode profile for the negative triangularity case but in contrast to positive triangular shapes the prediction shows no increase in pedestal height with increasing core pressure when triangularity is negative. This work provides a first model to predict when negative triangularity plasmas can be expected to access the H-mode.

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

Sponsoring Organization:: USDOE

Grant/Contract Number:: FC02-04ER54698; FG02-08ER54984; FG02-95ER54309; FG02-97ER54415

OSTI ID:: 1818123

Journal Information:: Plasma Physics and Controlled Fusion, Journal Name: Plasma Physics and Controlled Fusion Journal Issue: 10 Vol. 63; ISSN 0741-3335

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

References (38)

ELM divertor peak energy fluence scaling to ITER with data from JET, MAST and ASDEX upgrade Eich, T.; Sieglin, B.; Thornton, A. J. Nuclear Materials and Energy, Vol. 12 https://doi.org/10.1016/j.nme.2017.04.014	journal	August 2017
Numerical studies of edge localized instabilities in tokamaks Wilson, H. R.; Snyder, P. B.; Huysmans, G. T. A. Physics of Plasmas, Vol. 9, Issue 4 https://doi.org/10.1063/1.1459058	journal	April 2002
Erratum: “Neoclassical conductivity and bootstrap current formulas for general axisymmetric equilibria and arbitrary collisionality regime” [Phys. Plasmas 6 , 2834 (1999)] Sauter, O.; Angioni, C.; Lin-Liu, Y. R. Physics of Plasmas, Vol. 9, Issue 12 https://doi.org/10.1063/1.1517052	journal	December 2002
Advances in understanding quiescent H-mode plasmas in DIII-D Burrell, K. H.; West, W. P.; Doyle, E. J. Physics of Plasmas, Vol. 12, Issue 5 https://doi.org/10.1063/1.1894745	journal	May 2005
Development and validation of a predictive model for the pedestal height Snyder, P. B.; Groebner, R. J.; Leonard, A. W. Physics of Plasmas, Vol. 16, Issue 5 https://doi.org/10.1063/1.3122146	journal	May 2009
H-mode grade confinement in L-mode edge plasmas at negative triangularity on DIII-D Marinoni, A.; Austin, M. E.; Hyatt, A. W. Physics of Plasmas, Vol. 26, Issue 4 https://doi.org/10.1063/1.5091802	journal	April 2019
Influence of sheared poloidal rotation on edge turbulence Biglari, H.; Diamond, P. H.; Terry, P. W. Physics of Fluids B: Plasma Physics, Vol. 2, Issue 1 https://doi.org/10.1063/1.859529	journal	January 1990
Stable equilibria for bootstrap-current-driven low aspect ratio tokamaks Miller, R. L.; Lin-Liu, Y. R.; Turnbull, A. D. Physics of Plasmas, Vol. 4, Issue 4 https://doi.org/10.1063/1.872193	journal	April 1997
Scaling studies of the high mode pedestal Groebner, R. J.; Osborne, T. H. Physics of Plasmas, Vol. 5, Issue 5 https://doi.org/10.1063/1.872849	journal	May 1998
Neoclassical conductivity and bootstrap current formulas for general axisymmetric equilibria and arbitrary collisionality regime Sauter, O.; Angioni, C.; Lin-Liu, Y. R. Physics of Plasmas, Vol. 6, Issue 7 https://doi.org/10.1063/1.873240	journal	July 1999
The second region of stability against ballooning modes Greene, J. M.; Chance, M. S. Nuclear Fusion, Vol. 21, Issue 4 https://doi.org/10.1088/0029-5515/21/4/002	journal	April 1981
Ideal MHD ballooning stability in the vicinity of a separatrix Bishop, C. M.; Kirby, P.; Connor, J. W. Nuclear Fusion, Vol. 24, Issue 12 https://doi.org/10.1088/0029-5515/24/12/006	journal	December 1984
Divertor experiment on particle and energy control in neutral beam heated JT-60 discharges Nakamura, H.; Ando, T.; Yoshida, H. Nuclear Fusion, Vol. 28, Issue 1 https://doi.org/10.1088/0029-5515/28/1/004	journal	January 1988
H-mode experiments with outer and lower divertors in JT-60 Nakamura, H.; Tsuji, S.; Nagami, M. Nuclear Fusion, Vol. 30, Issue 2 https://doi.org/10.1088/0029-5515/30/2/004	journal	February 1990
Impact of plasma triangularity and collisionality on electron heat transport in TCV L-mode plasmas Camenen, Y.; Pochelon, A.; Behn, R. Nuclear Fusion, Vol. 47, Issue 7 https://doi.org/10.1088/0029-5515/47/7/002	journal	June 2007
RMP ELM suppression in DIII-D plasmas with ITER similar shapes and collisionalities Evans, T. E.; Fenstermacher, M. E.; Moyer, R. A. Nuclear Fusion, Vol. 48, Issue 2 https://doi.org/10.1088/0029-5515/48/2/024002	journal	January 2008
Pedestal stability comparison and ITER pedestal prediction Snyder, P. B.; Aiba, N.; Beurskens, M. Nuclear Fusion, Vol. 49, Issue 8 https://doi.org/10.1088/0029-5515/49/8/085035	journal	July 2009
A first-principles predictive model of the pedestal height and width: development, testing and ITER optimization with the EPED model Snyder, P. B.; Groebner, R. J.; Hughes, J. W. Nuclear Fusion, Vol. 51, Issue 10 https://doi.org/10.1088/0029-5515/51/10/103016	journal	August 2011
L–H transition studies on DIII-D to determine H-mode access for operational scenarios in ITER Gohil, P.; Evans, T. E.; Fenstermacher, M. E. Nuclear Fusion, Vol. 51, Issue 10 https://doi.org/10.1088/0029-5515/51/10/103020	journal	August 2011
Validation studies of gyrofluid and gyrokinetic predictions of transport and turbulence stiffness using the DIII-D tokamak Holland, C.; Kinsey, J. E.; DeBoo, J. C. Nuclear Fusion, Vol. 53, Issue 8 https://doi.org/10.1088/0029-5515/53/8/083027	journal	July 2013
Experimental survey of the L-H transition conditions in the DIII-D tokamak Carlstrom, T. N.; Gohil, P.; Watkins, J. G. Plasma Physics and Controlled Fusion, Vol. 36, Issue 7A https://doi.org/10.1088/0741-3335/36/7A/019	journal	July 1994
Edge localized modes (ELMs) Zohm, H. Plasma Physics and Controlled Fusion, Vol. 38, Issue 2 https://doi.org/10.1088/0741-3335/38/2/001	journal	February 1996
JET divertor geometry and plasma shape effects on the L–H transition threshold Andrew, Y.; Hawkes, N. C.; O'Mullane, M. G. Plasma Physics and Controlled Fusion, Vol. 46, Issue 5A https://doi.org/10.1088/0741-3335/46/5A/009	journal	April 2004
A quarter-century of H-mode studies Wagner, F. Plasma Physics and Controlled Fusion, Vol. 49, Issue 12B https://doi.org/10.1088/0741-3335/49/12B/S01	journal	November 2007
The effect of plasma triangularity on turbulent transport: modeling TCV experiments by linear and non-linear gyrokinetic simulations Marinoni, A.; Brunner, S.; Camenen, Y. Plasma Physics and Controlled Fusion, Vol. 51, Issue 5 https://doi.org/10.1088/0741-3335/51/5/055016	journal	March 2009
Pedestal properties of H-modes with negative triangularity using the EPED-CH model Merle, A.; Sauter, O.; Medvedev, S. Yu Plasma Physics and Controlled Fusion, Vol. 59, Issue 10 https://doi.org/10.1088/1361-6587/aa7ac0	journal	August 2017
Plasma performance and operational space without ELMs in DIII-D Paz-Soldan, C. Plasma Physics and Controlled Fusion, Vol. 63, Issue 8 https://doi.org/10.1088/1361-6587/ac048b	journal	June 2021
A gyrokinetic perspective on the JET-ILW pedestal Hatch, D. R.; Kotschenreuther, M.; Mahajan, S. Nuclear Fusion, Vol. 57, Issue 3 https://doi.org/10.1088/1741-4326/aa51e1	journal	January 2017
The effect of triangularity on fluctuations in a tokamak plasma Fontana, M.; Porte, L.; Coda, S. Nuclear Fusion, Vol. 58, Issue 2 https://doi.org/10.1088/1741-4326/aa98f4	journal	December 2017
Investigation of the role of pedestal pressure and collisionality on type-I ELM divertor heat loads in DIII-D Knolker, M.; Bortolon, A.; Canal, G. P. Nuclear Fusion, Vol. 58, Issue 9 https://doi.org/10.1088/1741-4326/aace92	journal	July 2018
L-mode-edge negative triangularity tokamak reactor Kikuchi, M.; Takizuka, T.; Medvedev, S. Nuclear Fusion, Vol. 59, Issue 5 https://doi.org/10.1088/1741-4326/ab076d	journal	April 2019
Direct gyrokinetic comparison of pedestal transport in JET with carbon and ITER-like walls Hatch, D. R.; Kotschenreuther, M.; Mahajan, S. M. Nuclear Fusion, Vol. 59, Issue 8 https://doi.org/10.1088/1741-4326/ab25bd	journal	July 2019
Diverted negative triangularity plasmas on DIII-D: the benefit of high confinement without the liability of an edge pedestal Marinoni, A.; Austin, M. E.; Hyatt, A. W. Nuclear Fusion, Vol. 61, Issue 11 https://doi.org/10.1088/1741-4326/ac1f60	journal	September 2021
Power requirement for accessing the H-mode in ITER Martin, Y. R.; Takizuka, T.; Group, the ITPA CDBM H-mode Threshold Data Journal of Physics: Conference Series, Vol. 123 https://doi.org/10.1088/1742-6596/123/1/012033	journal	July 2008
High Mode Number Stability of an Axisymmetric Toroidal Plasma Connor, J. W.; Hastie, R. J.; Taylor, J. B. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 365, Issue 1720 https://doi.org/10.1098/rspa.1979.0001	journal	February 1979
Role of Zonal Flow Predator-Prey Oscillations in Triggering the Transition to H-Mode Confinement Schmitz, L.; Zeng, L.; Rhodes, T. L. Physical Review Letters, Vol. 108, Issue 15 https://doi.org/10.1103/PhysRevLett.108.155002	journal	April 2012
Achievement of Reactor-Relevant Performance in Negative Triangularity Shape in the DIII-D Tokamak Austin, M. E.; Marinoni, A.; Walker, M. L. Physical Review Letters, Vol. 122, Issue 11 https://doi.org/10.1103/PhysRevLett.122.115001	journal	March 2019
Suppression of Large Edge-Localized Modes in High-Confinement DIII-D Plasmas with a Stochastic Magnetic Boundary Evans, T. E.; Moyer, R. A.; Thomas, P. R. Physical Review Letters, Vol. 92, Issue 23 https://doi.org/10.1103/PhysRevLett.92.235003	journal	June 2004

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70 PLASMA PHYSICS AND FUSION TECHNOLOGY
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