H-mode grade confinement in L-mode edge plasmas at negative triangularity on DIII-D

A. Marinoni; M. E. Austin; A. W. Hyatt; M. L. Walker; J. Candy; C. Chrystal; C. J. Lasnier; G. R. McKee; T. Odstrčil; C. C. Petty; M. Porkolab; J. C. Rost; O. Sauter; S. P. Smith; G. M. Staebler; C. Sung; K. E. Thome; A. D. Turnbull; L. Zeng

doi:10.1063/1.5091802

H-mode grade confinement in L-mode edge plasmas at negative triangularity on DIII-D

A. Marinoni, M. E. Austin, A. W. Hyatt, M. L. Walker, J. Candy, C. Chrystal, C. J. Lasnier, G. R. McKee, T. Odstrčil, C. C. Petty, M. Porkolab, J. C. Rost, O. Sauter, S. P. Smith, G. M. Staebler, C. Sung, K. E. Thome, A. D. Turnbull, L. Zeng

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Abstract

Plasmas with a negative triangularity shape have been created on the DIII-D tokamak that, despite maintaining standard L-mode edge radial profiles, reach volume averaged pressure levels typical of H-mode scenarios. Within the auxiliary power available for these experiments, plasmas exhibit near-zero power degradation while sustaining β_N = 2.7 and H_98,_y₂ = 1.2 for several energy confinement times. Detailed comparison with matched discharges at positive triangularity indicates that Trapped Electron Modes are weakened at negative triangularity, consistent with increased confinement and reduced intensity of fluctuations in electron density, electron temperature, and ion density. These results indicate that a negative triangularity plasma operating without an edge pedestal might provide an attractive scenario for operations in future reactors.

Original language	English
Article number	042515
Journal	Physics of Plasmas
Volume	26
Issue number	4
DOIs	https://doi.org/10.1063/1.5091802
State	Published - Apr 1 2019
Externally published	Yes

Funding

The authors wish to thank Dr. F. Turco for the valuable assistance with the CORSICA and DCON codes, as well as Dr. K. H. Burrell, Dr. T. C. Luce, Dr. T. W. Petrie, and Dr. T. L. Rhodes for the useful discussions. This material is based upon the work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Award Nos. DE-FC02-04ER54698, DE-FG02-94ER54235, DE-FC02-99ER54512, and DE-SC0016154. DIII-D data shown in this paper can be obtained in digital format by following the links at https://fusion.gat.com/global/D3DDMP. TRANSP simulations were performed on the PPPL cluster using version 2018-1.0, DOI: 10.11578/dc.20180627.4. Part of the data analysis was performed using the OMFIT framework.

Funders	Funder number
DOE Office of Science
U.S. Department of Energy
Office of Science
Fusion Energy Sciences

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Marinoni, A., Austin, M. E., Hyatt, A. W., Walker, M. L., Candy, J., Chrystal, C., Lasnier, C. J., McKee, G. R., Odstrčil, T., Petty, C. C., Porkolab, M., Rost, J. C., Sauter, O., Smith, S. P., Staebler, G. M., Sung, C., Thome, K. E., Turnbull, A. D., & Zeng, L. (2019). H-mode grade confinement in L-mode edge plasmas at negative triangularity on DIII-D. Physics of Plasmas, 26(4), Article 042515. https://doi.org/10.1063/1.5091802

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title = "H-mode grade confinement in L-mode edge plasmas at negative triangularity on DIII-D",

abstract = "Plasmas with a negative triangularity shape have been created on the DIII-D tokamak that, despite maintaining standard L-mode edge radial profiles, reach volume averaged pressure levels typical of H-mode scenarios. Within the auxiliary power available for these experiments, plasmas exhibit near-zero power degradation while sustaining βN = 2.7 and H98,y2 = 1.2 for several energy confinement times. Detailed comparison with matched discharges at positive triangularity indicates that Trapped Electron Modes are weakened at negative triangularity, consistent with increased confinement and reduced intensity of fluctuations in electron density, electron temperature, and ion density. These results indicate that a negative triangularity plasma operating without an edge pedestal might provide an attractive scenario for operations in future reactors.",

author = "A. Marinoni and Austin, {M. E.} and Hyatt, {A. W.} and Walker, {M. L.} and J. Candy and C. Chrystal and Lasnier, {C. J.} and McKee, {G. R.} and T. Odstr{\v c}il and Petty, {C. C.} and M. Porkolab and Rost, {J. C.} and O. Sauter and Smith, {S. P.} and Staebler, {G. M.} and C. Sung and Thome, {K. E.} and Turnbull, {A. D.} and L. Zeng",

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doi = "10.1063/1.5091802",

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Marinoni, A, Austin, ME, Hyatt, AW, Walker, ML, Candy, J, Chrystal, C, Lasnier, CJ, McKee, GR, Odstrčil, T, Petty, CC, Porkolab, M, Rost, JC, Sauter, O, Smith, SP, Staebler, GM, Sung, C, Thome, KE, Turnbull, AD & Zeng, L 2019, 'H-mode grade confinement in L-mode edge plasmas at negative triangularity on DIII-D', Physics of Plasmas, vol. 26, no. 4, 042515. https://doi.org/10.1063/1.5091802

TY - JOUR

T1 - H-mode grade confinement in L-mode edge plasmas at negative triangularity on DIII-D

AU - Marinoni, A.

AU - Austin, M. E.

AU - Hyatt, A. W.

AU - Walker, M. L.

AU - Candy, J.

AU - Chrystal, C.

AU - Lasnier, C. J.

AU - McKee, G. R.

AU - Odstrčil, T.

AU - Petty, C. C.

AU - Porkolab, M.

AU - Rost, J. C.

AU - Sauter, O.

AU - Smith, S. P.

AU - Staebler, G. M.

AU - Sung, C.

AU - Thome, K. E.

AU - Turnbull, A. D.

AU - Zeng, L.

PY - 2019/4/1

Y1 - 2019/4/1

N2 - Plasmas with a negative triangularity shape have been created on the DIII-D tokamak that, despite maintaining standard L-mode edge radial profiles, reach volume averaged pressure levels typical of H-mode scenarios. Within the auxiliary power available for these experiments, plasmas exhibit near-zero power degradation while sustaining βN = 2.7 and H98,y2 = 1.2 for several energy confinement times. Detailed comparison with matched discharges at positive triangularity indicates that Trapped Electron Modes are weakened at negative triangularity, consistent with increased confinement and reduced intensity of fluctuations in electron density, electron temperature, and ion density. These results indicate that a negative triangularity plasma operating without an edge pedestal might provide an attractive scenario for operations in future reactors.

AB - Plasmas with a negative triangularity shape have been created on the DIII-D tokamak that, despite maintaining standard L-mode edge radial profiles, reach volume averaged pressure levels typical of H-mode scenarios. Within the auxiliary power available for these experiments, plasmas exhibit near-zero power degradation while sustaining βN = 2.7 and H98,y2 = 1.2 for several energy confinement times. Detailed comparison with matched discharges at positive triangularity indicates that Trapped Electron Modes are weakened at negative triangularity, consistent with increased confinement and reduced intensity of fluctuations in electron density, electron temperature, and ion density. These results indicate that a negative triangularity plasma operating without an edge pedestal might provide an attractive scenario for operations in future reactors.

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DO - 10.1063/1.5091802

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SN - 1070-664X

VL - 26

JO - Physics of Plasmas

JF - Physics of Plasmas

IS - 4

M1 - 042515

ER -

H-mode grade confinement in L-mode edge plasmas at negative triangularity on DIII-D

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