The effects of main-ion dilution on turbulence in low q 95 C-Mod ohmic plasmas, and comparisons with nonlinear GYRO

P. Ennever; M. Porkolab; J. Candy; G. Staebler; M. L. Reinke; J. E. Rice; J. C. Rost; D. Ernst; J. Hughes; S. G. Baek

doi:10.1063/1.4960315

The effects of main-ion dilution on turbulence in low q ₉₅ C-Mod ohmic plasmas, and comparisons with nonlinear GYRO

P. Ennever, M. Porkolab, J. Candy, G. Staebler, M. L. Reinke, J. E. Rice, J. C. Rost, D. Ernst, J. Hughes, S. G. Baek

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4 Scopus citations

Abstract

Recent experiments on C-mod seeding nitrogen into ohmic plasmas with q₉₅ = 3.4 found that the seeding greatly reduced long-wavelength (ITG-scale) turbulence. The long-wavelength turbulence that was reduced by the nitrogen seeding was localized to the region of r/a≈0.85, where the turbulence is well above marginal stability (as evidenced by Q_i/Q_GB≫1). The nonlinear gyrokinetic code GYRO was used to simulate the expected turbulence in these plasmas, and the simulated turbulent density fluctuations and turbulent energy fluxes quantitatively agreed with the experimental measurements both before and after the nitrogen seeding. Unexpectedly, the intrinsic rotation of the plasma was also found to be affected by the nitrogen seeding, in a manner apparently unrelated to a change in the electron-ion collisionality that was proposed by other experiments.

Original language	English
Article number	082509
Journal	Physics of Plasmas
Volume	23
Issue number	8
DOIs	https://doi.org/10.1063/1.4960315
State	Published - Aug 1 2016
Externally published	Yes

Funding

This work was supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, under Award No. DE-FG02-94-ER54235, and using User Facility Alcator C-Mod, under Award No. DE-FC02-99-ER54512-CMOD.

Funders	Funder number
U.S. Department of Energy
Office of Science
Fusion Energy Sciences	DE-FC02-99-ER54512-CMOD, DE-FG02-94-ER54235

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title = "The effects of main-ion dilution on turbulence in low q 95 C-Mod ohmic plasmas, and comparisons with nonlinear GYRO",

abstract = "Recent experiments on C-mod seeding nitrogen into ohmic plasmas with q95 = 3.4 found that the seeding greatly reduced long-wavelength (ITG-scale) turbulence. The long-wavelength turbulence that was reduced by the nitrogen seeding was localized to the region of r/a≈0.85, where the turbulence is well above marginal stability (as evidenced by Qi/QGB≫1). The nonlinear gyrokinetic code GYRO was used to simulate the expected turbulence in these plasmas, and the simulated turbulent density fluctuations and turbulent energy fluxes quantitatively agreed with the experimental measurements both before and after the nitrogen seeding. Unexpectedly, the intrinsic rotation of the plasma was also found to be affected by the nitrogen seeding, in a manner apparently unrelated to a change in the electron-ion collisionality that was proposed by other experiments.",

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AU - Ennever, P.

AU - Porkolab, M.

AU - Candy, J.

AU - Staebler, G.

AU - Reinke, M. L.

AU - Rice, J. E.

AU - Rost, J. C.

AU - Ernst, D.

AU - Hughes, J.

AU - Baek, S. G.

PY - 2016/8/1

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AB - Recent experiments on C-mod seeding nitrogen into ohmic plasmas with q95 = 3.4 found that the seeding greatly reduced long-wavelength (ITG-scale) turbulence. The long-wavelength turbulence that was reduced by the nitrogen seeding was localized to the region of r/a≈0.85, where the turbulence is well above marginal stability (as evidenced by Qi/QGB≫1). The nonlinear gyrokinetic code GYRO was used to simulate the expected turbulence in these plasmas, and the simulated turbulent density fluctuations and turbulent energy fluxes quantitatively agreed with the experimental measurements both before and after the nitrogen seeding. Unexpectedly, the intrinsic rotation of the plasma was also found to be affected by the nitrogen seeding, in a manner apparently unrelated to a change in the electron-ion collisionality that was proposed by other experiments.

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The effects of main-ion dilution on turbulence in low q ₉₅ C-Mod ohmic plasmas, and comparisons with nonlinear GYRO

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