The effects of main-ion dilution on turbulence in low q95 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.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Aug 01, 2016
- Source ID
- 10.1063/1.4960315
Entities
People
- D. Ernst
- G. M. Staebler
- J. Candy
- J.E. Rice
- Jerry Hughes
- Jon Rost
- M. Porkolab
- Matthew Reinke
- P. Ennever
- S. G. Baek
- The Alcator C-mod Team
Organizations
- General Atomics
- Massachusetts Institute of Technology
- Oak Ridge National Laboratory
- United States Department of Energy