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Title: Simulation of density fluctuations before the L-H transition for Hydrogen and Deuterium plasmas in the DIII-D tokamak using the BOUT++ code

A six-field two-fluid model has been used to simulate density fluctuations. The equilibrium is generated by experimental measurements for both Deuterium (D) and Hydrogen (H) plasmas at the lowest densities of DIII-D low to high confinement (L-H) transition experiments. In linear simulations, the unstable modes are found to be resistive ballooning modes with the most unstable mode number n=30 or $$k_\theta\rho_i\sim0.12$$ . The ion diamagnetic drift and $$E\times B$$ convection flow are balanced when the radial electric field (E r) is calculated from the pressure profile without net flow. The curvature drift plays an important role in this stage. Two poloidally counter propagating modes are found in the nonlinear simulation of the D plasma at electron density $$n_e\sim1.5\times10^{19}$$ m -3 near the separatrix while a single ion mode is found in the H plasma at the similar lower density, which are consistent with the experimental results measured by the beam emission spectroscopy (BES) diagnostic on the DIII-D tokamak. The frequency of the electron modes and the ion modes are about 40kHz and 10 kHz respectively. The poloidal wave number $$k_\theta$$ is about 0.2 cm -1 ($$k_\theta\rho_i\sim0.05$$ ) for both ion and electron modes. The particle flux, ion and electron heat fluxes are~3.5–6 times larger for the H plasma than the D plasma, which makes it harder to achieve H-mode for the same heating power. The change of the atomic mass number A from 2 to 1 using D plasma equilibrium make little difference on the flux. Increase the electric field will suppress the density fluctuation. In conclusion, the electric field scan and ion mass scan results show that the dual-mode results primarily from differences in the profiles rather than the ion mass.
 [1] ;  [2] ;  [3] ;  [3] ; ORCiD logo [4] ;  [5] ;  [5]
  1. Chinese Academy of Sciences (CAS), Hefei (China). Inst.of Plasmas Physics; Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Univ. of Wisconsin, Madison, WI (United States)
  4. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  5. Chinese Academy of Sciences (CAS), Hefei (China). Inst.of Plasmas Physics
Publication Date:
Grant/Contract Number:
AC52-07NA27344; AC02-09CH11466; FC02-04ER54698; FG02-08ER54999; 2014GB106003; 11505221; 11675211; 11605244; 201504910132
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 58; Journal Issue: 2; Journal ID: ISSN 0029-5515
IOP Science
Research Org:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24); National Natural Science Foundation of China (NNSFC); Chinese Scholarship Council
Country of Publication:
United States
OSTI Identifier: