Global 3D Braginskii simulations of the tokamak edge region of IWL discharges

Journal Article · Fri Aug 18 00:00:00 EDT 2017 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/aa7f23· OSTI ID:1523624

Francisquez, M. ^[1]; Zhu, B. ^[1]; Rogers, B. N. ^[1]

---

1. Dartmouth College, Hanover, NH (United States)

A study of plasma turbulence and profile evolution in conditions of low (L-mode) and high (H-mode) confinement at the edge of an axisymmetric, nested circular flux-surface approximation to an inner wall limited (IWL) Alcator C-Mod discharge is presented, using numerical simulations with the global drift-ballooning (GDB) code. GDB solves drift-reduced Braginskii two-fluid equations for electromagnetic low-frequency turbulence in a 3D annulus centered on the last closed flux-surface (LCFS). Three simulations that investigate the conditions of a reference L-mode, a high density, and a high temperature (or H-mode-like) shot were performed using realistic parameters. L-mode transport appears to be largely driven by drift resistive ballooning structures. Its pressure profile exhibits a near-SOL breakpoint that Mirror Langmuir Probes (MLP) detect in C-Mod. The high density simulation sees an increase in the size of convective cells and enhanced turbulent transport, while H-mode conditions develop improved confinement, balanced $$E \times B$$ and ion diamagnetic drifts in the closed-flux region, and spontaneous generation of temperature pedestal with a density pedestal remaining absent. A statistical characterization of the turbulence both in the SOL and the closed-flux region is presented.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: SC0010508; AC02-05CH11231
• OSTI ID: 1523624
• Journal Information: Nuclear Fusion, Vol. 57, Issue 11; ISSN 0029-5515
• Country of Publication: United States
• Language: English