Gyrofluid simulations of turbulence suppression in reversed-shear experiments on the Tokamak Fusion Test Reactor

M. A. Beer, G. W. Hammett, G. Rewoldt, E. J. Synakowski, M. C. Zarnstorff, W. Dorland

Research output: Contribution to journalArticlepeer-review

Abstract

The confinement improvement in reversed-shear experiments on the Tokamak Fusion Test Reactor [Plasma Phys. Controlled Fusion 26, 11 (1984)] is investigated using nonlinear gyrofluid simulations including a bounce-averaged trapped electron fluid model. This model includes important kinetic effects for both ions and electrons, and agrees well with linear kinetic theory. Both reversed shear and the Shafranov shift reverse the precession drifts of a large fraction of the trapped electrons, which significantly reduces the growth rate of the trapped electron mode, found to be the dominant instability in the core. Two positive feedback transition mechanisms for the sudden improvement in core confinement are discussed: (1) Shafranov shift suppression of the trapped electron mode, and (2) turbulence suppression by radially sheared [formula omitted] flows. While both effects appear to be playing roles in the transition dynamics in most experiments, we show that Shafranov shift stabilization alone can cause a transition.

Original languageEnglish (US)
Pages (from-to)1792-1799
Number of pages8
JournalPhysics of Plasmas
Volume4
Issue number5
DOIs
StatePublished - May 1997
Externally publishedYes

Keywords

  • INSTABILITY GROWTH RATES
  • PLASMA CONFINEMENT
  • PLASMA FLUID EQUATIONS
  • PLASMA INSTABILITY
  • PLASMA SIMULATION
  • TFTR TOKAMAK
  • TRAPPED ELECTRONS
  • TURBULENCE

ASJC Scopus subject areas

  • Condensed Matter Physics

Fingerprint Dive into the research topics of 'Gyrofluid simulations of turbulence suppression in reversed-shear experiments on the Tokamak Fusion Test Reactor'. Together they form a unique fingerprint.

Cite this