The Dynamics of Strongly-Driven Electron Temperature Gradient Turbulence in a Slab

Electron Temperature Gradient (ETG) turbulence, enabled by curvature

in the magnetic field, has been known to cause strong transport of

electron heat in tokamak discharges for many years, and has been

widely studied. Recent modelling of steady inter-ELM pedestals on

modern tokamaks (Guttenfelder, et al) has revealed that ETG turbulence

may, in fact, play a measureable role in determining the inter-ELM

profiles.  Due to the extreme gradients in the pedestal, it is

possible for the turbulence to develop surprisingly

short correlation lengths along the magnetic field. In such a

situation, the effects of curvature may be sub-dominant.

We examine the nonlinear behavior of ETG turbulence in both unsheard

and sheared slab configurations by means of direct numerical

simulations.  These simulations are carried out with the GX code

(Mandell, et al).  We examine the flux-gradient relationship for slab

ETG turbulence and compare and contrast it with theories proposed for

core configurations, paying particular attention to the collisionality

dependence of the nonlinear turbulent state.  Ultimately, we compare

with simulations in toroidal geometry and attempt to determine if the

short-correlation-length state is realized in more comprehensive

simulations.