There are two widely separated scales for microturbulence in tokamak plasmas. ITG/TEM turbulent eddies are typically larger than the ion Larmor radius. ETG fluctuations are found at scales between the ion and electron Larmor radius. For deuterium plasmas, these scales are separated by a factor of 60.

Recently, ETG turbulence has been the subject of much interest, primarily because of observations of electron transport when ion-scale transport is strongly suppressed. Although ETG instabilities have very short wavelengths and therefore might be expected to cause weak energy transport, they have very fast growth rates and are therefore good candidates for surviving in circumstances when longer wavelength instabilities are stabilized by velocity shear. Interest grew when simulations and theory showed that toroidal ETG instabilities develop into anisotropic streamer structures which are capable of driving significant electron energy fluxes.

Thus, ETG turbulence is a good candidate for explaining electron energy transport in the absence of longer wavelength turbulent fluctuations. Such conditions arise in at least three interesting regimes: Ohmic discharges, high beta spherical torus plasmas, and in transport barriers.

Diagnostics exist in this area, and are currently funded. Codes also exist in this area, and are currently supported through the SciDAC Plasma Microturbulence Project. The missing element has been a framework to bring theory, computation, and experimental results together -- the CMPD provides this framework. Working with international collaborators, we will also begin to develop the capability to simulate plasmas in which both electron- and ion-scale fluctuations are excited. Multiscale algorithms will accelerate efforts to simulate ETG/ITG/TEM interactions with realistic mass ratios, and to calculate the transport consequences of ETG turbulence.