Energy confinement in Doublet III

Studies of ion confinement in Doublet III show that the ion thermal diffusivity chi _i exceeds the neoclassical value by a factor of two to four at r=0.2a increasing to a factor of ten at r=0.7a. It appears that chi _e and chi _i are always closely equal, suggesting turbulence underlies the diffusion. Scaling data for energy confinement time dependence on heating power, density, current, and toroidal field are reviewed to constrain the formulation of a transport model based on turbulence. A model based on trapped electron turbulence is proposed which produces the correct scaling behavior of tau _E in both low and high collisionality regimes.