Convective transport due to poloidal electric fields during electron cyclotron heating in IMS

Steady state hollow density profiles, observed during electron cyclotron resonant heating in the Interchangeable Module Stellarator (IMS), are shown to be consistent with a transport model that includes convection in the particle balance equation. The factor of two difference in the confinement time between a hollow profile and a fairly flat profile is due to particle convection and is in good agreement with that calculated from the equilibrium profiles. It is observed that the poloidal electric fields are greater for the hollow profile than for the less hollow case, indicating that they are most likely the cause of the convection. (author). Letter-to-the-editor. 13 refs, 3 figs