Determination of the Noninductive Current Profile in Tokamak Plasmas

The noninductive part of the measured current profile has been determined for DIII-D plasmas. A technique for determining the flux surface average of the quantity $\mathbf{E}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{B}$ and a model for the resistivity separates the current profile into inductive and noninductive portions. Analysis shows directly that neoclassical resistivity is adequate to explain the experimental observations, while Spitzer resistivity is not, and that a large noninductive current exists in plasmas for which large neutral beam current drive and pressure driven bootstrap currents are expected.