THE TRAPPED ION MODE IN HOT ION PLASMAS

In recent experiments on DIII-D, hot ion H-mode plasmas (T(i) >> T(e)) have been obtained in which the ion thermal diffusivity is substantially smaller than the electron thermal diffusivity in the central plasma region. Previous anomalous transport models, employing a combination of dissipative trapped electron mode and ion temperature gradient mode transport mechanisms, are not consistent with the observation of the hot ion H-mode. The collisionless trapped ion mode is proposed as an explanation of these results. The stability properties of the hot ion trapped ion mode are discussed and quasi-linear estimates of the radial heat fluxes are presented which support the observation that in the central region the ion thermal conductivity is much smaller than the electron thermal conductivity.