Observation of temperature-dependent transport in the TFTR tokamak

Local particle and heat transport coefficients have been measured in a temperature scan of neutral-beam--heated plasmas with n, ${\mathit{I}}_{\mathit{p}}$, and ${\mathit{B}}_{\mathit{c}\mathit{p}\mathit{h}\mathit{i}}$ held constant. The electron transport is ascertained from a flux analysis of a small density perturbation, and the heat transport is obtained from the equilibrium power balance. The transport coefficients vary as ${\mathit{T}}_{\mathit{e}}^{\mathrm{\ensuremath{\alpha}}}$, where \ensuremath{\alpha}=1.5--2.5. The observed temperature dependence is predicted by numerical calculations of anomalous transport due to trapped-particle drift-type microinstabilities.