EVIDENCE FOR A LOCAL DIFFUSIVE MODEL OF TRANSPORT IN A TOKAMAK

Three series of recent experiments on JET have been dedicated to energy transport studies. Experiments with pellet injection followed by off-axis ICRH produce a heat sink on axis resulting in an inward thermal heat flux. A diffusive model for thermal flux with no heat pinch can adequately describe the data. It also describes the data from current ramp experiments in which total current is transiently decorrelated from the current distribution. The effective thermal diffusivity in L-mode confinement is found to scale with normalised Larmor radius according to Bohm in a series of non-dimensional scaling experiments.