Advances in transport understanding using perturbative techniques in TFTR

The parametric dependence of transport in TFTR plasmas is investigated using perturbative techniques. By perturbing the current in L-mode plasmas; the thermal transport outside r approximately a/2 is found to be insensitive to the plasma current or its shape. As a consequence, it is found that the global confinement can be strongly enhanced or reduced relative to L-mode scaling at fixed I_p by modifying the current profile. The density profile has been perturbed in supershot plasmas to force the plasma far above the stability threshold for ITG-modes. The ion transport in supershots is found to not be governed by marginal stability to the ITG-mode. Density pulse propagation studies of L-mode plasmas indicate that the electron particle transport varies as T_e^1.5-2.5 and that the diffusivity of trace amounts of helium is similar to the thermal diffusivities. Both measurements are consistent with electrostatic transport models.