Modelling of PPCD in the reversed field pinch RFX by the transport code RITM

The modifications in plasma parameters and heating power under conditions of pulsed poloidal current drive (PPCD) in Reversed Field eXperiment (RFX) are modelled by the one-dimensional transport code RITM (Radiation from Impurities in Transport Model). Several channels for the PPCD effects on plasma confinement are taken into account: dissipation of externally driven poloidal currents, reduction in the electric field induced by the dynamo and decrease in magnetic fluctuations. It is demonstrated that the external currents are dissipated at the plasma edge and they cannot, alone, lead to any change in the temperature profile. The reduction in the dynamo electric field results in central peaking of the current and Ohmic power densities, accompanied, however, by a very modest rise in the central temperature. By taking into account the decrease in the level of magnetic fluctuations (predicted for PPCD conditions by non-linear MHD simulations) and the corresponding reduction of transport in the stochastic magnetic field, RITM reproduces, in agreement with experiments, a significant increase in the central temperature and a reduction in the loop voltage.