Comparison of particle transport properties in TPE-RX standard and PPCD plasmas

The global transport properties of a magnetic confinement device are strongly affected by the level of magnetic and electrostatic fluctuations. Transport in the plasma core of low current (Ip <= 0.6 MA) reversed field pinch devices is driven mainly by magnetic chaos associated with the presence of several MHD modes. In order to reduce the magnetic chaos, the technique of the pulsed poloidal current drive (PPCD) (Sarff et al 1994 Phys. Rev. Lett. 72 3670-3) has been applied to the TPE-RX plasma. This paper presents the comparison of the confinement properties in discharges with and without PPCD. It turns out that PPCD pulses show longer particle confinement time than standard plasmas. Moreover, for the first time, particle transport analyses have been carried out at TPE-RX both in standard and PPCD discharges to investigate the local particle diffusion coefficient. The comparison of the results confirms the strong reduction in the transport when the magnetic fluctuations are damped, in quantitative accordance with the theoretical predictions.