A statistical analysis of pulsed poloidal current drive in the Reversed Field eXperiment

Pulsed poloidal current drive (PPCD) experiments have been performed in the reversed-field pinch device RFX [G. Rostagni, Fus. Eng. Design 25, 301 (1995)], with various control techniques of the edge toroidal field. A detailed statistical analysis has been performed over ~430 RFX pulses and is presented in this paper. We have found that the temperature increase and m = 1 fluctuations reduction scale with the applied electric field E which is a control parameter for plasma performances. Soft x-ray imaging shows an increase in the core, where often an m = 1 helical coherent structure appears, similar to those observed during quasi-single helicity states in RFX. These phenomena are ultimately linked to the magnetic turbulence reduction and q profile modifications that take place during PPCD in the reversed-field pinch.