Experimental evidence of on axis q oscillations in ETA BETA II

Magnetic field profiles have been measured in the ETA BETA II reversed field pinch (RFP) experiment by a set of insertable probes for discharges in which both the plasma current and the toroidal field at the wall are sustained. At a high value of the pinch parameter large oscillations are externally measured on the toroidal flux and on the other global quantities during the sustainment of the discharge. These oscillations are found to correspond to large current redistributions in the plasma.