Resistive Wall Modes Identification and Control in RFX-mod low qedge tokamak discharges

In this work the MHD stability of RFX mode tokamak discharges with q$_{edge}<$3 will be studied. The target plasma scenario is characterized by a plasma current 100kA$<$Ip$<$150kA, a Greenwald density fraction included between 0.5 and 1 and a minimum q$_{edge}$=1.7 value. The operation in this regime is limited by the onset of a slowly rotating m=2 n=1 kink mode, which eventually locks to the wall and induces a disruption. The mode growth rates have been characterized with regard to the main plasma parameters and have been compared with predictions by the linear MHD code MARS-F, and the 3D finite elements code CARMA, permitting a full Resistive Wall Mode identification. The stability of the mode in the vicinity of the unstable operational space has been studied using MHD spectroscopy on the (2/1) mode. A good discharge behaviour with q$_{edge}<$2 has been routinely obtained using the RFX-mod MHD active control system, which is capable of fully stabilizing the mode acting on the radial magnetic field at the plasma edge.