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}<$2 has been routinely obtained using the RFX-mod MHD active control system, which is capable of fully stabilizing the mode acting on the radial magnetic field at the plasma edge.
Resistive Wall Modes Identification and Control in RFX-mod low qedge tokamak discharges
Giuseppe Marchiori;Lionello Marrelli;Roberto Paccagnella;Paolo Piovesan;Anton Soppelsa;
2011
Abstract
In this work the MHD stability of RFX mode tokamak discharges with q$_{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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
