Studies of Resonant Magnetic Perturbations in the STOR-M Tokamak

Who (supervisor): Sayf Gamudi Elgriw (Chijin Xiao)
Venue: College of Engineering Research Day, Sept. 20, 2012.
Abstract: The active control of magnetohydrodynamic (MHD) instabilities has been an intriguing topic in tokamak fusion research. Several methods have been developed to control the onset of MHD instabilities in tokamak plasmas. One of the methods involves the use of radial magnetic perturbations generated by helical coils wound around a tokamak. The purpose of influencing the plasma with resonant magnetic perturbations (RMP) is to manipulate the radial topology of magnetic islands through resonant interaction. A series of experiments has been carried out in STOR-M to examine the effect of the RMP on the (2, 1) tearing modes during an active MHD and low q ohmic discharge. The amplitude and frequency of (2, 1) island fluctuations were significantly reduced after the activation of RMP. Moreover, a phase of improved plasma confinement, characterized by a reduction in Hα emission level, a reduction of hard X-ray (HXR) emissions, and an increase in soft x-ray (SXR) emission, has been induced after the application of RMP. It has also been observed via ion Doppler spectroscopy (IDS) that RMP can strongly affect the plasma rotation in STOR-M. It has been found that during the RMP pulse, the toroidal velocity of CIII impurity (located at the plasma edge) increases in the co-current direction. However, the toroidal velocities of OV and CVI species (located near the plasma core) change direction from counter-current to co-current. Other effects of RMP, i.e. the reduction of floating potential and the increase of density, have been observed at the plasma edge using rake probes.