Rotation Studies on the C-2 FRC Experiment

Although high rotation velocity in a FRC may lead to rotational instabilities, it is also believe that shear flow helps in improving FRC stability and transport. In the C-2 experiment [1], diagnostics such as multi-chords and fast-response ion Doppler spectroscopy, multi-chords CO$_2$ interferometry, bolometer tomography, Doppler backscattering, Mirnov probe arrays and mach probes are available to measure the rotation, its profile and associated instabilities. In past, suppression of n=2 rotational mode and associated reduction in the rotation velocity have been reported on C-2 via the use of quadrupole magnetic field [2]. Recently, biased electrodes are used on C-2 to control the rotation profile of the edge plasma layer. Local velocity, rotation profile and macroscopic rotation measurements as well as mode analysis were performed. Results on FRC rotation and effects of electrode biasing will be presented.\\[4pt] [1] M.W. Binderbauer {\em et al}, Phys.Rev.Lett. {\bf 105}, 045003 (2010)\\[0pt] [2] H.Y. Guo {\em et al}, Phys.Plasmas {\bf 18}, 056110 (2011)