Plasma Physics Seminar ( Phys 769)

Yi-Min Huang
Department of Physics, University of Maryland

MHD Stability of Centrifugally Confined Plasmas

Centrifugally confined plasmas utilize centrifugal forces from plasma rotation to augment magnetic confinement, as an alternative approach to
fusion.  One magnetic geometry is mirror-type, with rotation about the axis induced from a central, biased core conductor.  The outward
centrifugal forces from the rotation have a component along the field lines, thus confining ions to the center.  The immediate concern, of
course, is that the system could be flute unstable to the interchange.  The antidote here is that the radial shear in the rotation could stabilize
the flute.  Our 2D simulations show, first, that plasma pressure is highly peaked at the center away from the mirror end coils.  Next, 3D simulations
show unequivocally that velocity shear is providing the stability.  Further study indicates that the flute stability is sensitive to the
density profile.  A favorable density profile could be achieved by judiciously placing the particle source, also necessary for a steady state
centrifuge.  As flows approach the Alfven speed, electromagnetic modes could be involved.  The latter is motivated by the question of whether
magnetorotational instability, thought to be an angular momentum transporter in accretion disks, could be found in centrifugal plasmas,
since all the ingredients are there.  We show that the MRI as understood should be stable; however, a related astrophysical instability, the Parker
instability, could arise.  The Parker instability results in plasma accumulating in regions of bent field lines, further accentuating the bending.