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SUMMARY:Transport-driven Toroidal Rotation in the Tokamak Edge
DTSTART:20120911T140000
DTEND:20120911T150000
DTSTAMP:20260919T215239Z
UID:d22867eb55a574d8e67514f401b0e07b2b9471ee2e79aa8f7ad58163
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. T. Stolzfus-Dueck\, MPI-Greifswald\, Germany\nThe edge of
  H-mode tokamak plasmas without external momentum input almost always rota
 tes toroidally in the co-current direction\, which has prompted a theoreti
 cal search for non-diffusive momentum transport mechanisms. In contrast to
  these efforts\, the present work treats a model kinetic ion equation for 
 the pedestal and SOL containing only parallel free streaming\, magnetic dr
 ifts\, and spatially inhomogeneous but purely diffusive transport. The sol
 ution demonstrates that passing-ion orbits and spatially inhomogeneous dif
 fusion interact to cause a variation of the orbit-averaged diffusivities t
 hat depends on the sign of the parallel velocity\, typically resulting in 
 preferential transport of counter-current ions. The resulting rotation dri
 ve is independent of the toroidal velocity and its radial gradient\, repre
 senting a residual stress. When momentum transport through the pedestal is
  required to vanish (intrinsic rotation case)\, the pedestal-top rotation 
 reaches experimentally relevant values and exhibits several features in qu
 alitative agreement with experiment. It is almost always in the co-current
  direction\, with a rate that is proportional to ion temperature over plas
 ma current\, in accord with experimental observations. A co-current spin-u
 p at the transition to H-mode is predicted\, due to an increase of ion tem
 perature and steepening gradients. Untested predictions of the model inclu
 de a sensitivity of the rotation to the major-radial position of the X-poi
 nt\, with a more inboard (outboard) X-point leading to more co-current (co
 unter-current) rotation. Beyond intrinsic rotation predictions\, compariso
 n of heat and momentum transport reveals that neutral beam injection must 
 be significantly unbalanced in the counter-current direction to cause zero
  toroidal rotation at the pedestal top.
LOCATION:PPB 019
STATUS:CONFIRMED
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