TRANSPORT BARRIERS WITH AND WITHOUT SHEAR FLOWS IN A MAGNETIZED PLASMA
Por:
Martinell, Julio J.
Publicada:
1 ene 2014
Categoría:
Physics and Astronomy (miscellaneous)
Resumen:
Different ways of producing a transport barrier in a toroidal magnetized
plasma are discussed and the properties of the barriers are analyzed.
The first mechanism is associated with the presence of a sheared plasma
flow that is present in a limited region of the plasma, which creates a
zonal flow. In contrast to the usual paradigm stating that the sheared
flow reduces the turbulence correlation length and leads to suppression
of the fluctuation driven transport in the region of highest shear, it
is shown that from the perspective of chaotic transport of plasma
particles in the fluctuation fields, the transport barrier is formed in
the region of zero shear and it can be destroyed when the fluctuation
level is high enough. It is also shown that finite gyro-radius effects
modify the dynamics and introduces new conditions for barrier formation.
The second mechanism considers a method in which radio-frequency waves
injected into the plasma can stabilize the drift waves and therefore the
anomalous transport is reduced, creating a barrier. This process does
not involve the presence of sheared flows and depends only on the effect
of the RF wave field on the drift waves. The stabilizing effect in this
case is due to the nonlinear ponderomotive force which acts in a way
that offsets the pressure gradient destabilization. Finally, a mechanism
based on the ponderomotive force of RF waves is described which produces
poloidal plasma rotation around the resonant surface due to the
asymmetry of induced transport; it creates a transport barrier by shear
flow stabilization of turbulence.
Filiaciones:
Martinell, Julio J.:
Univ Nacl Autonoma Mexico, Inst Ciencias Nucl, Mexico City 04510, DF, Mexico
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