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SUMMARY:Intrinsic Poloidal Flow Generation and its Role in Sustaining Mean
  Profiles in a Simple Toroidal Plasma
DTSTART:20120921T103000
DTEND:20120921T113000
DTSTAMP:20260510T131933Z
UID:b7745954d13c2ed69aa4814442642f0d3746659b0531b803dff7b04a
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. T. Shekar Goud\, Institute for plasma research\, Gandhina
 gar\, Gujarat\, India\, 382428\nIn a simple toroidal plasma\, it is well k
 nown that single particle confinement and hence the equilibrium does not e
 xist. The observed plasma confinement time in the experiments is\, however
 \, found to be atleast an order higher than that is theoretically predicte
 d using single particle and E x B drifts. It is understood\, therefore\, t
 hat there must be some mechanism similar to rotational transform in tokama
 ks. The classical or Bohm diffusion are found to be insufficient to remove
  the excess charge injected by the filament in BLAAMANN experiments\, and 
 hence the cross-field diffusion must be anomalous in nature. More recent o
 bservations have lead to understand that the anomalous transport in the po
 loidal cross-section is connected with coherent structures and blobs. In t
 he present work\, the role of fluctuations and intrinsic poloidal flows in
  sustaining mean profiles in a simple magnetized toroidal plasma has been 
 observed. The experiments have been carried out in BETA\, a simple toroida
 l device at IPR\, Gandhinagar\, India.\n\nTo begin with\, the existence of
  large fluctuations and filling of plasma in the entire radial domain are 
 observed to be associated with each other. Simultaneous measurements on hi
 gh field side (HFS) and low field side (LFS) have indicated that the onset
  of fluctuations on LFS is followed by density build up on HFS. In order t
 o understand this correlation more quantitatively\, various poloidal flow 
 quantities are obtained. It is observed that the measured average fluctuat
 ion driven flow velocity is of the order of mean electric field driven pol
 oidal flow. Interestingly\, the fluctuation induced flow is opposite in di
 rection to the mean electric field driven flow\, partially accounting for 
 the observed difference between the net flow and the mean electric field d
 riven flow. On increasing the toroidal magnetic field strength\, a transit
 ion occurs in the nature of fluctuations\, from highly coherent at low mag
 netic field to turbulent at high magnetic field\, accompanied by the enhan
 ced poloidal flow and increased densities on HFS. The present work demonst
 rates that in a toroïdal compressible plasma\, the intrinsically generate
 d flows triggered by fluctuations\, play a role of "effective rotational t
 ransform".
LOCATION:PPB 019
STATUS:CONFIRMED
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