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SUMMARY:Using non-axisymmetric scrape-off layer perturbations to control t
 he tokamak edge plasma
DTSTART:20120529T093000
DTEND:20120529T103000
DTSTAMP:20260407T175735Z
UID:28e9e2e3422dc95263a21a8e7c154f1da1c84f8de8e0273e62c2dd8f
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr Ilon Joseph\, Lawrence Livermore National Laboratory\, USA
 \nTokamak fusion reactors require the ability to control the power exhaust
 ed to the divertor target plates\, including both the time-averaged heat l
 oads and the impulsive fluxes that accompany edge-localized modes. Driving
  toroidally-asymmetric perturbations through the scrape-off layer (SOL) pl
 asma can be used to broaden the SOL by generating potentials that drive ra
 dial convection [1] and to control the edge pedestal pressure gradient by 
 generating currents that drive external magnetic perturbations [2]. The ge
 neration of additional convective transport via steady-state convective ce
 lls or increased turbulence drive requires that the electric potential per
 turbations exceed a threshold in amplitude that is optimized at higher rad
 ial and toroidal mode number.  The generation of a coherent resonant magn
 etic perturbation requires a coherent SOL current along the separatrix and
  can be optimized by choosing the appropriate width and phasing of the bia
 sing region at the target plate. Longer toroidal wavelength modes produce 
 a larger effect because they are not sheared as strongly by the magnetic X
 -point. Generation of the necessary currents is challenging due to the pos
 sibly substantial power requirements and the possible need for internal in
 sulators. Reactor-relevant passive current-drive mechanisms rely on contro
 lling the thermo-electric potential in a toroidally asymmetric fashion nea
 r the target plate.  The technique of puffing and pumping of neutral gas 
 in order to control the target plate electron temperature is analyzed usin
 g the UEDGE code.\n*Prepared for US DOE by LLNL under Contract # DE-AC52- 
 07NA27344.\n[1] R. H. Cohen and D. D. Ryutov. Nucl. Fusion 37\, 621 (1997)
 .\n[2] I. Joseph\, R. H. Cohen and D. D. Ryutov\, Phys. Plasmas 16\, 05251
 0 (2009).
LOCATION:PPB.019
STATUS:CONFIRMED
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