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SUMMARY:Energetic ion dynamics and confinement in 3D saturated MHD configu
 rations
DTSTART:20150519T103000
DTEND:20150519T113000
DTSTAMP:20260406T063922Z
UID:9ebd02d0b83f6795eb6d03c06753a472d7e165c8f31b0f76ead2e567
CATEGORIES:Conferences - Seminars
DESCRIPTION:David Pfefferlé\, CRPP-EPFL\nEnergetic ions arise in fusion p
 lasmas from heating systems such as ICRH\, NBI and fusion reactions. Their
  transport is well understood in axisymmetric tokamak fields\, but is sign
 ificantly more complex in the presence of non-axisymmetric deformations an
 d/or 3D internal structures\, for example due to external perturbations\, 
 MHD activity or the intricate geometry as in stellarators. The lack of sym
 metry spoils the existence of magnetic flux-surfaces and gives rise to mag
 netic islands and field-line stochasticity. Toroidal momentum is no longer
  conserved along particle trajectories and\, in some cases\, the guiding-c
 entre approximation becomes inadequate at first-order. The VENUS-LEVIS orb
 it solver was designed with these issues in mind\, in order to investigate
  supra-thermal particle redistribution and evaluate fast ion losses in the
  presence of general 3D fields. The code combines flexibility in the choic
 e of coordinate system and a  strict Hamiltonian formulation of both guid
 ing-centre and full-orbit equations. 3D MHD equilibria\, with nested flux-
 surfaces and a single magnetic axis\, are computed within the VMEC code. T
 hese non-linear solutions to the MHD force balance\, obtained via the Krus
 kal-Kulsrud energy minimisation principle\, conveniently describe tokamak/
 stellarator saturated plasma states. Helical core deformations and resonan
 t magnetic perturbations are studied with VMEC. Their effect on NBI fast i
 on populations is simulated within VENUS-LEVIS and compared against the ex
 perimental data with qualitative agreement.
LOCATION:PPB 019
STATUS:CONFIRMED
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