Energetic ion dynamics and confinement in 3D saturated MHD configurations
Event details
| Date | 19.05.2015 |
| Hour | 10:30 › 11:30 |
| Speaker | David Pfefferlé, CRPP-EPFL |
| Location |
PPB 019
|
| Category | Conferences - Seminars |
Energetic ions arise in fusion plasmas from heating systems such as ICRH, NBI and fusion reactions. Their transport is well understood in axisymmetric tokamak fields, but is significantly more complex in the presence of non-axisymmetric deformations and/or 3D internal structures, for example due to external perturbations, MHD activity or the intricate geometry as in stellarators. The lack of symmetry spoils the existence of magnetic flux-surfaces and gives rise to magnetic islands and field-line stochasticity. Toroidal momentum is no longer conserved along particle trajectories and, in some cases, the guiding-centre approximation becomes inadequate at first-order. The VENUS-LEVIS orbit 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 choice of coordinate system and a strict Hamiltonian formulation of both guiding-centre and full-orbit equations. 3D MHD equilibria, with nested flux-surfaces and a single magnetic axis, are computed within the VMEC code. These non-linear solutions to the MHD force balance, obtained via the Kruskal-Kulsrud energy minimisation principle, conveniently describe tokamak/stellarator saturated plasma states. Helical core deformations and resonant magnetic perturbations are studied with VMEC. Their effect on NBI fast ion populations is simulated within VENUS-LEVIS and compared against the experimental data with qualitative agreement.
Practical information
- Informed public
- Free
Organizer
- Prof. P. Ricci
Contact
- Prof. P. Ricci