Numerical investigation of nonperturbative kinetic effects of energetic particles on toroidicityinduced Alfvén eigenmodes in tokamaks and stellarators
Abstract
The resonant interaction of shear Alfvén waves with energetic particles is investigated numerically in tokamak and stellarator geometry using a nonperturbative MHDkinetic hybrid approach. The focus lies on toroidicityinduced Alfvén eigenmodes (TAEs), which are most easily destabilized by a fastparticle population in fusion plasmas. While the background plasma is treated within the framework of an idealMHD theory, the drive of the fast particles, as well as Landau damping of the background plasma, is modelled using the driftkinetic Vlasov equation without collisions. Building on analytical theory, a fast numerical tool, STAEK, has been developed to solve the resulting eigenvalue problem using a Riccati shooting method. The code, which can be used for parameter scans, is applied to tokamaks and the stellarator Wendelstein 7X. High energeticion pressure leads to large growth rates of the TAEs and to their conversion into kinetically modified TAEs and kinetic Alfvén waves via continuum interaction. To better understand the physics of this conversion mechanism, the connections between TAEs and the shear Alfvén wave continuum are examined. It is shown that, when energetic particles are present, the continuum deforms substantially and the TAE frequency can leave the continuum gap. The interaction of the TAE with the continuum leadsmore »
 Authors:

 MaxPlanckInstitut für Plasmaphysik, D17491 Greifswald (Germany)
 Publication Date:
 OSTI Identifier:
 22599864
 Resource Type:
 Journal Article
 Journal Name:
 Physics of Plasmas
 Additional Journal Information:
 Journal Volume: 23; Journal Issue: 9; Other Information: (c) 2016 EURATOM; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070664X
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BOLTZMANNVLASOV EQUATION; EIGENFUNCTIONS; EIGENVALUES; GEOMETRY; INTERACTIONS; LANDAU DAMPING; MAGNETOHYDRODYNAMICS; NUMERICAL SOLUTION; PARTICLES; PLASMA; SINGULARITY; STELLARATORS; TAIL IONS; TOKAMAK DEVICES
Citation Formats
Slaby, Christoph, Könies, Axel, and Kleiber, Ralf. Numerical investigation of nonperturbative kinetic effects of energetic particles on toroidicityinduced Alfvén eigenmodes in tokamaks and stellarators. United States: N. p., 2016.
Web. doi:10.1063/1.4961916.
Slaby, Christoph, Könies, Axel, & Kleiber, Ralf. Numerical investigation of nonperturbative kinetic effects of energetic particles on toroidicityinduced Alfvén eigenmodes in tokamaks and stellarators. United States. doi:10.1063/1.4961916.
Slaby, Christoph, Könies, Axel, and Kleiber, Ralf. Thu .
"Numerical investigation of nonperturbative kinetic effects of energetic particles on toroidicityinduced Alfvén eigenmodes in tokamaks and stellarators". United States. doi:10.1063/1.4961916.
@article{osti_22599864,
title = {Numerical investigation of nonperturbative kinetic effects of energetic particles on toroidicityinduced Alfvén eigenmodes in tokamaks and stellarators},
author = {Slaby, Christoph and Könies, Axel and Kleiber, Ralf},
abstractNote = {The resonant interaction of shear Alfvén waves with energetic particles is investigated numerically in tokamak and stellarator geometry using a nonperturbative MHDkinetic hybrid approach. The focus lies on toroidicityinduced Alfvén eigenmodes (TAEs), which are most easily destabilized by a fastparticle population in fusion plasmas. While the background plasma is treated within the framework of an idealMHD theory, the drive of the fast particles, as well as Landau damping of the background plasma, is modelled using the driftkinetic Vlasov equation without collisions. Building on analytical theory, a fast numerical tool, STAEK, has been developed to solve the resulting eigenvalue problem using a Riccati shooting method. The code, which can be used for parameter scans, is applied to tokamaks and the stellarator Wendelstein 7X. High energeticion pressure leads to large growth rates of the TAEs and to their conversion into kinetically modified TAEs and kinetic Alfvén waves via continuum interaction. To better understand the physics of this conversion mechanism, the connections between TAEs and the shear Alfvén wave continuum are examined. It is shown that, when energetic particles are present, the continuum deforms substantially and the TAE frequency can leave the continuum gap. The interaction of the TAE with the continuum leads to singularities in the eigenfunctions. To further advance the physical model and also to eliminate the MHD continuum together with the singularities in the eigenfunctions, a fourthorder term connected to radiative damping has been included. The radiative damping term is connected to nonideal effects of the bulk plasma and introduces higherorder derivatives to the model. Thus, it has the potential to substantially change the nature of the solution. For the first time, the fastparticle drive, Landau damping, continuum damping, and radiative damping have been modelled together in tokamak as well as in stellarator geometry.},
doi = {10.1063/1.4961916},
journal = {Physics of Plasmas},
issn = {1070664X},
number = 9,
volume = 23,
place = {United States},
year = {2016},
month = {9}
}