Study of Alfvén eigenmode stability in Quasi-Poloidal Stellarator (QPS) plasma using a Landau closure model Articles uri icon


publication date

  • May 2023

start page

  • 1

end page

  • 14


  • 5(056010)


  • 63

International Standard Serial Number (ISSN)

  • 0029-5515

Electronic International Standard Serial Number (EISSN)

  • 1741-4326


  • The aim of this study is to analyze the linear stability of Alfvén eigenmodes (AE) in the QPS
    device heated by a tangential neutral beam injector (NBI). The analysis is performed using the
    gyro-fluid code FAR3d, that solves the reduced MHD equations for the thermal plasma coupled
    with moments of the kinetic equation for the energetic particles (EP). The AE stability is
    calculated in several operational regimes of the tangential NBI: EP β between 0.001 and 0.1, EP
    energy between 12 and 180 keV and different radial locations of the beam. The analysis is
    performed for vacuum and finite β equilibria as well as QPS configurations with two and three
    periods. The EP β threshold in the vacuum case is 0.001 and the AE frequency is lower as the
    energy of the EP population decreases. Toroidal Alfvén eigenmodes with f = 80–120 kHz and
    elliptical AE between f = 120–350 kHz are triggered between the middle-outer plasma region
    (r/a > 0.5). The AE stability improves in the simulations with finite β equilibria and three
    period configurations with respect to the vacuum case with two periods because the continuum
    gaps are slender, leading to a higher threshold of the EP β, above 0.03 for the AEs triggered by
    the helical mode families. Helical effects are not strong enough to destabilize Helical Alfvén
    eigenmodes, the AEs with the largest growth rates are triggered by the n=1 and n=2 toroidal


  • Physics


  • stellarator; quasi-poloidal stellarator; magnetohydrodynamics; alfvén eigenmodes; energetic particles