High frequency Alfvén eigenmodes detected with ion-cyclotron-emission diagnostics during NBI and ICRF heated plasmas on the ASDEX Upgrade tokamak - Observatoire de Paris Accéder directement au contenu
Article Dans Une Revue Nuclear Fusion Année : 2020

High frequency Alfvén eigenmodes detected with ion-cyclotron-emission diagnostics during NBI and ICRF heated plasmas on the ASDEX Upgrade tokamak

R. Ochoukov
R. Bilato
  • Fonction : Auteur
V. Bobkov
  • Fonction : Auteur
S.C. Chapman
R. Dendy
  • Fonction : Auteur
M. Dreval
  • Fonction : Auteur
H. Faugel
  • Fonction : Auteur
A. Kappatou
Ye.O. Kazakov
M. Mantsinen
  • Fonction : Auteur
K.G. Mcclements
D. Moseev
  • Fonction : Auteur
S.K. Nielsen
J.M. Noterdaeme
  • Fonction : Auteur
M. Salewski
  • Fonction : Auteur
P. Schneider
  • Fonction : Auteur
M. Weiland
  • Fonction : Auteur

Résumé

Abstract The paper presents the first reported observation of high frequency Alfvén eigenmode excitation on the ASDEX Upgrade tokamak. The mode is driven in a novel way using radio frequency (RF) wave acceleration of either beam-injected deuterium ions or thermal He-3 minority ions in a three-ion heating scenario. In the case of beam ion acceleration, the instability only appears during deuteron acceleration at the third beam ion cyclotron harmonic (wave frequency ω = 3Ω D where Ω D is the deuterium cyclotron frequency), as the mode is not detected during the more commonly used second harmonic/minority heating scenario or in the absence of beam-injected ions. The mode frequency is around 0.6–0.7Ω D , where Ω D is evaluated in the low-field side plasma edge, and tracks the magnetic field B and the edge plasma electron density n e via the Alfvénic relation ω ∼ B n e −1/2 . The mode does not appear as a single frequency wave but as a bundle of closely spaced (in frequency) sub-modes. When the parallel beam ion velocity component is increased, the sub-mode frequency spacing is observed to decrease, possibly due to a change in the eigenmode structure. Under certain conditions, typically in discharges with a relatively low plasma current, I P < 0.7 MA, the mode appears to be driven directly by sub-Alfvénic deuterium beam ions. Absolute measurements of the mode amplitude show that at least 1% of the beam-injected power is transferred non-collisionally to the instability. While this is too low for practical alpha-channeling applications, discharges are planned with the aim of increasing the level of power transferred non-collisionally between fast ions and the instability.

Dates et versions

obspm-03901635 , version 1 (15-12-2022)

Identifiants

Citer

R. Ochoukov, R. Bilato, V. Bobkov, S.C. Chapman, R. Dendy, et al.. High frequency Alfvén eigenmodes detected with ion-cyclotron-emission diagnostics during NBI and ICRF heated plasmas on the ASDEX Upgrade tokamak. Nuclear Fusion, 2020, 60 (12), pp.126043. ⟨10.1088/1741-4326/abb79f⟩. ⟨obspm-03901635⟩

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