Experiments on excitation of Alfvén eigenmodes by alpha-particles with bump-on-tail distribution in JET DTE2 plasmas

Nuclear Fushion

article

S.E. Sharapov¹  H.J.C. Oliver¹  J. Garcia²  D.L. Keeling¹  M. Dreval³  V. Goloborod’Ko⁴  Ye.O. Kazakov⁵  V.G. Kiptily¹  Ž. Štancar¹  P.J. Bonofiglo⁶  R. Coelho⁷  T. Craciunescu⁸  J. Ferreira⁷  A. Figueiredo⁷  N. Fil¹  M. Fitzgerald¹  F. Nabais⁷  M. Nocente⁹  P.G. Puglia^1,11  J. Rivero-Rodriguez¹  P. Rodrigues⁷  M. Salewski^1,12  R.A. Tinguely^1,13  L.E. Zakharov^1,14 

[1] UKAEA;CEA;Institute of Plasma Physics, National Science Center KIPT;Institute for Nuclear Research;Laboratory for Plasma Physics;Princeton Plasma Physics Laboratory, Princeton;Instituto de Plasmas e Fusao Nuclear, IST, Universidade de Lisboa;National Institute for Laser;Dipartimento di Fisica ‘G.Occhialini’, Universit`a di Milano-Bicocca;Institute for Plasma Science and Technology, National Research Council;EPFL, Swiss Plasma Center;Department of Physics, Technical University of Denmark;MIT Plasma Science and Fusion Center;Helsinki University

关键词: DT;    alpha-particles;    Alfven;    JET;    plasma;    fusion;   

DOI  :  10.1088/1741-4326/acee10

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

Dedicated experiments were performed in JET DTE2 plasmas for obtaining anα -particle bump-on-tail (BOT) distribution aiming at exciting Alfvén eigenmodes (AEs). Neutral beam injection-only heating with modulated power was used so that fusion-bornα -particles were the only ions present in the MeV energy range in these DT plasmas. The beam power modulation on a time scale shorter than theα -particle slowing down time was chosen for modulating theα -particle source and thus sustaining a BOT in theα -particle distribution. High-frequency modes in the toroidicity-induced Alfven eigenmode (TAE) frequency range and multiple short-lived modes in a wider frequency range have been detected in these DT discharges with interferometry, soft x-ray cameras, and reflectometry. The modes observed were localised close to the magnetic axis, and were not seen in the Mirnov coils. Analysis with the TRANSP and Fokker-Planck FIDIT codes confirms thatα -particle distributions with BOT in energy were achieved during some time intervals in these discharges though no clear correlation was found between the times of the high-frequency mode excitation and the BOT time intervals. The combined magneto-hydrodynamic (MHD) and kinetic modelling studies show that the high-frequency mode in the TAE frequency range is best fitted with a TAE of toroidal mode numbern = 9. This mode is driven mostly by the on-axis beam ions while the smaller drive due to the pressure gradient ofα -particles allows overcoming the marginal stability and exciting the mode (Oliveret al2023Nucl. Fusionsubmitted). The observed multiple short-lived modes in a wider frequency range are identified as the on-axis kinetic AEs predicted in Rosenbluth and Rutherford (1975Phys. Rev. Lett.341428).

【 授权许可】

Unknown