Analysis of beam ion driven Alfvén eigenmode stability induced by Tungsten contamination in EAST

The EAST Team

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Abstract

Alfvén eigenmodes (AE) activity is observed in the EAST high β N and low BT discharge 93910, operation scenario dedicated to explore the ITER baseline scenario. AEs are triggered after the plasma is contaminated by Tungsten that causes an abrupt variation of the thermal plasma and energetic particles (EPs) profiles. The aim of the present study is to analyze the AE stability in the 93910 discharge using the gyro-fluid code FAR3d, identifying the AE stability trends by comparing the plasma before and after the Tungsten contamination. Tungsten contamination causes the destabilization of Toroidal AEs (TAE) and Energetic particle modes (EPMs) in the same frequency range and radial location with respect to the experimental observation and M3D-K/GTAW code results. Next, a set of parametric studies are performed to analyze the effect of the thermal plasma and EP parameters on the AE stability. The analysis indicates a lower EP β threshold for the AEs destabilization if the EP energy increases, an improved AE stability of on-axis NBI configurations due to the stronger continuum damping in the inner plasma region as well as a large enhancement of the EP drive as the thermal ion density increases due to a higher ratio of the EP and Alfven velocities. Consequently, the simulations indicate the increment of the thermal ion density after the Tungsten contamination could be the main cause of the AE/EPM destabilization.

Original languageEnglish
Article number016028
JournalNuclear Fusion
Volume64
Issue number1
DOIs
StatePublished - Jan 2024

Funding

This work is supported by the project National Key Research and Development Program of China No. 2019YFE03020004, National Natural Science Foundation of China under Grant No. 11975276, Anhui Provincial Natural Science Foundation No. 2008085J04, Anhui Provincial Key R&D Programmes No. 202104b11020003 and the Excellence Program of Hefei Science Center CAS No. 2021HSC-UE015. The work is also supported by the Comunidad de Madrid under the project 2019-T1/AMB-13648. The numerical study in this paper was performed on the ShenMa High Performance Computing Cluster in Institute of Plasma Physics, Chinese Academy of Sciences.

Keywords

  • AE
  • EAST
  • energetic particles
  • tokamak

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