Discrete Alfvén Eigenmodes in High Performance Scenarios with ITBs on EAST

doi:10.19596/j.cnki.1001-246x.8636

Abstract

Abstract:

In this paper, the instability of the discrete Alfvén eigenmodes (αTAEs, where α denotes a parameter of plasma pressure gradient) are simulated in the high performance plasma with internal transport barriers (ITBs) on the EAST. The simulation results show that there is an abundance of αTAEs on EAST, and it mainly locates in the core region within the ITB foot, where the temperature or the density gradient varies abruptly. Because the ITBs observed in the EAST are relatively localized and close to the core, the distribution of αTAEs in the radial radius is narrow.In the high performance scenario with localized magnetic shear reversal, the ITB region is closer to the plasma edge, the αTAEs locate in a larger radial region. However, in the ITB region, due to the strong negative magnetic shear, the αTAEs are only found near the ITB foot; the αTAEs frequency decreases as the pressure gradient decreases closer to the ITB foot. In addition, the αTAEs in the scenarios with localized magnetic shear reversal on the DIII-D and China Fusion Engineering Test Reactor (CFETR) are also compared, and it is similar to that on EAST, where the αTAEs do not exist in the strong magnetic shear region. The simulations on CFETR show that there are higher frequencies αTAEs in the core region and more abundant αTAEs are excited into unstable modes by energy particles.

Key words: Alfvén eigenmodes, tokamak, instabilities, energetic particles

Wanpo ZHU, Shuanghui HU, Xuefeng OUYANG, Sijie OUYANG, Yuandan LAN. Discrete Alfvén Eigenmodes in High Performance Scenarios with ITBs on EAST[J]. Chinese Journal of Computational Physics, 2023, 40(4): 461-472.

Figures/Tables 11

Fig.1 In EAST#73126 discharge, the distribution of the real and imaginary frequency of αTAE (1, 0) mode versus ρ

Fig.2 In EAST, (a) potentials V(θ) at ρ=0.14; mode structures of (b) αTAE(1, 0) mode and (c) αTAE(2, 0) (s=-0.12, α=1.32, ε0=0.2)

Fig.3 Real frequency and growth rates of αTAE with vE/vA0

Fig.4 Real frequency and growth rates of αTAE with βE0

Fig.5 Operating parameters (s, α) for (a) EAST#80307 discharge and (b) EAST#80399 discharge, respectively; distributions of the real and imaginary frequency of αTAE (1, 0) mode versus ρ in (c) EAST#80307 and (d) EAST#80399 discharge, respectively

Fig.6 (a) Real frequency and growth rate of αTAEs with vE/vA0; (b) potentials V(θ), (c) αTAE(3, 0), (d) αTAE(2, 0), (e) αTAE(1, 0) mode structure excited by energetic particles (s=-0.19, α=2.11, q=2.06)

Fig.7 Pressure profiles of (a) EAST preview scenario discharge and DIII-D#159220 discharge; distributions of αTAE (1, 0) mode versus ρ of (c) EAST and (d) DIII-D, respectively.

Fig.8 (a) The operating parameters (s, α) in EAST; (b) the real and imaginary frequency of αTAE(1, 0) mode vary with magnetic shear s at for α=2.14

Fig.9 For (a) EAST at ρ=0.53 and (b) DIII-D at ρ=0.63 the real frequency and growth rate of αTAE vary with vE/vA0

Fig.10 The distributions of the real and imaginary frequencies of αTAE(1, 0) modes along ρ for (a) scheme 1 and (b) scheme 2

Fig.11 In CFETR, (a) real frequency (─) and growth rate (┄) of αTAEs vary with vE/vA0 at ρ=0.3; (b) potentials V(θ); (c) αTAE(4, 0); (d) αTAE(3, 0), (e) αTAE(1, 0), (f) αTAE(3, 1), (g) αTAE(1, 2), (h) αTAE(1, 4)mode structure excited by energetic particles

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