Hybrid Simulation of Non-resonant Fishbone Instabilities Excited by Passing Energetic Particles in EAST Tokamak

doi:10.19596/j.cnki.1001-246x.8565

Abstract

Abstract:

A hybrid simulation of non-resonant fishbone (NRF) instabilities with reversed safety factor profile is investigated with a global kinetic-magnetohydrodynamic (MHD) code (M3D-K). With EAST parameters, NRF instability can be driven by energetic particles as minimum safety factor is a little greater than unity. With analysis on energy resonance, physical mechanism of NRF excited by energetic particles at different angles is studied. Parameters such as injection energy E, P_hot/P_total, are scanned to find parameter thresholds and change of fishbone instability. In addition, we analyze slowing-down distribution of energetic particles, evolution of mode structure and fishbone mode sweep in nonlinear process. A flattening trend of nonlinear slowing-down distribution at Λ = 0.6, 0.7, 1.0 is consistent with that of energetic particles in experiments. Mode structure evolves from that of NRF mode to those of other high-frequency modes at Λ = 0.6. The upward sweep frequency of fishbone is consistent with the sweep frequency of classical fishbone at Λ = 0.6.

Key words: non-resonant fishbone instability, reversed safety factor profile, passing energetic particles, energy resonance relation

Jingkun XU, Weihua WANG. Hybrid Simulation of Non-resonant Fishbone Instabilities Excited by Passing Energetic Particles in EAST Tokamak[J]. Chinese Journal of Computational Physics, 2023, 40(3): 291-300.

Figures/Tables 14

Fig.1 Equilibrium profiles of total pressure and safety factor q

Fig.2 Slowing-down function of energetic particles

Fig.3 Linear growth rate and mode frequency as functions of Λ at different pressure fraction Phot/Ptotal

Fig.4 Velocity stream function U at 310 τA (a) Λ = 1.0; (b) Λ = 0.9; (c) Λ = 0.8; (d) Λ = 0.7

Fig.5 Energy resonance excited by energetic particles (The red '.' represents energy change. The yellow and blue areas are the distribution of energetic particles. The red line is the main area of energy change.) (a) Λ = 1.0; (b) Λ = 0.9; (c) Λ = 0.8; (d) Λ = 0.7

Fig.6 Energy resonance excited by energetic particles at Λ = 0.6 (The red line represents the main area of energy change. The yellow and blue areas are the distribution of energetic particles.) (a) Phot/Ptotal = 0.4; (b) Phot/Ptotal = 0.5;(c) Phot/Ptotal = 0.6; (d) Phot/Ptotal = 0.7

Fig.7 At Λ = 0.6, linear growth rate and mode frequency as functions of injection energy E (The initial injection energy E0=18.25 keV.)

Fig.8 Energy evolution at different pitch angles

Fig.9 At a pitch angle 1.0, energy evolution with different Phot/Ptotal

Fig.10 Slowing-down distributions (Λ = 0.6) at different time

Fig.11 Slowing-down distributions (Λ = 0.7) at different time

Fig.12 (a) Energy evolution at Λ = 1.0; (b)Slowing-down distribution at Λ = 1.0 at different time

Fig.13 Mode structures of nonlinear evolution (Λ = 0.6) at (a) 660 τA; (b) 1 460 τA; (c) 2 010 τA; (d) 2 710 τA

Fig.14 Upward sweep frequency of non-resonant fishbone at Λ = 0.6

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