Title: Nonlinear fishbone dynamics in spherical tokamaks

Abstract

Linear and nonlinear kinetic-MHD hybrid simulations have been carried out to investigate linear stability and nonlinear dynamics of beam-driven fishbone instability in spherical tokamak plasmas. Realistic NSTX parameters with finite toroidal rotation were used. The results show that the fishbone is driven by both trapped and passing particles. The instability drive of passing particles is comparable to that of trapped particles in the linear regime. The effects of rotation are destabilizing and a new region of instability appears at higher q min (>1.5) values, q min being the minimum of safety factor profile. In the nonlinear regime, the mode saturates due to flattening of beam ion distribution, and this persists after initial saturation while mode frequency chirps down in such a way that the resonant trapped particles move out radially and keep in resonance with the mode. Correspondingly, the flattening region of beam ion distribution expands radially outward. A substantial fraction of initially non-resonant trapped particles become resonant around the time of mode saturation and keep in resonance with the mode as frequency chirps down. On the other hand, the fraction of resonant passing particles is significantly smaller than that of trapped particles. Our analysis shows that trapped particles providemore » the main drive to the mode in the nonlinear regime.« less

Authors:

Wang, Feng; Fu, G.Y.; Shen, Wei

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+ Show Author Affiliations

1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Dalian Univ Technol, Sch Phys & Optoelect Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.
2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Institute for Fusion Theory and Simulation and Department of Physics Hangzhou, Zhejiang University, Hangzhou, 310027, People's Republic of China
3. Institute of Plasma Physics, Chinese Academy of Science, Hefei 230031, People's Republic of China

Publication Date:

Sun Jan 01 00:00:00 EST 2017

DOE Contract Number:  

AC02-09CH11466

Research Org.:

Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Collaborations:

This work is supported by the Department of Energy Scientific Discovery through Advanced Computing (SciDAC) under Grant No. DE-AC02-09CH11466, the National Natural Science Foundation of China under Grant No. 11505022, China Postdoctoral Science Foundation under Grant No. 2014M561218, and the CASHIPS Director's Fund under Grant No. YZJJ201510.

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Keywords:

NSTX; fishbone; frequency chirping; nonlinear dynamics; wave-particle; interaction; clump pair creation; internal kink; plasmas; simulations; instability; modes;

OSTI Identifier:

1367618

DOI:

https://doi.org/10.11578/1367618