Energetic particle modes of q = 1 highorder harmonics in tokamak plasmas with monotonic weak magnetic shear
Abstract
Linear and nonlinear simulations of highorder harmonics q=1 energetic particle modes excited by trapped energetic particles in tokamaks are carried out using kinetic/magnetohydrodynamic hybrid code M3DK. It is found that with a flat safety factor profile in the core region, the linear growth rate of highorder harmonics (m=n>1) driven by energetic trapped particles can be higher than the m/n=1/1 component. The high m=n>1 modes become more unstable when the pressure of energetic particles becomes higher. Moreover, it is shown that there exist multiple resonant locations satisfying different resonant conditions in the phase space of energetic particles for the highorder harmonics modes, whereas there is only one precessional resonance for the m/n=1/1 harmonics. The fluid nonlinearity reduces the saturation level of the n=1 component, while it hardly affects those of the high n components, especially the modes with m=n=3,4. The frequency of these modes does not chirp significantly, which is different with the typical fishbone driven by trapped particles. Lastly, in addition, the flattening region of energetic particle distribution due to highorder harmonics excitation is wider than that due to m/n=1/1 component, although the m/n=1/1 component has a higher saturation amplitude.
 Authors:
 Dalian Univ. of Technology, Dalian (China). Key Lab. of Materials Modification by Laser, Ion and Electron Beams, School of Physics
 Zhejiang Univ., Hangzhou (China). Inst. for Fusion Theory and Simulation and Dept. of Physics; Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
 Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics
 Publication Date:
 Research Org.:
 Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
 Sponsoring Org.:
 USDOE; National Magnetic Confinement Fusion Science Program of China; Fundamental Research Funds for the Central Universities
 OSTI Identifier:
 1378441
 Grant/Contract Number:
 2013GB111000; 2014GB124000; 11322549; 11605245; 11675038; DUT15YQ103
 Resource Type:
 Journal Article: Accepted Manuscript
 Journal Name:
 Physics of Plasmas
 Additional Journal Information:
 Journal Volume: 24; Journal Issue: 5; Journal ID: ISSN 1070664X
 Publisher:
 American Institute of Physics (AIP)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Particle distribution functions; Magnetohydrodynamics; Tokamaks; Chirping; Hybrid methods
Citation Formats
Ren, ZhenZhen, Wang, Feng, Fu, G. Y., Shen, Wei, and Wang, ZhengXiong. Energetic particle modes of q = 1 highorder harmonics in tokamak plasmas with monotonic weak magnetic shear. United States: N. p., 2017.
Web. doi:10.1063/1.4981935.
Ren, ZhenZhen, Wang, Feng, Fu, G. Y., Shen, Wei, & Wang, ZhengXiong. Energetic particle modes of q = 1 highorder harmonics in tokamak plasmas with monotonic weak magnetic shear. United States. doi:10.1063/1.4981935.
Ren, ZhenZhen, Wang, Feng, Fu, G. Y., Shen, Wei, and Wang, ZhengXiong. Mon .
"Energetic particle modes of q = 1 highorder harmonics in tokamak plasmas with monotonic weak magnetic shear". United States.
doi:10.1063/1.4981935. https://www.osti.gov/servlets/purl/1378441.
@article{osti_1378441,
title = {Energetic particle modes of q = 1 highorder harmonics in tokamak plasmas with monotonic weak magnetic shear},
author = {Ren, ZhenZhen and Wang, Feng and Fu, G. Y. and Shen, Wei and Wang, ZhengXiong},
abstractNote = {Linear and nonlinear simulations of highorder harmonics q=1 energetic particle modes excited by trapped energetic particles in tokamaks are carried out using kinetic/magnetohydrodynamic hybrid code M3DK. It is found that with a flat safety factor profile in the core region, the linear growth rate of highorder harmonics (m=n>1) driven by energetic trapped particles can be higher than the m/n=1/1 component. The high m=n>1 modes become more unstable when the pressure of energetic particles becomes higher. Moreover, it is shown that there exist multiple resonant locations satisfying different resonant conditions in the phase space of energetic particles for the highorder harmonics modes, whereas there is only one precessional resonance for the m/n=1/1 harmonics. The fluid nonlinearity reduces the saturation level of the n=1 component, while it hardly affects those of the high n components, especially the modes with m=n=3,4. The frequency of these modes does not chirp significantly, which is different with the typical fishbone driven by trapped particles. Lastly, in addition, the flattening region of energetic particle distribution due to highorder harmonics excitation is wider than that due to m/n=1/1 component, although the m/n=1/1 component has a higher saturation amplitude.},
doi = {10.1063/1.4981935},
journal = {Physics of Plasmas},
number = 5,
volume = 24,
place = {United States},
year = {Mon Apr 24 00:00:00 EDT 2017},
month = {Mon Apr 24 00:00:00 EDT 2017}
}
Web of Science

Roles of poloidal rotation in stabilizing the m/n=1/1 kinktearing mode and exciting its highorder harmonic tearing modes are numerically investigated by using a reduced magnetohydrodynamic model. It is found that the highorder harmonic tearing modes, such as m/n=2/2, m/n=3/3, or even much higherm harmonics, can be destabilized so significantly by rotation shear as to be more unstable than or comparable to the m/n=1/1 mode. Moreover, the short wavelength Kelvin Helmholtz (KH) instabilities can be excited in the large rotation shear regime. The scaling power laws of the linear growth rate for each harmonic mode in different rotation shear regimes aremore »

Hybrid simulation of energetic particle effects on tearing modes in tokamak plasmas
The effects of energetic ions on stability of tearing mode are investigated by global kinetic/MHD hybrid simulations in a low beta tokamak plasma. The kinetic effects of counter circulating energetic ions from the nonadiabatic response are found to be strongly destabilizing while the effects from the adiabatic response are stabilizing. The net effect with both adiabatic and nonadiabatic contributions is destabilizing. On the other hand, the kinetic effects of cocirculating energetic ions from the nonadiabatic response are calculated to be weakly stabilizing while the corresponding adiabatic contribution is destabilizing for small energetic ion beta. The net effect is weakly stabilizing.more » 
Observation of an EnergeticParticleDriven Instability in the WallStabilized Highbeta Plasmas in the JT60U Tokamak
We have observed a bursting mode in the highbeta plasmas above the ideal beta limit without a conducting wall. The mode frequency is chirping down as the mode amplitude increases, and its initial value is close to the precession frequency of the trapped energetic particle from the perpendicular neutral beams. The mode structure is radially extended with a peak around the q=2 surface. This mode can finally trigger the resistive wall mode (RWM) despite enough plasma rotation for RWM stabilization. It is concluded that the mode is driven by trapped energetic particles. The mode is attributed to the interaction betweenmore » 
Internal kink modes with m>1 in a high. beta. /sub J/, lowshear tokamak
The internal kink modes with m>1 are studied in a tokamak of circular cross section with low shear and a high value of the parameter ..beta../sub J/, which is the ratio of the average plasma pressure to the average pressure of the poloidal magnetic field. The results show that a lowshear tokamak is more stable than a highshear tokamak with respect to these modes. 
Second stable regime of internal kink modes excited by barely passing energetic ions in tokamak plasmas
The internal kink (fishbone) modes, driven by barely passing energetic ions (EIs), are numerically studied with the spatial distribution of the EIs taking into account. It is found that the modes with frequencies comparable to the toroidal precession frequencies are excited by resonant interaction with the EIs. Positive and negative density gradient dominating cases, corresponding to off and nearaxis depositions of neutral beam injection (NBI), respectively, are analyzed in detail. The most interesting and important feature of the modes is that there exists a second stable regime in higher {beta}{sub h} (=pressure of EIs/toroidal magnetic pressure) range, and the modesmore »