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  • AIP Publishing  (5)
  • 1
    Online Resource
    Online Resource
    Nonlinear mode couplings between geodesic acoustic mode and toroidal Alfvén eigenmodes in the EAST tokamak
    AIP Publishing ; 2022
    In:  Physics of Plasmas Vol. 29, No. 6 ( 2022-06-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 29, No. 6 ( 2022-06-01)
    Abstract: Multiple toroidal Alfvén eigenmodes (TAEs) driven unstable by energetic electrons and a geodesic acoustic mode (GAM) have been successively observed in the Experimental Advanced Superconducting Tokamak (EAST) low-density Ohmic discharges. Nonlinear mode couplings among these modes are conclusively identified. Theoretical analysis suggests that the coupling of simultaneously driven TAEs is the mechanism for GAM excitation. These results experimentally show the potential role of nonlinear mode coupling to the saturation of energetic-particle driven TAE instability, which may nonlinearly transfer energy of energetic particles to bulk plasma and heat fuel ions via low frequency mode such as GAM.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/5.0088839
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 1472746-8
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  • 2
    Online Resource
    Online Resource
    Fast equilibrium reconstruction by deep learning on EAST tokamak
    AIP Publishing ; 2023
    In:  AIP Advances Vol. 13, No. 7 ( 2023-07-01)
    Details
    In: AIP Advances, AIP Publishing, Vol. 13, No. 7 ( 2023-07-01)
    Abstract: A deep neural network is developed and trained on magnetic measurements (input) and EFIT poloidal magnetic flux (output) on the EAST tokamak. In optimizing the network architecture, we use automatic optimization to search for the best hyperparameters, which helps in better model generalization. We compare the inner magnetic surfaces and last-closed-flux surfaces with those from EFIT. We also calculated the normalized internal inductance, which is completely determined by the poloidal magnetic flux and can further reflect the accuracy of the prediction. The time evolution of the internal inductance in full discharge is compared with that provided by EFIT. All of the comparisons show good agreement, demonstrating the accuracy of the machine learning model, which has high spatial resolution compared with the off-line EFIT while still meeting the time constraint of real-time control.
    Type of Medium: Online Resource
    ISSN: 2158-3226
    URL: Article
    DOI: 10.1063/5.0152318
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 2583909-3
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  • 3
    Online Resource
    Online Resource
    Kinetic-MHD hybrid simulation of fishbone modes excited by fast ions on the experimental advanced superconducting tokamak (EAST)
    AIP Publishing ; 2017
    In:  Physics of Plasmas Vol. 24, No. 3 ( 2017-03-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 24, No. 3 ( 2017-03-01)
    Abstract: Kinetic-MagnetoHydroDynamic hybrid simulations are carried out to investigate fishbone modes excited by fast ions on the Experimental Advanced Superconducting Tokamak. The simulations use realistic equilibrium reconstructed from experiment data with the constraint of the q = 1 surface location (q is the safety factor). Anisotropic slowing down distribution is used to model the distribution of the fast ions from neutral beam injection. The resonance condition is used to identify the interaction between the fishbone mode and the fast ions, which shows that the fishbone mode is simultaneously in resonance with the bounce motion of the trapped particles and the transit motion of the passing particles. Both the passing and trapped particles are important in destabilizing the fishbone mode. The simulations show that the mode frequency chirps down as the mode reaches the nonlinear stage, during which there is a substantial flattening of the perpendicular pressure of fast ions, compared with that of the parallel pressure. For passing particles, the resonance remains within the q = 1 surface, while, for trapped particles, the resonant location moves out radially during the nonlinear evolution. In addition, parameter scanning is performed to examine the dependence of the linear frequency and growth rate of fishbones on the pressure and injection velocity of fast ions.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.4978562
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2017
    detail.hit.zdb_id: 1472746-8
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  • 4
    Online Resource
    Online Resource
    Simulations of toroidal Alfvén eigenmode excited by fast ions on the Experimental Advanced Superconducting Tokamak
    AIP Publishing ; 2018
    In:  Physics of Plasmas Vol. 25, No. 5 ( 2018-05-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 25, No. 5 ( 2018-05-01)
    Abstract: Kinetic-MagnetoHydroDynamic (MHD) hybrid simulations are carried out to study fast ion driven toroidal Alfvén eigenmodes (TAEs) on the Experimental Advanced Superconducting Tokamak (EAST). The first part of this article presents the linear benchmark between two kinetic-MHD codes, namely MEGA and M3D-K, based on a realistic EAST equilibrium. Parameter scans show that the frequency and the growth rate of the TAE given by the two codes agree with each other. The second part of this article discusses the resonance interaction between the TAE and fast ions simulated by the MEGA code. The results show that the TAE exchanges energy with the co-current passing particles with the parallel velocity |v∥|≈VA0/3 or |v∥|≈VA0/5, where VA0 is the Alfvén speed on the magnetic axis. The TAE destabilized by the counter-current passing ions is also analyzed and found to have a much smaller growth rate than the co-current ions driven TAE. One of the reasons for this is found to be that the overlapping region of the TAE spatial location and the counter-current ion orbits is narrow, and thus the wave-particle energy exchange is not efficient.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.5023538
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2018
    detail.hit.zdb_id: 1472746-8
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  • 5
    Online Resource
    Online Resource
    Simulation of fast-ion-driven Alfvén eigenmodes on the Experimental Advanced Superconducting Tokamak
    AIP Publishing ; 2016
    In:  Physics of Plasmas Vol. 23, No. 2 ( 2016-02-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 23, No. 2 ( 2016-02-01)
    Abstract: Kinetic-MHD hybrid simulations are carried out to investigate possible fast-ion-driven modes on the Experimental Advanced Superconducting Tokamak. Three typical kinds of fast-ion-driven modes, namely, toroidicity-induced Alfvén eigenmodes, reversed shear Alfvén eigenmodes, and energetic-particle continuum modes, are observed simultaneously in the simulations. The simulation results are compared with the results of an ideal MHD eigenvalue code, which shows agreement with respect to the mode frequency, dominant poloidal mode numbers, and radial location. However, the modes in the hybrid simulations take a twisted structure on the poloidal plane, which is different from the results of the ideal MHD eigenvalue code. The twist is due to the radial phase variation of the eigenfunction, which may be attributed to the non-perturbative kinetic effects of the fast ions. By varying the stored energy of fast ions to change the fast ion drive in the simulations, it is demonstrated that the twist (i.e., the radial phase variation) is positively correlated with the fast ion drive.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.4941970
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2016
    detail.hit.zdb_id: 1472746-8
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