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Trigger mechanism for the abrupt loss of energetic ions in magnetically confined plasmas. Sci Rep 2018; 8:2804. [PMID: 29434239 PMCID: PMC5809513 DOI: 10.1038/s41598-018-21128-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 01/30/2018] [Indexed: 12/04/2022] Open
Abstract
Interaction between a quasi-stable stationary MHD mode and a tongue-shaped deformation is observed in the toroidal plasma with energetic particle driven MHD bursts. The quasi-stable stationary 1/1 MHD mode with interchange parity appears near the resonant rational surface of q = 1 between MHD bursts. The tongue-shaped deformation rapidly appears at the non-resonant non-rational surface as a localized large plasma displacement and then collapses (tongue event). It curbs the stationary 1/1 MHD mode and then triggers the collapse of energetic particle and magnetic field reconnection. The rotating 1/1 MHD mode with tearing parity at the q = 1 resonant surface, namely, the MHD burst, is excited after the tongue event.
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Du XD, Toi K, Ohdachi S, Watanabe KY, Takahashi H, Yoshimura Y, Osakabe M, Seki R, Nicolas T, Tsuchiya H, Nagaoka K, Ogawa K, Tanaka K, Isobe M, Yokoyama M, Yoshinuma M, Kubo S, Sakakibara S, Bando T, Ido T, Ozaki T, Suzuki Y, Takemura Y. Suppression of Trapped Energetic Ions Driven Resistive Interchange Modes with Electron Cyclotron Heating in a Helical Plasma. PHYSICAL REVIEW LETTERS 2017; 118:125001. [PMID: 28388197 DOI: 10.1103/physrevlett.118.125001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Indexed: 06/07/2023]
Abstract
The resistive interchange mode destabilized by the resonant interaction with the trapped energetic ions is fully suppressed when the injected power of electron cyclotron heating exceeds a certain threshold. It is shown for the first time that the complete stabilization of the energetic-particle-driven mode without relaxing the energetic particle (EP) pressure gradient is possible by reducing the radial width of the eigenmodes δ_{w}, especially when δ_{w} narrows to a small enough value relative to the finite orbit width of EP.
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Affiliation(s)
- X D Du
- National Institute for Fusion Science, 509-5292 Toki, Japan
| | - K Toi
- National Institute for Fusion Science, 509-5292 Toki, Japan
| | - S Ohdachi
- National Institute for Fusion Science, 509-5292 Toki, Japan
- Department of Fusion Science, The Graduate University for Advanced Studies, 509-5292 Toki, Japan
| | - K Y Watanabe
- National Institute for Fusion Science, 509-5292 Toki, Japan
- Department of Fusion Science, The Graduate University for Advanced Studies, 509-5292 Toki, Japan
| | - H Takahashi
- National Institute for Fusion Science, 509-5292 Toki, Japan
- Department of Fusion Science, The Graduate University for Advanced Studies, 509-5292 Toki, Japan
| | - Y Yoshimura
- National Institute for Fusion Science, 509-5292 Toki, Japan
| | - M Osakabe
- National Institute for Fusion Science, 509-5292 Toki, Japan
- Department of Fusion Science, The Graduate University for Advanced Studies, 509-5292 Toki, Japan
| | - R Seki
- National Institute for Fusion Science, 509-5292 Toki, Japan
- Department of Fusion Science, The Graduate University for Advanced Studies, 509-5292 Toki, Japan
| | - T Nicolas
- National Institute for Fusion Science, 509-5292 Toki, Japan
| | - H Tsuchiya
- National Institute for Fusion Science, 509-5292 Toki, Japan
| | - K Nagaoka
- National Institute for Fusion Science, 509-5292 Toki, Japan
| | - K Ogawa
- National Institute for Fusion Science, 509-5292 Toki, Japan
- Department of Fusion Science, The Graduate University for Advanced Studies, 509-5292 Toki, Japan
| | - K Tanaka
- National Institute for Fusion Science, 509-5292 Toki, Japan
| | - M Isobe
- National Institute for Fusion Science, 509-5292 Toki, Japan
- Department of Fusion Science, The Graduate University for Advanced Studies, 509-5292 Toki, Japan
| | - M Yokoyama
- National Institute for Fusion Science, 509-5292 Toki, Japan
- Department of Fusion Science, The Graduate University for Advanced Studies, 509-5292 Toki, Japan
| | - M Yoshinuma
- National Institute for Fusion Science, 509-5292 Toki, Japan
- Department of Fusion Science, The Graduate University for Advanced Studies, 509-5292 Toki, Japan
| | - S Kubo
- National Institute for Fusion Science, 509-5292 Toki, Japan
| | - S Sakakibara
- National Institute for Fusion Science, 509-5292 Toki, Japan
- Department of Fusion Science, The Graduate University for Advanced Studies, 509-5292 Toki, Japan
| | - T Bando
- Department of Fusion Science, The Graduate University for Advanced Studies, 509-5292 Toki, Japan
| | - T Ido
- National Institute for Fusion Science, 509-5292 Toki, Japan
| | - T Ozaki
- National Institute for Fusion Science, 509-5292 Toki, Japan
| | - Y Suzuki
- National Institute for Fusion Science, 509-5292 Toki, Japan
- Department of Fusion Science, The Graduate University for Advanced Studies, 509-5292 Toki, Japan
| | - Y Takemura
- National Institute for Fusion Science, 509-5292 Toki, Japan
- Department of Fusion Science, The Graduate University for Advanced Studies, 509-5292 Toki, Japan
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Abrupt onset of tongue deformation and phase space response of ions in magnetically-confined plasmas. Sci Rep 2016; 6:36217. [PMID: 27796370 PMCID: PMC5087079 DOI: 10.1038/srep36217] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 10/12/2016] [Indexed: 11/10/2022] Open
Abstract
An abrupt onset of the new tongue-shaped deformation of magnetic surface in magnetized plasmas, which was conjectured in since the 1960s but has not been observed, is experimentally identified just before an abrupt onset of a large-scale collapse event. Two novel properties of the event are identified. First, the transition of symmetry of perturbation (rather than a growth of linearly unstable MHD modes) was found to be a key for the onset of abrupt collapse, i.e., the transition of symmetry gives a new route to the collapse from stable state. Second, as a phase-space response of ions, the distortion from Maxwell-Boltzmann distribution of epithermal ions was observed for the first time.
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