Imada, K. orcid.org/0000-0002-8128-2438, Wilson, H. R. orcid.org/0000-0003-3333-7470, Connor, J. W. et al. (2 more authors) (2018) Nonlinear Kinetic Ion Response to Small Scale Magnetic Islands in Tokamak Plasmas:Neoclassical Tearing Mode Threshold Physics. Physical Review Letters. 175001. ISSN 1079-7114
Abstract
A new drift-kinetic theory of the ion response to magnetic islands in tokamak plasmas is presented. Small islands are considered, with widths w much smaller than the plasma radius r, but comparable to the trapped ion orbit width ρbi. An expansion in w/r reduces the system dimensions from five down to four. In the absence of an electrostatic potential, the ions follow stream lines that map out a drift-island structure that is identical to the magnetic island, but shifted by an amount ∼ few ρbi. The ion distribution function is flattened across these drift islands, not the magnetic island. For small islands, w∼ρbi, the shifted drift islands result in a pressure gradient being maintained across the magnetic island, explaining previous simulation results [E. Poli et al., Phys. Rev. Lett. 88, 075001 (2002)PRLTAO0031-900710.1103/PhysRevLett.88.075001]. To maintain quasineutrality an electrostatic potential forms, which then supports a pressure gradient in the electrons also. This influence on the electron physics is shown to stabilize small magnetic islands of width a few ion banana widths, providing a new threshold mechanism for neoclassical tearing modes - a key result for the performance of future tokamaks, including ITER.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Dates: |
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Institution: | The University of York |
Academic Units: | The University of York > Faculty of Sciences (York) > Physics (York) The University of York > Faculty of Social Sciences (York) > Economics and Related Studies (York) > School of Politics, Economics and Philosophy (York) The University of York > Research Groups (York) > School of Politics, Economics and Philosophy (York) |
Depositing User: | Pure (York) |
Date Deposited: | 12 Nov 2018 10:20 |
Last Modified: | 02 Apr 2025 23:14 |
Published Version: | https://doi.org/10.1103/PhysRevLett.121.175001 |
Status: | Published |
Refereed: | Yes |
Identification Number: | 10.1103/PhysRevLett.121.175001 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:138481 |