GATO: An MHD stability code for axisymmetric plasmas with internal separatrices

Lachaise, Bernard; Helton, F.J.; Moore, Reagan

doi:10.1016/0010-4655(81)90160-0

Cited by 212 publications

(125 citation statements)

References 9 publications

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“…Immediately after initiation of early neutral beam injection into an ohmic equilibrium with qo > 1, the plasma becomes unstable to m/n = 2/1 MHD modes, consistent with internal kink modes predicted by the GATO [5] code using experimentally measured pressure profiles. As the plasma relaxes on resistive time scales, the current profile broadens and qo gradually increases as the current density on axis decreases.…”

Section: Quiescent Operationsupporting

confidence: 73%

Milestone report: Status report on high {beta}p experiments at high plasma current

Casper¹,

James²,

Rice³

et al. 1995

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Section: Quiescent Operationsupporting

confidence: 73%

Milestone report: Status report on high {beta}p experiments at high plasma current

Casper¹,

James²,

Rice³

et al. 1995

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“…With this definition, C b ¼ 0 represents beta at the no-wall limit, and C b ¼ 1 represents beta at the ideal-wall limit. The stability limit was calculated using MARD2D 22 in JT-60U and GATO 23 and DCON 24 in DIII-D.…”

Section: Experimental Arrangementmentioning

confidence: 99%

Off-axis fishbone-like instability and excitation of resistive wall modes in JT-60U and DIII-D

Okabayashi¹,

Matsunaga²,

deGrassie³

et al. 2011

Physics of Plasmas

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An energetic-particle (EP)-driven "off-axis-fishbone-like mode (OFM)" often triggers a resistive wall mode (RWM) in JT-60U and DIII-D devices, preventing long-duration high-b N discharges. In these experiments, the EPs are energetic ions (70-85 keV) injected by neutral beams to produce high-pressure plasmas. EP-driven bursting events reduce the EP density and the plasma rotation simultaneously. These changes are significant in high-b N low-rotation plasmas, where the RWM stability is predicted to be strongly influenced by the EP precession drift resonance and by the plasma rotation near the q ¼ 2 surface (kinetic effects). Analysis of these effects on stability with a self-consistent perturbation to the mode structure using the MARS-K code showed that the impact of EP losses and rotation drop is sufficient to destabilize the RWM in low-rotation plasmas, when the plasma rotation normalized by Alfvén frequency is only a few tenths of a percent near the q ¼ 2 surface. The OFM characteristics are very similar in JT-60U and DIII-D, including nonlinear mode evolution. The modes grow initially like a classical fishbone, and then the mode structure becomes strongly distorted. The dynamic response of the OFM to an applied n ¼ 1 external field indicates that the mode retains its external kink character. These comparative studies suggest that an energetic particle-driven "off-axis-fishbone-like mode" is a new EP-driven branch of the external kink mode in wall-stabilized plasmas, analogous to the relationship of the classical fishbone branch to the internal kink mode.

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“…Burke et al [15] discusses an example of the impact of mapping errors. In that work, the nimrod extended-MHD code is benchmarked with the linear-MHD codes gato [16] and elite [17] on peelingballooning modes in tokamak equilibria. gato, like other global linear-MHD codes, uses mapped equilibria while elite uses Miller equilibria [18] that effectively act to provide the same accuracy as resolving the Grad-Shafranov equation.…”

Section: Introductionmentioning

confidence: 99%

Effect of scrape-off-layer current on reconstructed tokamak equilibrium

et al. 2017

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Methods are described that extend fields from reconstructed equilibria to include scrape-off-layer current through extrapolated parametrized and experimental fits. The extrapolation includes both the effects of the toroidal-field and pressure gradients which produce scrape-off-layer current after recomputation of the Grad-Shafranov solution. To quantify the degree that inclusion of scrapeoff-layer current modifies the equilibrium, the χ-squared goodness-of-fit parameter is calculated for cases with and without scrape-off-layer current. The change in χ-squared is found to be minor when scrape-off-layer current is included however flux surfaces are shifted by up to 3 cm. The impact on edge modes of these scrape-off-layer modifications is also found to be small and the importance of these methods to nonlinear computation is discussed. Published version: Phys. Plasmas 24, 012504 (2017) [http://dx

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GATO: An MHD stability code for axisymmetric plasmas with internal separatrices

Cited by 212 publications

References 9 publications

Milestone report: Status report on high {beta}p experiments at high plasma current

Milestone report: Status report on high {beta}p experiments at high plasma current

Off-axis fishbone-like instability and excitation of resistive wall modes in JT-60U and DIII-D

Effect of scrape-off-layer current on reconstructed tokamak equilibrium

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