Simulation of intermittent beam ion loss in a Tokamak Fusion Test Reactor experiment

Todo, Y.; Berk, H. L.; Breǐzman, B. N.

doi:10.1063/1.1580122

Cited by 63 publications

(82 citation statements)

References 17 publications

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“…In simulations of beamion transport, Carolipio et al computed losses of a few percent for global TAEs at an amplitude of B r /B 0 = 4 × 10 −3 . In their simulations of the first beam-driven TFTR experiments, Todo et al [6] calculated saturated mode amplitudes in excess of 10 −2 . All of these simulations made assumptions about the mode polarization similar to ours.…”

Section: Discussionmentioning

confidence: 99%

“…The damage was explained qualitatively in terms of wave-particle resonances and orbital effects but no quantitative comparisons between the measured fluctuation levels and the expected transport were given in these publications. In the only quantitative comparisons between theory and experiment [5][6][7], wave amplitudes an order of magnitude larger than the measured values were needed to predict the large losses observed experimentally.…”

Section: Introductionmentioning

confidence: 99%

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Central flattening of the fast-ion profile in reversed-shear DIII-D discharges

et al. 2008

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Neutral beam injection into a plasma with negative central shear produces a rich spectrum of toroidicity-induced and reversed-shear Alfvén eigenmodes in the DIII-D tokamak. The application of fast-ion D α (FIDA) spectroscopy shows that the central fast-ion profile is flattened in the inner half of the discharge. Neutron and equilibrium measurements corroborate the FIDA data. The temporal evolution of the current profile is also strongly modified. Studies in similar discharges show that flattening of the profile correlates with the mode amplitude and that both types of Alfvén modes correlate with fast-ion transport. Calculations by the ORBIT code do not explain the observed fast-ion transport for the measured mode amplitudes, however. Possible explanations for the discrepancy are considered.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Central flattening of the fast-ion profile in reversed-shear DIII-D discharges

et al. 2008

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“…Since the publication of the ITER Physics Basis, research has focused on the Alfvén frequency range (ω ∼ = v A /qR), where different types of Alfvén eigenmodes (AEs) can interact resonantly with particles travelling at the Alfvén speed. This is because present day experiments show that the Alfvén type instabilities, such as toroidal AEs (TAEs), are the most efficient in transporting the energetic ions [109]. To become unstable, the global drive for such modes has to exceed the global damping from the background thermal plasma and the fast ions themselves.…”

Section: Linear Stability Of Fast Particle Driven Collective Modesmentioning

confidence: 99%

Chapter 5: Physics of energetic ions

et al. 2007

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This chapter reviews the progress accomplished since the redaction of the first ITER Physics Basis Nucl. Fusion 39 2137 in the field of energetic ion physics and its possible impact on burning plasma regimes. New schemes to create energetic ions simulating the fusion-produced alphas are introduced, accessing experimental conditions of direct relevance for burning plasmas, in terms of the Alfvénic Mach number and of the normalised pressure gradient of the energetic ions, though orbit characteristics and size cannot always match those of ITER. Based on the experimental and theoretical knowledge of the effects of the toroidal magnetic field ripple on direct fast ion losses, ferritic inserts in ITER are expected to provide a significant reduction of ripple alpha losses in reversed shear configurations. The nonlinear fast ion interaction with kink and tearing modes is qualitatively understood, but quantitative predictions are missing, particularly for the stabilisation of sawteeth by fast particles that can trigger neoclassical tearing modes. A large database on the linear stability properties of the modes interacting with energetic ions, such as the Alfvén eigenmode has been constructed. Comparisons between theoretical predictions and experimental measurements of mode structures and drive/damping rates approach a satisfactory degree of consistency, though systematic measurements and theory comparisons of damping and drive of intermediate and high mode numbers, the most relevant for ITER, still need to be performed. The nonlinear behaviour of Alfvén eigenmodes close to marginal stability is well characterized theoretically and experimentally, which gives the opportunity to extract some information on the particle phase space distribution from the measured instability spectral features. Much less data exists for strongly unstable scenarios, characterised by nonlinear dynamical processes leading to energetic ion redistribution and losses, and identified in nonlinear numerical simulations of Alfvén eigenmodes and energetic particle modes. Comparisons with theoretical and numerical analyses are needed to assess the potential implications of these regimes on burning plasma scenarios, including in the presence of a large number of modes simultaneously driven unstable by the fast ions.

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“…The calculation of the electromagnetic field of the Alfvén eigenmodes from their potential harmonics is illustrated in Ref. [4]. The frequencies are renormalized to the experimental values, 55 kHz for the lower frequency TAE shown in Fig.…”

Section: Phase Space Structure Of Energetic Ionsmentioning

confidence: 99%

Simulation Study of Energetic Ion Transport due to Alfvén Eigenmodes in LHD Plasma

Todo

Nakajima

Osakabe

et al. 2008

Plasma and Fusion Research

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The creation of holes and clumps in an energetic ion energy spectrum associated with Alfvén eigenmodes was examined using the neutral particle analyzer (NPA) on the LHD shot #47645. The difference in slowingdown times between the holes and clumps suggested that the energetic ions were transported over 10% of the plasma minor radius. The spatial profile and frequency of the Alfvén eigenmodes were analyzed with the AE3D code. The phase space structures of the energetic ions on the NPA line-of-sight were investigated with Poincaré plots, where an oscillating Alfvén eigenmode was employed for each plot. The phase space regions trapped by the Alfvén eigenmodes appeared as islands in the Poincaré plots. The radial width of the islands corresponded to the transport distance of the energetic ions. Since island width depends on Alfvén eigenmode amplitude, it was found that Alfvén eigenmodes with amplitude δB r /B ∼ 10 −3 transported energetic ions over 10% of the minor radius.

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Simulation of intermittent beam ion loss in a Tokamak Fusion Test Reactor experiment

Cited by 63 publications

References 17 publications

Central flattening of the fast-ion profile in reversed-shear DIII-D discharges

Central flattening of the fast-ion profile in reversed-shear DIII-D discharges

Chapter 5: Physics of energetic ions

Simulation Study of Energetic Ion Transport due to Alfvén Eigenmodes in LHD Plasma

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