Observation of Peak Neoclassical Toroidal Viscous Force in the DIII-D Tokamak

Cole, Andrew J.; Callen, J. D.; Solomon, W. M.; Garofalo, A. M.; Hegna, C. C.; Lanctot, M. J.; Reimerdes, H.

doi:10.1103/physrevlett.106.225002

Cited by 42 publications

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“…The large radial drift can be seen by the ω E ∼ 0 case in Fig. 2, as orbits are nearly closed without the precession, as often called the superbanana plateau resonance [16]. As ω E is increased (3ω E < ω b ), one can see the decrease of the radial drift, which is due to the random phasemixing.…”

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confidence: 83%

“…The collisionality is one of critical parameters, as well known by the 1/ν regime [13] in the relatively high collisionality and the ν − √ ν regime [14] with the very low collisionality. The E × B precession drift is another dominant parameter [15], as the very low E × B precession rate ω E can lead to the superbanana plateau regime [16]. Analytic treatments have been quite successful to capture the essential physics in these regimes, but in practice the connection among different regimes is required to make a prediction in tokamaks, which are almost always composed of multiple regimes across the volume [17,18].…”

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confidence: 99%

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Numerical Verification of Bounce-Harmonic Resonances in Neoclassical Toroidal Viscosity for Tokamaks

2013

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confidence: 83%

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confidence: 99%

Numerical Verification of Bounce-Harmonic Resonances in Neoclassical Toroidal Viscosity for Tokamaks

2013

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“…Recent experiments at DIII-D have confirmed the existence of this peak in the NRMF torque. 46 This enhanced NRMF torque at low rotation has been exploited to expand the operating space of QH-mode plasmas. 47 Since NRMFs add a countertorque to the plasma ͑at least when below the offset rotation͒, this is able to help maintain a higher counter-rotation for the same level of external counter-NBI torque, which is beneficial to QH-mode operation.…”

Section: Enhancement Of Nrmf Drive At Low Radial Electric Fieldmentioning

confidence: 99%

Mechanisms for generating toroidal rotation in tokamaks without external momentum input

et al. 2010

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Recent experiments on DIII-D ͓J. L. Luxon, Nucl. Fusion 42, 614 ͑2002͔͒ and National Spherical Torus Experiment ͑NSTX͒ ͓M. Ono et al., Nucl. Fusion 40, 557 ͑2000͔͒ have focused on investigating mechanisms of driving rotation in fusion plasmas. The so-called intrinsic rotation is generated by an effective torque, driven by residual stresses in the plasma, which appears to originate in the plasma edge. A clear scaling of this intrinsic drive with the H-mode pressure gradient is observed. Coupled with the experimentally inferred pinch of angular momentum, such an edge source is capable of producing sheared rotation profiles. Intrinsic drive is also possible directly in the core, although the physics mechanisms are much more complex. Another option which is being explored is the use of nonresonant magnetic fields for spinning the plasma. It is found beneficially that the torque from these fields can be enhanced at low rotation, which assists in spinning the plasma from rest, and offers increased resistance against plasma slowing.

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“…[4][5][6][7][8] The neoclassical transport in non-axisymmetry, often called neoclassical toroidal viscosity (NTV) transport in tokamaks, is intrinsically non-ambipolar, 9 and highly complex depending on parametric regimes. Progress has been substantially made by various analytical attempts, [10][11][12][13][14] but the analytic studies were limited in narrow regimes or strong approximations on particle orbits, geometries, and collisions. Therefore, a numerical approach with more realistic physics models is eventually required to achieve a precise and selfconsistent description by directly following complex guidingcenter orbits of particles without any approximation.…”

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δf Monte Carlo calculation of neoclassical transport in perturbed tokamaks

et al. 2012

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Non-axisymmetric magnetic perturbations can fundamentally change neoclassical transport in tokamaks by distorting particle orbits on deformed or broken flux surfaces. This so-called non-ambipolar transport is highly complex, and eventually a numerical simulation is required to achieve its precise description and understanding. A new df particle orbit code (POCA) has been developed for this purpose using a modified pitch-angle collision operator preserving momentum conservation. POCA was successfully benchmarked for neoclassical transport and momentum conservation in the axisymmetric configuration. Non-ambipolar particle flux is calculated in the non-axisymmetric case, and the results show a clear resonant nature of nonambipolar transport and magnetic braking. Neoclassical toroidal viscosity (NTV) torque is calculated using anisotropic pressures and magnetic field spectrum, and compared with the combined and 1= NTV theory. Calculations indicate a clear dB 2 scaling of NTV, and good agreement with the theory on NTV torque profiles and amplitudes depending on collisionality.

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Observation of Peak Neoclassical Toroidal Viscous Force in the DIII-D Tokamak

Cited by 42 publications

References 20 publications

Numerical Verification of Bounce-Harmonic Resonances in Neoclassical Toroidal Viscosity for Tokamaks

Numerical Verification of Bounce-Harmonic Resonances in Neoclassical Toroidal Viscosity for Tokamaks

Mechanisms for generating toroidal rotation in tokamaks without external momentum input

δf Monte Carlo calculation of neoclassical transport in perturbed tokamaks

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