Neoclassical theory inside transport barriers in tokamaks

Shaing, K. C.; Hsu, Chiou-Ting

doi:10.1063/1.3682044

Cited by 13 publications

(66 citation statements)

References 38 publications

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“…Rosenbluth's result 7 is reproduced but with the shear flow modification. The fraction of the trapped particles estimated here is the same as Shaing's 5 , however, diffusivity scaling on shear flow is different.…”

Section: Introductionsupporting

confidence: 65%

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Diffusivity Scaling on Shear Flow

Wang¹,

He²,

Dong³

et al. 2014

AJMP

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Diffusivity scaling on shear flow is investigated. Radial electrical field is the drive of the flow. The turning points of the trapped particle are not on the drift surface, but modified by the radial electrical field. For the first time, an analytical expression of the banana width in presence of shear flow is accurately derived. The particle diffusivity given by Rosenbluth is reproduced but with the shear flow modification.

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Section: Introductionsupporting

confidence: 65%

“…There are renewed interests in the neoclassical fluxes [4][5][6] inside the thermal barriers. The diffusivity scaling on the shear flow presented by Catto 6 and Shaing 5 are different. There are intense arguments 6 on this topic.…”

Section: Introductionmentioning

confidence: 99%

Diffusivity Scaling on Shear Flow

Wang¹,

He²,

Dong³

et al. 2014

AJMP

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“…To obtain (42), the fact that ω ≈ 0 has been used to simplify the energy scattering operator. Similar procedures have been employed in approximating the collision operator for squeezed orbits induced transport in large aspect ratio tokamaks (Shaing et al 1994;2012).…”

Section: Transport Fluxes In the Superbanana Regimementioning

confidence: 99%

“…Similar procedures have been employed in approximating the collision operator for squeezed orbits induced transport in large aspect ratio tokamaks (Shaing et al 1994;2012). Similar procedures have been employed in approximating the collision operator for squeezed orbits induced transport in large aspect ratio tokamaks (Shaing et al 1994;2012).…”

mentioning

confidence: 99%

Superbanana and superbanana plateau transport in finite aspect ratio tokamaks with broken symmetry

Shaing

2014

J. Plasma Phys.

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Superbanana and superbanana plateau transport processes are critical to plasma confinement in tokamaks with broken symmetry. The transport is caused by the superbanana resonance, which occurs at a pitch angle that makes the toroidal drift speed vanish, i.e. the tips of the superbananas. The physics consequences of the resonance on the symmetry breaking induced toroidal momentum damping and on the energetic alpha particle transport have been demonstrated using large aspect ratio expansion. Here, the existing theory for the superbanana and superbanana plateau transport is extended for finite aspect ratio tokamaks with broken symmetry. The effects of finite plasma β, and magnetic field shear are naturally included. Here, β is the ratio of the thermal plasma pressure to the magnetic field pressure. The explicit expressions for the transport fluxes in these regimes in terms of the equilibrium quantities are presented. It is shown that the main effects are to modify the resonance function G(k) and the expression for the pitch angle parameter k in the existing theory.

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“…As a result, a strong radial electric field shifts the trapped–passing boundary (Shaing, Hsu & Dominguez 1994 a ), and causes an exponential decrease proportional to the radial electric field in plasma viscosity (Shaing et al. 1994 a ) and radial heat flux (Kagan & Catto 2010; Shaing & Hsu 2012). The mean parallel flow is also affected by a strong radial electric field and can change direction (Kagan & Catto 2010).…”

Section: Introductionmentioning

confidence: 99%

Neoclassical transport in strong gradient regions of large aspect ratio tokamaks

et al. 2023

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We present a new neoclassical transport model for large aspect ratio tokamaks where the gradient scale lengths are of the size of the ion poloidal gyroradius. Previous work on neoclassical transport across transport barriers assumed large density and potential gradients but a small temperature gradient, or neglected the gradient of the mean parallel flow. Using large aspect ratio and low collisionality expansions, we relax these restrictive assumptions. We define a new set of variables based on conserved quantities, which simplifies the drift kinetic equation whilst keeping strong gradients, and derive equations describing the transport of particles, parallel momentum and energy by ions in the banana regime. The poloidally varying parts of density and electric potential are included. Studying contributions from both passing and trapped particles, we show that the resulting transport is dominated by trapped particles. We find that a non-zero neoclassical particle flux requires parallel momentum input which could be provided through interaction with turbulence or impurities. We derive upper and lower bounds for the energy flux across a transport barrier in both temperature and density and present example profiles and fluxes.

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Neoclassical theory inside transport barriers in tokamaks

Cited by 13 publications

References 38 publications

Diffusivity Scaling on Shear Flow

Diffusivity Scaling on Shear Flow

Superbanana and superbanana plateau transport in finite aspect ratio tokamaks with broken symmetry

Neoclassical transport in strong gradient regions of large aspect ratio tokamaks

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