Stability Limitations on High-Beta Tokamaks

Todd, A.M.M.; Chance, M. S.; Greene, J. M.; Grimm, R.C.; Johnson, John L.; Manickam, J.

doi:10.1103/physrevlett.38.826

Cited by 86 publications

(49 citation statements)

References 6 publications

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“…(4) 3/2 Without the correction term of order (a/R) ' , we may note that our result is in surprisingly close agreement with the exact numerical results of Ref. [1]. In Ref.…”

Section: Stability Limit On Beta In a Tokamaksupporting

confidence: 81%

“…"ballooning" instabilities impose a fairly severe limit on f}, the ratio of 2 , plasma pressure p to magnetic pressure B /i., in a tokamak. Ballooning modes have been identified in numerical minimizations of the MHD energy principle [1,2] , and in time-dependent computations [3j ; analytic models have also been developed [4] that give good agreement with these numerical results.…”

mentioning

confidence: 94%

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Stability limit on beta in a tokamak using the collisionless energy principle

Rutherford¹,

Chen²,

Rosenbluth³

1978

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“…(4) 3/2 Without the correction term of order (a/R) ' , we may note that our result is in surprisingly close agreement with the exact numerical results of Ref. [1]. In Ref.…”

Section: Stability Limit On Beta In a Tokamaksupporting

confidence: 81%

mentioning

confidence: 94%

Stability limit on beta in a tokamak using the collisionless energy principle

Rutherford¹,

Chen²,

Rosenbluth³

1978

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“…It was recognized quite early (i.e., well before the availability of experimental data) that high-n ballooning and lower-n kink modes were the main beta-limiting ideal MHD instabilities for tokamaks. [371][372][373] In Ref. 372, for example, it was predicted that the tokamak b limit increases as the inverse of the tokamak aspect ratio A R 0 /a, where R 0 is the tokamak plasma major radius and a is the minor radius, (i.e., b / 1/A).…”

Section: Appendix B: Brief Background For Sts and Tokamaksmentioning

confidence: 99%

Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ∼ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ∼ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of an attractive fusion energy power source. Since the start of the two mega-ampere class ST facilities in 2000, the National Spherical Torus Experiment in the United States and Mega Ampere Spherical Tokamak in UK, active ST research has been conducted worldwide. More than 16 ST research facilities operating during this period have achieved remarkable advances in all fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.

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“…In toroidal geometry, this leads to the ballooning mode since the interchange effect is destabilising only on the outer part of the torus, where the radius of curvature and gradient-B vectors become parallel to the pressure gradient. The ideal form of this dynamics as an instability in toroidal geometry was discovered in attempts to explain curious observations of magnetic fluctuations localised to the outboard side of the PLT tokamak [14]. These fluctuations were explained as ideal ballooning modes, which were treated conventionally [15] as well as with what became known as the ballooning transformation [16,17,18].…”

Section: Introduction -More Than One Eigenmode In Turbulencementioning

confidence: 99%

Drift wave versus interchange turbulence in tokamak geometry: Linear versus nonlinear mode structure

2005

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The competition between drift wave and interchange physics in general E-cross-B drift turbulence is studied with computations in three dimensional tokamak flux tube geometry. For a given set of background scales, the parameter space can be covered by the plasma beta and drift wave collisionality. At large enough plasma beta the turbulence breaks out into ideal ballooning modes and saturates only by depleting the free energy in the background pressure gradient. At high collisionality it finds a more gradual transition to resistive ballooning. At moderate beta and collisionality it retains drift wave character, qualitatively identical to simple two dimensional slab models. The underlying cause is the nonlinear vorticity advection through which the self sustained drift wave turbulence supersedes the linear instabilities, scattering them apart before they can grow, imposing its own physical character on the dynamics. This vorticity advection catalyses the gradient drive, while saturation occurs solely through turbulent mixing of pressure disturbances. This situation persists in the whole of tokamak edge parameter space. Both simplified isothermal models and complete warm ion models are treated.

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Stability Limitations on High-Beta Tokamaks

Cited by 86 publications

References 6 publications

Stability limit on beta in a tokamak using the collisionless energy principle

Stability limit on beta in a tokamak using the collisionless energy principle

Recent progress on spherical torus research

Drift wave versus interchange turbulence in tokamak geometry: Linear versus nonlinear mode structure

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