Dual equilibrium in a finite aspect ratio tokamak

Gourdain, P. A.; Leboeuf, J. N.

doi:10.1016/j.physleta.2008.08.004

Cited by 2 publications

(5 citation statements)

References 14 publications

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“…The surrounding plasma becomes the 'perfectly conducting wall' which stabilizes the external kink mode of the inner high beta equilibrium. An example is shown in figure 18 [92]. Unlike the 'conventional' current hole equilibrium, a peaked pressure profile with a large outward shift is observed.…”

Section: Other Types Of Current Holementioning

confidence: 96%

“…Such equilibria were shown to be stable to low n internal kink modes but unstable to n = 1 external kink [91]. The equilibrium with a zero toroidal current region stable to the external kink mode is obtained by inserting the high beta equilibrium solution inside a 'conventional' current hole equilibrium [92,93]. This 'dual equilibrium' has a central zero toroidal current region surrounded by a finite current region.…”

Section: Other Types Of Current Holementioning

confidence: 99%

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Tokamak equilibria with nearly zero central current: the current hole

Fujita

2010

Nucl. Fusion

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The observation of stable sustainment of the ‘current hole’, namely the nearly zero current density region in the central part of a tokamak plasma, has opened a new class of configurations in tokamak plasmas, and a variety of research from the viewpoints of equilibrium, magnetohydrodynamics (MHD) stability, particle orbits and radial transport has been generated. Some theories and codes have been tested and extended by being applied to extreme conditions in the current hole with very weak poloidal field. The current hole is generated due to a transient negative toroidal electric field established when a large off-axis non-inductive current is rapidly formed. It has been observed in high confinement plasmas with a large fraction of bootstrap current in advanced tokamak operation. The current hole is very stiff against current drive, which suggests that it is a saturated or self-organized system. Appearance of the current hole in ITER and DEMO would be expected in some of the operation scenarios, and its influence and its control methods have been studied. Results of experimental and theoretical studies on the current hole are reviewed.

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Section: Other Types Of Current Holementioning

confidence: 96%

Section: Other Types Of Current Holementioning

confidence: 99%

Tokamak equilibria with nearly zero central current: the current hole

Fujita

2010

Nucl. Fusion

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“…This can be simply explained by the dual equilibrium structure. 4 The outer equilibrium is a current hole, where flux surfaces are tightly packed on both sides of the plasma. The inner equilibrium has a large ␤ and it is diamagnetic.…”

Section: B Dual Equilibrium Scenariosmentioning

confidence: 99%

“…To re-establish stability, it is sufficient to add a paramagnetic layer of plasma around the diamagnetic core to increase magnetic field compressibility at the plasma periphery. 4 In the case we chose to study in this paper, high-n ballooning modes are stable. Figure 7͑a͒ shows that the criterion computed by DCON is positive everywhere ͑a sign of sta-bilitity͒.…”

Section: Stabilitymentioning

confidence: 99%

“…Such configurations are called dual equilibria. 4 They combine an inner diamagnetic equilibrium, increasing core pressure, with an outer paramagnetic equilibrium, improving free-boundary mode stability. 5 In the rest of this paper we look at a potential high ␤ tokamak reactor with the following parameters: B toro ϳ 5 T, I p ϳ 15-25 MA, and plasma elongation ϳ1.8.…”

Section: Introductionmentioning

confidence: 99%

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Hollow current profile scenarios for advanced tokamak reactor operations

Gourdain

Leboeuf²

2009

Physics of Plasmas

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Advanced tokamak scenarios are a possible approach to boosting reactor performances. Such schemes usually trigger current holes, a particular magnetohydrodynamics equilibrium where no current or pressure gradients exist in the core of the plasma. While such equilibria have large bootstrap fractions, flat pressure profiles in the plasma core may not be optimal for a reactor. However, moderate modifications of the equilibrium current profile can lead to diamagnetism where most of the pressure gradient is now balanced by poloidal currents and the toroidal magnetic field. In this paper, we consider the properties of diamagnetic current holes, also called "dual equilibria," and demonstrate that fusion throughput can be significantly increased in such scenarios. Their stability is investigated using the DCON code. Plasmas with a beta peak of 30% and an average beta of 6% are found stable to both fixed and free-boundary modes with toroidal mode numbers n =1-4, as well as Mercier and high-n ballooning modes. This is not surprising as these scenarios have a normal beta close to 3.

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Dual equilibrium in a finite aspect ratio tokamak

Cited by 2 publications

References 14 publications

Tokamak equilibria with nearly zero central current: the current hole

Tokamak equilibria with nearly zero central current: the current hole

Hollow current profile scenarios for advanced tokamak reactor operations

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