Feedback stabilization of disruption precursors in a tokamak

Aw, Morris; Tc, Hender; Hugill, J.; Ps, Haynes; Pc, Johnson; Lloyd, B.; Dc, Robinson; Silvester, C; Arshad, S.; Gm, Fishpool

doi:10.1103/physrevlett.64.1254

Cited by 78 publications

(56 citation statements)

References 4 publications

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“…In axisymmetric systems, it influences the dynamics of wall modes, 1-4 the interaction between the various internal modes, 5,6 and the effect of externally imposed perturbations such as feedback corrections [7][8][9] and error fields. [10][11][12][13][14][15][16][17][18][19][20][21][22][23] In helical systems a favorable magnetic well has been shown to lead to the healing of magnetic islands.…”

Section: Shielding Of Resonant Magnetic Perturbations In the Long Meamentioning

confidence: 99%

Shielding of resonant magnetic perturbations in the long mean-free path regime

Waelbroeck

2003

Physics of Plasmas

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The effect of diamagnetic drifts and of long electron mean free path on the shielding of resonant magnetic perturbations by plasma rotation is investigated. The nature of the force exerted on a moving plasma by a resonant perturbation is qualitatively altered by both drift and long mean-free-path effects. The force is found to have three minima, each of which is a possible locus for discontinuous transitions in plasma velocity. Between these minima are two points where the force exerted by the perturbation is resonant. These points describe locked states where shielding is ineffective and a magnetic island will grow. They correspond to rotation velocities such that either the electrons or the ions are at rest in the frame of the perturbation. The ion root, however, is unstable.

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Section: Shielding Of Resonant Magnetic Perturbations In the Long Meamentioning

confidence: 99%

Shielding of resonant magnetic perturbations in the long mean-free path regime

Waelbroeck

2003

Physics of Plasmas

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“…For the healing of plasma modes, experiments with additional heating [33,34,35] have been performed. The heating is of particular interest for plasma states which are close to a radiative collapse, e.g.…”

Section: Introductionmentioning

confidence: 99%

A new disruption mitigation valve (DMV) and gas flow in guiding tubes of different diameter

2011

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A new disruption mitigation valve, the DMV-30, has been developed and tested. The orifice output area of the valve is a factor of 2.4 and 12.25 times larger than that of its predecessors, DMV 20 and DMV 10, and the gas reservoir amounts to 1.3 l while the older version used at JET had only 0.65 l. The coil which provides the magnetic field pulse for the activation of the piston by an eddy current is outside of the working gas volume such that now all gas volumes are now made of stainless steel. The valve has the advantages of the previous developments: it is robust and reproducible, opens fully within three milliseconds and releases 50% of the gas within about 5 ms (He) to 10 ms (Ar). The valve is attached subsequently to two different guiding tubes, one with an inner diameter of 38 mm as used presently at JET and one with 102 mm inner diameter; an aim of this article is the analysis of the gas flows for the different diameters. The front of the gas pulse propagates with a Mach number of about 2.5 through the tubes, independent of the two diameters. This high speed agrees with theoretical expectations of a flow expansion of a half infinite tube in vacuum. In the quasi-stationary phase of the expansion, the gas flows with about sound speed in the 102 mm tube and with about half of the sound speed in the 38 mm tube.

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“…A number of proposals have been suggested and studied relative to stabilizing magnetic island formation in tokamaks which are resistive MHD unstable. In particular, these methods include using applied resonant field errors with negative feedback, [11][12][13][14][15] local heating of the island region, [16][17][18][19][20][21][22][23] and local current drive mechanisms. [24][25][26][27][28] We extend these studies and use a similar procedure to study the local heating and current drive effects on neoclassical MHD tearing modes.…”

Section: Introductionmentioning

confidence: 99%

On the stabilization of neoclassical magnetohydrodynamic tearing modes using localized current drive or heating

1997

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The effectiveness of using localized current drive or heating to suppress the formation and growth of neoclassical magnetohydrodynamic ͑MHD͒ tearing modes is addressed. The most efficient way to use an auxiliary current source is to cause current to flow in the same direction as the equilibrium bootstrap current and phase the current relative to the magnetic island such that the current is deposited on the O-point of the island. Theoretical estimates for the amount of required current to suppress the formation of a large magnetic island is of order a few percent of the equilibrium current. If the suppression is successful, the magnetic island will saturate at a width of order the radial localization width of the current source. Localized heating at the O-point of the magnetic island can also produce stabilizing effects relative to magnetic island growth. The effects of the driven current or heating can be illustrated by using a phase diagram of the island growth. © 1997 American Institute of Physics.

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Feedback stabilization of disruption precursors in a tokamak

Cited by 78 publications

References 4 publications

Shielding of resonant magnetic perturbations in the long mean-free path regime

Shielding of resonant magnetic perturbations in the long mean-free path regime

A new disruption mitigation valve (DMV) and gas flow in guiding tubes of different diameter

On the stabilization of neoclassical magnetohydrodynamic tearing modes using localized current drive or heating

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