### Abstract

Original language | English |
---|---|

Pages (from-to) | 022516 |

Journal | Physics of Plasmas |

Volume | 25 |

Issue number | 2 |

DOIs | |

Publication status | Published - 1 Feb 2018 |

Externally published | Yes |

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### Cite this

*Physics of Plasmas*,

*25*(2), 022516. https://doi.org/10.1063/1.5011176

}

*Physics of Plasmas*, vol. 25, no. 2, pp. 022516. https://doi.org/10.1063/1.5011176

**Algebraic motion of vertically displacing plasmas.** / Pfefferlé, D.; Bhattacharjee, A.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Algebraic motion of vertically displacing plasmas

AU - Pfefferlé, D.

AU - Bhattacharjee, A.

PY - 2018/2/1

Y1 - 2018/2/1

N2 - The vertical motion of a tokamak plasma is analytically modelled during its non-linear phase by a free-moving current-carrying rod inductively coupled to a set of fixed conducting wires or a cylindrical conducting shell. The solutions capture the leading term in a Taylor expansion of the Green's function for the interaction between the plasma column and the surrounding vacuum vessel. The plasma shape and profiles are assumed not to vary during the vertical drifting phase such that the plasma column behaves as a rigid body. In the limit of perfectly conducting structures, the plasma is prevented to come in contact with the wall due to steep effective potential barriers created by the induced Eddy currents. Resistivity in the wall allows the equilibrium point to drift towards the vessel on the slow timescale of flux penetration. The initial exponential motion of the plasma, understood as a resistive vertical instability, is succeeded by a non-linear "sinking" behaviour shown to be algebraic and decelerating. The acceleration of the plasma column often observed in experiments is thus concluded to originate from an early sharing of toroidal current between the core, the halo plasma, and the wall or from the thermal quench dynamics precipitating loss of plasma current.

AB - The vertical motion of a tokamak plasma is analytically modelled during its non-linear phase by a free-moving current-carrying rod inductively coupled to a set of fixed conducting wires or a cylindrical conducting shell. The solutions capture the leading term in a Taylor expansion of the Green's function for the interaction between the plasma column and the surrounding vacuum vessel. The plasma shape and profiles are assumed not to vary during the vertical drifting phase such that the plasma column behaves as a rigid body. In the limit of perfectly conducting structures, the plasma is prevented to come in contact with the wall due to steep effective potential barriers created by the induced Eddy currents. Resistivity in the wall allows the equilibrium point to drift towards the vessel on the slow timescale of flux penetration. The initial exponential motion of the plasma, understood as a resistive vertical instability, is succeeded by a non-linear "sinking" behaviour shown to be algebraic and decelerating. The acceleration of the plasma column often observed in experiments is thus concluded to originate from an early sharing of toroidal current between the core, the halo plasma, and the wall or from the thermal quench dynamics precipitating loss of plasma current.

U2 - 10.1063/1.5011176

DO - 10.1063/1.5011176

M3 - Article

VL - 25

SP - 022516

JO - Physics of Plasmas

JF - Physics of Plasmas

SN - 1070-664X

IS - 2

ER -