Modelling of parallel dynamics of a pellet-produced plasmoid

Runov, A.; Aleynikov, P.; Arnold, A.; Breǐzman, B. N.; Helander, P.

doi:10.1017/s0022377821000714

Cited by 6 publications

(30 citation statements)

References 12 publications

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“…It was predicted that approximately 50 % of plasmoid electron heating power is transferred to ions in the form of flow velocity due to the ambipolar expansion. However, with the reduction in plasmoid electron heating, we expect an even larger transfer of energy to the ions (Runov et al 2021), thereby increasing the plausibility of ambipolar expansion as a mechanism for an increased T i /T e ratio after pellet injection in W7-X (Baldzuhn et al 2019(Baldzuhn et al , 2020.…”

Section: Discussionmentioning

confidence: 93%

“…Previous work on modelling the parallel expansion of fuel pellet plasmoids did not consider a self-consistent well, thereby overestimating the heating of plasmoid electrons (Aleynikov et al 2019;Arnold et al 2021;Runov et al 2021). It was predicted that approximately 50 % of plasmoid electron heating power is transferred to ions in the form of flow velocity due to the ambipolar expansion.…”

Section: Discussionmentioning

confidence: 99%

“…This kind of model treats the plasma independently 'on each field line'. This 1D description is ubiquitously employed in the description of plasmoids, particularly those in the context of fuel pellet injection in magnetic confinement fusion (MCF) devices (Gurevich, Pariiskaya & Pitaevskii 1966;Mora 2003;Aleynikov et al 2019;Runov et al 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Previous work on plasmoid dynamics in one dimension assumed the electrons to be in either global Boltzmann equilibrium (Gurevich et al 1966;Mora 2003;Aleynikov et al 2019;Arnold et al 2021) or in local equilibrium with spatially dependent temperature (Runov et al 2021). The difference in the temperatures of plasmoid electrons and ambient electrons was accounted for by introducing a collisional heating term to the equation governing plasmoid electron temperature.…”

Section: Introductionmentioning

confidence: 99%

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Electron kinetics in a high-Z plasmoid

2023

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The problem of the electron dynamics on a closed magnetic field line passing through a high- $Z$ plasmoid is considered. The electron kinetic equation is integrated over bounce motion and pitch angle, reducing the independent variables to a single adiabatic invariant plus time. Integration of the full Landau self-collision operator is carried out exactly, resulting in a nonlinear integro-differential operator in the new invariant. Conservation laws and the $H$ theorem of the integrated self-collision operator are proven. Numerical solutions of the integrated kinetic equation are obtained with a self-consistent quasineutral electric potential, given the initial condition of a cold plasmoid immersed in a hot ambient plasma. The fact that cold electrons are deeply trapped in a potential with a parabolic peak leads to exactly 3/4 the usual rate of collisional heating by the ambient plasma, independent of any other parameters.

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Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electron kinetics in a high-Z plasmoid

2023

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“…If one assumes the electric field dominantly determines the destabilized fluctuation propagation, the velocity of E × B drift of ~ 1000–3000 m/s should be induced by the perpendicular electric field of ~ 10–30 V/cm at the magnetic strength B = 1 T. An electric field in the perpendicular direction to a field line can be present even in the plasmoid 44 , although some modeling studies neglect the electric field inside a plasmoid along a field line since the potential structure is homogenized along a field line quickly due to the high conductivity inside the plasmoid 45 . A schematic of this simple interpretation described above is summarized in Fig.…”

Section: Resultsmentioning

confidence: 99%

Three-dimensional dynamics of fluctuations appearing during pellet ablation process around a pellet in a fusion plasma experiment

Ohshima

Suzuki

Matoike

et al. 2022

Sci Rep

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Understanding pellet ablation physics is crucial to realizing efficient fueling into a high temperature plasma for the steady state operation of ITER and future fusion reactors. Here we report the first observation of the formation of fluctuation structures in the pellet plasmoid during the pellet ablation process by a fast camera in a medium-sized fusion device, Heliotron J. The fluctuation has a normalized fluctuation level of ~ 15% and propagates around the moving pellet across the magnetic field. By comparing the fluctuation structures with the shape of magnetic field lines calculated with the field line tracing code, we successfully reconstruct the spatio-temporal structure of the fluctuations during the pellet ablation process. The fluctuations are located at the locations displaced toroidally from the pellet and propagate in the cross-field direction around the pellet axis along the field line, indicating a three-dimensional behavior and structure of fluctuations. The fluctuation would be driven by a strong inhomogeneity formed around the pellet and invoke the relaxation of the gradient through a cross-field transport induced by the fluctuations, which could affect the pellet ablation and pellet fueling processes. Such fluctuations can be ubiquitously present at the inhomogeneity formed around a pellet in the pellet ablation process in fusion devices.

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Drift of ablated material after pellet injection in a tokamak

et al. 2023

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Pellet injection is used for fuelling and controlling discharges in tokamaks, and it is foreseen in ITER. During pellet injection, a movement of the ablated material towards the low-field side (or outward major radius direction) occurs because of the inhomogeneity of the magnetic field. Due to the complexity of the theoretical models, computer codes developed to simulate the cross-field drift are computationally expensive. Here, we present a one-dimensional semi-analytical model for the radial displacement of ablated material after pellet injection, taking into account both the Alfvén and ohmic currents which shortcircuit the charge separation creating the drift. The model is suitable for rapid calculation of the radial drift displacement, and can be useful for e.g. modelling of disruption mitigation via pellet injection.

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Modelling of parallel dynamics of a pellet-produced plasmoid

Cited by 6 publications

References 12 publications

Electron kinetics in a high-Z plasmoid

Electron kinetics in a high-Z plasmoid

Three-dimensional dynamics of fluctuations appearing during pellet ablation process around a pellet in a fusion plasma experiment

Drift of ablated material after pellet injection in a tokamak

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