Three-dimensional effect of particle motion on plasma filament dynamics

Hasegawa, H.; Ishiguro, Seiji

doi:10.1063/1.5093561

Cited by 3 publications

(2 citation statements)

References 32 publications

(34 reference statements)

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“…Our approach employs a fully-kinetic code, BIT1 [23,24], which is a particle-in-cell Monte-Carlo collisions (PIC-MCC) code [25]. The PIC approach is a rare case [26][27][28][29] of its use in the fusion community and its outcome shows the fully-kinetic (particle) feature of fusion plasma which is, in several aspects, different than its fluid counterpart. To our knowledge, our PIC-MCC model is the only one, so far, in the fusion community that can treat the whole length of a flux tube in a fully-kinetic manner.…”

Section: Introductionmentioning

confidence: 99%

“…To our knowledge, our PIC-MCC model is the only one, so far, in the fusion community that can treat the whole length of a flux tube in a fully-kinetic manner. Our model does not presume an established blobfilament with prescribed properties, as in [26], but generates it naturally from a plasma source at the separatrix at the outer midplane.…”

Section: Introductionmentioning

confidence: 99%

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Particle-in-cell simulations of parallel dynamics of a blob in the scrape-off-layer plasma of a generic medium-size tokamak

Costea¹,

Kovačič²,

Tskhakaya³

et al. 2021

Plasma Phys. Control. Fusion

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In this work we investigate, in a fully-kinetic particle approach, the evolution of a blob inside a flux tube in the scrape-off-layer (SOL) plasma of a generic diverted medium-size tokamak and its contribution to the recorded particle and energy flux densities at the divertor. Initially, a steady-state background plasma is reached, with realistic plasma profiles in the parallel direction. On top of it, a blob source with given intensity and temperature is superimposed at the outer midplane. The blob source is active for 10 μ s in order to emulate a generic blob with 1 cm diameter crossing the magnetic flux tube with a typical 1 km s−1 radial drift velocity. We have observed that most of the blob’s hot electrons are screened off by the cold electrons of the SOL plasma and can travel towards the two divertors free of the initial ambipolar forces. Performing a density scan and having a blob-to-background density ratio n b l o b / n b k g , S O L ≈ 5 in the source region, we observe that due to Coulomb collisions these hot electrons can reach the outer divertor or also the inner one, depending on the density of the background SOL plasma. Consequently, the midplane–divertor potential difference increases and the sheath expands leading to a significant increase in the background ion energy flux density onto the divertor. We also observe that when the blob ions reach the divertor the electron flux density on the divertor increases due to ambipolar forces. Through Coulomb collisions, a part of the thermal energy of the hot blob ions is transferred to the main (background) plasma, depending on the plasma density. Most of the energy deposited into the divertor is brought by the ions and the blob-induced background ion energy flux density becomes comparable (low-density case) or much higher (high-density case) than the blob ion energy flux density.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Particle-in-cell simulations of parallel dynamics of a blob in the scrape-off-layer plasma of a generic medium-size tokamak

Costea¹,

Kovačič²,

Tskhakaya³

et al. 2021

Plasma Phys. Control. Fusion

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Reduction of blob-filament radial propagation by parallel variation of flows: Analysis of a gyrokinetic simulation

Myra

Russell

et al. 2020

Physics of Plasmas

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Data from the XGC1 gyrokinetic simulation are analyzed to understand the three-dimensional spatial structure and the radial propagation of blob-filaments generated by quasi-steady turbulence in the tokamak edge pedestal and scrape-off layer plasma. Spontaneous toroidal flows vary in the poloidal direction and shear the filaments within a flux surface, resulting in a structure that varies in the parallel direction. This parallel structure allows the curvature and grad-B induced polarization charge density to be shorted out via parallel electron motion. As a result, it is found that the blob-filament radial velocity is significantly reduced from estimates that neglect parallel electron kinetics, broadly consistent with experimental observations. Conditions for when this charge shorting effect tends to dominate blob dynamics are derived and compared with the simulation.

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Experiments and gyrokinetic simulations of the nonlinear interaction between spinning magnetized plasma pressure filaments

Sydora,

Simala-Grant,

Karbashewski

et al. 2024

Physics of Plasmas

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A set of experiments using controlled, skin depth-sized plasma pressure filaments in close proximity have been carried out in a large linear magnetized plasma device. Two- and three-filament configurations have been used to determine the scale of cross field nonlinear interaction. When the filaments are separated by a distance of approximately five times the size of a single filament or less, a significant transfer of charge and energy occurs, leading to the generation of inter-filament electric fields. This has the effect of rotating the filaments and influencing the merging dynamics. Nonlinear gyrokinetic simulations using seeded filaments confirm the presence of unstable drift-Alfvén modes driven by the steep electron temperature gradient. When the filaments are within a few collisionless electron skin depths (separations twice the size of a single filament), the unstable perturbations drive the convective mixing of the density and temperature and rearrange the gradients such that they maximize in the region surrounding the filament bundle.

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Three-dimensional effect of particle motion on plasma filament dynamics

Cited by 3 publications

References 32 publications

Particle-in-cell simulations of parallel dynamics of a blob in the scrape-off-layer plasma of a generic medium-size tokamak

Particle-in-cell simulations of parallel dynamics of a blob in the scrape-off-layer plasma of a generic medium-size tokamak

Reduction of blob-filament radial propagation by parallel variation of flows: Analysis of a gyrokinetic simulation

Experiments and gyrokinetic simulations of the nonlinear interaction between spinning magnetized plasma pressure filaments

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