7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Effects of End Plates and Kinetic Dynamics on Filamentary Plasma Structure
Formations
Hiroki Hasegawa1, 2 and Seiji Ishiguro1, 2National Institute for Fusion Science, National Institutes of Natural Sciences
2Fusion Science Program, The Graduate University for Advanced Studies, SOKENDAI
e-mail (speaker): hasegawa.hiroki nifs.ac.jp
1(PS)” (NEC SX-Aurora TSUBASA) of NIFS with thesupport and under the auspices of the NIFS
Collaboration Research programs (NIFS22KISS004) andsupported by JSPS KAKENHI Grant Number
JP19K03787.
w/o end plates-Γxe / (n 0 c s)

Recently, the intermittent filamentary plasma
structures called “blob” have been investigatedexperimentally, theoretically, and numerically by many
authors since such structures are thought to play asignificant role in a radial non-diffusive plasma transport
in boundary layers of various magnetic confinement
fusion devices. In most of the theoretical and numericalstudies, the filament formation mechanism andpropagation dynamics have been considered on the basisof two-dimensional reduced fluid models [1, 2]. On theother hand, we have performed simulations of filament
propagations with the three-dimensional (3D)electrostatic particle-in-cell (PIC) simulation code called“p3bd” [3-5] in order to study microscopic properties on
the propagation. Using the 3D-PIC simulation, we
showed a self-consistent current system in a filament [6],a temperature structure in a filament [6], and an ion
temperature effect on the filament dynamics [7, 8]. Also,interactions between a filament and impurity ions havebeen investigated [9, 10].
However, in these previous works, we simulated only
the propagation dynamics of a filament structure whichis initially given in a simulation system. That is, afilament formation mechanism has been beyond thescope of our previous works. In order to study theformation mechanism with the 3D-PIC simulation, we
need to carry out large-scale simulations. Therefore, wehave developed the upgraded-p3bd (up3bd) code inwhich the one or two dimensional domain decomposition
is applied [11, 12]. In the simulation with the up3bd code
in which only a plasma density gradient perpendicular to
the magnetic field is initially given in the systemrepresenting boundary layer configuration, we haveobserved the non-diffusive plasma transport induced byinstability. In the early stage, the growth of density
perturbation with the short-wavelengths in the direction
parallel to the magnetic field is observed, while that withthe long-wavelengths is found in the next stage [13].
In this study, we have studied effects of end plates on
the non-diffusive plasma transport. Figure 1 shows thetime variations of electron radial fluxes for the caseswith / without end plates. Here, in the case without end
plates, the periodic boundary condition is applied in thedirection parallel to the magnetic field. This figure
indicates that the flux without end plates becomes larger
than that with end plates after Ωi t ~ 160. This fact isthought to arise from the significant growth oflong-wavelength perturbation in the case without endplates. Also, effects of ion heating with an induced wave
will be discussed in the presentation.
This work was performed on the “Plasma Simulator

0.1

withend plates

00100Ωi t200

Figure 1. Time variations of averaged electron radial
fluxes for the cases with / without end plates at thedensity transition region, x = Lx / 2. Here, -x is the radial
direction, the initial plasma density is given by n0 { tanh[( x - Lx / 2 ) / ∆] + 1 }, ∆ is the transition width, and themagnetic field strength is set as B = 2 Lx B0 / ( 3 Lx - x ).
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[6] H. Hasegawa and S. Ishiguro, Phys. Plasmas 22,102113 (2015).
[7] H. Hasegawa and S. Ishiguro, Plasma 1, 61 (2018).
[8] H. Hasegawa and S. Ishiguro, Phys. Plasmas 26,062104 (2019).
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[13] H. Hasegawa and S. Ishiguro, 31st International
Toki Conference, P2-4F02 (2022)