27aC02
プラズマコヒーレント構造の輸送ダイナミクスの粒子シミュレーション
Particle Simulation of Plasma Coherent Structure Transport Dynamics
長谷川裕記1, 2, 石黒静児1, 2
HASEGAWA Hiroki1, 2 and ISHIGURO Seiji1, 2
核融合研1, 総研大2
NIFS1, SOKENDAI2
In recent magnetic confinement fusion device
experiments, it has been found that the density
profile in the far scrape-off layer (SOL) is flatterthan the exponential distribution which is expectedfrom a diffusion model [1]. Motivated by such
experiments, some authors have studied the plasmatransport in SOL theoretically. Then a theory ofplasma blob dynamics has been suggested as themechanism of the non-diffusive (convective) radialtransport [2]. The plasma blob is an intermittent
filamentary coherent structure along the magnetic
field line and propagates from the edge of coreplasma to the first wall. Such structures are thought
to play an important role in plasma particles andheat flux transports into the far SOL acrossmagnetic field lines. Many theoretical andnumerical studies about dynamics of blobs on thebasis of two-dimensional reduced fluid models havebeen conducted [3, 4]. In such kind of macroscopic
fluid models, however, kinetic effects (such as
sheath formation between plasma and divertor
plates, velocity difference between ions andelectrons, temporal and spatial variations of particle
velocity distributions, etc.) are treated under someassumptions and parameterization.
Thus, in this study, we have investigatedmicroscopic dynamics in a blob by means of athree-dimensional electrostatic plasma particle
simulation code with particle absorbing boundaries[5, 6]. In our previous study, we had investigatedthe configurations of spontaneous particle flows ina plasma coherent structure [7]. In this paper, wehave confirmed the presence of the net poloidal
current in a blob (see Fig. 1). Also, Fig. 2 indicatesthat the toroidal current from the divertor plate isalmost converted to the poloidal current.
Furthermore, in our previous study, we hadstudied kinetic effects on plasma blob dynamics inthe system where the periodic boundary condition isapplied in the direction parallel to the magnetic
field line and found that the symmetry breaking inblob propagation occurs by the kinetic effect. On
the other hand, in this paper, we have applied theparticle absorbing boundaries to the ends in thedirection parallel to the magnetic field line andstudied such kinetic effects with the plasma sheath.
In the simulation, not only the symmetry breaking
shown in the previous study but also otherproperties which were not found in the periodic
boundary case have been observed.

Fig. 1. Net poloidal currents at the backgroundplasma (Iy0) and in the blob (Iy0) as functions of z.

Fig. 2. Net poloidal current (Iy1-Iy0) and net toroidal
current (Iz) as functions of z.
[1] M. V. Umansky et al., Phys. Plasmas 5, 3373 (1998).
[2] S. I. Krasheninnikov, Phys. Lett. A 283, 368 (2001).
[3] S. I. Krasheninnikov, D. A. D’Ippolito, and J. R.
Myra, J. Plasma Phys. 74, 679 (2008) and references
therein.
[4] D. A. D'Ippolito et al., Phys. Plasmas 18, 060501(2011) and references therein.
[5] S. Ishiguro and H. Hasegawa, J. Plasma Phys. 72,1233 (2006).
[6] H. Hasegawa and S. Ishiguro, Plasma Fusion Res. 7,2401060 (2012).
[7] H. Hasegawa and S. Ishiguro, Phys. Plasmas 22,102113 (2015).