27E02P
ヘリオトロンJにおけるプラズマ流に対する磁場リップルの影響	 
Effect of Magnetic Ripple on Plasma Flow in Heliotron J
李 炫 庸 1、小林 進二2、横山 雅之3、原田 伴誉1、水内 亨2、長崎 百伸2、岡田 浩之2、
南 貴司2、村上 定義4、山本 聡2、大島 慎介2、史 楠2、臧 臨閣1、中村 祐司1、木島 滋2、
荒井 翔平1、釼持 尚輝1、永榮 蓉子1、沙 夢雨1、和多田 泰士1、福島 浩文1、杉本 幸薫1、中村 雄一1、橋本 紘平1、安田 圭佑1、笠嶋 慶純1、大谷 芳明1、佐野 史道2
H.Y. Lee1, S. Kobayashi2, M. Yokoyama3, T. Harada1, T. Mizuuchi2, et al.
京大院エネ科1、京大エネ研2、核融合研3、京大院工4
GSES Kyoto Univ.1, IAE Kyoto Univ.2, NIFS3, GSE Kyoto Univ.4
The transit frequency of ions, ωti, for a helical device
can be expressed as ωti = M/R(2eTi/mi)1/2, where M isthe helical pitch number of helical coil. The effective
parallel viscosity coefficient is defined as µ||eff ≡dF||ext/nimidv||, where F||ext is the external momentum
input by NBI calculated by the FIT code [6]. We
assumed that electron density profile is ne(ρ) =ne(0)(1-ρ2), where line-averaged electron density isapproximately 1.0×1019 m-3, and that effective charge
number (Zeff) is 2. The effective parallel viscosity getsclose to the NC parallel viscosity as γ increases.
However, µ||NC is still smaller than µ||eff even in thehigh mirror configuration. This result suggests thatµ||eff cannot be explained by µ||NC alone, and theperpendicular viscosity, such as momentum diffusion,
should be taken into account.
In this presentation, the viscous damping of v||,
including the perpendicular viscosity, will also bediscussed.
15

ρ = 0.07µ||eff/µ||NCThe plasma flows have been investigatedexperimentally and theoretically in magneticallyconfined plasmas for a variety of reasons; those relate
to transport barrier and improved confinement, suchas L-H transition with a reduction of edge turbulencein tokamak and stellarator/heliotron devices [1,2].
In Heliotron J [3], which is a helical-axis
heliotron device, the effect of magnetic ripple on theviscous damping of parallel flow v|| during Neutral
Beam Injection (NBI) has been investigated in thethree mirror configurations: high, standard andreversed mirror configurations [4]. The mirrorconfiguration is characterized by the magnetic ripple
strength, γ, which is defined as γ = {<(∂B/∂l)2/B2>}1/2.
Here, l is the length along the magnetic field line and<•••> is the flux surface averaged value. The values ofmagnetic ripple strengths at ρ = 0.07 in the high,standard and reversed mirror configurations are 0.073,0.03 and 0.029 m-1, respectively. The radial profiles ofv|| are measured using a Charge-eXchange
Recombination Spectroscopy (CXRS) system for NBI
plasmas. The line-averaged electron densities were0.8-1.0×1019 m-3 in the three mirror configurations. In
the region of ρ < 0.5, v|| in the high mirror
configuration is 2-3 times smaller than those in thestandard and reversed mirror configurations. The
difference of external momentum input by NBI
between the three mirror configurations is small [4],thus the cause of difference on v|| is attributed to thedifference in viscous damping effects.
To investigate the effect of parallel viscousdamping force, we have compared the neoclassical(NC) parallel viscosity with the effective parallelviscosity near the plasma center. Figure 1 shows theratio of the effective parallel viscosity coefficient µ||effto the NC parallel viscosity coefficient µ||NC as afunction of γ at ρ = 0.07. The NC parallel viscosity
coefficient is given by [2, 5] as follow:
eTi ,(1)µ||NC ≈ ξ1 πγ 2miω tiwhere mi is the mass of the ion and ξ1 is the energy
integral coefficient. In the plateau regime, ξ1 = 2 [2, 5].

HighSTDRev.

105000.05

γ (m-1)

0.1Fig 1. Ratio of µ||eff to µ||NC as a function of γ at ρ = 0.07.

Reference[1] J.S. deGrassie, Plasma Phys. and Control. Fusion, 51 (2009)
124047.
[2] K. Ida et al., Plasma Phys. and Control. Fusion, 40 (1998) 1429.
[3] M. Wakatani et al., Nucl. Fusion 40, (2000) 569.
[4] H.Y. Lee et al., Submitted to Plasma Phys. and Control. Fusion(2012).
[5] K. C. Shaing and J. D. Callen, Phys. Fluids, 26 (1983) 1526.
[6] S. Murakami et al., Fusion Technology, 27 (1995) 259.