28D41P
プラズモイド放出を用いた動的ダイバータの実験的・数値的実証	 
Experimental and numerical studies of dynamic divertor by plasmoid ejection	 
井上	  静雄(1)、小野	  靖(1)、神納	  康宏(1)、宇佐見	  俊介(2)、大谷	  寛明(2)、堀内	  利得(2)S. Inoue(1), Y. Ono(1), Y. Kaminou(1), S. Usami(2), H. Ohtani(2), R. Horiuchi(2)(1)東京大学工学系研究科、 (2)核融合科学研究所(1) Graduate School of Engineering, University of Tokyo, (2) National Institute for Fusion Science
figure 1. The blue region indicates SOL ions are
confined in the plasmoid, not diffuse directly to thedivertor plate. The common flux for the main anddivertor plasmas have to be reduced to zero together
with the plasmoid forming alternatively at the rightand left sides in our ideal doublet dynamic divertor
configuration. In this case, we can transport all
particle/heat flux from the core plasma to theplasmoid, therefore, the alternate left-side andright-side plasmoid ejections can maintain thecontinuous blue region, as shown in figure 2(b).
These results verified the controlled plasmoid
ejection from the main ST plasma together with theSOL heat flux transportation to it. The remaining
challenge of our experiment is to annihilate thecommon flux between the core and the divertor
plasmas for the heat flux suppression and to simulate
the radiation cooling effect of gas puff / impurity
pellet injection using the measured magnetic
configuration.
[1] S. Inoue et al., IEEJ Trans. FM, 131, 11, 963 (2011).
[2] S. Inoue et al., 24th IAEA FEC, PD/P8-17 (2012).
0.7

636 [μs]

430 [μs]R [m]651 [μs]

699 [μs]

0.1
0.3 Core
0.1

603 [μs]
Divertor -0.4
plasmaplasma0.0Z [m]0.50
Psi[mWb]

10627 [μs]-10Plasmoid

Fig. 1 Poloidal flux contours of plasmoid ejected fromthe main plasma to the divertor in the TS-4.
(a)

1.3

(b)

0.6
530700̭
Doublet Dynamic Divertor Conf.

Poloidal flux at initial
ion position[-mWb](R,Z=Variable, -0.4).

We demonstrated periodic ejections of "plasmoid"-closed magnetic island- from the main plasma, its
transportation and reconnection with a divertor plateusing our TS-4 spherical tokamak experiment and our2-D MHD simulation code[1,2]. The series ofoperations are keys for a new “Dynamic divertor”
whose unique magnetic separation of divertor plasma
is expected to significantly reduce heat flux to thedivertor plate.
The divertor is a key component for fusion reactors
to remove helium ash with heat flux from the mainplasma. The severe heat load limitation for thedivertor plate can tolerates the grassy (small) ELM(Edge Localized Mode) but not the Type-I ELM,regulating the high-beta tokamak operation. The
super-X type and the snowflake type divertors
increase the wetted divertor plate area to reduce theheat load. Unlike these new-type divertors, thedynamic divertor has the divertor plate magneticallyisolated from the main plasma and the heat flux istransported in forms of the plasmoid (in other word,
the heat flux is confined in the closed magnetic fieldline), brings a number of advantages. The long
distance (or small conductance) between the coreplasma and the divertor plate means lesstransportation of injected neutral gas or impurities andseparation by the magnetic field means no recyclingions. We can easily handle the power of the plasmoidby the radiation cooling of Argon gas puff and/orpellet injection.
Figure 1 shows R-Z poloidal flux contours ofplasmoid ejected from the main plasma to the divertor
in one cycle of the dynamic divertor motion, whichwere measured by two-dimensional (2-D) arrays ofpickup coils in the TS-4. The main ST plasma wasformed on the left side both by inductions of the flux
cores and the center solenoid coil. In our present
experiments, the inductive current drive by the center
solenoid (CS) causes expansion of the main plasma at
the bad curvature corner at t~603µs, generating aplasmoid from t~603 to 627µs and then ejecting it to
the divertor coil region by the help of pull force of thedivertor coil. We demonstrated for the first time one
cycle of the dynamic divertor operation, though theplasmoid ejection occurs once due to the waveform
limitation of the coil current under the present setup.
Figure 2(a) shows our ion orbit simulation resultsin the SOL region (vth=5eV, Z=-0.4m) in the case ofLeft side&RQrQHGLQWKHFRUH&RQrQHGLQWKHSODVPRLG*RRXWWRGLYHUWRUUHJLRQRight side

Pout・・・Periodic・・・PoutTConfined and easily cool down

Fig. 2 (a) Particle orbit simulation of SOL ions, (b) SOL
ion transport in the doublet dynamic divertor motion.