24P034-P
L/H transition simulation with integrated modellingof core and SOL/divertor transport
コアと周辺プラズマ輸送の統合モデルによる	 LH遷移のシミュレーション	 
Katsuhiro Shimizu 1, Tomonori Takizuka 1, Mitsuru Honda 1, Nobuhiko Hayashi 1,Kazuo Hoshino 2, Atsushi Fukuyama 3, Masatoshi Yagi 2, 4
清水勝宏１, 滝塚知典１, 本多充１, 林伸彦１,星野一生２, 福山淳３, 矢木雅敏２,４
1 Japan Atomic Energy Agency, Mukouyama, Naka, Ibaraki 311-0193, Japan
2 Japan Atomic Energy Agency, Rokkasho-mura, Kamikita-gun, Aomori 039-3212, Japan
3 Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
4 RIAM, Kyushu University, Kasuga, Fukuoka 816-8580, Japan１日本原子力研究開発機構 〒039-3212 青森県上北郡六ヶ所村
２日本原子力研究開発機構 〒311-0193 茨城県那珂市向山３京都大学 〒606-8501 京都府左京区
４RIAM 九州大学	  〒816-8580	  福岡県春日We have developed a self-consistent integrated modelling of core and SOL/divertor transport, i.e. a 1.5Dcore code TOPICS-IB and a 2D divertor code SONIC have been successfully coupled. The dynamic
simulations are carried out for JT-60SA with this integrated code including a CDBM transport model,
where particle and heat transports are suppressed by the ExB shearing effect. The L/H transition is
successfully demonstrated based on the turbulent suppression transport model and the self-consistentboundary condition. It is interesting to note that the fluctuating nature appears in the divertor plasma after
the transition.

1. Introduction
Control of the power and particle exhaust is
one of the most critical issues to achieve thefusion reactors, such as ITER and DEMO. To
investigate the control method by the divertor, wehave developed a 2D divertor code, SONIC [1].
In order to investigate the interactions between
core and SOL/divertor transport, SONIC has been
consistently coupled to a 1.5 D tokamak transport
code (TOPICS-IB [2]). The predictive simulation
studies were carried out for JT-60SA with thisintegrated code [3]. Dynamic change in particle
and heat fluxes into the SOL region after an
H-mode transition had a significant influence on
the characteristics of divertor plasma. In thesesimulations, the timing of the H-mode transition
and the anomalous heat diffusivities before andafter the transition were specified as input data.
We have recently improved the core transportmodel based on the current-diffusive ballooning
model (CDBM) [4]. Some parameters and thedependence of F(s,α) (see Eq.(1)) in the heattransport coefficient in the CDBM model wereadjusted so that the transition threshold power andthe energy confinement time were roughly equal tothe values estimated from theirs scalings [5].
The dynamic simulations for the L/H transition

in JT-60SA are carried out with the integrated code
including the new tuned CDBM transport model,
where particle and heat transports are suppressed by
the ExB shearing effect. It should be noted that theL/H transition timing and the particle and heattransport coefficients before and after the transition
are consistently determined, in contrast with thesimulations carried out so far.
2. CDBM transport model
A heat transport coefficient based on the CDBM
model is given asχCDBM = |α|3/2 F(s, α) (c/ωpe)2(vA/qR),(1)

with α = −q2Rdβ/dr, where we assume q=qeng=2πκr2Bt/µ0RI(r) and I(r) is the plasma current insidea minor radius r. The expression for F is modified
and its value for the weak/negative shear regime is
2~3 times larger than original one. The suppressionof transport by the E×B shear flow is introduced asχ0= χCDBM C1/{1 + (C2ωEXB/γCDBM)K}(2)

where γCDBM=|α|1/2 F(s, α) (vA/qR) is the growth rateof CDBM and ωEXB=(RBθ/Bt)|d/dr(Er/RBθ)| is the
ExB shearing rate. The radial electric field Er is
simply assumed to balance with the ion pressuregradient-dpi/dr +eniEr = 0.

(3)

In Eq. (2), C1 = 1.5 is selected by adjusting so thatthe HH factor ~ 0.5 in the L-mode phase, C2 = 15 isselected by adjusting so that an L/H transition
occurs at P ~ Pthr anticipated from the threshold
power scaling (Pthr ~ 5 MW). The power index K ischosen as 3 so that the pedestal profiles in thedensity and temperature are formed remarkably.
The ion heat diffusivity χi is given by the sum of
χ0 and χNEO (ion neoclassical diffusivity). We set
for simplicity the electron heat diffusivity χe equal
to χi. The particle diffusion coefficient is set by D =χ/3. The particle pinch term is not included.
To validate the tuned CDBM model [5], thesimulation of the L/H transition is carried out withthe 1D core transport code (TOPICS-IB). The
JT-60SA simulations are carried out for conditionsof R = 3 m, a = 1.1 m, κ = 1.8, δ = 0.55, Ip = 4 MA,and Bt = 2.3 T. The simulation start with weakneutral beam heating (PNB = 0.5 MW) and ohmic
heating of POH = 3.1 MW and then neutral beam
heating is increased up to PNB = 8 MW at t = 3.0 s.
Figure 1 shows the evolution of electron
temperature profile Te, and heat diffusivity profile χ.
An L/H transition occurs around t = 3.1 s. The χ isdrastically dropped in the edge region and thepedestals are clearly formed on Te profiles. The HH
factor is about 0.5 during L-mode phase andincreases to ~0.85 at t = 4.0 s in the H-mode phase.
25t = 4.0 s

4

3.2 s

Te

χ

1.5

3.1 s

21

3.05 sχ (m2/s)Te (keV)6

32D SONIC code vice-versa. The edge region ρc < ρ< 1 is overlapped for both codes. The transportcoefficients in the SOL/divertor region, χi, χe and D,
are assumed uniform and their values are set equal
to those at the separatrix boundary calculated by theCDBM model.
Figure 2 shows the time evolution of ion density
and temperature (nid, Ted) at outer divertor strike
point and (ni,SOL, Te,SOL) at the outer mid-planethrough the L/H transition. The ion density at thestrike point nid drops rapidly from ~7x1019 m-3 to~2x1019 m-3, and the electron temperature Ted
increases from ~10 eV to ~50 eV. On the contraryat the mid-plane, the ion density ni,SOL is almost
unchanged at ~1x1019 m-3.
The L/H transition is successfully demonstrated
based on the tuned CDBM model. Although results
shown here are preliminary, it should be noted thatthe fluctuating nature appears in the divertor plasma
after the transition. Further examination of thenumerical accuracy and analysis on the physicalmechanisms are required.

t = 3.0 s
0.5

1Fig. 2 Time evolution of electron density andtemperature at outer divertor strike point and outer
mid-plane through the L/H transition at t=3.1 s.

Fig. 1 Evolution of electron temperature profile and heatdiffusivity profile.

Acknowledgement
This work is partly supported by a Grant-in-Aid for
Scientific Research of Japan Society for the Promotionof Science.

3. Dynamics of the L/H transition in JT-60SA
The coupling between core transport code
TOPICS-IB and SOL/divertor transport code
SONIC are performed as follows. From the 1D coretransport code the fluxes (Γ, Qe, Qi) at ρ=ρc (= 0.82for the present coupling) are sent to 2D SONIC
code, while the plasma quantities (ni, Te, Ti) at theouter mid-plane are sent to the 1D core code fromReferences[1] K. Shimizu et al.: Nucl. Fusion 49 (2009) 065028.
[2] N. Hayashi et al.: Phys. Plasmas 17 (2010) 056112.
[3] K. Shimizu et al.: 23rd IAEA Fusion Energy
Conference, (Daejeon, 2010) IAEA/THD/5-2Ra.
[4] A. Fukuyama et al.: Plasma Phys. Control. Fusion 37(1995) 611.
[5] M. Yagi et al.: 13th Int. Workshop on Plasma Edge
Theory in Fusion Devices, (USA, 2011).

00.2

0.4

ρ

0.6

0.8

1.0