04aE38P
ITERにおけるペレット入射によるELM制御の統合シミュレーション	 Integrated simulation of ELM control by Pellet Injection in ITER
林	  伸彦1、相羽信行1、滝塚知典2、大山直幸1
N. Hayashi 1, N. Aiba 1, T. Takizuka 2, N. Oyama 1
1

原子力機構、2 阪大工
JAEA, 2 Osaka Univ.

1

The energy loss caused by the edge localized
mode (ELM) needs to be reduced for ITER
operations with ELMy H-mode plasmas. The pellet
injection is considered as one possible method toreduce the ELM energy loss by increasing the ELM
frequency (so called ELM pacing). The ELM
pacing requires the significant reduction of ELM
energy loss, small impact on the plasma
performance, and less particle fueling. The
reduction of ELM energy loss by the pellet
injection for ELM pacing has been studied by an
integrated core / scrape-off-layer / divertor transport
code TOPICS-IB with an MHD stability code and apellet model taking account of the ExB drift ofpellet plasma cloud [1]. It was found that the ELM
energy loss can be significantly reduced by thelow-field-side injection of a pellet with about 1 %of pedestal particle content and a speed fast enoughto approach the pedestal top when the pedestalpressure is about 95 % of natural ELM onset [2]. In
this paper, we do simulations of JT-60U plasmas
with various parameters and ITER plasmas ofstandard operation scenario, examine theeffectiveness of the above suitable conditions for
ELM pacing and evaluate the pellet particle content
required for ELM pacing.
Figure 1 shows the ELM energy loss ΔWELM
normalized by the pedestal stored energy Wped as afunction of pellet position at the ELM onset ρpel,onset
for JT-60U and ITER simulations, where mode
locations are also shown. As the same as theprevious result, with the suitable conditions, a pellet
can significantly reduce the ELM energy loss bypenetrating deeply into the pedestal and triggering
ELM localized near the pedestal top. Thus, theeffectiveness of suitable conditions has beenconfirmed. Figure 2 shows the relation between thepellet particle content Np (normalized by thepedestal particle content Nped) required for ELM
pacing and the variation of normalized pressure
gradient Δα (normalized by the critical gradient αcrof ideal ballooning mode (IBM)) required todestabilize IBM. The pellet particle content
required for ELM pacing is larger for the pedestal

plasma with higher density and farther from theIBM stability boundary near the pedestal top. ForITER, the required pellet particle content is within
the range of present empirically-designed value andthus our evaluation gives the physical backgroundto the design.
[1] N. Hayashi et al, Nucl. Fusion 51 (2011) 103030.
[2] N. Hayashi et al, accepted in Nucl. Fusion[3] A. Loarte et al, 24th IAEA FEC, San Diego, 2012

FIG.1. Dependence of ΔWELM/Wped on pellet position
at ELM onset for JT-60U simulations (blue open)
and an ITER simulation (red closed), wherehorizontal solid lines denote mode locations, circle
symbols do results with suitable conditions of pellet
injection for ELM pacing, a square symbol does anexample without suitable conditions and shaded
regions denote other results in JT-60U. Vertical andhorizontal dotted lines denote pedestal top position
and ΔWELM of natural ELM level, respectively.

FIG.2. Dependence of Np/Nped on Δα/αcr for JT-60U(blue open) and ITER (red closed) simulations,where shade region denote pacing pellet size ofpresent ITER design [3]. In ITER simulations,normalized internal inductance li is varied from atypical value to ITER lower limit (A→B).