24C11
Impact of Te/Ti on confinement properties with emphasis on profile shapes
Te/Tiの閉じ込め性能に対する寄与と分布形状効果に関する研究
Emi Narita1, Tomonori Takizuka1,2, Nobuhiko Hayashi2, Takaaki Fujita2, Shunsuke Ide2,Mitsuru Honda2, Yasuyuki Tanaka1, Akihiko Isayama2, Kiyoshi Itami2 and Takeshi Fukuda1
成田絵美1, 滝塚知典1,2，林伸彦2，藤田隆明2，井手俊介2，本多充2，田中靖之1，諌山明彦2，
伊丹 潔2，福田武司11

Osaka University
2-1 Yamadaoka, Suita, Osaka 56-0871, Japan
大阪大学大学院 〒565-0871 大阪府吹田市山田丘2-1
2Japan Atomic Energy Agency
801-1 Mukouyama, Naka, Ibaraki 311-0193, Japan
日本原子力研究開発機構 〒311-0193 茨城県那珂市向山801-1
In order to know the impact of the temperature ratio Te/Ti on confinement properties, the updated DB3v10
database has been analyzed It is suggested that the increasing in Te/Ti deteriorates the confinement inpeaked density regime. This result has been checked against the simulation for JT-60SA using the transport
code TOPICS with the GLF23 transport model module and the GS2 code. As a consequence, these results
qualitatively agree with each other.

1. Introduction
The IPB98(y,2) scaling law[1], which has been
widely used for predicting the performance offuture devices, was elaborated from largely consistsof dominantly ion-heated discharges. In a futureburning machine, like ITER, on the contrary, it isexpected that Te/Ti is larger than unity due to thestrong alpha heating. In order to understand theimpact of Te/Ti on confinement properties, we havestudied the updated DB3v10 database[1,2], withemphasis on the Te/Ti effect. The impact has been
also investigated by using the transport code
TOPICS[3] with GLF23 transport model module andthe code GS2[4].
2. Scaling analyses with emphasis on the Te/Ti
The 317 data from JET, 67 from AUG and 68
from C-Mod have been extracted from the database.
For these data, the central temperature ratio Te0/Ti0
is limited in the range 0.5< Te0/Ti0<1.5, the peaking
factor, which is defined as the ratio of central
density and line averaged density, is limited in therange 1.0<ne0/ne<1.6, and the line averaged density
is lower than 60% of nGW. As a consequence ofregression analyses, we have obtained following
scaling expressions in two peaking factor regimes;sc1 = 0.0777Ip0.91Bt0.11ne0.28PL-0.59R1.73M0.270.540.41,; 1.0<ne0/ne<1.1 (flat density case),(1)
sc2 = 0.0594Ip0.90Bt0.08ne0.34PL-0.63R1.78M0.160.410.72,; 1.1<ne0/ne<1.6 (peaked density case).
(2)
The notations comply with conventional definitions.
Histograms of th/sc1 and th/sc2 for Te0/Ti0<1 andTe0/Ti0>1 are shown in Fig.1. Fig.1(a) and (c)describe that the peaked density profile improves
the confinement for discharges with Te0/Ti0<1,whereas, it works adversely in the Te0/Ti0>1 case.

Fig.1. Histograms th/sc1 and th/sc2. (a) and (b) flat
density case, (c) and (d) peaked density case. Te0/Ti0<1
data are shown in (a) and (c). Te0/Ti0>1data are shown in(b) and (d).

For the latter, we have further developed a scaling
expression including Te/Ti for peaked density case.
We incorporated 3 nondimensional variables[5],namely BtR1.25, ne/nGW*, and q in addition to Te/Ti.

Here, ne/nGW* is dimensionless normalized density.
The dependences on ne/nGW* and q were weak, andthe following new expression was obtained; which
reduce the standard deviation remarkably,sc3 = sc2{1-0.157(Te0/Ti0-1)(BtR1.25)0.59}.
(3)
Here, we find that the confinement time decreases
with increasing Te0/Ti0[6]. The correction term
f=0.157(Te0/Ti0-1)(BtR1.25)0.59 in (3) was plottedagainst ne0/ne for large and small values of Te0/Ti0. It
is deduced that peaked density profiles contribute toan improvement for low value of Te0/Ti0 region anddeteriorate for high value of the ratio region.

Fig. 3. (a) Dependence of HH-factor on Te0/Ti0 fordifferent density profiles. (b) Derivatives of HH-factor for
Te0/Ti0 against the density peaking factor. Here, Ip
2.3MA, Bt 1.7T, q95  4.7,  1.9 and  0.49.

indicates increased linear growth rate and larger
amplitude of potential fluctuation at larger Te0/Ti0 in
higher normalized wave number. Fig. 4(a) also
shows that the effect of Te0/Ti0 on linear growth rateis slightly higher in the peaked density profile atlarger Te0/Ti0, and Fig. 4(b) shows that the effect onenergy flux is stronger in the peaked density profile.
These impacts of Te0/Ti0 and ne0/ne are consistent
with results of the database analyses.
Fig. 2. Dependence of the correction term f in (3) on
peaking factor ne0/ne for large and small values oftemperature ratio.

3. Simulations with GLF23 and GS2
The impact of Te/Ti on confinement withemphasis on the density profile is demonstrated bysimulations using the transport code TOPICS withthe GLF23 transport model module and using thecode GS2. GLF module suggests that the transport
is enhanced for large Te/Ti regime[7], and the code
GS2 is effective to investigate the low-frequency
turbulence in magnetized plasmas.
We investigated the effect of Te0/Ti0 in four typesof density profiles using TOPICS with GLF23. The
value of Te0/Ti0 is varied by the ratio between
heating power for electrons and that for ions. The
effects of  stabilization and ExB shear
stabilization are included in these simulations. Fig.
3(a) shows the dependence of HH-factor on Te0/Ti0
for different density profiles. Here, HH-factor isdefined as HH=th/IPB98(y,2). The dependence ofderivative value of HH-factor with respect to Te0/Ti0
as a function of peaking factor is demonstrated inFig.3(b). The effect of Te0/Ti0 becomes more
profound with the increasing of peaking factor. Thisagrees with the results from scaling analyses.
The influences of Te0/Ti0 and ne0/ne have also
been investigated with the GS2 code. Fig. 4Fig. 4. Dependences of (a) growth rate and (b) amplitude
of potential fluctuation on normalized wave number.
Here, q95  3.03,  1.66 and  0.429.

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downloadedfrom
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http://ocs.ciemat.es/EPS2011PAP/pdf/P2.121.pdf[7] R. E. Waltz, et al., Phys. Plasmas 4, 2482 (1997)