IAEA-FEC 2014
St. Petersburg, Russia
PPC/2-1
Integrated discharge scenario
for high-temperature helical plasma on LHD
K. Nagaoka
National Institute for Fusion Science
H. Takahashi1, S. Murakami3, H. Nakano1, Y. Takeiri1,2, H. Tsuchiya1, M.
Osakabe1, K. Ida1,2, M. Yokoyama1,2, M. Yoshinuma1, S. Morita1,2, M. Goto1,2,
T. Oishi1,2, N. Pablant4, K. Fujii5 K. Tanaka1, N. Tamura1, Y. Nakamura1,2, D.
Xiaodi2, T. Ido1, A. Shimizu1, S. Kubo1, H. Igami1, R. Seki1, C. Suzuki1, Y.
Suzuki1,2, K. Tsumori1,2, K. Ikeda1, M. Kisaki1, Y. Yoshimura1, T. Shimozuma1,
T. Seki1, K. Saito1, H. Kasahara1, S. Kamio1, T. Mutoh1,2, O. Kaneko1,2, H.
Yamada1,2, A. Komori1,2, and LHD Experiment Group
1National
Institute for Fusion Science, Toki, 509-5292, Japan
School for Advanced Studies (SOKENDAI), Toki 509-5292, Japan
3Department of Nuclear Engineering, Kyoto University, Kyoto 606-8501, Japan
4Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
5Department of Mechanical Engineering and Science, Kyoto University, Kyoto 615-8540, Japan
2Graduate
Contents
1. Introduction
2. Discharge Scenario of ion ITB
Ion ITB plasma in LHD
Wall conditioning effects
3. Integration of ion ITB and electron ITB
Strongly focused ECH
Transport characteristics
4. Summary
Characteristics of heat transport
-density dependencecentral Te
central Ti
10
Ti0 [keV]
Te0 [keV]
10
1
0.1
1
0.1
1
Scale length of grad Te
R/LTe(reff/a99=0.45)
Scale length of grad Ti
10
10
1
0.1
0.1
1
ne
ne
R/LTi(reff/a99=0.45)
• The density dependence of
achievable temperature is
different in low density
regime.
• The ion temperature decreases
with the decrease of density,
while electron temperature
increases in low density.
• The scale length of ion
temperature gradient also
decreases with the decrease
of density, while the
maximum of scale length of
electron temperature gradient
is unchanged with the density.
1
ne
10
1
0.1
0.1
1
ne
10
Effect of density profile change
1.2
-3
High Ti
Discharges
High Ti
Discharges
W/O Calibration
-4
10
1
0.8
-5
10
H2
p
ICRH Wall
Conditioning
ion heating power efficiency
10
0.6
-6
10
-7
0.4
(a) 2013/10/22
10
10:00
11:00
0.2
12:00
Time [s]
13:00
119084
119128
0
0
0.2
0.4 0.6
reff/a99
0.8
• The helium wall conditioning decreases the hydrogen recycling and changes
the change of density profile more peaked.
• The ion heating power was calculated by FIT-3D code and became peaked
profile after helium conditioning discharges.
• The peaking factor of ion heating power (Pi(reff/a99<0.5)/Pi_total) increases
from 0.48 to 0.55 after helium conditioning discharges.
1
Effect of charge exchange loss of
energetic ions
K. Fujii, RSI 2014, EXC/P6-31
(b)
• Energy spectra of NBI ions were
calculated with / without charge
exchange loss.
• The CX loss becomes significant
in low energy regime, indicating
reduction of ion heating power.
• The neutral density profile was
evaluated from a high-dynamic
range of Balmer-a spectroscopy
measurement.
• It was identified that the reduction
of ion heating power from 14%
to 7% in total ion heating power
due to the reduction of CX loss of
energetic ions.
Introduction
-Extension of temperature regime• Recently, the temperature regime of
helical plasma has been significantly
extended in LHD.
• The central ion temperature of 8.1keV has
Ion and el. ITBs
been achieved in low Zeff plasma with
intense helium wall conditioning.
• Te ~ Ti regime has been also extended by
integration of ion ITB and electron ITB.
Ion ITB
• Improved factor of global confinement
Wall conditioning
with respect to normal confinement is 1.5
for ion ITB and 1.7 for ion and electron
ITBs are achieved based on ISS04 scaling.
In this talk, discharge scenario of high Ti plasma is presented and effects of wall
conditioning is discussed. Then the integration of discharge scenarios of ion
and electron ITBs are presented
. The characteristics of heat transport in high temperature regime are
discussed.
Wall conditioning effects
on the core plasma
Charge exchange loss
no CX loss
K. Fujii, RSI 2014, EXC/P6-31
nH=1x1013 m-3
Profile change
3. 0
2. 5
2. 0
E
n o r m a l iz e d P i
a ft e r
19
(b)
-3
1x1015
be for e
0
50
10 0
after
1. 0
= 18 0 k e V
1x1014
ne [1x 10 m ]
1. 5
be a m
1 50
200
E be a m = 4 0 k e V
b e fo r e
0. 5
0. 0
0 .0
0 .2
0 .4
0. 6
r ef f / a 9 9
0 .8
1 .0
0
10
20
30
40
E n erg y [k eV ]
50
60
• The edge density become lower. The ion heating power calculated by FIT-3D
code became peaked profile after helium conditioning discharges.
• The peaking factor of ion heating power (Pi(reff/a99<0.5)/Pi_total) increases
from 0.48 to 0.55 after helium conditioning discharges.
• The charge exchange loss of energetic ions was calculated and neutral density
profile was measured with a high-dynamic range of Balmer-a spectroscopy.
• The loss of energetic ions reduced from 14% to 7% in ion heating power is
identified in this comparison.