japan atomic energy agency
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Japan Atomic Energy Agency Naka Fusion Institute. Dependence of H-mode pedestal and heat transport on toroidal rotation in JT-60U. H. Urano, H. Takenaga, T. Fujita, Y. Kamada, K. Kamiya, Y. Koide, N. Oyama, M. Yoshida and the JT-60 Team. Japan Atomic Energy Agency. - PowerPoint PPT PresentationTRANSCRIPT
H. Urano, H. Takenaga, T. Fujita, Y. Kamada, K. Kamiya, Y. Koide, N. Oyama, M. Yoshida and the JT-60 Team
Japan Atomic Energy Agency
JT-60U Tokamak: p. 1The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
Japan Atomic Energy Agency Naka Fusion Institute
Dependence of H-mode pedestal and heat transport on toroidal rotation in JT-60U
JT-60
T-NBIP-NBI
P
JT-60U has 11 PNBs (~85keV) and 2 NNBs (~350-420keV).
Widely variations in combination of tang. (co/bal/ctr) and perp. injection.
After the installation of FSTs, accessible dynamic range of VT has become extended towards co-direction.
Introduction
0.7
0.8
0.9
1
1.1
1.2
0.3 0.4 0.5
ne/ nGW
HH
98y2
co-inj.
balanced-inj.
ctr-inj.
0.7
0.8
0.9
1
1.1
1.2
0.3 0.4 0.5
ne/ nGW
HH
98y2
co-inj.
balanced-inj.
ctr-inj.
H. Shirai et al, NF 39 (1999) 1713H. Urano et al, NF 47 (2007) 706
-NBIT-NBI
P-NBI
P-NBI
P-NBI
CO dir.
CTR dir.
#2
#3, 4 #6
#7, 8
#9, 10#12#13, 14
Ip
2 co-tang. NNB (4MW)
7 perp. PNBs(~15.75MW)
2 ctr-tang. PNBs(~4.5MW)
2 co-tang. PNBs(~4.5MW)
JT-60U Tokamak: p. 2The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
Energy confinement is improved with toroidal rotation in co-direction during conventional ELMy H-mode plasmas.
However, the mechanism how this confinement improvement is obtained with the change of toroidal rotation is not yet clear.
Objectives
Clarify the mechanism of energy confinement improvement with co-toroidal rotation in conventional ELMy H-modes.
(1) Dependence of H-mode pedestal and ELMs on edge toroidal rotation(2) Dependence of heat transport in the plasma core on toroidal rotation profile.
JT-60U Tokamak: p. 3The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
Pedestal
boundary condition
p, T
ETB
T(r) Tped
0 1r/a
stiffness
heat flux Q(r)
VT (r) ?
pol
ELM
Wth = Wped + Wcore
B.C.
VT(r)
nped, Tped, ped, …
core
pedestal
(r), T(r), n(r), …
pol
?
e.g. LT, …
Locally affected in H-modes?
resilience
ELM
15
02
03
01.5
04
04
04
0
[MW
][1
020m
-2]
[MJ]
[a.u
.][a
.u.]
[a.u
.]
PNBI
neTL
WDIA
pol
D
D
D
4 8 96 75time [s]
(co-NBI)
(bal-NBI)
(ctr-NBI)
0
0.5
1
1.5
0 2 4 6 8 10 12
PABS [MW]
Wth [
MJ] bal-inj.
co-inj.
ctr-inj.
Experiments on power scan with the variation of toroidal momentum source
co-NBI bal-NBI ctr-NBI Total and thermal stored energy become higher when co-NBI is applied.
tangential NB
perp. NBsLine-averaged ne does not change in the variation of tang. NBs.
LH transition occurs with lower heating power in case of ctr-NBI.
JT-60U Tokamak: p. 4The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
200
0200
0200
0
[Hz]
[Hz]
[Hz]
fELM
fELM
fELM
0
20
40
60
80
100
ELM frequency becomes lower and ELM energy loss becomes larger with co-toroidal rotation
At a given Psep, ELM frequency fELM is clearly reduced as the toroidal rotation increases in co-direction.
-1 0 1VT
ped [105m/s]
f EL
M [
Hz]
co-NBIbal-NBIctr-NBI
Psep ~ 5MW, ne ~ 2x1019m-3
JT-60U Tokamak: p. 5The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
0
2
4
6
8
10
-1 0 1
VTPED [105m/s]
WE
LM
/ W
pe
d [
%]
Psep ~ 5MW, ne ~ 2x1019m-3
co-NBIbal-NBIctr-NBI
With increasing toroidal rotation towards co-direction, ELM energy loss WELM clearly becomes larger with the decrease of fELM.
Large ELM affected area in case of co-NBI
ELM affected area also extends more inward in case of co-NBI.
JT-60U Tokamak: p. 6The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
In case of co-NBI, ELM frequency is lower and drop of edge Te profile becomes larger.
co-NBI
15
10
5
03
2
1
0
2
1
02
1
0
2
1
0
1
0
1
0
PNBI
neTL
WDIA
D
p
Te
ne
4 5 6 7 8 9time [s]
[keV
][a
.u.]
[1020
m-2]
[MW
]
[MJ]
[1019
m-3]
A B C D
JT-60U Tokamak: p. 7
Pedestal pressure enhanced with increased pol during type-I ELMy H-mode
Enhanced pol with sufficient central heating can increase the height of the H-mode pedestal during type-I ELMy H-mode phase.
Ip = 1.2MA, BT = 2.6T, q95 ~ 4, ~ 0.35
The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
P. B. Snyder et al, H-mode WS (2007)
0
1
2
0 1 20 1 2
ne (r ~ 0.9a) [1019m-3]T
e(r
~ 0
.9a
) [k
eV
]
OH
type-III
onset type-I ELM
p
0
2
4
6
8
0
2
4
6
8
0 0.2 0.4 0.6 0.8 10 0.2 0.4 0.6 0.8 1
r/a
Ti[k
eV
]
ABCD
AB
C
D
JT-60U Tokamak: p. 8
Reduced heat diffusivity at the plasma core in case of co-NBI
TG becomes larger at the plasma core when co-NBI is applied.
Heat diffusivity is reduced at a given Pabs in case of co-NBI.
Core heat transport given by Q/(nT) in a steady state is enhanced when ctr-NBI is applied.
0
1
2
3
4
5
0 2 4 6
dTi/dr [keV/m]Q
i/ni [
Wm
3]
co-NBIbal-NBIctr-NBI
CTR
COr/a = 0.6
8
Is core TG scale length shortened by enhanced VT in co-direction?
0
2
4
6
8
0.2 0.4 0.6 0.8r/a
i [
m2/s
]
co-NBI
bal-NBI
ctr-NBI
0
2
4
6
8
0.2 0.8r/a
He
at
Flu
x Q
i [M
W] co-NBI
bal-NBIctr-NBI
-2
-1
0
1
2
0 0.2 0.4 0.6 0.8 1r/a
VT [
105
m/s
]
co-NBI
bal-NBI
ctr-NBI
The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
JT-60U Tokamak: p. 9
Self-similar temperature profile raised with co-NBI leading to highly sustained energy
Core temperature increases throughout minor radius when co-NBI is applied.
0
2
4
6
8
10
0 0.2 0.4 0.6 0.8 1r/a
Ti [
keV
]
co-NBIbal-NBIctr-NBI
Heat transport varies with sustaining self-similar temperature profiles in the variations of toroidal rotation.
Does increased pedestal temperature with co-toroidal rotation play a role as a key factor for better confinement?
1
10
0 0.2 0.4 0.6 0.8 1r/a
Ti [
keV
]Logarithmic plot
The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
JT-60U Tokamak: p. 10
Pedestal structure varies together with edge toroidal rotation
The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
0
1
2
3
-505101520Distance from separatrix [cm]
Ti [
keV
]
0
2
4
6
8
-1 -0.5 0 0.5 1VT
ped [105m/s]
ppe
d [k
Pa
]
co-NBIbal-NBI
ctr-NBI
Pabs ~ 8MW
Pedestal temperature is increased with toroidal rotation.
co-NBIbal-NBIctr-NBI
Steep dT/dr in the ETB layer might be caused by increased pol in case of co-NBI.
Examine heat transport in the plasma core when boundary condition is fixed in cases of co-and ctr-NBI.
pol = 1.3
pol = 1.1
Pedestal pressure increases weakly with the increase of VT
ped into co-direction.
-2
-1
0
1
2
0 0.2 0.4 0.6 0.8 10 0.2 0.4 0.6 0.8 1r/a
0
1
2
3
4
5
0 0.2 0.4 0.6 0.8 1r/a
0
2
4
6
8
10
0 0.2 0.4 0.6 0.8 1r/a
0
2
4
6
8
10
0 0.2 0.4 0.6 0.8 1r/a
VT
[10
5 m/s
]n
e[1
019
m-3
]
Ti[k
eV
]T
e[k
eV
]
co-NBI: 8.9MWctr-NBI: 6.8MW
0.2 0.8r/a
Qi[M
W]
co-NBI
ctr-NBI
0
2
4
6
8
0
2
4
6
8
0
2
4
6
8
0.2 0.8r/a
i[m
2/s
]
0
2
4
6
JT-60U Tokamak: p. 11The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
Identical temperature profiles for cases of co- and ctr-NBI at fixed Tped adjusted by density
When density is raised in co-case to reduce Tped to the level of ctr-case, identical T profiles are obtained in spite of totally different VT profiles.Heat diffusivities are also similar at Q/n ~ const. because of similar T profiles (dT/dr = const.).
0
1
2
3
4
5
0 1 2 3Ti /Ti [m-1]
Qi /
ni [
10-1
3W
m3]
Difference of TG scale length is small in the variations of VT profiles
co-NBIbal-NBIctr-NBI
r/a = 0.6
1
10
0 0.2 0.4 0.6 0.8 1
r/a
Ti [
keV
]
Heat flux is enhanced while sustaining self-similar Ti profile in the variations of toroidal rotation.
High pedestal temperature is a key factor for confinement improvement with toroidal rotation.
TG scale length does not clearly change with VT and remains roughly constant in core region.
JT-60U Tokamak: p. 12The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
JT-60U Tokamak: p. 13
Summary:Schematic view of H-mode confinement
When VT increases in co-direction, pedestal pressure becomes larger.Heat transport in the core is reduced with toroidal rotation while sustaining self-similar temperature profile with higher Tped.
Energy confinement in the variation of VT is determined by increased pedestal and reduced transport brought on by stiffness in standard H-mode plasmas.
The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
Pedestal
boundary condition
p, T
ETB
T(r) Tped
0 1r/a
stiffness
heat flux Q(r)
pol
ELM
Wth = Wped + Wcore
B.C.
VT(r)
nped, Tped, ped, …
core
pedestal
(r), T(r), n(r), …
pol
e.g. LT, …
resilience
ELM
very weak in standard H-mode
0.8
1
1.2
1.4
1.6
1.8
-3 -2 -1 0 1 2 3VT (r=0.2a) [105m/s]
ne (r
=0
.2a
) /
neU
2
0.6
0.8
1
1.2
1.4
1.6
-3 -2 -1 0 1 2 3
0
1
2
3
-3 -2 -1 0 1 2 3
VT (r=0.2a) [105m/s]
neU
2 [1
019
m-3]
0
1
2
3
-3 -2 -1 0 1 2 3
VT (r=0.2a) [105m/s]
neU
2 [1
019
m-3]
VT (r=0.2a) [105m/s]
ne (r
=0
.2a
) /
neU
2
co-NBIbal-NBI
ctr-NBI
Electron density profiles are insensitive to torodial rotation except outward shifted case
Density profiles or peaking factor does not largely change with VT at the plasma core.
However, in case of outward shifted large volume plasma, density profile tends to be peaked at the center when ctr-NBI is applied.
Operational range of ne remains roughly constant.
Effect of fast ion loss?Er, impurity, …
JT-60U Tokamak: p. 14The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
0
2
4
6
8
10
0 1 2 30
2
4
6
8
10
0 1 2 30
2
4
6
8
10
0 1 2 3
co-NBI
X
Y
X
Y
X
Y
bal-NBIctr-NBI
Ti0.2a – Ti
ped
X =0.7a x 0.5 x (Ti
0.2a + Tiped)
Y = Pabs – Prad – dW/dt
JT-60U Tokamak: p. 15
~ 1 / LTi
TG scale length in DB analysis
Enhanced heat flux at global TG boundary in the plasma core is similar in the variations of the direction of tang-NBI.
Larger volume plasmas have more stiff Ti profiles against heating power.Remove the effect of mean dT/dr caused by power deposition.
The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
Height and width of the H-mode pedestal of Ti profile becomes greater when co-NBI is applied.
Compare the pedestal profiles with VTped
into co- and ctr-direction.
JT-60U Tokamak: p. 16The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007
0
1
2
0
1
2
-0.0500.050.1 -0.0500.050.1
distance from separatrix [m]T
iped
[keV
]
pedestal shoulder
(A) co-NBI
(B) ctr-NBI
neped ~ 1.5x1019m-3
0
2
4
6
8
10
0
2
4
6
8
10
-1 -0.5 0 0.5 1-1 -0.5 0 0.5 1
VTped [105m/s]
p pe
d[k
Pa
]
(A)(B)
Pedestal pressure tends to increase weakly with toroidal rotation into co-direction
Pedestal pressure increases weakly with the increase of VT
ped into co-direction at fixed power.
Psep ~ 5MW
Type-I ELMs