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Experimental study of effect of poloidal flow on island. ISHW09 October 2009 PPPL. Experimental study of effect of poloidal flow on stability of magnetic island in LHD and TJ-II. Y. Narushima, F. Castejón a , K.Y. Watanabe, S. Sakakibara, T. Estrada a , F. Medina a , - PowerPoint PPT Presentation
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ISHW09 October 2009 PPPL
Experimental study of effect of poloidal flow on stability of magnetic island in LHD and TJ-IIY. Narushima, F. Castejóna, K.Y. Watanabe, S. Sakakibara,T. Estradaa, F. Medinaa, D. Lopez-Brunaa, M. Yokoyama, K. Ida,LHD Experiment Group National Institute for Fusion Sciencea) Laboratorio Nacional de Fusión. CIEMAT 1
Experimental study of effect of poloidal flow on island
Outline
Introduction-Experiment device-Island physics & effects on
plasma-Previous study in LHD and TJ-II
Poloidal flow and island--Ion polarization current effect--Application to LHD and TJ-II
Future joint works Summary
Experimental study of effect of poloidal flow on island
Introduction
Flow & island
Future works
Summary
2
ISHW09 October 2009 PPPL
Experimental study of effect of poloidal flow on island
Introduction
Exp. device
Flow & island
Future works
Summary
Experiment device
3
ISHW09 October 2009 PPPL
TJ-II
-Major radius R0 = 1.5[m]-Minor radius a ~ 0.22[m]-Magnetic field Bt 1[T]-32 toroidal coils-Two central coils (circular and helical)-Two pairs of vertical field coils
-Ohmic current can be induced, which can modify profile
LHD
-Major radius R0 = 3.5~4.1[m]-Minor radius a ~ 0.6[m]-Magnetic field Bt 3[T]-Super conductor coils A pair of helical coils L/M = 2/10 3 pairs of poloidal coils -Perturbation coil system makes static magnetic island
Experimental study of effect of poloidal flow on island
IntroductionRole of island
Flow & island
Future works
Summary
For a good confinement -> Nested flux surfaces
Study of dynamics of magnetic island is important
Island physics & effects on plasma
4
ISHW09 October 2009 PPPL
Control of magnetic islands is critical issue
Effect of magnetic island
[K. Ida et al. NF 44 (2004) 290]
MHD
Flattening of pressure profile
NTM
DestabilizedStabilized(?)
Transport
Island with low m/n mode number
Formation of transport barrier[K. Ichiguchi et al.
NF 41 (2001) 181][Many papers]
Dynamics of magnetic island
5
-Growth and healing depends on and -More sensitive to
-Transition of island at ~ 0.3[%]-Nonlinear behavior
ISHW09 October 2009 PPPL
Region of growth & healing
Structure of perturbed field b (by island)
0 0.2 0.4 0.6 0.8
0.01
0.1
1
10h*@/2=1
[%]@/2=1
Growth
Healing
Growth
Transition
Healing0
1
2
0 0.2 0.4 0.6 0.8
-1
0
1
c
bpl
n=1 /b e
xtn=
1
1.0>h*>0.1
(a)
[%]@/2=1
(b)
n=
1[ r
ad]
Experimental study of effect of poloidal flow on island
Introduction
Prev. study LHD
Flow & island
Future works
Summary
0 0.2 0.4 0.6 0.8
0.01
0.1
1
10h*@/2=1
[%]@/2=1
0
1
2
0 0.2 0.4
-1
0
1
HINT calc.
bpl
n=1 /b e
xtn=
1
[%]@/2=1
n=
1[ r
ad]
BS current(VENUS-f)
PS current(HINT)
BS & PS currents cannot explain
6
-b is one order or more smaller than experiment-Self-healing does not appear
ISHW09 October 2009 PPPL
Ctr- BS
Co- BS
-Direction of BS current is sensitive to rather than
Experimental study of effect of poloidal flow on island
Introduction
Prev. studyLHD
Flow & island
Future works
Summary
CERC
Positive Er increases after CERC formation
CERC phenomena
7
ISHW09 October 2009 PPPL
(Core Electron Root Confinement) Er > 0CERC formation by introducing resonances
n/m = 3/2
n/m = 4/3
[Estrada et al. PPCF 46 (2004) 277][F. Castejón et al. NF 44 (2004) 593]
Resonant surface and positive Er are important to trigger CERC formation
Experimental study of effect of poloidal flow on island
Introduction
Prev. studyTJ-II
Flow & island
Future works
Summary
CERC
dTe/d ~ 0
dTe/d 0
8
Increase of positive Er
--> Island stabilizing
ISHW09 October 2009 PPPL
Healing of island in CERC
[T. Estrada et al. NF 47 (2007) 305]
Island healing is produced just simultaneously to CERC onset
Experimental study of effect of poloidal flow on island
Introduction
Prev. studyTJ-II
Flow & island
Future works
Summary
Experimental study of effect of poloidal flow on island
Introduction
Prev. studyTJ-II
Flow & island
Future works
Summary
• A1=0.823, A2= 6.34, cb≈1, q is the safety factor (the inverse of the rotational transform). All the quantities are evaluated at the resonant radius.
• Time Scale:
Stabilising
A1
dw
dt ' A2cb p'q
q'Bpw
' A2cb
p' 'Bpw
t ~w2
w' 6 p Bp
9
In rough agreement with experimental data
ISHW09 October 2009 PPPL
Healing in CERC in TJ-IITime scale of healing
[F. Castejón, et al. 35th EPS 32D, P-1.025 (2008)][Q. Yu, et al. PoP 1 (2004) 140]
Experimental study of effect of poloidal flow on island
Introduction
Prev. studyTJ-II
Flow & island
Future works
Summary
10
Mode stabilization in CERC
-CERC without temperature flattening has been observed-Mode stabilization is observed, nevertheless
ISHW09 October 2009 PPPL
[T. Estrada et al. PPCF 47 (2005) L57]
Experimental study of effect of poloidal flow on island
Introduction
Flow & island
Future works
Summary
11
LHD-BS & PS currents cannot explain behavior of islandTJ-II-Island is stabilized in CERC
ISHW09 October 2009 PPPL
-We pay attention to radial electric field--->Poloidal flow and island
-15 -10 -5 0 5
-40
-20
0
20
40
Er[kV]
a pc
*pi2 [
a.u.
]
Unstable
Stable
(dpi/dr)/eni
0 5[kV/m] 10[kV/m]
Radial electric field effectTheoretical predictionIndex of ion polarization current effect apc
[K. Itoh, et al., PoP 12 (2005) 072512]
12
Er > 0 : Stabilizing
Er < 0 : |EB| > |*pi| Stabilizing|EB| < |*pi| Destabilizing
ISHW09 October 2009 PPPL
apc= (- *pi)*pi-2
= -EB = EB/(rsB2)EB drift
*pi = Bpi/(rsniqiB)Ion dia. drift
Experimental study of effect of poloidal flow on island
Introduction
Flow & island
Theory
Future works
Summary
Er > 0 : Stabilizing
Er in island healing in TJ-II
13
Positive Er corresponds to stabilization
ISHW09 October 2009 PPPL
Experimental study of effect of poloidal flow on island
Introduction
Flow & island
TJ-II
Future works
Summary
Positive Er increases Healing is produced
CERC
dTe/d ~ 0
dTe/d 0
[T. Estrada et al. NF 47 (2007) 305]
after CERC formation
-10
-5
0
0 0.2 0.4 0.6 0.8 1.00
5
10
15
#86405 t = 4.3[s]
Er[k
v/m
]p e
[kPa
]
Typical pe and Er profile
0 0.2 0.4 0.6 0.8
0.01
0.1
1
10
Healing
Growth
h*@
/2=
1
[%]@/2=1
Er < 0 : Ion root
Assumption Te = Ti
and ne = ni
Neoclassical ambipolar Er
(GSRAKE)
14
Er < 0 : Ion root=> Magnitude relation of EB & *pi
ISHW09 October 2009 PPPL
Healing plasma is in Er < 0
Calculation
Experiment
Experimental study of effect of poloidal flow on island
Introduction
Flow & island
LHD
Future works
Summary
|EB| > |*pi| is satisfied
0 0.2 0.4 0.6 0.8 1.0-10
-5
00
5
10
ExB
[kra
d/s]
#86405 t = 4.3[s] *
pi[k
rad/
s]
EB = EB/(rsB2)
Typical EB and *pi profile
15
|EB| > |*pi| corresponds to stabilization of the island
ISHW09 October 2009 PPPL
AssumptionTe = Ti and ne = ni
*pi = Bpi/(rsniqiB)
*pi <~ 5[krad/s]
EB ~ -5[krad/s]
Transition can be explained? How about dependence?
0 0.2 0.4 0.6 0.80
1
2
[%]@/2=1b
pln=
1 /b e
xtn=
1
Experimental study of effect of poloidal flow on island
Introduction
Flow & island
LHD
Future works
Summary
0 0.2 0.4 0.6 0.8
-10
-5
0
5
10 *pi ExB
[10
3 rad
/s]@
/2=
1
@/2=1[%]
16
Dependence of *pi & EB on
Transition cannot be explainedOther mechanism should exist
*pi increases with EB keeps constantIn ~ 0.2[%], EB is dominant
Healing
ISHW09 October 2009 PPPL
0 0.2 0.4 0.6 0.80
1
2
[%]@/2=1
bpl
n=1 /b e
xtn=
1
Growth
Experimental study of effect of poloidal flow on island
Introduction
Flow & island
LHD
Future works
Summary
Future joint works
17
Study of magnetic island has been progressed
LHD (Er < 0 Ion root)Detailed investigation of
transition of magnetic island
TJ-II (Er > 0 Electron root)Further studies on island width
and time scale growing and healing dependences on collisionality etc.
ISHW09 October 2009 PPPL
Experimental study of effect of poloidal flow on island
Introduction
Flow & island
Future works
Summary
Experimental study of effect of poloidal flow on island
Introduction
Flow & island
Future works
Summary
Summary
18
LHD-Dynamics of magnetic island depending on and show nonlinear behavior. -Poloidal flow might affect on island for stabilization in Er < 0 condition
ISHW09 October 2009 PPPL
TJ-II-Magnetic island is present with ambient Er > 0 before CERC; at CERC onset Er becomes more intense, magnetic island is stabilized and associated coherent oscillation vanishes
To clarify behavior of island, further joint works are required
Recommended