JT-60U -1- Access to High b p (advanced inductive) and Reversed Shear (steady state) plasmas in JT-60U S. Ide for the JT-60 Team Japan Atomic Energy Agency the 7 th Integrated Operation Scenarios Topical Group Meeting Kyoto University, Kyoto, Japan, 18th – 21st October 2011
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JT-60U -1- Access to High p (advanced inductive) and Reversed Shear (steady state) plasmas in JT-60U S. Ide for the JT-60 Team Japan Atomic Energy Agency.
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JT-60U
-1-
Access to High bp (advanced inductive) and Reversed Shear (steady state)
plasmas in JT-60U
S. Ide for the JT-60 Team
Japan Atomic Energy Agency
the 7th Integrated Operation Scenarios Topical Group MeetingKyoto University, Kyoto, Japan, 18th – 21st October 2011
JT-60U
-2-
high bp and RS plasmas in JT-60U
• How to access these plasmas?
In JT-60U, the AT development has been pursued base on two types of internal transport barrier (ITB) plasmas mainly with pedestal.
10
pres
sure
r
weak
strong
ITB
H-modepedestal
1
2
3
10
q
r2
3
4
10
q
r
• High bp plasma (since 1994)
• Reversed shear (RS) plasma (since1996)
• Monotonic/weak shear, bN5, fBS70%, full CD
• ITB are sometimes very weak• Candidate for advanced inductive
• RS w or w/o current hole, bN2.5, fBS80%, full CD
• Can be fully non-inductive with fBS~50%• Not sensitive care is required at ramp-up phase.• NB injection start, just before reaching flattop or even after. So
injected energy during ramp-up is not important.• A simple empirical recipes exists
– start (strong) NB heating just before sawtooth starts.– central NB deposition is important.– for above two, keeping low density before NB heating is
preferred.
JT-60U
-4-
ITBs in a high bp mode
JT-60U
-5-
ITERAdvanced Op.
Inductive Op.
sustained duration (s)
sust
ain
ed b
N
time (s)
Ip
(MA)PNB
(MW)
ne/1019
(m-3)
E44092, Bt = 1.56 T
bN
Da
(a.u.)
Te,i
(keV)
bN=2.3 sustained for 22.3s(~13.1tR)
P-NBN-NB
TeTi
bN=2.3
Long Sustainment of High bN
In ITER, bNH89p/q952 = 0.4: standard (Q=10) and =0.3: steady state
(Q=5)=> ITER Hybrid operation
q95~3.1-3.2H89p~1.9
bNH89p/q952 > 0.4
bN=2.5 and 2.3
fBS~35-40%bN= 2.3x22.3s
bN=2.5x16.5s
T. Suzuki (EX/1-3, Tue.)
tR : Dr. D. R. MikkelsenPhys. Fluids B 1 (1989) 333.
JT-60U
-6-
Wd
ia (
MJ)
Pabs (MW)
Pth can be also found by power step-up
again no Bt dependence
time [sec]
ITB
JT-60U
-7-
High fusion performance with full CD
- High d~0.34 at high Ip=1.8 MA and high power N-NB (5.7 MW)bN=2.3-2.5, HHy2 = 1.2, nD(0)tETi(0) = 3.1x1020 m-3skeV, full non-
inductive CD (BS:50%)
was suppressed by tailoring p(r)&q(r) in low collsionality regime (ne*~0.02~ITER).
JT-60U
-8-
r
j tot,j
BS,
j NB (
MA
/m-2)
q
jNB
jBS
8.3sjtot
fBS~45% sustained for 5.8s (~2.8tR) under nearly full CD in weak shear (qmin~1.5)
• Can be fully non-inductive with fBS<~85%• Empirical recipes
– start NB heating as early as possible. For this divertor configuration stars at very early of a discharge (<0.5s from breakdown).
– central NB deposition is important.– NB heating at early time, when q is reversed, triggers ITB. The
ITB raises the BS current at ITB. The BS current enhances or keep the q profile reversed.
JT-60U
-10-
reversed shear plasmas
• ITB formation– Reversed shear is believed to be an enough condition for ITB
formation, but sometimes not sufficient.– Pth to form Ti ITB seems to be lower for lower Ip. Once ITB is
formed it is easier to maintain the reversed shear. Therefore, typical recipe to establish a good RS discharge is early NB injection.
– For Te ITB formation, Pth seems to be very low or even almost zero if the q profile is reversed.
– W/O ITB formed very early in a discharge, target reversed q profile can hardly be maintained until Ip flattop. Therefore early NB injection is required.
– However with LHCD, reversed q can be maintained and late ITB formation is possible.
JT-60U
-11-
fBS~75% sustained for 7.4s (2.7tR) under nearly full CD in reversed shear plasma
• Very high confinement characteristics:HH98(y,2)~1.7 (H89p~3.0), fBS~75%, fBD~20%, bp=2.2-2.3, bN~1.7, ne/nGW~0.55
• Although q95 is yet high, demonstrates steady state with high fBS
Ip
(MA)
bp, bN
Vloop
(V)
Dadiv
(a.u.)
time (sec)
PNB
(MW)
r
Ti
(keV)
q
0.8MA, 3.4T,q95~8.6
Y. Sakamoto (EX/4-3, Wed.)
JT-60U
-12-
Ti ITB formation - NB power scan -Experimental condition: