T. Nakano, N. Asakura, H. Takenaga, H. Kubo, Y. Miura, S. Konoshima, K. Masaki, S. Higashijima and...
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Transcript of T. Nakano, N. Asakura, H. Takenaga, H. Kubo, Y. Miura, S. Konoshima, K. Masaki, S. Higashijima and...
JAERI
T. Nakano, N. Asakura, H. Takenaga, H. Kubo, Y. Miura, S. Konoshima, K. Masaki, S. Higashijima
and the JT-60Team
Japan Atomic Energy Research Institute, Ibaraki, Japan.
Impact of nearly-saturated divertor plates on particle control
in long and high-power-heated discharges in JT-60U
20th IAEA Fusion Energy ConferenceVilamoura, Portugal, 1-6 November 2004
JAERI Background
ISSUE: Experience and knowledge of operation with Rrecycling ~ 1
JT-60Sec.
Long pulse, steady-state operation
JT-60NCTMin.
ITERMin.~ Hour
DEMODay - Year
ConditionedRrecycling < 1
UnconditionedRrecycling ~ 1 or >1(Wall saturation)
wall
15s => 65sa
JAERI IntroductionParticle control; For a constant density Fueled = Pumpedaaaaaaaaaaaaaaaa
Short pulse:Divertor-pumping
+Wall-pumping
Long pulse:Divertor-pumping
+ (Co-deposition?)
Long pulse in JT-60Pheat~12 MW, 30s
Particle control at wall saturated
First w
all
Gas-puffPellet
NB
Core Plasma
Baffle
Divertor-Pumping
BafflePlates
Divertor
JAERI Outline
2.0
1.0
0.0
x101
9
403020100Time (sec)
20
10
0 RG
as
( P
am3 /
s)
n e (
x 1
019 m
-3 )
Gas
ne
1.0
0.5
0.0
x102
0
D
( a.
u. )
1.0
0.0
I p (
MA
)
10
0
PN
B (
MW
)
P-NB
N-NB
Ip
E043178
•Density controllability
w at wall
saturation
•Identification
of wall saturation
•Summary
JAERI No “carbon bloom”
Energy Input : 350 MJ
Div. surface temperature : ~ 1300 K
0.4
0.2
0.0
C V
I in
tens
ity (
a.u
.)
3002001000Input Energy ( MJ )
Open divertorW-shaped divertor( ~ 1999) ( ~ 2004)
JAERI
Identification of Wall Saturation
JAERI
8
6
4
2
0
x102
2
403020100Time ( sec )
Injected ( NB + Gas )
Pumped
WallPar
ticle
s (
x 1
022
)
4
2
0
x102
1 (
x 1
021
/ s )
PumpGas
E043860
420
x102
0
1050
1050
x102
0 N-NB
P-NB
( M
W ) ( x 10
20/ s )
1.0
0.5
0.0
4
2
0x10
19 n e
Ip
( x 10
19
m-3)
( M
A )
Wall Saturation identified in long pulse operation
t = 20 - 27s, constant wall retention Wall saturation ELMy H-mode Zeff ~3,H89PL~1.7Then, MARFE ( detach )
MARFE
Saturation
Quasi-steady-state, Vp dnp/dt ~ 0, Vn dnD0/dt ~ 0, Rwall = RP-NB + RN-NB
+ RGas - Rpump
JAERI Saturation Area, Wider than Divertor platesParticle Balance between pulses •Until 44018,
Wall retention increases•Wall saturation•After 44019, 3x1022 are released. 3x1022
Saturation level of D+ to C tile at 300eV = 1x1021m-2 Saturation area (Minimum) = 3x1022/ 1x1021m-2
= 30 m2
> Divertor plates ( 20 m2 )
1.0
0.5
0.0
x102
3
201510Time (sec)
Injected ( NB + Gas )
Pumped
Wall Retention
Par
ticle
s (
x 10
23 )
•During 44020, 3x1022 retained in walls.Active wall-pumping capacity ~ 3x1022
Particle Balance during 44020
1.5
1.0
0.5
0.0Par
ticle
s (
x 10
23 )
440204401944018440174401644015Shot Number
Injected
Pumped
JAERI
6 6
3 3
0 0
x102
1
353025201510Time ( sec )
Rw
all
( x1
021 /
s )
10 10
5 5
0 0
-5 -5x1
022 Injected ( NB )
Wall Retention
Pumped
Twall = 520 KIdentical discharge condition;
Ip,Bt,ne,PNB,H89PL,Tsurfdiv
,,,
Release-Rate from walls
Significant Particle Release at Twall = 520 K
Twall = 420 K
The only difference : first-wall-temperature Suggests particle release from first wall / Baffle plates
Gas-Puff-Rate6
3
0
x102
1
201510Time ( sec )R
ga
s (
x 10
21 /
s )
10
5
0
-5
x102
2
Injected ( NB + Gas )
Pumped
Wall Retention
Par
ticle
s (
x 10
22 )
JAERI
1017
1018
1019
1020
1021
Inte
nsi
ty (
ph
/ sr
m2 s
)
222018161412108642
Viewing Chord ( ch )
Source of particles, Baffle Plates
Twall= 420 K Twall= 520 K
Divertor similar
First wall >
Baffle <
1ch
8ch
11ch 20ch
19ch
Viewing chord for DDivertorInnerBaffle
OuterBaffle
Main ChamberFirst wall
D Brightness
Twall = 520 KNo gas-puff
Twall = 420 KGas-Puff
JAERI
Density Controllability by
Active Divertor-Pumping
at Wall Saturation
JAERI
PumpingG
AP
x1019
Density controllability of divertor-pumping
GAP 9.5 cm 4.5 cm
P0 + ~ 0, -
ne >
Wall saturation
3
2
1
0
x101
9 n e
( x
10
19
m-3
)
0.12
0.08
0.04
0.00
Pre
ssur
e (
Pa
)
30252015105Time ( sec )
Pe
nning
gag
e
Suggests;Large GAP => Increase of P0 => Increase of ne
With Gas-puff
No gas-puf
JAERIHigh pumping-rate suppresses increase of plasma particles
Difficult to prevent undesirable density rise of high plasmas ( Large GAP )
Limited period of high N; ex. 22.3 s for N = 2.3Higher pumping-rate is required even for
low plasmas ( Small GAP )
Condition : wall saturationDensity : ne/ne
GW = 62-66%
Decreasing Gap
2
1
0
x101
9
543210x10
21
d N
i / d
t (
x 10
19 /
s )
Pumping-Rate ( x 10 21
/ s )
Wall-pumping effective
JAERIControllability of detachmentby divertor-puming at R = 1
SOLDOR simulation
RPum
p
6x10 21/s
Rrecycle =1
3x1021/s10 MW
e = i = 1 m2/s, D = 0.3 m2/s
Indicates higher pumping speed by a factor of 2 - 3 can avoid MARFE at the end of long pulse discharges
R Gas
3x1021 /s
Pumping speed 25m3/s 50m3/s
P0OutDiv 2.0 Pa 1.2 Pa
neOutDiv 4x1020m-3 2x1020m-3
TeOutDiv 0.8 eV 9.7 eV
1.0
0.5
0.0Pre
ssur
e R
atio
1007550250Pumping Speed ( m
3 / s )
JT-
60U
14
.8 m
3 /s
Detach AttachInter-mediate
( D
iver
tor
/ M
idpl
ane
)
JAERI Summary• Modification for Long Pulse Operation, 15 sec => 65 sec• ELMy H-mode plasma
( ~30 s ,~ 12 MW, 350 MJ, No “carbon bloom”)• Wall saturation was identified
(Minor role of co-deposition)
Divertor plates
Wall/baffle plates <= important particle source at Rrecy > 1
• No sudden changes of plasma ( Zeff, H89PL )
• Undesirable increase of plasma density
=> Confinement Degradation, MARFE• Higher divertor-pumping efficiency ( x 2 - 3 )
required to avoid MARFE
NB 10 sec => 30 sec