Download - T. Nakano , N. Asakura, H. Takenaga, H. Kubo, Y. Miura, S. Konoshima, K. Masaki, S. Higashijima
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