The « hybrid » scenario in JET: towards its validation for ... · 2. Hybrid scenario are behaving...
Transcript of The « hybrid » scenario in JET: towards its validation for ... · 2. Hybrid scenario are behaving...
Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 1
The « hybrid » scenario in JET:
towards its validation for ITER
E. Joffrin, A. C. C. Sips, J. F. Artaud, A. Becoulet, R. Budny, P. Buratti, P. Belo,
C. D. Challis, F. Crisanti, M. de Baar, P. de Vries, C. Gormezano, C. Giroud, O.
Gruber, G.T.A. Huysmans, F. Imbeaux, A. Isayama, X. Litaudon, P. J.
Lomas, D. C. McDonald, Y. S. Na, S. D. Pinches, A. Staebler, T. Tala, A.
Tuccillo, K.-D. Zastrow and JET-EFDA Contributors to the Work Programme.
Outline:
- Introduction to the hybrid scenario in JET
- Physics analysis (MHD, current, transport)
- Projections to ITER burning plasma for the
hybrid scenario
Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 2
ITER scenario for steady state burning conditions
Maximise: G = N . H / q952 Iboot / Ip ~ N . q95 n ~ 0.85 nGreenwald
AUG: A. Staebler EX/4-4
DIII-D: M. Wade EX/4-1
JET has started the study of the « hybrid » regime in the 2003 campaign
Ip
q95
N . H98 y2
Burn time
Q
15MA
3
1.8 x 1.0
400s
10
NTM with sawteeth
High Ip disruptions
Current control
High MHD
9MA
5.3
2.95x1.6
>3000s
6
Non-inductive RS
12MA
~4
~3 x 1.0
~2000s
~10
Hybrid scenario
0 0.5 1
q-profile
H-mode inductive scenario
Normalised radius
2
1
3
4
5
Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 3
JET hybrid regime (1.7T, 1.4MA)
Identity experiment with ASDEX Upgrade:
1. Matched magnetic configurations.
2. Similar * & q (qo ~1 and q95=4).
Bo IPB98(y,2) *-2.70 -0.90 *-0.01 q-3.0 0.73 3.3
3. N controlled in real time with PIN
4. *(JET)=0.08 *(AUG) = 0.15
Hybrid scenario reproduced in JET with similar
phenomenology than in AUG.
10
2
4
0.4
0.5
0 5 10 150
4
0.2
Ip [MW]
PNBI [MW]
4 x li
H89
N
G=H89. N / q952
Fishbones n=1
Mild 3/2
(NTM)
Pulse 58323 (q95=4, =0.22)
D
0
2.0
PLH [MW]
Times [s]
Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 4
Hybrid regimes in JET
JET can bridge the gap between machines like ASDEX Upgrade and ITER
The hybrid regime has been
achieved in JET:
• with AUG configuration =0.45
• with ITER configuration =0.45
• at 2.4T (lower *) and =0.22
• at 2.4T (lower *) and =0.45
Development of the hybrid regime towards the ITER domain
1 2 3 4 5 6 7 8 9 100
0.5
1
1.5
2
2.5
3
x 103
N
*
1.7 TFor q95~4
AUGJET
2.4T
=0.2 (circles)
=0.45 (triangles)
3.4T
DIII-D
(AUG & DIII-D from ITPA database)
MHD limited
ITER
3.1T
With more available power,
future experiments areplanning to explore the low *
region reachable by ITER
JET-AUG Identiy
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1.4
2/1
NTM
Sawteeth
0
10
20
0
1
2
0 5 10 150
2
N
Ip [MA]
PNBI [MW]
Times [s]
PLH [MW] (x5)Pulse 58323 & 58324
NTM control in hybrid regime
Benign NTMs in main heating phase at high N
Wisland~3-4cm impact on confinement ~5%
In JET, NTM are avoided by tuning the target q profile above 1 in the preheat phase
In JET, the hybrid scenario can operate at N>2.5 with moderate
NTM activity as in other devices (ASDEX Upgrade & DIII-D)
1/1 mode &
fishbones
4/3 mode
3/2 mode
Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 6
q(0)=1.07
p =1.25
q(0)=1.07
p =1.25
m=1
m=3
m=2
Ideal MHD in hybrid regimeJET has reached ~95% of the ideal kink limit so far.
Ideal m=1 kink mode behaviour predicted in JET using MISHKA code.
0.002
0.004
p
0.4 0.6 0.8 1 1.2
q(0)=1.01
q(0)=1.03
q(0)=1.05
q(0)=1.07
q(0)=1.07(no wall)
Growth rate
Strong increase of the ideal kink growth rate as plasma pressure increases.
Also suggests that control of the q profile is necessary to keep q away from unity
Mode localisation
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Current balance in the hybrid regime
INBCD / Ip=35%; Iboot / Ip=25%
q contours from the CRONOS code (58323)
0
0.2
0.4
0.6
0.8
2 4 6 8 10 12 14
0
0.2
0.4
0.6
0.8
Vloop [V]
PNBI [MW]
q=1
q=4/3
q=3/2
q=2
q=5/2
q=3q=4
Times [s]
Current diffusion analysis with the CRONOS code
At N=2.8, non-inductive current sources are sufficient to maintain a steady state q profile
0 0.2 0.4 0.6 0.8 10.0
0.1
0.2
0.3
0.4
0.5 JTOT[MA/mJTOT[MA/m2]
JNBCD2
JNBCD [MA/m]2
JBOOT [MA/m2]JBOOT
Pulse 58323, N=2.8From TRANSP
Normalised radius
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Confinement in the hybrid regime
(Cordey et al., IT/P3-32
• In JET at high N hybrid regime have an
improved confinement of up to 20 % with
respect to IPB98y2.
• IPB98(y,2): *-2.70 -0.90 *-0.01 q-3.0
• Recent dedicated studies have shown that
confinement has a weaker negativedependence on :
At high N, he higher confinement observed in hybrid regime could be
related to the -0.90 dependence of the IPB98(y,2) scaling
1 1.5 2 2.5 31
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8Wth exp [MJ]
(for BT=1.7T & N>2)
Wth scaling [MJ]
IPB98y2
+20%
Pure
gyro-Bohm
• Pure gyro-Bohm scaling: *-3 0 *-0.1 q-1.7
Gives a reasonable fit to the data.
& McDonald, EX/6-6)
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Comparative transport property of the hybrid regime
1. As expected, ITB discharges are
showing ion temperature gradients
well above the predicted critical
gradients for ITGs
2. Hybrid scenario are behaving in the
same way as the standard ELMy H-
mode.
Supported by turbulence measurements
with reflectometry.
In JET, it appears that the confinement in hybrid regimes is not
significantly different than in the standard ELMy H-mode scenario.
15
For s>0.2 & R/Ln<2
0 5 100
5
10
15
20
25
ITB regime
ELMy H-mode
Hybrid regime
R/LTi critical from theory
R/LTi (exp)
(Jenko et al., PoP, 2002)
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Tritium and impurity transport
D [m2/s]
V [m/s]
Pulse 61389 ( N=2.7)
3
2
1
0
-5
-10
Dneo [m2/s]
Normalised radius
0 1 0.5
Vneo [m/s]
Tritium and impurity diffusion and convection in hybrid regime
are dominated by turbulent transport.
(D. Stork, OV/4-1 &
McDonald, EX/6-6)
Tritium
Normalised radiusNormalised radius
62490 (B T=2.4T ; =0.45)
60932 (B T=2.4T ; =0.20)
Neoclassical -----
0 0.2 0.4 0.6 0.8 1.0
5
4
3
2
1
2
1
-1
-2
0
D [m2/s]
V [m/s]
62490 (B T=2.4T ; =0.45)
60932 (B T=2.4T ; =0.20)
Neoclassical -----
0 0.2 0.4 0.6 0.8 1.0
5
4
3
2
1
2
1
-1
-2
0
D [m2/s]
V [m/s]
Neon (Z=10)
Particle and impurity diffusion and convection inferred from the SANCO +
UTC codes constrained by experimental data
Trace tritium injection
( Neutron monitor + fit )
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ITER projections with the hybrid scenario
Scaling used
Pfus
[MW]
Paux
[MW]N Density
peaking
Qfus q95 Ip
[MA]
Projections for burning hybrid regime in ITER with the integrated 1D code CRONOS
Hypothesis: - HH=1
- Gyro-Bohm transport normalised to scaling laws.
- Pedestal height from pedestal database scaling law.
- Zeff=1.8, He concentration 3%
Reaching high N requires the fine tuning of plasma current
IPB98y2 (PPA) 400 73 1.9 0 5.4 3.3 13.8
IPB98y2 570 73 2.1 0 7.8 3.3 13.8
Comparison
with PPA
IPB98y2 160 73 1.6 0 2.2 4 11.3
Pure Gyro-Bohm 285 73 2.25 0 3.9 4 11.3
Scaling
comparison
Pure Gyro-Bohm 337 73 2.4 neo=1.5 x neped 4.6 4 11.3With ne peaking
Pure Gyro-Bohm 600 50 2.85 neo=1.5 x neped 12 3.5 13Lower q95
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Conclusions
1. The steady state “hybrid” scenario has been successfully reproduced in JET
by the mean of an identity experiment approach with ASDEX-Upgrade.
2. In JET, current control is a key factor in avoiding NTM activity during the
main heating phase of the scenario.
3. The JET hybrid scenario does not show any obvious sign of improved heat
and particle confinement with respect to standard ELMy H-modes. On theother hand, its improved stability allows operation at higher N close to the
ideal limit.
4. The maximisation of confinement and stability properties provides to the
hybrid regime a good probability for achieving high fusion gain at reduced
current (~13MA) for more than 2000s.
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Performance overview towards ITER
Bootstrap fraction from TRANSP data
(q95=4)
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0.3 0.4 0.5 0.6 0.7 0.8
Ti(0)/Te(0)
ne/ne GREENWALD
ITER
=0.22
=0.45
JET Hybrid regime are situated in the right ball park in terms of Ti/Te,
density and plasma performance
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1/1 mode &
fishbones
Spectrogram of magnetic fluctuations
NTM in hybrid regime
4/3 mode
3/2 mode
Coupled
Islands size is 3 to 4cm
located at r/a=0.3-0.4
Limited impact on
global confinement
few percent
In JET, the hybrid scenario can operate at N>2.5 with moderate
NTM activity as in other devices (ASDEX Upgrade & DIII-D)
Neoclassical tearing mode behaviour in the hybrid regime
1 < q < 1.3 in plasma core
ELMs ~40Hz
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Summary of advanced modes development
ITER (PPA Q=5.4, Tburn=1000s):= 0.48 q95=3.5 fGW=0.85 H=1
N=1.9 fBS=17%
ITER (Q=5 Steady State):=0.49 q95=5.5 fGW=0.8 H=1.5
N=3 fBS=50%
Hybrid Mode or improved H-mode
(new on JET)
Plasmas with ITBs