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Page 1: The « hybrid » scenario in JET: towards its validation for ... · 2. Hybrid scenario are behaving in the same way as the standard ELMy H-mode. Supported by turbulence measurements

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

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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

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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]

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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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Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 5

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

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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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Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 7

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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Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 8

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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Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 9

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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Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 10

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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Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 11

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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Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 12

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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Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 13

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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Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 14

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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Emmanuel Joffrin XXth Fusion Energy Conference, November 2004 15

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