TEC Trilateral Euregio Cluster Institut für PlasmaphysikAssoziation EURATOM-Forschungszentrum...

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Trilateral Euregio ClusterInstitut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich

IEA Large Tokamak IA Workshop on Edge Transport in Fusion Plasmas, Krakow

Influence of the Dynamic Ergodic Divertor (DED) on ELM activities

and on confinement

K.H. Finken1, S. Abdullaev1, J. Coenen1, A. M. Jakubowski1, R. J. E. Jaspers2, A. Krämer-Flecken1, M. Lehnen1, Y. Liang1, B. Unterberg1, M. von Hellermann2, Y. Xu3, R. C. Wolf1, U. Samm1, O. Schmitz1, and the TEXTOR Team

1) Institut für Plasmaphysik, Forschungszentrum Jülich, Association EURATOM/FZJ, Trilateral Euregio Cluster, D-52425 Jülich, Germany, www.fz-juelich.de2) FOM-Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, Trilateral Euregio Cluster, PO Box 1207, 3430 BE Nieuwegein, The Netherlands, www.rijnh.nl3) Laboratoire de Physique des Plasmas - Laboratorium voor Plasmafysica, Association 'Euratom- Belgian state', Ecole Royale Militaire - Koninklijke Militaire School, B-1000 Brussels, Belgium*

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#94809

LFS HFS DED topics:

Helical divertor

Field line and plasma topology

Impurity shielding

Field line penetration

Tearing modes

Suppression of tearing modes

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Outline:

• Introduction to DED

• Effect of the perturbation field on ELMs

• Improved confinement by DED

• Summary

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m = 6, n = 2

m = 12, n = 4

m = 3, n = 1

Base modes for DED operation

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H-mode characterization and ELM suppression by DED-field

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2 2.2 2.4 2.6 2.8 30

1

2

3x 10

19

ne /

m- 3

2 2.2 2.4 2.6 2.8 30

5

10

15TEXTOR # 97315

I DE

D /

kA

2 2.2 2.4 2.6 2.8 30

1

2

3x 10

6

W

1.8 2 2.2 2.4 2.6 2.8 30

5x 10

4

ED

ia /

J

time / s

Ptot

Prad

Basic scenario: Ip= 240 kA/ Bt= 1.2 T-1.4 T, plasma shifted to HFS (R=1.68m / a=0.4m)

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~ 500 Hz

ALTH - drop

DED

0 0.5 1 1.5 2 2.5 30

5

10

15

H /

a.u

.TEXTOR # 97315

2.5 2.505 2.51 2.515 2.520

5

10

time / s

H /

a.u

.

Characterization of H-mode

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1 1.2 1.4 1.6 1.8 20

500

1000

1500

N

EL

M /

Hz

ELM frequencies TEXTOR limiter H-mode

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Power threshold about twice the L-H threshold in divertor tokamaks – “typical” for limiter H-modes

4 5 6 7 8 9 10x 10

5

0.8

1

1.2

1.4

1.6

1.8

2

P sep /

W x

10

6

PL-H thresh, IAEA96 / W

o no DED

+ with DED

# 97300/1, 97312/14/15, # 98296, 98491, 99595

with ELM signature w./o. ELM signature

"dithering"

continued ELM - signature over 1s

# 97314

# 98491 (L-H transition)

Predictive RITM code calculations for 1.3 MW heating power and

H/ (H+D) = 40%

and TEXTOR data

D. Kalupin,

M. Tokar

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Evolution of edge pressure HFSTEXTOR # 97315 (thermal He beam*)

R= 1.3 m

L-H –transition

H- L –transitionwith DED

*extension of CR model by courtesy of M. Brix

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Substantial spin up of poloidal rotation

in electron diamagnetic drift direction (indicating more negative Er)

Pnbi=2.8 MW

~18 km/s~3.6 km/s

Reflectometry

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2.2 2.4 2.6 2.8 30

1

2TEXTOR # 97315

D /

a.u

.

2.2 2.4 2.6 2.8 30

5

10

15

I DE

D /

kA

2.2 2.4 2.6 2.8 3-1000

0

1000

v /

m/s

(C

III)

time / s

L-H transition DED induced back transition

ELM mitigation in 12/4 base mode

ELM suppression starts at 3 kA

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ELM mitigation in 12/4 base modeTEXTOR # 97315

2.8 2.85 2.9 2.95 3 3.050

10

20

2.8 2.85 2.9 2.95 3 3.050

5

10

15

2.8 2.85 2.9 2.95 3 3.050

1

2x 10

19

t / s

D / a.u.

IDED

/ kA

nel / pedestal top

H-mode Mitigation mode

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ELM mitigation in 12/4 base mode

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2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6-1

0123

TEXTOR # 98296 (Ip = 250 kA / BT = 1.4 T, R= 1.72 m, a= 0.44 m)

2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.60

2

4x 10

6

Pto

t / W

2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.60

5

D /

a.u

.

2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.60

1

2

time / s

Te /

a.u

. (

~0.

9)

ne / 1019 m-3

IDED

/ kA (AC 1 kHz)

ELM mitigation in AC 3/1 base mode

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Improvement of energy confinement during H-mode modest some reduction of energy confinement with DED

0.015 0.02 0.0250.015

0.016

0.017

0.018

0.019

0.02

0.021

0.022

0.023

0.024

0.025E / s

E, ITERH89P / s

w./o. ELM signature with ELM signature

o no DED

+ with DED

H89=1

H89= 1.25

TEXTOR # 97300/1, 97312/14/15

R= 1.68m

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Confinement improvement with DED in

m/n = 6/2 base mode

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Best conditions have been observed for

• strongly inward shifted plasmas

• low density plasmas, low collisionality

• Co-NBI heating

• Ip = 310 kA; Bt = 1.9 T

• IDED = 7.5 kA

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Stepwise density increase during DED-ramps

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Density profile Density time trace

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temperature time trace pressure time trace

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time [ms]

-

polo

idal

ang

le [

deg]

#100972, evolution of heat flux density at toroidal angle - = 208°

1600 1800 2000 2200 2400 2600 2800 3000150

160

170

180

190

200

210

0

2

4

6

8

10

12x 10

5#100972, evolution of heat flux density at toroidal angle - = 208°

time [ms]

- po

loid

al a

ngle

[de

g]

1600 1800 2000 2200 2400 2600 2800 3000150

160

170

180

190

200

210

0

1

2

3

4

5

Related to the stepwise increase of density are characteristic heat deposition patterns

Start of a new pattern is interpreted as opening of magnetic flux tubes from new island chain to wall

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3.75kA 4/2

9/4

5/2

FP = +80V

FP = +120V

6/2

Electric potential at divertor target probes

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Poincaré plots at first and third density step

Before step After step

1. step

3. step

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Hypothesis for confinement improvement:

Important are the open magnetic field lines connecting inner islands with the wall.

The improved confinement may be related to potential exchange between wall and inner islands

This is effective only in low collisional plasmas

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Summary

Confinement improvements have been observed for some plasma / DED conditions.

Best conditions were found for strongly heated low density plasmas shifted strongly towards the HFS (DED).

Improvement has a resonance character with respect to q(a) and the DED-current.

On TEXTOR, a limiter H-mode has been obtained.

The ELMs were reduced at moderate ergodization levels.

12/4 and AC 3/1 base modes have been applied successfully.

The energy confinement is slightly reduced by DED.

TEC Trilateral Euregio Cluster Institut für PlasmaphysikAssoziation EURATOM-Forschungszentrum...

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