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

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Trilateral Euregio ClusterInstitut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich

21st IAEA Fusion Energy Conference, 16 - 21 October 2006 , Chengdu, China

Influence of the Dynamic Ergodic Divertor on TEXTOR

Discharges

K.H. Finken, Y. Xu, S.S. Abdullaev, M. Jakubowski, M. Lehnen, M. F. M. de Bock, S. Bozhenkov, S. Brezinsek, C. Busch,

I.G.J. Classen, J.W. Coenen, D. Harting, M. von Hellermann, S. Jachmich, R.J.E. Jaspers, Y. Kikuchi, A. Krämer-Flecken, M. Mitri,

P. Peleman, Pospieszczyk, D. Reiser, D. Reiter, U. Samm, D. Schega, A.O. Schmitz, S. Soldatov, B. Unterberg, M. Van Schoor, M. Vergote,

R.R. Weynants, R. Wolf, O.Zimmermann, and the TEXTOR Team

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#94809

LFS HFS DED topics:

Helical divertor

Field line and plasma topology

Impurity shielding

Field line penetration

Interaction with MHD

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Outline:

• Introduction to DED

• Effect of the perturbation field on ELMs

• Improved confinement by DED

•Turbulence reduction by DED

• Summary

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16 DED coils

Max. current per coil: 15 kA

DC and AC up to: 10 kHz

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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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~ 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-modeBasic 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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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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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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Evolution of edge pressure HFSTEXTOR # 97315 (thermal He beam)

R= 1.3 m

L-H –transition

H- L –transitionwith DED

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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 mode

DED threshold:3 kA

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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 change 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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pressure time trace

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Comparison of pressure profiles for discharges with and without DED

(from Thomson scattering)

Ne Ne*Te

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3.75kA 4/2

9/4

5/2

FP = +80V

FP = +120V

6/2

Plasma rotation

Poloidal rotation CIII

Heat pattern and

electric potential

Related effects

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Field line structure at density step

q=2.0 island

Poincaré plot Laminar plot

Starting ergodization of q=2 surface

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Effect of the DED on turbulence

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Turbulence-probe3 strokes during one discharge

Effect of the DED on turbulence

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Turbulence-probe head (RS-probe)

“Reynolds stress probe”:o measures:

• floating and plasma potential• electron temperature• electron density and particle flux

o main feature:• small pins dedicated to measurefluctuations of poloidal and radial velocity => Reynolds stress Zonal flows

o min radius: 42 cm (217 cm)

Boron-nitride body(isolator)

Tungsten pins(d = 1-2 mm)

, , , , , , , , , , , ( , )e e fl pl r e e r rn T E n T E E v v S k

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Ergodic zonea=45.7cm

Equilibrium profiles (6/2 DED)

Vf Te

Before DED DED ramp DED plateau

ne

r (cm)r (cm)

a=45.7cm

Er

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Turbulence with / without DED in 3/1 DED~

in 6/2 DED~

Before DED DED ramp DED plateau

S(f)

a

r (cm)

lc (cm)

lcr (cm)

Ergodic zone

Coherent modes reduced

Size of turbulent cells reduced

Inward flux with DED

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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.

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Summary continued

Probe measurements:

Strong effect of DED on equilibrium values of F(r) and Er.

Turbulent flux reverses sign.

Size of large turbulent structures reduced.

Coherent modes strongly reduced.

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

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